(511) Wall, R. A., J . Chromatogr., 37, 549 (1968). \ - - - - ,
(512) Warburton, J. A,, J . .4ppl. Meteoiol., 8, 464 (1969). (513) Washizuka, S., Ando, K., Ito, H., Sakamoto, T., C . A . , 70, 63772 (1969). (514) Watanabe, H., Suzuki, T., Bunsekz Kagaku, 17, 1264 (1968). (515) Iveaver, 1‘. C., Z. Anal. Chem., 243, 491 (1968). (516) Webber, H. AI., Wilson, A . L., Analyst, 94, 110 (1969). (517) Wheelwright, E. J., J . Znorg. Sucl. Chem., 31, 3287 (1969).
(518) Winget, J. O., Lindstrom, 11. E., Separation Sci., 4, 209 (1969). (519) Winowski, Z., Chem. Anal., (Warsaw), 13, 583 (1968). (520) Wodkiewicz, L., Dybczynski, R., Chem. Anal. (Warsaw), 14, 437 (1969). (521) Wodkiewicz, L., Dybczynski, It., Inst. ,Vucl. Res., Warsaw, Rep. 1967, No. 860/VII/C; C.A., 69, 24089m. (522) Wodkiewicz, L., Dybczynski, It., J . Chromatogr.,32, 394 (1968). (523) Wolcotk, J. F., U . S. Atomic Energy Commission, 1968, IS-T-223.
(524) Wolf, F., Hauptmaiin, R., Warnecke, l)., Z. Anal. Chem., 238, 432 (1968). (52,5) Yamabe, T., Yamagata, Y., Seno, M., IVippon Kagaku Zasshi, 89, 772 (1968). (526) Yoshikawa, Y., Yamaaaki, K., Znorg. Nucl. Chem. Lett., 4, 697 (1968). (527) Zalevskaya, T. L., Starobinets, G. L., Zh. Anal. Khim., 24, 721 (1969). (528) Zaye, I). F., Frei, 11. W., Frodyma, bf. M., Anal. Chim. Acta, 39, 13 (1967). (529) Zlatkis, A., Bruening, W., Bayer, E., ANAL.CHEY.,41, 1692 (1969).
Inorganic Analysis Philip W . West, Coates Chemical laboratories, louisiana State University, Baton Rouge, l a . 70803 Foymae K . West, Gulf State Research Institute, Baton Rouge, l a . 70803
T
of inorganic analysis is a n extension of the earlier reviews of inorganic microchemistry. T h e broader base of the present review might suggest that a n extensive, compendium would be in order. I t is true that hundreds arid even thousands of references have been collected and organized during the past two years. h great deal of excellent work could be discussed but it seems more appropriate that a critical review be evolved. I t may be unfortunate that our personal bias may show a t times but we hope that certain trends and observations will be of interest to those who must deal with inorganic analysis. Obviously the accompanying reviews deal with topics that are of fundamental importance and we would be the first to admit the heart of inorgaiiic analysis lies in various optical techniques or electroanalytical methods together with the necessary separation processes. Gravimetry and titrimetry are important, of course, but it is iiot reasonable to expect many exciting iiew advances in these established fields. The development of analytical methods for inorganic analysis seems to lie in the use of ion-selective electrodes, atomic and flame spectroscopy, and atomic fluorescence spectroscopy. Real significance must be attached to the increasing use of catalytic methods and special attention is directed to the developmeiit of amplification techniques for iiicreaaing the sensitivity of many quantitative and qualitative methods. The use of ternary complexes as a tool for increasing sensitivity and selectivity is also a very important development. This review is a continuation of that published in 1968 (141). Other rev i e w that have been published during the past two years may also be of substantial aid in gaining perspective or valuable detailed information. Amplification methods which have now HE REVIISW
been used for over one hundred years have been reviewed by Belcher (9) because of the revived interest in t’his technique as a means of increasing the sensitivity of trace analysis and because these methods often lead to enhanced precision. Beamish (6) has provided a n extensive review of electroanalytical methods for the noble metals and also a critical review of atomic absorption, spectrochemical, and X-ray fluorescence methods used for the determination of noble metals (7‘). Malissa and Jellinek (91) have discussed automation in analytical chemistry. Busev (19) has summarized the work done during the past fifty years in the USSR 011 the analytical chemistry of rare elements and Feigl has reviewed (38) a number of spot tests that can be based on the formation and reactions of mercuric cyanide. An important review has appeared dealing with the applications of digital computers in analytical chemistry ( 2 4 , and interesting discussions have appeared dealing