A N A L Y T I C A L CHEMISTRY, VOL. 51, (415) Wedler. G.; Colb, K. G.; Heinrich, W.; McElhiney, G. Appi. Surf. Sci. 1978, 2 , 85. (416) Wedler, G.; Colb. K. G.; McElhiney, G.; Heinrich. W. Appl. Surf. Sci. 1978, 2 , 30. (417) Wedler, G.; Geuss, K. P.; Colb, K G.; McElhiney, G. Appl. Surf. Sci. 1978. 1 , 455. (418) Wehking. F.; Beckermann, H.; Niedermayer, R. Surf. Sci. 1978, 71, 364. (419) Weizer, V. G.; Andrews, C. W. "Proc. Scanning Electron Microscopy"; Johari, 0.. Ed.; IIT Research Institute: Chicago, Ill., 1977; Vol. I , p 183. (420) Wells, M. G.; Cant, N. W.; Greenler, R. G. Surf. Sci. 1977, 6 7 , 541. (421) Whalley, W. B. "Proc. Scanning Electron Microscopy"; Johari, 0.. Ed,; Scanning Electron Microscopy Inc.: O'Hare, IiI., 1978; Vol. I,p 353. (422) White, S. J.; Woodruff, D. P. Surf. Sci. 1977, 6 4 , 131. (423) White, S. J.; Woodruff, D. P.; Holland, B. W.: Zimmer, R . S. Surf. Sci. 1977, 6 8 , 457. (424) White. S. J.; Woodruff, D. P.; Holland, 8. W.; Zimmer, R. S. Surf. Sci. 1978, 74, 34. (425) Whitton, J. L.; Tanovic, L.; Williams, J. S. Appl. Surf. Sci. 1978, 1 , 408. (426) Wilf, M.; Dawson, P. T. Surf. Sci. 1977, 65, 399. (427) Wille, R. A.; Netzer, E. P.; Matthew, D. Surf. Sci. 1977, 68, 259. (428) Wilmoth, R. G.; Fisher, S. S. Surf. Sci. 1978, 72, 693. (429) Wilmsen, C. W.; Kee, R. W. J . Vac. Sci. Technol. 1977, 14, 953.
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(430) Wilmsen, C. W.; Kee, R. W. J . Vac. Sci. Techno/. 1978, 15, 1513. (431) Wilson, A. D. "Proc. Scanning Electron Microscopy"; Johari, O., Ed.; IIT Research Institute: Chicago, IIi., 1977; Voi. I , p 719. (432) Windawk, H.; Katzer, J. R. Surf. Sci. 1978, 75, L761. (433) Winkler, H.; Hanisch, S. Surf. Sci. 1978, 76, 519. (434) Withrow, S. P.; Luscher, P. E.; Propst, F. M.; Weinberg, W. H. J . Vac. Sci. Teclinoi. 1978, 15, 511. (435) Wktberg, T. N.; Hoenigman, J. R.; Moddeman, W. E.; Cothern, C. R.; Gulett. M. R. J . Vac. Sci. Technol. 1978, 15, 348. (436) Williams, J. S. N u d . Instrum. Methods 1978, 149, 207. (437) Wu, K. J.: Chou, A. C.; Hu, D. C., "Proc. Scanning Electron Microscopy", Johari, O., Ed.; IIT Research Institute: Chicago, Ill., 1977, Vol. I.p 117. (438) Yabumoto, M.; Watanabe, K.; Yamashina, T. Surf. Sci. 1978, 77, 615. (439) Yaniv, A. E.; Lumsden, J. B.; Staehle, R . W. J . Electrochem. SOC.1977, 124, 490. (440) Yasuda, H.; Hsu, T. Surf. Sci. 1978, 76, 232. (441) Yoshida. K.; Somorjai, G. A. Surf. Sci. 1978, 7 5 , 46. (442) Zhdan, P. A.; Boreskov, G. K.: Boronin, A. I.; Schepelin, A . P.; Egelhoff, W. F.; Weinberg, W. H. Appi. Surf. Sci. 1977, 1 , 25. (443) Zhdan, P. A.; Boreskov, G. K.; Boronin, A. I.; Schepelin, A . P.; Egelhoff, W. F.: Weinberg, W. H. Surf. Sci. 1978, 7 1 , 267. (444) Zuhr. R. A.; Hudson, J. B. Surf. Sci. 1977, 66, 405.
Water Analysis M. J. Fishman" and D. E. Erdmann
U.S. Geological Survey, Lakewood, Colorado 80225
This eighteenth review of literature of analytical chemistry applied to water analysis covers the period from October 1976 through September 1978. The present review follows the plan of previous reviews, the last of which appeared in Analytical Chemistry for April 1977 ( 7 ) ;however, the editors of ANALYTICAL CHEMISTRY requested that review authors cover their respective fields in a more selective manner and not attempt to provide an all-inclusive bibliography. Therefore, references used in preparing this review come mainly from major analytical journals and United States Government publications. Conference proceedings, obscure foreign journals, and most trade journals are generally excluded. A review of literature on water pollution control, which includes a section on analytical methods and instrumentation, is published annually by the Water Poliution Control Federation. T h e 1976 reviews by Shuman and Fogleman (13), Chian and DeWalle ( 4 ) ,and Brezonik and Carriker (2) include 895 references and cover such topics as inorganics, organics, continuous monitoring, automated analysis, and sampling procedures. The 1977 reviews by Leland, Luoma, and Wilkes ( I O ) , Brezonik, Hendry, and Prentice (3)include 436 references and cover the same topics. Uses of neutron activation analysis, atomic absorption spectrometry, fluorimetry, emission spectrometry, colorimetry, X-ray fluorescence, mass spectrometry, and electrochemical methods in t h e analysis of water for inorganic elements are compared by Baudin ( I ) . Segar and Cantillo ( 2 2 ) reported on chromatography-atomic spectroscopy combination techniques to identify and determine metallic species. Potential applications are diverse, allowing many solid-phase column materials and eliients, sample types, and separation conditions. Epstein, Rains, and O'Haver (6) compared factors affecting accuracy in atomic emission and atomic absorption spectrometry using a graphite furnace for determining trace metals in water. Emission spectrometry is limited by the intense blackbody radiation from the heated graphite tube, which increases photon shot-noise and causes erratic emission intensity. Close bracketing of samples by standards is required. Atomic absorption spectrometry is limited by scatter and/or absorption of source radiation by sample matrix constituents. Evaluation of accuracy of the two methods can be made only for individual elements in a particular sample.