with the appraisal of various analytical methods (134) in which the classical methods are compared with some of the modern “instrumental” techniques. Among the books that have appeared, attention is called to the series dealing with advances in analytical chemistry and instrumentation (112), the second edition of “Complexometric Titrations” (123) has now been published, a treatise dealing with principles of flame emission and atomic absorption spectrometry ( l o g ) ,and the Guide to the Selection of Methods for the Study of Air Pollution (69) may be of some special value because of the rapidly developing interest in air pollution and the difficult problem associated with its study. OPTICAL METHODS
Optical methods seem, without exception, to provide basically sound and reliable procedures for the analysis of
inorganic substances. The impact of atomic absorption spectroscopy during the past few years has been most impressive and current developments of flame emission spectroscopy and X-ray fluorescence give promise of providing additional powerful tools. Although more detailed reviews of these methods appear elsewhere, some mentioii of them must be made in any discussion of inorganic analysis. I t is significant, for example, that Goleb has successfully applied atomic absorption spectrophotometry (49) to the determination of neon and argon in helium. Likewise, Jungreis and Anavi (66)have proposed a method for the determination of sulfite (or sulfur dioxide) by atomic absorption spectroscopy. Their method employs a n ion-release reaction whereby sulfite ion reacts in a suspension of mercury (11) oxide to form the soluble disulfitomercurate(I1) which is subsequently isolated and determined by atomic absorption spectroscopy. Sullivan and Walsh (131) have continued their investigations of resonance lamps as monochromators in atomic absorption spectroscopy. Such units hold considerable promise for future application in the determination of a number of metals such as calcium, magnesium, sodium, potassium, and lead. West’ and Williams (143) have described the construction and operation of a n atom reservoir for use in atomic absorption and fluorescence spectroscopy. Other significant work contributed from those laboratories include the use of separated nitrous oxide-acetylene flames in thermal emission spectroscopy (YS),the applications of molecular emission spectroscopy in cold flames (29),and studies of the possible use of the atomic hydrogen plasma torch ( 3 ) . .itomic absorption with a n electrodeless highfrequency plasma torch has been proposed (SO), and Larach has studied the application of cathode-ray-excited emis-
ANALYTICAL CHEMISTRY, VOL. 42, NO. 5, APRIL 1970
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sion spectroscopy for the determination of trace amounts of rare earths (82). It can be anticipated that atomic fluorescence spectroscopy will find increasing use in studies of environmental pollution and other fields where sensitivity, convenience, and reliability are of great importance. Dagnall and coworkers have compared results obtained by flame photometry and atomic fluorescence spectroscopy for the determination of silicon(28). Luke(86) has proposed a method for determining trace elements in which he employs coprecipitation for isolating the desired species and follows this with X-ray fluorescence spectroscopy as a sensitive and reliable finish. The proposed method is widely applicable. Robinson and Hsu (116), have applied atomic fluorescence spectroscopy to the determination of beryllium and have demonstrated the lack of interferences from the cations studied. Some anionic interferences Fere noted but these were eliminated through the use of E D T A . Kanogram amounts of chromium in urine have been determined by X-ray fluorescence spectroscopy (12), and copper can be determined over a wide range of concentrations with a detection limit of 0.003 pg/ml by means of atomic fluorescence spectrometry employing a n inexpensive single beam unmodulated instrument (128). 911 electronically modulated electrodeless discharge tube has been proposed as a source for the determination of tin by atomic fluorescence (17') and the simultaneous determination of vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc in sea water by means of X-ray fluorescence spectrometry has been demonstrated by Morris (95).