Harrison (8) described electrical detection problems that affect accuracy of spark source mass spectrometry, when instrumentation is applied to water-related problems. Determination of organic substances in natural and sewage waters by gas chromatography is reviewed by Yavorovskaya and Anvaer ( I 7 ) . 0ne.hundred-eighty-three references are given. A review with 143 references on application of ion-selective electrodes in water analvsis is given bv Troianowicz and Hulanicki (14). KemBf (9) discussed analvtical methods used for the determination of traces of inofganic contaminants in water in a review with 12 references. Ronan and Kunselman ( 2 2 ) reported on an inductively coupled argon plasma multielement direct-reader system, which can analyze one sample every 30 seconds, using a cycle time which includes sample rinse, 10-second integration, and teletype printout of results for 23 elements. T h e method is compared to EPA accepted methods for the determination of metals by atomic absorption spectrometry. Clean laboratory methods to achieve contaminant-free processing and determination of ultra-trace samples in marine environmental studies are reviewed by Wong et al. (16). Problems, techniques, storage, and preservation of individual and composite water samples are discussed in a review by Wagner ( 1 5 ) . Development of analytical standards for water quality is considered by Egan ( 5 ) on a historical basis, and the present day position is reviewed in relation to other bases for quality assessment. Some analytical problems which arise in examination of rivers and oceans are considered together with the automation of methodology.
ALKALI METALS A N D ALKALINE EARTH METALS Gardner, Pritchard, and Sadler (4A) determined ultra-trace concentrations of sodium in water by flameless atomic absorption spectrometry. The analytical curve is linear from 0.13 to 0.92 pg/kg with a corresponding standard deviation range of 0.006 t o 0.021 pg/kg. As little as 0.011 pg/kg of sodium can be detected. Results are compared to those obtained using a sodium ion-selective electrode method.
This article not subject to U.S. Copyright. Published 1979 by the American Chemical Society
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Discrepancies between results are attributed to the sluggish response of the electrode system. Neutron activation analysis was applied by Higuchi e t al. (6A) for determination of sodium in high-purity water samples. Sodium-24 was separated from other alkali elements and other nuclides by adsorption on hydrated antimony pentoxide. Contamination of sodium from container walls during neutron irradiation was also studied. Belen’kii e t al. ( 2 A ) described a photometric method for determining sodium in water in the range of 5 to 15 pg/L. A 1-mL sample is mixed with tetramethylammonium hydroxide and a n acetone solution containing 5-nitro-2-(3-methyl-5oxoisoxazol-4-y1azo)benzenesulfonicacid. Color is stable for 40 minutes in a quartz cell or 7 minutes in a glass cell. Soldan and Curtius (17A) stated that both atomic absorption and flame emission spectrometry can be used without pretreatment of the sample to determine lithium in seawater. Chloride produces t h e greatest interference; however. interference can be eliminated by the method of standard additions or by calibration using artificial seawater. Katz and Taitel (10A) reported that calcium interferes in the flameless atomic absorption spectrometric determination of lithium. This is caused by dissociation of calcium chloride in the graphite tube cavity. T h e chlorine atoms formed react with gaseous lithium to form lithium chloride which is rapidly swept away by the purge gas. Addition of a moderate excess of sulfuric acid relative to the amount of chloride present completely removes the interference-forming hydrochloric acid a n d calcium sulfate. Continuous isolation and separation of rubidium and cesium from seawater and concentration of cesium on a n inorganic ion-exchanger by the method of 2-dimensional chromatography was studied by Moskvin and Mei’nikov (13A). The cylindrical ion-exchange apparatus contained ammonium molybdophosphate combined with polytetrafluoroethylene. A study was made by Gladney and Goode ( 5 A ) on the behavior of 1 ppb beryllium in solution over relatively long storage times in different containers. The best container material was polycarbonate, with either 0.1 7 c hydrochloric acid, or sulfuric acid, or hydrofluoric acid as the preservative. An atomic absorption spectrometric method is described by Korkisch, Sorio, and Steffan ( I I A ) for the determination of beryllium in water after separation by solvent extraction and cation-exchange. Beryllium is first isolated bq chloroform extraction of its acetylacetonate complex from a solution at p H 7 containing EDTA. T h e extract is then tnixed with tetrahydrofuran and methanol containing nitric acid and passed through a column of Dowex 50-X8(H’ form). The column is washed with methanol-nitric acid and beryllium eluted with 6 M hydrochloric acid; as little as 0.01 pg/L of beryllium is detected. Sato and Saitoh ( I 6 A )determined beryllium and bismuth in spring water by atomic absorption spectrometry using a carbon tube atomizer. These metals are coprecipitated with zirconium hydroxide and filtered. The residue is dissolved in boiling 2 N hydrochloric acid, and an aliquot injected into the carbon tube. Beryllium (0.05 pg) and bismuth (2.5 p g ) , added to 1000 mL of acidified seawater, gave recoveries of 100 f 4 and 100 f 3 % , respectively. Hulanicki a n d Trojanowicz (8A) described a calcium ion-selective electrode procedure used to determine calcium in water. T h e PVC membrane, containing calcium di-noctylphenyl phosphate, is in direct contact with the internal electrode made of silver/silver chloride or Teflonized graphite. Hulanicki, Maj-Zurawska, and Trojanowicz ( 7 A )used a liquid junction ion-selective electrode to continuously monitor calcium in water a t levels of 100 ppm. lnterferences are eliminated by addition of a complexation buffer. The procedure is based on continuous sampling of water from the stream using a peristaltic pump, which provides mixing with proper buffer solution and air se mentation. Results are comparable to those obtained by E6TA titration. .Jagner and Oestergaard-Jensen ( 9 A ) also studied various calcium electrodes based on metal salts of di-(n-octylpheny1)phosphoric acid. T h e electrodes are used for potentiometric titrations of calcium in seawater. Effect of varying the membrane solvent and chelate metal was also studied. Rands and Stoica (In‘A)reported that the divalent electrode, primarily designed for measuring water hardness and determining calcium and magnesium activity, responds only to unassociat,ed calcium
and magnesium ions in aqueous solution; thus, significant error results, when water hardness is measured where calcium and magnesium may be extensively bound. Watanabe and Tanaka (18A) used dual-wavelength spectrophotometric measurements for the determination of magnesium with Xylidyl Blue I and Triton X100. The difference between absorbance readings at 515 and 620 nm is used to measure the magnesium concentration in rainwater. Relative standard deviations are 0.8 and 2.0% for 1.0 and 0.080 pg/mL of magnesium, respectively. A high-precision computerized titrimetric method for determining calcium and magnesium in seawater is described by Anfalt and Graneli ( 1 A ) . A new probe photometer based on modern optoelectronic components is used. The calcium end point is determined with zinc-zincon indicator, while magnesium is determined with Calcon. Precision for calcium and magnesium is 0.03 and 0.04%, respectively. Miller and Edwards (12A) described a double capillary sy$em which provides a convenient method to pretreat and dilute natural water samples as they are aspirated directly into the burner mixing chamber of an atomic absorption spectrometer. The system is used to determine calcium arid magnesium. Ebdon, Hutton, and Ottaway (3A) determined barium in potable waters and sediments by carbon-furnace atomic emission spectrometry. Calcium does not interfere. T h e working range is 0.01 to 0.2 pg/mL of barium, although the detection limit is 0.002 pg/mL. Results are compared with those obtained by atomic absorption spectrometry using a nitrous oxide-acetylene flame. A semi-automated method for separation and determination of barium and strontium in surface waters by atomic emission spectrometry is described by Pierce and Brown ( I 4 A ) . It eniploys a semi-automated separation technique using ion exchange and automated aspiration. Forty samples can be prepared in approximately 90 minutes. Detection limits for barium and strontium are 0.008 and 0.00045 mg/L,, respectively.