Fluorescence characteristics of inorganic complexes in hydrochloric acid medium a t liquid nitrogen temperatures has been studied by Kirkbright, Saw, and West (74). Fifty-five elements were studied and the detection limits found were very gratifying. The quenching of fluorescence has been employed as a means of determining hydrogen sulfide in the sub-parts per billion range (5) and quenching techniques have also been employed (36) for the determination of submicrograni amounts of silver. Pal and Ryan have proposed a method for the determination of manganese based on the oxidation reaction of permanganate with oxine-5-sulfonic acid to produce a highly fluorescent product. The method is one hundred times more sensitive than the conventional permanganate method (101), the method is relatively free from interference and the results are highly reliable. The use of infrared for the determination of trace amounts of polyatomic inorganic ions has been demonstrated 100R
(83) and mass spectrometry has been employed for the analysis of nanogramsize samples of lead (20). hlyers and White (98) have proposed a single filament, thermal ionization source for the mass spectrometric assay of trace metals. ELECTROANALYTICAL M E T H O D S
Although many electroanalytical techniques find important applications in inorganic analysis, the most spectacular developments certainly must be those connected with ion-selective electrodes. The ultimate importance of such electrodes can be inferred from the work of blontalvo and Guilbault (94) who used a commercially available cationic electrode and coated it with a film of immobilized urease enzyme for the determination of ammonium ion. The ideal example of the value of ion selective electrodes is probably gained by reference to the single crystal fluoride electrodes which have been demonstrated to be sensitive and reliable for the determination of fluoride activities. hlacdonald and T o t h (87) have described fluoride-sensitive membrane electrodes and Vanderborgh (137) has evaluated the use of the lanthanum fluoride membrane electrode in acidic solutions. Srinivasan and Rechnitz have made significant studies (129, 130) of the fluoride-selective electrode, and Raby and Sunderland (108) have demonstrated the value of the fluoride electrode in the direct determination of fluoride in tungsten. The reliability of the sodium ion-selective electrode has been demonstrated (46, 56) and the Sernstian behavior of a calcium activity liquid ion exchange electrode has been demonstrated (60). Anion electrodes based on association extraction systems have been studied by Coetzee and Freiser (27). A membrane electrode for nitrate and other univalent anions has been described (33) and the iodide-selective electrodes have been demonstrated to be more trustworthy than the usual Ag/hgI electrode in dilute solutions of iodides (144). Rechnitz has discussed the selectivity of calcium ion membrane electrodes (111) in a n exchange of comments and Brand and Rechnitz (15) have presented an equivalent circuit model for a glass membrane electrode. Pungor and Szepesvary (104) have studied the behavior of a new type graphite electrode prepared by mixing special graphite with silicone rubber followed by cold vulcanization. The selectivity and sensitivity of silicone rubber impregnated membrane electrodes have also been studied for the transition metal ions (18). As would be espected, ion-selective electrodes are proving valuable for use as indicating electrodes in poten-
ANALYTICAL CHEMISTRY, VOL. 42, NO. 5, APRIL 1970
tiometric titrations of various types (61, 62, 119). Apart from ion-selective electrodes, the piezoelectric transducer for determining metals in dilute systems is of interest. Jones and Mieure (65) have used such a device for the essentially nondestructive determination of cadmium in the concentration range of 5.0 X to 5.0 X 10-8.V. STANDARDS A N D REAGENTS
Organic reagents for titrimetry, gravimetry, spectrophotometry, and fluoromet,ry are obviously of great importance. Likewise, reagents used as indicators are of interest and new ligands for use as masking agents are of great usefulness. Materials used as primary or secondary standards are also of special significance and Schlitt and Simpson (122) have studied variables in the standardization of cerium(1V) solutions against arsenic (111) oxide. Chalmers and Gmar have described the preparation of several acetylacetonates (92) which are proposed as secondary standards for the metals they cont'ain or for use as standards in elementry analysis. Freeman and Paulson (43) have used neutron activation for studying the sodium content of single beads of homogeneously sulfonated styrene-divinylbenzene copolymer and have established a simple relationship between bead diameter and sodium content. I t is suggested that such beads can be used as microchemical standards. It is of interest to note than an error of 0.0030.005 p H unit has been found in t'he use of equimolal disodium hydrogen phosphate-potassium dihydrogen phosphate buffer solution (8)which indicates its unsuitability as a primary standard for glass electrode measurements of critical pH. Sodium hydroxide solutions, which are notably impure, can be prepared free of bobh calcium and carbonate by a simple method (80) suggested by Kuczerpa. Among new organic reagents of interest are certain derivat'ives of chromotropic acid which hold promise as reagent,s for the detection of alkaline earth metals in the nanogram to microgram range (79). Thiodibenzoylmethane (136) has been introduced as a n extraction, photometric, and gravimetric reagent for cobalt, and di-2pyridyl ketosime has been introduced as a new reagent (57) for the rapid gravimetric determination of palladium. Although new reagents for iron and copper hold little interest generally, Ryan and his associat,es have shown thiobenzoyl-N-phenylhydroxylthat amine quantitatively precipitates iron (111) in 1F acid solution without interference from aluminum, chromium, manganese, or many other common accompanying elements (1) and has also shown that quinoline-2-aldehyde-2-
quinolylhydrazone is a uniquely selective and sensitive reagent for copper (126). Grob and his associates have shown (52) that 1,l-iminodi-(6-chloroanthraquinone) is a promising new reagent for the spectrophotometric determination of traces of boron. Hulanicki (58) has studied the complexation reactions of disubstituted dithiocarbamates and has recorded detailed studies of the composition and stability of various metal complexes. T h e properties of metal-dithiocarbamate complexes are related to the nature of the substituents in the ligand molecule. SEPARATIONS
The importance of analytical separations cannot be minimized even with the development of new instruments and new techniques that might seem to sound the death knell of gravimetric and titrimetric methods. The actual practice of analytical chemistry is st'ill very dependent on separation processes although often the emphasis is more on the isolation and concentration of some trace material prior to a n analytical finish than it is on the separation from interfering species. T h e problem of interferences is still of great significance, but analytical measurements are being made a t presect with more selective and reliable measurement devices. hfasking has become the standard tool for eliminating interferences. The simple expedience of adding a complexing ligand to sequester objectionable ions is obviously a nice way of avoiding the tedium of physical separation of species. I n spite of all of these developments, however, solvent extraction, ion-exchange, volatilization, and even precipitation must be considered essential for the ultimate exploitations of inorganic analytical processes. T h e great interest in the study of environmental pollution has accelerated the development of trace analytical studies of the atmosphere, waters, food, and the sea. Because of the unquestioned significance of trace substances present in parts per million and parts per billion concentrations, a great deal of work is under way to provide better methods for isolating and concentrating trace pollutants. The separation steps are usually integral part of the measurement process. Sachdev and West h a r e proposed a method for the preconcentration and determination of a number of metals that are significant to the study of water and air pollution. The procedure involves the isolation of the metal dithizonates using ethyl propionate as the solvent (120). T h e estracted chelates are stable and there is 110 loss of trace amounts of material to the container walls, a problem which otherwise often introduces serious errors in trace analysis. Furthermore, the