IRON, MANGANESE, ALUMINUM, A N D CHROMIUM Kollins and Oldham (26B) developed a spectrophotometric method for the determination of iron in fresh and saline waters. The method is based on the piirple-violet colored complex which is formed with iron and 3-(2-pyridyl)-5,6diphenyl-1,2,4-triazine. As little as 1 ppb iron is detected. Sugimoto, Matsushita, and Furuhashi (30B) described an extraction-spectrophotometric method for determination of /ron(III) in water, using 2,4,5,7-octanetetraone to complex the iron. The orange-red complex is extracted into butyl acetate at pH 2.7, and the absorbance is measured at 500 nm. Beer’s law is obeyed for 0.4to 40 pg/mL of iron. Measurement of ferrous iron in wat,ers containing both ferrous and ferric iron by the 2,2’-bipyridyl colorimetric method and by polarography was compared by Heaney and Davison (1OR). Gadia and Mehra (5R)determined t o t d iron spectrophotometrically with pentacyanoammineferroate and ferrozine, where&? ferrous iron is determined directly with ferrozine. Linear response is obtained between 0.025 and 1.75 ppm. Analytical studies and applications of ferroin type chromogens immobilized by adsorpt,ion on a styrene-divinylbenzene copolymer were reported by Lundgren and Schilt ( I 7B). Of the ferroin chromogens tested, 3-(2-pyridyl)-5,6diphenyl-1,2,4-triaine( P D T ) proved to be the most effectively adsorbed on Amberlite XAD-2, and it was applied to the determination of iron in seawater. A met,hod is described t i y Davison and Rigg ( 3 H ) for the determination of total iron in fresh water, using a wet-oxidation procedure followed by spectrophotometric measurement, in approximately 6 M hydrochloric acid at 360 nni. Copper is the only substance to interfere significantly; below 0.1 mg/L, it has a negligible effect. Relative standard de\Tiations a t 0.2 and 3 mg/L are 4.4 and 1.5?%, respectively. Crowther ( 1 R ) used autoclave digestion (acid-reducirig media a t 1 2 1 “C for 1 h) to solubilize iron in water. Determination of total iron is completed by using an automated 2,4,G-tri(2-pyridyl)-1,3,5-tr;azine colorimetric procedure. A new radioisotope dilution method for direct determination of ionic iron in small volumes of ocean wat,er is described by Sharnia and DuRois (2RR). Known amounts of unlabeled
A N A L Y T I C A L CHEMISTRY, VOL. 51, NO. 5, APRIL 1979
Marvln J. Fishman, born in Denver, Colo., received his B.A. degree (1954) and M.S. degree (1956) from the University of Colorado. He has been employed by the Water Resowces Division, U.S. Geological Survey, Denvr since 1956. His research interests are centered on development of methods for water analysis, including atomic absorption. He is a member of the Society for Applied Spectroscopy, and the American Society for Testing and Materials (W.Fishman serves on ASTM Committee D 1 9 on water). He has published about 40 papers related to methods for water analysis.
Davld E. Erdmann has been a chemist with the Water Resources Division of the U.S. Geological Survey since 1968. He received his B.S. degree from Winona State College and his M.S. and W.D. degrees from the University of Nebraska. His research interests are concerned with the development and automation of methods for water analysis. He is a member of the American Chemical Society, Sigma Xi, and Phi Lambda Upsilon Societies.
ferrous ions are added to aliquots of the radioactive ferrous ions, and the mixtures are reacted with bathophenanthroline to yield a [iron(batho),]*+complex. Concentration of iron in a sample is obtained by observing the percent radioactivity of t h e labeled iron bound by bathophenanthroline after radiodilution by unlabeled iron present in a known volume of sample. Interference from cuprous ion is eliminated with neocuproine. Hoffmeister (12B)determined iron in ultrapure water by flameless atomic absorption spectrometry. Samples are preconcentrated by evaporation prior to analysis. At 0.25 ppb iron, reproducibility is approximately 1090. Nikolelis and Hadjiioannou (20R)determined manganese in water based on its catalytic effect on the IO4 HLPOP reaction carried out at 32.5 “C. ’rime required to consume a fixed amount of IO4 is automatically measured and is directly related to the concentration of metal. In the 12 to 120 ng range, a nitrilotriacetic acid activator is required. An automatic spectrophotometric kinetic method for the microdetermination of manganese in natural waters based on its catalytic effect on the periodate- acetylacetone reaction is described by Nikolelis and Hadjiioannou (21R). T h e time required for formation of a small fixed amount of colored product is measured automatically and related directly to the manganese. At the I x 10 to 1 x 10 M level, average error is about 2 9 ~ Hadjiioannou . et al. ( 9 R )studied the applicativn of a miniature centrifugal analyzer to the determination of ultramicro concentrations of manganese by a kinetic method. A spectrophotometric reaction-rate met hod is based on the otassium iodate diethylaniline reaction which is catalyzed y manganese. Results agreed with those obtained by neutron activation. Sikorska-Tomicka (29B)reported that binazine forms a 3:l complex with manganese(II1, which is then measured at 420 nm. The technique is used to determine manganese in ground water. Grzegrzolka ( 8 R ) determined manganese in water spectrophotometrically with l-(thiazolylazo)-2-naphthol.The complex is extracted at pH 9.2 to 9.8 into chloroform, and the absorbance of the organic phase measured a t 580 nm. Beer’s law is obeyed for 0.1 to 1.3 pg/mL of manganese. Crowther ( 2 H ) determined total manganese in water using batch digestion, by autoclaving in acid medium followed by automated colorimetry based on formation of the manganese-formaldoxine complex. Cation interference is suppressed by complexing agents while color is eliminated by using a blank synchronized with the sample In the range of 0.006 to 0.20 mg/L of manganese, accuracy and precision are comparable to results obtained by flame atomic absorption spectrometry.