metal chelates can be subsequently determined by atomic absorption spectroscopy with enhanced sensitivity because the atomization of the ethyl propionate solution gives significantly better sensitivity t h a n t h a t obtained with aqueous systems. The extraction step itself, of course, provides great flexibility in establishing t h e desired concentrating effect for trace studies. Chau, Sim, and R o n g (26) have employed atomic absorption spectroscopy for the determination of chromium in sea water based on the prior concentration of the chromium through extraction of chromium acetylacetonate into methyl isobutyl ketone. Although a detailed review of the multitude of extraction methods is beyond t h e scope of this discussion, some specific examples are cited for emphasis. Quddus and Bell (106) have studied the extraction of metal complexes of pyridine2-aldehyde-2-pyridylhydrazone. The ligand is dissolved in chloroforni, and a number of the metal chelates that it extracts can be measured spectrophotometrically. Benzene solutions of salicylaldoxime (32) have been studied for the separation and determination of various divalent metals. Schweitzer and Anderson h a r e studied the extraction of indium (111) with carboxylic acids dissolved in various solvents (124) and Schneitzer and Sanghvi (125) have investigated the isolation of thallium using aliphatic monocarboxylic acids. Sat0 has employed long-chain aliphatic amines for the extraction of thorium from nitric acid solutions (121). Grimanis and Hadzistelios have estracted antimony from bromic acid into benzene (51), and a similar system has been employed by McGee et al., for the isolation of selenium (88). The solvent extraction of tantalum and niobium fluorides has been studied (37) by Erskine, Sink, and Varga. Riley and Taylor have investigated the use of chelating ion-exchange resins in the determination of molybdenum and vanadium in sea water (113) and have denionstrated that the resins are remarkably efficient for the isolation of many of the important trace metals. The resins have been used in conjunction with a n atomic absorption spectrophotometry finish for the simultaneous determination of zinc, cadmium, copper, and cobalt in sea water. These same investigators have employed chelating ion-exchange (214) for the determination of molybdenum and vanadium in sea water. M a t t h e m and Riley (93) have developed a n anion exchange scheme for the pre-concentration and alnio$t specific separation of microgram and submicrogram amounts of thallium in the study of silicate rocks, marine sediments, and sea water. A wide range of elements have been determined in natural water through use
of a preliminary sorption on a mixed bed of activated charcoal and chlorinated lignin (16), and iron(II1) hydroxide has been studied as a collector of rnolybdenum from sea water ('71). T h e determination of microgram quantities of tin(1V) by combining ion-exchange with X-ray fluorescence has been described by Chamberlain and Leech (%), and zone melting has been applied to metal chelate systems as a means of concentrating trace amounts of metal acetylacetonates prior to their determination by emission spectrography (68). Husler and Cruft have employed atomic absorption spectroscopy for the determination of trace elements concentrated from solution using as a collector, cadmium together with three organic ligands (59). Jackwerth (63) has studied the concentration of trace elements by selective eo-precipitation. The ring-oven technique introduced some years ago by Weisz is a remarkably simple, yet elegant technique. Although there are a number of papers dealing with this method, obviously its potential value in applied chemistry, as well as in teaching has been generally overlooked. A perspective regarding this technique can be obtained from the paper by Jungreis and R e s t (61) which describes a specific method for t h e microdetermination of vanadium (V) using the ring-oveii or from the paper by Sachdev aiid West (120) which deals with its applications in the microdetermination of orthophosphate. Klockow and Bohnier have used the ring-oven technique for the radiochemical separation of 144Pr from 144Ce ( W ) , and Ghose and Dey have described a method of separation and microdetermination of aluminium, indium, gallium, and thallium, in a single drop of solutio11 (4'7). Thin-layer chromatography is finding increased applications in inorganic analysis. For example, Galik and Vincourova (45) have described the chromatographic separation of the chelates of copper, cobalt, nickel, and iron while Hashmi aiid Adil (55) have used circular thin-layer chromatography for the separation of noble metals. MASKING