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Goto et al. (7R) reported that 1-(2-pyridylazo)-2-naphthol reagent is four times more sensitive than formaldoxine reagent in the spectrophotometric determination of manganese. Details of the method are given; Beer’s law is obeyed u p to 2 ppni. The method is applied to the determination of manganese in natural water. U p to 10 ppm lead can be tolerated. Iron, cadmium, zinc, cobalt, and nickel interfere. These interactions are masked with potassium cyanide. Direct-injection flameless atomic absorption spectrometry has been used by McArthur (18B) to determine manganese in seawater. Matrix interferences are eliminated by charring with ammonium nitrate and with a slow temperature increase. Presence of nitric acid depresses the sensitivity. Pakalnins and Hsu (23B) concentrated trace quantities of manganese by extraction with dithizone in ethyl propionate at a p H of 8.5. Manganese in the extract is determined by atomic absorption spectrometry. Manganese (I\’ and VII) are reduced to manganese(I1) before extraction. Goto (6B) determined trace concentrations of manganese in river water by atomic absorption spectrometry, after complexing manganese with thiocyanate and extracting the complex with trioctylmethylammonium chloride into ethyl acetate. The analytical curve is linear to 12 pg manganese, and the relative standard deviation for 5 pg manganese is 1.0290. Iron(II1) concentrations greater than 100 pg give a positive error, but other ions do not interfere. T o determine manganese in environmental waters by atomic absorption spectrometry, Kato ( 1 4 B ) extracted the manganese with thenoyltrifluoroacetone in methyl isobutyl ketone. A number of other metals interfere; iron is the most severe. I t is removed by extraction with methyl isobutyl ketone before addition of thenoyltrifluoroacetone. At 5 and 50 p g / L relative standard deviations are 7 and 1 % , respectively. Satake et al. (27B) used the combination of chelating ion-exchange separation and atomic absorption spectrometry to determine manganese in brackish and coastal waters. The sample at p H 6 to 8 is passed through a column of the chelating resin, which absorbs the manganese completely, and the manganese is then eluted with 1 N nitric acid; the eluant is then analyzed. The method has the advantage that it can concentrate manganese from a large volume of water. An ac polarographic method was developed by Lapitskaya, Proleskovskii, and Sviridenko (IE;R)for the determination of manganese in stratal waters. A fluorometric method for determining aluminum in water using the reagent Lumogallion ha3 been investigated by Hydes and Liss (13R);it is found to have a detection limit of 0.05 pg/L, with a coefficient of variation of 5 and 2.7% a t the 1.0 and 22 fig L levels, respectively. Fluoride interference is eliminate by using an incremental calibration procedure. There is no significant effect from iron concentrations less than 100 pg/L. Ultraviolet irradiation will eliminate any effect from waters containing significant quantities of organic material. Pakalns and Farrar (24B) studied the effect of a number of cationic, anionic, and nonionic surfactants on the determination of aluminum, using the eriochrome cyanine R, ferron-orthophenanthroline, and chrome azurol S methods. Levels at which interference occurs are reported. Nakata and Hayakawa (19B) determined chromium(V1) colorimetrically with diphenylcarbazide in the presence of reductants such as sulfide, sulfite, thiosulfate, dithionate, nitrate, oxalate, and hydroxylamine. In the presence of reductants, reaction of chromium(V1) with diphenylcarbazide takes place only under alkaline conditions. Details of the procedure are given. Interference levels of reductants are reported. Hiiro et al. ( I ZR) described both flame and graphite furnace atomic absorption spectrometric procedures for determining hexavalent chromium in seawater. Chromium(V1) is complexed with diethyldithiocarbamate and extracted into methyl isobutyl ketone. Sensitivity is 0.4 ppb for 19 absorption with the flame method, and 0.02 ppb by the graphite furnace method. A gas chromatographic method for determining chromium in natural waters was reported by Lovett and Lee (16B). Chromium is chelated with (trifluoroacetyl) acetone and the chelate is extracted into benzene; as little as 0.1 pg/L can be detected. Osaki et al. (22H) determined hexavalent chromium and total chromium after oxidation in seawater by isotope-dilution
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mass spectrometry. Samples are spiked with isotopic chromium chelated with ammonium pyrrolidine-dithiocarbamate, and, at p H 2, extracted into chloroform. Detection limit is 0.001 pg/L. Van der Sloot (31B) determined chromium in water by neutron activation. Chromate is reduced a t p H 1.5 with sodium sulfite, and then concentrated from neutral solution on activated carbon. By preconcentration on activated carbon, a differentiation between tervalent and hexavalent chromium is possible. Limit of detection, which depends on the value of the carbon blank, is 0.05 pg/L of chromium with a precision of 20%. Using cation- and anion-exchange resins in series, Dempsey ( 4 B ) developed a column chromatographic method for field preconcentration of trace metals. Both tervalent and hexavalent chromium are separated by this technique. A spectrophotometric method for the microdetermination of iron and chromium based on direct measurement of ionexchange resin phase absorption after sorption of the sample complex species is described by Yoshimura, Waki, and Ohashi (32B). For the determination of chromium with diphenylcarbazide and iron with 1,lO-phenanthroline, sensitivity is approximately 10 times that for conventional colorimetry. Rigin and Blokhin (25B) described a chemiluminescence method for the determination of traces of iron, chromium, copper, and cobalt in water in the presence of each other. The method is based on the selective masking of catalytic action of metal ions with complexons, during oxidation of luminol. Limits of detection for iron, chromium, copper, and cobalt are 3, 0.6, 0.5, and 0.2 pg/L, respectively.
COPPER, ZINC, LEAD, CADMIUM, NICKEL, COBALT, A N D BISMUTH Mann and Deutscher (28'2) determined copper in water in the 3 to 100 pg/L range by anodic-stripping pulse voltammetry. Addition of thiocyanate permits determination of copper in the presence of lead. T h e peak for copper occurs at approximately -0.20 V, clearly resolved from the rising portion of the curve caused by mercury oxidation. Deguchi et al. (13C) used atomic absorption spectrometry to determine copper in artificial seawater and groundwater. Copper is extracted with thiothenoyltrifluoroacetone in xylene at p H 3 t o 8. T h e organic phase is then aspirated in an air-acetylene flame. Relative standard deviations for 2 and 10 pg copper are 2.4 and 1.370,respectively. A rapid technique was developed by Boyle and Edmond CSC) for concentrating trace metals from aqueous solutions. The metals are coprecipitated as dithiocarbamate chelates by adding an excess of another dissolved metal. The technique is coupled with atomic absorption spectrometry for the determination of copper in seawater. Churella and Copeland ( I I C ) studied the concentration-dependent interferences of several alkali and alkaline earth halides, in the determination of copper in seawater by atomic absorption spectrometry using a carbon cup electrothermal atomizer. Addition of sodium peroxide eliminates or substantially reduces the interferences caused by these salts. Occlusion of analyte is proposed as the primary mechanism of these interferences. Rice and Jasinski (39C) reported that sample pretreatment is not necessary when continuously monitoring copper in seawater with an ion-selective electrode. Necessary sensitivity of the copper selective electrodes is achieved by preconditioning the electrodes and using a flow-cell configuration. Response times even at concentrations below 0.5 pg/L are adequate. Other problems associated with the system are discussed. T h e possibility of determining copper down to 6 pg/L by standard addition in natural waters using direct potentiometry with a chalcocite copper-sensitive ion-selective electrode was tested by Hulanicki, Trojanowicz, and Krawczynski (18C). A Tris-fluoride buffer solution containing Tris, potassium fluoride, and potassium nitrate was proposed as a medium. Midgley (29C) reported that, of four types of cop er ion-selective electrodes tested at concentrations below 10 mol/L, none has a Nernstian response in dilute copper solutions in this concentration range, though their responses are linear in pCu buffer solutions; causes of deviations are discussed. Murozumi, Nakamura, and Ito (34C) and Murozumi, Ito, and Nakamura ( 3 1 C ) described isotope dilution mass spectrometric methods with a single Re filament to determine
B
copper in sea and river waters. The sample is spiked with @Cu, and the copper loaded as the perchlorate with silica gel and phosphoric acid. Detection limit, and relative standard deviat.ion are approximately lo-" g and 1.5%, respectively. Desai. Padmanabhan, and Venkateswarlu ( I 4 C ) collected copper from distilled water onto a carboxylate exchanger and irradiated it with thermal neutrons. By com arison of the induced activity of the 0.51-MeV photopeak of %Cu with that of a standard, irradiated under comparable conditions, copper at ppb levels is easily determined. Lo, Wei, and Yeh (292) preconcentrated copper from seawater with lead diethyldithiocarbamate and chloroform. The concentrate is then irradiated, and copper determined by neut,ron activation. Sodium and bromide, which interfere, are completely removed from the sample by this procedure. Hirayama ( I 7C) developed a spectrophotometric method for the determination of copper in water based on the catalytic action of copper on the oxidation of o-aminophenol by dissolved oxygen. The phenoxazine derivative formed is extracted into chloroform after a predetermined time. A linear relationship is obtained up to 20 pg/L; as little as 0.1 pg/L of copper can be detected. Ferric iron int,erference is eliminated by addition of fluoride ion. Odashima and Ishii (37C) used furfural-2-benzothiaolylhydrazone to determine copper in water spectrophotometrically. Maximum absorbance is at 41 5 nm. A dual-wavelength spectrophotometric method to determine copper was proposed by Watanabe and Miura ( 4 7 0 . Copper is reacted a t a p H less than 2.7 with a zincdithizone complex in water containing Triton X 100. Ferric iron interferes by oxidizing the dithizone; this is prevented by addition of pyrophosphate ion. Copper is determined by measuring the differential absorbance at 510 and 617 nm. Beer's law is obeyed from 0 to 50 pg/L. Precision at the 95% confidence level is f0.06 pg for 1.48 pg copper. Tolerance limits for other ions are given. Automated column procedures for the separation and preconcentration of copper(I1) from natural waters by using either 8-hydroxyquinoline immobilized on glass or an anion-exchange resin were compared by Guedes d a Mota, Roemer, and Griepink (16C). Both techniques showed about the same performance; the first one is less time- and laborconsuming. Akaiwa, Kawamoto, and Ogura ( 3 C ) determined zinc in water by isotope dilution. A known amount of zinc containing 6sZn is added to test solut,ion which is then stirred with Diaion SA 100 resin loaded with a substiochiometric amount of 8-quinolinol-5-sulfonicacid. After filtration, activity of the resin is measured using a T1-drifted NaI detector. Krishnamurty and Reddy (22C) stated that tris(pyrro1idine dithiocarbamato)cobalt(III) is a good matrix for preconcentrating lead and several other metals from water by coprecipitation. Concentration factors of 40 to 400 are obtained. Flame atomic absorption spectrometry is then used for measuring the concentration of lead. Principal lead transport processes occurring in anodic stripping voltammetric analysis of seawater were studied by Petrie and Baier (38C) using liquid scintillation spectrometry oi' "OPb. From an initial lead concentration of 6.3 x 10.' M, the concentration is reduced greatly depending on the pH. Primary losses are due to adsorption onto cell and electrode materials. Significant chemisorption of lead associated with chloride occurs at the platinum wire counter electrode. Data support a diffusion-limited adsorption mechanism as the primary transport for lead from solution. Murozumi et al. (32C) determined trace amounts of lead in river water by isotope dilution with a *08Pb spike and ionization mass spectrometry. Details of the procedure are given. Chau, Wong, and Goulden ( I O C ) used gas chromatography-atomic absorption spectrometry for the determination of tetraethyllead compounds. Use of a silica furance enhances sensitivity by three orders of magnitude. Anodic stripping voltammetry a t a mercury film electrode in an ammonium acetate-acetic acid buffer was employed by Zur and Ariel (51C) for the determination of cadmium in aqueous solutions containing humic acids. Continuously renewed electrodes are advantageous for avoiding electrode blockage by adsorbed humic acid. Addition of mercuric ion leads to partial displacement of cadmium from humic acid complexes and improves sensitivity.
A N A L Y T I C A L CHEMISTRY, VOL. 51, NO. 5, APRIL 1979
hTurozumi et al. (35C) determined cadmium in soil and in river- and seawater by isotope dilution and surface emission mass spectrometry. Cadmium-116 is used as a spike. T h e method can be used to determine the '"Cd/"'Cd ratio with a 0.4 to 1.1% relative standard deviation. Detection limit for to 1 X g. In a later publication, cadmium is 1 X Murozumi et al. (33C) used the same technique to determine copper, cadmium, and lead. Rosman and De Laeter (4OC) determined sub-ppb levels of cadmium in river water with a solid-source mass spectrometer, after preconcentration of cadmium on an ion exchanger. The sample is spiked with a known weight of isotopically enriched ll1Cd tracer. Liardon and Ryan ( 2 4 C ) preconcentrated nickel from seawater by precipitation with a-benzildroxime at pH 9.5. The precipitate is then filtered, washed, dried, and packed in a cell; the reflectance of the solid is measured at 431 nm; less than 1 ppb nickel can be detected. Kiriyama and Kuroda ( 2 I C ) used a strong basic anion exchanger Amberlite CG 400 to concentrate cobalt from seawater. Cobalt is eluted with 3 M perchloric acid. A 4(2-pyridy1azo)resorcinol solution in the presence of EDTA and potassium cyanide is then used to determine cobalt spectrophotometrically. Detection limit is about 0.1 to 0.2 pg/L. Flame and flameless atomic absorption techniques are heavily used by investigators for several of the metals. Zawadzka, Baralkiewicz, and Elbanowska (49C) used Dowex A-1 to concentrate cobalt, cadmium, lead, nickel. copper, and zinc in natural waters. Anion- and cation-exchange columns in series were used by Shuman and Dempsey ( 4 3 0 to concentrate cadmium, chromium, copper, lead, and zinc. Satake et al. ( 4 I C ) concentrated copper, zinc, lead, and cadmium in brackish and coastal waters with a chelating ion-exchange resin. Inoue et al. ( 1 9 C ) extracted dimercaptomaleonitrile complexes of cadmium, copper, lead, and zinc into methyl isobutyl ketone with tetrabutylammonium ion. Campbell and Ottaway (9C)determined cadmium and zinc in seawater directly on diluted samples