One of the most verqatile and useful adjuncts in analytical chemistry is t h a t of masking. Although the theoretical basis for selecting suitable masking agents is well understood, the practical approach to applying this technique is still based mainly on experience and intuition. Masking is normally a process of complexation in which a number of equilibrium systems may be evolved. The current literature discloses thousands of applications of masking, most of which involve ligands such as EDTA, fluoride, tartrate, etc. While it is not practical to review the field of masking,
ANALYTICAL CHEMISTRY, VOL. 42, NO. 5, APRIL 1970
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a few instances are cited as examples or because of their special interest. A very cute and practical application of masking has been cited by Nisli and Townshend (99) who have describeo a spot-test for detection of iodate in the presence of periodate. The critical step in the test is the masking of the periodate by means of a n excess of molybdate. This qualitative study was extended by Belcher and Townshend (11) who proposed a method for the consecutive titration determination of iodate and periodate on a single aliquot of solution. The iodate is first titrated in the presence of the periodate masked with molybdate. The periodate is subsequently demasked by the addition of oxalate which complexes and removes the molybdenum and permits the final titration of the periodate. The use of masking is also nicely illustrated by the paper of Puschel and Lassner (106) who have used various ligands as masking agents to attain selectivity in the spectrophotometric determination of titanium. Likewise, Donaldson, Charette, and Rolko have used atomic absorption spectroscopy for determining traces of cobalt and zinc in high purity metals. A critical step in their method is the chloroform extraction of thiocyanate-diantipyrylmethane ion-association complexes in which interfering metals are masked (34). An important use of masking is apparent in complexometric titrations. A selective complesometric method for the determination of mercury has been described by Singh (127) in which thiourea is used as a masking agent. The determination is performed by adding a n excess of E D T A and the excess reagent then back-titrated with lead nitrate. Thiourea is then added to decompose the mercury-EDTA complex and the liberated E D T A is again backtitrated with lead nitrate to determine the amount of mercury present. Fog has proposed a method for the complexometric determination of magnesium (42) in which manganese is masked by oxidation with hydrogen peroxide in the presence of cyanide. Triethanolamine is used to mask traces of coprecipitated aluminum and the magnesium can then be titrated with EDTA\.
ruthenium and may be used in the range of to 2 X lO-sM of ruthenium with a coefficient of variation of 4.8’%. Rhenium, iridium, and osmium, were the only three serious interferences found. West and Ramakrishna (142) have developed a very sensitive and specific method for the determination of selenium. The method is ideally suited for the determination of selenium in air pollution studies and is also finding application in determining selenium levels in cigarette papers, tobaccos, and foods. Kawashima and Tanaka have also proposed a catalytic method for determining submicrogram amounts of selenium (70) which is simple, sensitive, and relatively free of interferences. Molybdenum has been determined by its catalytic effect on the reaction between selenate and tin(I1) in a n acidic medium (84), and catalytic methods have been proposed (13, 14) for the ultra-microdetermination of silver. Copper and nickel have been determined catalytically in concentrations of a few parts per billion (93, 103). Mottola and Freiser (97) have employed metal ion catalysis for the detection and determination of microamounts of complexing agents such as cyanide. h number of studies (77, 117, 118, 136), have appeared dealing with the catalytic action of iodide on the reaction between cerium(1V) and arsenic(II1). Of general interest in the discussion of catalytic methods is the use of catalytic titrants and the catalytic indication of end points, as summarized by Mottola (96). An excellent review of the applications of Landolt reactions 111 quantitative catalytic analysis has been presented by Svehla (132). James and Pardue (64) have devised a small digital computer for use in rate-reaction analyses. Pausch and ?\largerum (108) have applied differential kinetic methods for the rapid qualitative and quantitative determination of magnesium, calcium, and barium, and llargerum, Pausch, Xyssen, and Smith (98) have reported kinetic data for more than 30 metal ions for use in applying rate methods for the quantitative and qualitative analysis of miytures of metal ions. AMPLIFICATION M E T H O D S
CATALYSIS
Rate methods are becoming more widely used as it becomes more generally appreciated that catalysis is not only a sensitive means of detection and determination, but is also a remarkably selective tool for analytical studies, Ottoway, Fuller, and -illan (100) have determined ruthenium, based on its catalytic effect on the periodate oxidation of the tris(1,lO-phenanthroline) iron(I1) complex, The reaction permits the detection of as little as 10-loAII 102 R
Amplification methods are available for various cations and anions. X1though such methods were first iiitroduced many years ago, very little general use has been made of them until recently. Belcher (9) has reviewed typical examples of amplification reactions and has pointed out the geiiera1 merits of this technique. Weisz and Gonner (140) have described a new type of amplification reaction in which the effective mass of a substance to be determined is increased by successive
ANALYTICAL CHEMISTRY, VOL. 42, NO. 5, APRIL 1970
stoichiometric processes. The reactions are carried out on a chromatography tube using a suitable substrate and the accumulated amplified reaction product is finally eluted from the column and titrated. The method is illustrated with three systems and the examples given show that a t least two orders of amplification can be readily obtained and the technique can be automated if desired. Belcher, Hamya, and Townshend (IO), have described a n amplification method for the determination of cobalt, and Kirkbright, Smith, and R e s t have described a selective amplification method for the determination of microgram quantities of phosphate (72). Amplification methods have been applied in atomic absorption spectroscopy. Ramakrishna, Robinson, and R e s t (110) have utilized the formation of the heteropoly-molybdenum acids of phosphorous, arsenic, and silicon for the solvent extraction and separation of these three elements. The atomic absorption spectroscopy applied to the molybdate species provides excellent enhancement of sensitivity (110). similar approach for the determination of niobium by atomic absorption spectroscopy has been described (73), by Kirkbright, Smith aiid R e s t . A \
TERNARY COMPLEXES
Ternary or addition complexes have been used for a t least three decades but only recently has there been any general recognition of t’heir merits. The compounds formed by the reaction of complex species with large organic molecules or other complex species often provide the advantage of enhanced sensitivity aiid significant improvement in selectivity. The formation of ternary complexes often provides for the selective isolation of a desired complex through solvent extraction. El-Ghamry and Frei (35) have employed the formation of ternary complexes in the spectrophotometric determination of trace amounts of platilium (117). The hexaammine-platinum (IV) complex cation is reacted with 2,4,5,7,-tetrabromofluoresceiii ethyl ester as the counter-ion. The red ternary complex forms instantaneously and remains stable for a t least an hour. T h e reaction is very sensitive aiid no interferences are encountered, even without the use of masking agents, except for rhodium(II1) and iron(II1). Dagnall, El-Ghamry, and West, have used a similar approach for the spectrophotometric deterniinatioii of trace amounts of palladium(I1). X palladium coniples is formed with 1 , l O phenanthroline or pyridine and Rose Bengal Extra (31). E D T A is employed as a masking agent whereby any interference from some 22 cations arid seven aiiioiis is minimized to a point
where the method is both reliable and very sensitive. An attractive method for the determination of iron has been proposed (78), based on the extraction of associates of the iron(I1)-phenanthroline complexes, and titanium has been determined (2) b y the extraction of a ternary complex. T h e determination of anions is often difficult b u t the formation of ternary complexes provides a new and promising approach. Such a n approach has been employed for the determination of cyanide (SO), fluoride (64), sulfide (81), perchlorate (13S), and various anions (145). MISCELLANEOUS