with a carbon furnace using standard addition. A method for minimization of matrix interference using lanthanum nitrate in the determination of lead and cadmium in nonsaline waters by electrothermal atomization is reported by Thompson, Wagstaff, and Wheatstone ( 4 5 C ) . Batley, Matousek, and Jaroslav (5C) determined lead. cobalt. and nickel in seawater after electrodeposition on pyrolytic graphite-coated tubes. Boyle and Edmond (7C)used APDC chelate coprecipitation to determine copper, nickel. and cadmium in seawater by the flameless technique. Tikhomirova, Patin. and Morozov (46C) concentrated mercury, lead, and cadmium in seawater with copper sulfide, and measurement of these metals by both flame and flameless methods. A variety of voltammetric methods are being widely used for simultaneous determination of metals discussed in this section. Miwa and Mizuike (3CIC)applied differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode to the determination of copper, lead, cadmium, and zinc. Abdullah, Berg, and Kiimek ( I C ) determined zinc, cadmium, lead, and copper in seawater by DPASV using a mercury film electrode. A hanging mercury drop electrode and a rotating glassy carbon electrode mercury plated in situ were used by Lund and Onshus (26C) for the determination of copper, lead, and cadmium by DPASY. Nuernberg et al. (3GC)determined cadmium, lead, and copper in sea or inland waters by DPASV using a rotating glassy carbon electrode coated with a mercury film. Abdullah. El-Rayis, and Riley (2C) studied the behavior of chelating ion-exchange resin Chelex-100 for collection of copper, lead, cadmium, and zinc from seawater for determination by anodic stripping voltammetry (AS\.'). Experience on application of AS\' is discussed by Branica et al. (SC) with regard to direct determination of the concentration of metal ions (Cd, Pb, Cu, and Zni. Characterization of species act~ually present, and chelation, hydrolysis, and other interactions between metallic ions and organic ligands in natural aquatic systems are also discussed. Shuman and Woodward (44C) reported that several copper-zinc intermetallic compounds form during AS\' analysis of solutions containing both copper and zinc. Schieffer and Blaedel ( 4 2 C ) ,using portable battery-operated equipment, described, tested, and characterized performance of ASV with collection on two mercury-coated
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glassy carbon tubular electrodes in series. The equipment is used to determine cadmium, lead, and copper in tap water at subnanomolar levels. A computerized electroanalytical procedure for multiscanning ASV and its application for the determination of copper, lead, zinc, bismuth, and cadmium in seawat.er was reported by Jagner and Kryger (2GC). ASV was applied by Barley and Florence (4C) for the determination of cadmium, lead, and copper in seawater. Olein and Hodgson ( 1 2 C ) investigated ozone oxidation of organic sequestering agerits in water prior to determination of trace metals (Pb and Cd) by ASV. Zirino and Lieberman (50C) determined copper, zinc, cadmium, and lead in seawater by automated anodic stripping voltammetry using a tubular mercury-graphite electrode. A method was developed by Lapitskaya, Proleskovskii, and S\ririderiko (23C) for the determination of copper, zinc, and manganese in stratal waters by ac polarography. A polarographic method for detection of cadmium and copper in bilge water was reported by Gomba, Oldham. and Morris ( I 5 C ) . A spectrophotometric method for the microdetermination of copper and cobalt based on direct measurement of ionexchange resin-phase absorption. after sorption of the sample complex species, is described by Yoshimwa, \Vaki, and Ohashi (48C). For the determination of copper with zincon and cobalt with thiocyanate, sensitivity is approximately 10 times that for conventional colorimetry. Analytical studies and applications of ferroin type chromogens immobilized by adsorptiun on a styrene-divinylbenzene copolymer was reported by Lundgren and Schilt (27C). Of the ferroin chromogens tested. 3-(2-pyridyl)-5,6diphenyl-l,2,4triazine proved to be the most effectively adsorbed on Amberlite XAD-2. The method was applied to the determination of cobalt. nickel, copper, and zinc in seawater.
MERCURY AND GOLD Preservation of mercury in water has heen and still is of considerable interest; a number of' papers have been published during the past two years. No uniform method of preservation exists. Ambe and Suwabe ( 3 0 ) reported that addition of sodium chloride to dilute mercury solutions below p H 1 improves stability. and that solutions containing 1 to 1000 ppb sealed in Pyrex glass ampules are stable and usable for 18 months. Sanemasa et al. (220)prevented loss of mercury from solution during storage in polyethylene containers by adding enough nitric acid to produce a Concentration equal to or greater than 0.1 M. Sample containers and preservatives for storage of synthetic and natural low-level (sub-ppb) mercury samples were studied by Carron and Agemian (50).They showed that storage in glass containers with 1 cia sulfuric acid and 0.05% potassium dichromate solution is most advantageous with respect t u accuracy, precision. and practical aspects, such as low detection limits and adaptability to the automated cold-vapor atomic absorption technique. Mahan and Mahan (191))reported that mercury it., not lost as rapidly from samples of natural water as from those made up of deionized water. Data indicate that mercury in natural water can be stabilized well enough to ohtain reliable analysis on the same day as collection, withou: addition of strong acids or oxidants. by rinsing containers throughly u-ith water characeristic of the sample, and keeping samples well agitated. Das and Vander S h o t (71)) discussed problems in collection of samples for mercury; they proposed collecting the mercury on activated charcoal. Procedures for isolating inorganic mercury, inorganic plus organic mercury, and mercury on sediments are also given. Thermal neutron activation is used to measure mercury present: detect ion limit is approximately 1 ng/L. Analytical application of organic reagents in hydrophobic-gel media in selective separation and preconcentration of mercury was reported by Ide, Yano. and Ileno ( I X I ) , and Yano et al. ( 2 9 0 ) . Both dithizone and tliiothenoyltrifluoroacetone gels were used; details on preparation of' gel were giveri. Frimnie! and Winkier ( 1 111) used atornic absorption spectronietry for the determination oi inorganic mercury, and gas chromatopaphy-mass spectrometry for the determination of organic mercury compounds in water. A method for the determination of total dissolved mercury in fresh and saline waters by incorporating ultraviolet digestion