A number of items have appeared which do not fall readily into other categories. Hopefully, a trend for future research is the method described for determining a complex species, namely, fluorophosphate, which can be isolated by means of its reaction with ferroin and subsequently measured by a spectrophotometric finish (4). Likewise, the hexamminecobalt (111) complex has been determined gravimetrically by its precipitation (129) as the perchlorate. LLIajer has studied metal chelates by forming the acetylacetonates of aluminum, copper, and chromium and then separating these chromatographically and determining the individual species by means of mass spectrometry (89). Majer, Reade, and Stephen (90) have applied mass spectrometry to the study of the oxinates of a number of metals. Feigl has described spot tests for the detection of arsenic (S9), and has developed specific spot tests based on the release of hydrogen cyanide from acidic mercury (11) cyanide solution (41). Feigl and Caldas (40) have developed spot tests for calcium sulfate, lead sulfate, silver, thallium, and formaldehyde utilizing reactions with selenosulfate. It is interesting t h a t two very sensitive methods have been proposed for t h e detection of iron particles. Vittori (139) has detected iron in ice by forming the dipyridyl complex and reacting this with mercury(I1) as the counter-ion. Lodge and Lodge (86), have detected micron-sized iron particles in air samplps by sampling with membrane filters and applying ammonium ferrocyanide as the reagent. Induced precipitation has been used for the detection of barium or strontium (138) or barium (53). A radio-release method has been utilized for the determination of fluoride ion (21) and the ion-exchange bead technique has been applied for the detection of nanogram amounts of zinc or copper (44) and iron (107). Robertson (116) has discussed the problem of absorption of trace elements in sea water on various container surfaces and Chao, Fishman, and Ball (25)
have determined silver in t h e parts per billion range in water by employing extraction on anion resins followed by atomic absorption spectrophotometry. T h e technique avoids losses to container surfaces. A rapid method for the calibration of micropipets has been described by Goggins and Tanzcr (48). CONCLUSION
A new decade begins with the obvious need of more and better analytical methods. For inorganic analysis, it is to be hoped t h a t there will be increased effort devoted to meeting the needs of modern science. Unless truly unique and useful complexometric titrations can be suggested, it would be better to work on new methods t h a t can be applied to the study of complexes themselves. Particularly now, with t h e great interest in environmental pollution, we need methods that will serve for the detection and determination of various complex and molecular species. It is shocking to realize that no one has ever truly determined all of the constituents in a surface water. It seems to have been universally overlooked that fluorides, phosphates, oxalates, titrates, and formates, for example, must surely be present in many surface waters. One would be naive to think that iron or aluminum can be present in these waters in uncomplexed form. Someone should provide a means of detecting and determining the individual complexes present. These observations lead to the conclusion also that more effort should be devoted to the study of metallo-organic species. T h e challenge is apparent and the prospects are exciting. With new tools such as the laser, ion-selective electrodes, and a multitude of sophisticated gadgets, it is to be hoped that the future will be one of great progress. LITERATURE CITED
(1) Abraham, I. D., Abraham, J., Ryan, D. E., Anal. Chim. Acta, 48, 95-98 (1969). (2) Afghan, B. K., hlarryatt, R . G., Ryan, D. E., ibid., 41, 131-138 (1968). (3) Aldous, K. AI., Dagnall, R. M., Thompson, K. C., West, T. S., ibid., pp 380-384. (4) Archer, V. S., Doolittle, F. C., AXAL. CHEV.,39, 371-373 (1967). (5) Axeldod, H. D., Cary, J. €I., Bonelli, J. E., Lodge, J. P., Anal. Chim. Acta, 41, 1856 (1969). (6) Beamish, F. E., ibid., 44, 253-286 (1969). (7) Beamish, F. E., Lewis, C. L., Van Loon, J. C., Talanta, 16, 1 (1969). (8) Beck, W. H., Botton, A. E., Covington, A. K., Anal. Chim. Acta, 40, 401 (1968). (9) Belcher, R., Talanta, 15, 357 (1968). (10) Belcher, R., Hamya, J. W.,Townshend, A., Anal. Chim. Acta, 47, 1491.51 ilSfi9). --, (11) Belcher, R., Townshend, A., ibid., 41, 359-397 (1968). \ - -
(12) Beyermann, K., Rose, Jr., Christian, R. P., ibid., 45, 51-55 (1969). (13) Bonchev, P. R., Aleksiev, A. A,, Microchem. Acta, 4 , 875-882 (1968). 1141 Bontschev. P. R.. Alexiev. A.. Dimi' trova, N., Tulanta, '16, 597 (1969). (15) Brand, hI. J., Rechnitz, G. A., ANAL. CHEM.,41, 1788 (1969). (16) Brodskaya, Tu'. I., Vychuzhanina, I.
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