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into the automated cold vapor atomic absorption spectrometric technique is described by Agemian and Chau ( I D ) . Ultraviolet irradiation as a means of degrading organomercurials removes interference of chloride, which is encountered in most automated chemical oxidation techniques. Precision of the method a t levels of 0.07, 0.28 and 0.55 pg/12 of mercury is *6, kt3.8, and *l.O%, respectively. Detection limit is 0.02 pg/L. T h e Environmental Monitoring and Support Laboratory, Quality Assurance Branch of EPA, in a report by Winter et al. ( 2 8 0 ) gave conclusions and statements on precision and accuracy of the cold-vapor atomic absorption spectrometric method for the determinat,ion of mercury in water. The method includes an acid-permanganate -persulfate digestion step. followed by reduction and measurement of mercury vapor a t 253.7 nm. A cold-trap preconcentration procedure incorporated into a st,andard flameless atomic absorption spectrometric method for the determination of mercury in environmental samples was used by Fitzgerald ( 1 O L ) ) for both shipboard and laboratory determination of mercury in seawater. The coefficient of variation for seawater containing 25 ng/L of mercury is 15%. Dogan and Haerdi ( 8 D ) stated that preconcentration of volatile organomercury and metallic mercury on silver wool is particularly suitable for determination of t,hese compounds in air and water samples. The microcolumn containing silver wool is coupled to a cell for mercury determination hy flameless atomic absorption spectrometry. With this technique, approximately 1 ng of mercury can be detected. A number of other investigators have used the standard cold-vapor or flameless, atomic absorption spectrometric technique. Kock et al. (16D) determined mercury i n drinking water, using sodium borohydride as the reductant; Simpson and Nickless (230)determined mercury a t the nanogram level, in water, sediment, and other materials; Robertson 120D3, in addition to using this technique, discussed the effect of contamination, sampling, storage, handling, and interpretation of error; Sontag, Kerschbaumer, and Kainz (24~9)determined mercury, in surface, spring, and ground water by electrolytic deposition on a gold electrode followed by volatilization by heating. Chelating resins which have a selective adsorption for methylmercury were investigated by Egawa and Tajinia ( 9 D ) as a means of preconcentrating methylmercury from seawater. Methylmercury is extracted wit,h benzene, then wit,h glutathione solution from benzene, and determined hy flameless atomic absorption spectrometry. Fujiwara, Sato, and Fuwa ( 1 2 0 ) determined mercury in water by a carbon rod atomizer--atomic absorption spectrometric method. T h e effect of various preservative reagents on volatilization of mercury was tested. T h e most effective reagent is potassium permanganate, which enhances the atomization peak and allows determination of 0.1 ng mercury. Gilbert (140) develoed a cold-vapor introduction system for rapid detection of sub-nanogram amounts of mercury in seawater by plasma emission Spectrometry. Operational parameters affecting response are evaluated, and optimum values are presented. The system appears to be free of spectral interferences. A rapid colorimetric spot test for the determination of mercury in seawater during expeditions is reported by Ryabinin, Romanov, and Miroshnichenko ( B I D ) . Mercury compounds are reduced to metallic mercury with stannous chloride, extracted with a n air stream, and passed over a filter treated with cupric iodide. A colored spot is formed. Sensitivity is between 0.25 and 0.6 p g / L Microdetermination of mercury species in natural water systems by liquid chromatography is discussed by Raltisberger ( 4 0 ) . Metallic mercury is in equilibrium with mercuric ion, which is slow to be established. Measurement and differentiation of inorganic and organic mercury cations by ionexchange chromatography, and analysis by flameless atomic absorption spectrometry are given. 'l'alnii and Norvell (26U) suggested the use of gas chromatography with a microwave-emission spectrometric detector for t h e determination of methylmercury chloride in water. Methylmercury chloride is extracted from the water sample with 0.5% tertiary amine in benzene. and injected into the gas chromatograph. It is eluted into a low-power argon plasma, is fragmentated, a n d its concentration determined hy
measuring atomic emission intensity produced a t 253.7 nm. Detection limit is 4 to 10 x g. Fukai and Huynh ( 1 3 D ) determined mercury in seawater by anodic stripping voltammetry with graphite electrodes, using perchloric acid solution as the stripping medium. Mercury concentrations as low as 5 ng/L are detected in ,iO-mL samples with minimum pret,reatment. Clechet (611) concentrated mercury on anionic-exchange paper prior to determination by X-ray spectrometry. Ten elutions are required to achieve adequate retention level of mercury on the paper for concentrations of 1 mg mercury per kilogram. Limit of detection is 20 kg/I,. Tseng (271)) determined mercury in water by neutron activation with a flux of 1 X 10" neutrons per cm2 second. The irradiated sample is digested to decompose organic material, and mercury is extracted into a lubricating base oil. The organic solution is counted with a 38-mL Ge(Li) detector, and the 77.1-keV peak of "'Hg is detected. Only silver and gold interfere. Kraemer and Neidhart ( 1 7 0 ) used an aniline sulfur resin for selective enrichment of ppb levels of dissolved mercury compounds and their determination by neutron activation. Interferences from other elements, such as sodium, selenium, uranium, and gold, can be avoided by following defined preconcentration and elution conditions. A nondestructive determination of mercury and gold in seawater by neutron activation after preconcentration on a 2-cm lead sulfide column is proposed by Alexandrov (20). Tracer studies showed that mercury and gold retentions are 98 and 97%, respectively. After concentration, lead sulfide matrix is irradiated with 1 X t0l2 neutrons per cm2 second, and mercury and gold determined by gamma spectrometry. I,o. Wei, and Yeh ( 1 8 0 ) used lead diethyldithiocarbamate for preconcentrating mercury and gold prior to irradiation by neutron activation. These metals in seawater are highly and selectively concentrated from a large volume of water to a small volume of diethyldithiocarbamate in chloroform. Sodium and bromide which can cause interference are not extracted. Stary et al. (2*5D3reported that extraction chromatography and dithizone extraction are the most promising methods to preconcentrate phenylmercury, methylmercury, and inorganic mercury from 100- to 500-mL aqueous samples. In this manner, sensitivity of previously developed radioanalytical methods is increased to about 0.01 ppb.
MOLYBDENUM, TUNGSTEN, VANADIUM, URANIUM, THORIUM, THALLIUM, A N D CERItJM Nakagawa and Ward (19E) described a field-applicable coloriniet,ric method for the determination of molybdenum in natural waters and brines. Molybdenum is collected by passing water through a chelating resin. Following elution with a dilute alkaline solution, molybdenum is complexed with thiocyanate and measured; a little as 0.2 ppb can be det,ected. The method eliminates the need for transporting bulky water samples to the laboratory. Otto and Mueller ( 2 1 E ) report,ed that sensitivity for determining molybdenum by catalyzed oxidation of 1naphthylamine by bromate ion is increased by extracting molybdenum as the oxinate into chloroform from 0.06 M sulfuric acid solution. Concentrations greater than 2.7 X lW9 M are determined with a relative error of 10%. Other heavy metals are masked with EDTA. An electron paramagnetic resonance spectrometric method for determining molybdenum in saline waters in the microgram per liter range is presented by Hanson, Szabo, and Chasteen (13E). T h e method, based on extraction of Mo(SCN):, into isoamyl alcohol, is rapid, requires only 10 mL of sample, and has a detection limit of 0.46 pg/L with a relative precision of 4.7% at the 11 pg/L level. A thermal neutron activation method is described by Van der Sloot. Wals, and Das (25E) for the determination of both molyhdenum and tungsten in sea and surface water. Molybdenum and tungsten are first concentrated on activated charcoal b y adsorption as ammonium--pyrrolidinedithiocarbamate complexes at pH 1.3. Detection limits are 0.05 wg/L for each constituent. Ilemkin ( 6 E ) simultaneously determined traces of tungsten and molybdenum in natural thermal waters by oscillography. The method is based on use of the hydrogen catalytic wave
ANALYTICAL CHEMISTRY, VOL. 51, N O . 5, APRIL 1979
in the presence of tungsten, and the hydrogen peroxide catalytic wave in the presence of molybdenum, Detection M for tungsten, and 5 X lo-' M for molimits are 1 x lybdenum. Korob, Cohen, and Agatiello (18E)coprecipitated tungsten and molybdenum from water with n-benzoinoxinie prior to activation analysis. Molybdenum is used as a tracer to calculate sample-to-standard yield for tungsten. Gladney and Owens ( I I E )combined ion exchange on aluminum oxide and neutron activation to determine tungsten in natural water. T h e procedure requires short thermal-neutron irradiation. rapid ion-exchange without chemical manipulations. and short y-ray counts on a Ge(Lij detector. Detection limit is 0.05 ppb. A sensitive, selective method is described by Fukasawa and Yamane (9E) for determination of as little as 0.03 ppb vanadium in natural water. Vanadium is separated and concentrated by a combined cation- and anion-exchange procedure in 0.05 M hydrochloric acid-0.1 % hydrogen peroxide medium. Vanadium is then determined colorimetrically by the catalytic effect of vanadium on the oxidation of gallic acid by bromate. Van der Sloot and Das ( 2 4 E ) determined vanadium in sea and surface water by preconcentrating vanadium on active charcoal a t p H 3.6, followed by instrumental neutron activation analysis of the charcoal adsorbers, and measurement of 52V.Detection limit is 0.01 pg/L. Extension of adsorption colloid flotation to the separation of vanadium from seawater, and determination by atomic absorption spectrometry are discussed by Hagadone and Zeitlin ( I Z E ) . Preconcentration takes about 5 minutes. Weiss et al. (27E) reported that vanadium in seawater was determined independently a t two laboratories by neutron activation analysis and atomic absorption spectrometry. Average concentration of vanadium in Pacific Ocean waters was 2.00 f 0.09 and 1.86 0.12 gg I, by neutron activation and atomic absorption, respective y. Korkisch and Krivanec (16E) determined vanadium and molybdenum in t a p water and mineral water by atomic absorption spectrometry after anion-exchange separation. The sample is acidified and heated t o remove carbon dioxide. Sodium citrate and ascorbic acid are added, and the resulting solution a t p H 3 is passed through the strongly basic anion-exchange resin Dowex 1-X8. Vanadium and molybdenum are adsorbed as anionic citrate complexes. Vanadium is eluted with 6 M hydrochloric acid, and molybdenum is eluted with 2 M perchloric arid--] M hydrochloric acid. Uranium in seawater was collected by Ohnishi, Hori, and Tomari (20E)on Dowex A-1 resin in the presence of Dotite CyDTA and eluted from the resin with ammonium carhamate solution. T h e uranium was then reduced to the +4 valence state with zinc, and complexed with Arsenazo 111; absorbance of the complex was measured spectrophotometrically at 665 nm. Isaeva, Golovanov, and Presnyakova (15E)also proposed a spectrophotometric Arsenazo I11 method for the determination of uranium in seawater. Uranium is first extracted from 5 liters of an acidified sample with a chloroform-oxychinoline solution. Uranium is then reextracted with hydrochloric acid and complexed with Arsenazo 111. EDTA and ammonium acetate are used to mask interferences. Vernon, Kyffin, and Nyo (26Ej described a spectrophotometric method for determining uranium. T h e method involved extraction with trioctylamine in petroleum ether containing 2-octanol, back-extraction with nitric acid, and finally extraction with 8-hydroxyquinoline in carbon tetrachloride. Barhano and Rigali (3E)used Aliquat-336 to extract uranium from seawater and then measured the absorbance of the solution spectrophotometrically. T o determine uranium fluorometrically in natural waters, Hues e t al. (24E) pipetted sub-microliter aliquots of sample onto pellets of a lithium fluoride-sodium fluoride flux. The pellets are dried under heat lamps and then fused over special propane burners. T h e fused pellets are transferred to a fluorometer, excited with ultraviolet radiation, and the fluorescence is measured; sensitivity of the method is about 0.2 ppb uranium. Stephens, Haugen, and Richardson (23E) used a laser-induced fluorescence technique to extend limits of detection for measuring uranium in natural water. Burba, Gleitsmann, and Lieser ( 5 E )used chelating cellulose ion-exchangers to separate and concentrate uranium from natural water prior to determination by energy-dispersive X-ray fluorescence.
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A method was developed by Ferguson et al. (8E)to rapidly analyze natural water samples for ng/L levels of uranium using a cutstom-built thermal-emission mass spectrometer. A uranium concentration of 3 ng/L yields a count rate 3 times greater than the standard deviation plus the mean of the background; it is defined as the lowest determinable concentration. Brits and Smit ( 4 E ) preconcentrated uranium in natural water as its uranyl thiocyanate complex on an anion-exchange resin. Uranium on the resin is then directly determined by delayed-neutron cnunting. Detection limit for a 1-L sample is 0.01 p g / L A differential-pulse polarographic met,hod for the determination of uranium in natural waters is described by Deutscher and Mann (7E). Vranium is extracted from an acidified sample containing ascorbic acid with trioctylphosphine oxide-cyclohexane. Lithium perchlorate is added; the solution is deoxygenated; and a polarogram is made using a dropping-mercury electrode. Alder and Das ( 2 E ) described an ion-exchange preconcentration technique to determine ur,mium in water. Uranium is concentrated by passage through Amberlite IRC-50 cation-exchange resin and eluted with 3 M sulfuric acid. T h e uranium is then determined indirectly by both flame and graphite furance atomic absorption spectrometry, using a method based on the reduction of copper(I1j by uranium(IV), followed hy complexation of the copper(1) with neocuproine. The complex is extracted with chloroform, back-extracted with 3 N HCI, and the acid solution analyzed. A spectrophotometric method for the simultaneous determination of uranium and thorium in water using Arsenazo I11 is proposed hy Weissbuch, Botezatu, and Gradinaru (28E). T h e method is based on the separation of uranium from thorium, and subsequent purification on strongly basic anion-exchange resin. Korkisch arid Krivanec ( I 7 E ) also used ion-exchange adsorption on Dowex I -X8 resin, to separate uranium and thorium prior to spectrophotometric measurement of a thorium- Arsenazo I11 complex and fluorometric measurement of uranium. To determine thallium in natural water. Shevchenko, Portretnyi, and Chuiko (22Bj first precoricentrated thallium by coprecipitation with magnesium hydroxide. Thallium is then determined polarographically with a mercury-graphite electrode and a saturated-calomel reference electrode. Detection limit is 0.1 ng/L for a IOO-mI, sample. A spectrophotometric method for determining thallium based on ligand exchange a t p H 6.8 from the surface of the solid ligand bis[2.4,6-tris(2-pyridyI)-s-triazine]iro11(111) tetraphenylhorate is described by Gadia and Mehra ( I O E ) . The precipitate is filtered off, and the absorbance of the irontriaiine cation is measured at ,596 nm and related to thallium con cen t r at i on. Agrawal ( I E ) determined ceriumtIY) in seawater by extraction of its complex with N-g-tolsbenzohvdroxamic acid into chloroform at'pH 8.4 to 9 . k The complex is measured spectroDhotornetricallv a t 465 nm.
BORON, PHOSPHORUS, AND SILICA Goulden and Kakar (.iF) described modifications in the curcumin and dianthrimide methods for determination of tioron in the presence
