R., Drug Cosmetic I n d . 86, 758-9, 837-40 (1960). (471) Theimer, E. T., Somerville, \Y. T., 3fitzner. B.. Lembere. - S.. , J . Ora. C h e w 27, 635-7 (i962). (472) Thomas, R.. Annlyst 85, 551-6 (1960). (473) Ting, S. V., Deszyck, E. J., .Tuture 183,1404-5(1959). (474) Todd, P. H., Jr., Perun, C., Food Technol. 14, 270-2 (1961). (475) Trabert, C . H., Arch. Pharm. 294, 246-54 (1961). (476) Tucakov, J., Am. Perjumer Aromat. 75, SO. 6, 85-6 (1960). (477) Turgel, E. O., Kashanova, T. V., Gidroliz. a Lesokhim. Prom. 14, S o . 1, 16-18 (1961). (478) Tyihak, E., drch. Pharm. Hung. 30, 283-6 (1960). (479) Vasiliev, R., Sisman, E., hlangu, hI., Farmacia (Bucharest) 9, 723-7 (1961). (480) Venkatasn-arlu, IC., Mariam, S., 2. Phystk 168, 195-8 (1962). (481) Verma, S. hI., Current Sci. (India) 29, 345-6 (1960). (482) Vietti-RIichelina, M., Pilleri, R., Rass. Chzm. 13, Yo. 1, 13-14 (1961). (483) Vogel, A. XI., Quattrone, J . J., Jr., . ~ N A L . CHEX 32, 1754-7 (1960).
(484) Vrkoc, J., Herout, V., Sorm, F., Collection Czechoslov. Chem. Conimun.
26,3183-5 (1961). (485) Waginaire, L., Guillot, B., Fette, Seijen, Anstrichmittel 63, 1084-6 (1961). (486) Wagner, F. A,, Vincent, hI. C., J . Pharnz. Sci. 51,365-6 (1962). (487) Wagner, H. G., Ishermood, F. A., Analyst 86,260-6 (1961). (488) Watkin. J. E.. Chem. Znd. (London) 1960, 378. 1489) \Vet,herell. H. R.. Hendrickson. 31. J., J . Orq.-ChlG. 24,710-11 (1959).’ (490) Wheeler, 0. H., Gaind, V. S., Rosado, O., Ibid., 26, 3537-8 (1961). 1491) Wheeler, 0. H., Sieto, M. A., de Stbrer, C. B., Antunano, X. C., hledina, V. J., Rev. Col. Quim Puerto Rico 18, 31-2 11961). (492) T$hite, L. J., Eiserle, R. J., Znd. Eng. Chem. 53, 421-7 (1961). (493) Woggon, H., Kohler, U., Ernuhrungsjorschung 5, 402-9 (1960). 1494) Woeeon. H., Rauschler, K., Kohler, U., Na&ng4, 347-89 (1960). (495) Yaklovleva, T. V., Maslennikova, A. G., Petrov, A. A., Optika i Spektroskopiya KO. 1, 131-3 (1961). (496) Yamaguchi, I., Bull. Chem. SOC. Japan 34, 1602-6 (1961). \---,
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I
~1
Tsentral. 1Vauch. Znst. Rastenievudstvo, Bzilgar. d k a d . . T a d 10, 131-5 (1961). (508) Zubyk, W J., Conner, -4. Z., ANAL.CHEU.32, 912-17 (1960).
Fertilizers E. D.
Schall
Department of Biochemistry, Purdue University, lafayette, Ind.
T
covers the literature reported from September 1, 1960 to September 1, 1962, and includes procedures recorded in readily available journals, in Chemical Abstracts, and in Analytical Abstracts. Some selectivity has been exercised t o include only those procedures especially pertinent to, or which, in the author’s judgment, could be adapted easily to, fertilizer analytical problems. The most recent review in the series appeared in April 1961 (65). Other reviews appearing during the biennium include the excellent and comprehensive report covering present methods for 15 fertilizer nutrients presented a t the Joint Symposium on Fertilizer Analysis organized by the Fertilizer Society and the Society for ilnalytical Chemistry (49). A review of conventional solubilization procedures as applied to fertilizer analysis also appeared (56). HIS REVIEW
OFFICIAL METHODS
The Association of Official Agricultural Chemists (AOAC) gave “official” status t o the method for the direct determination of available P2Os by the photometric niolybdovanadophosphate procedure and adopted as “first action” the direct determination of available P206by the official volumetric method. Also given first action status was the quinolinium phosphomolybdate method for total and insoluble P206.
58 R
ANALYTICAL CHEMISTRY
SAMPLING
I n a study of sampling bagged fertilizer, three sampling instruments (tubes) were compared with each other and with riffling (64). The experiment offered little evidence of systematic variations in the use of the three sampling tubes, but did show evidence that samples taken b y the tubes yielded results that were different from those obtained b y riffling. Factors contributing to segregation in batch-type and in continuous production of fertilizers were investigated, and the problems of sampling were discussed in relation to these variations (22). I n a related study the expected reliability of screen analyses and of average particle size of screen separates was determined ( 6 2 ) . WATER
The water content of fused ammonium nitrate-limestone and of crystalline or prilled urea was determined from the change in the dielectric constant of technical benzene containing these products (74). Results were obtained in 5 minutes and were in close agreement with those b y the Karl Fischer method. The vacuum oven treatment for 2 hours at 50” under a t least 20 inches of vacuum appeared t o be a generally reliable and relatively rapid method for the determination of moisture in fertilizers and most fertilizer materials
(12). However, it was not satisfactory for fertilizer grade diammonium phosphate, 85Tc phosphoric acid, or for mononiagnesiumphosphate tetrahydrate. NITROGEN
The reduced iron method for samples containing nitrates in combination with other forms of nitrogen continued to receive attention during the biennium. I n one modification proposed, the amount of H2S04added was increased to permit continued digestion in the normal Kjeldahl manner follonTing the nitrate reduction (29). With this change the procedure was applicable to all types of fertilizers, including those with high chloride-nitrate ratios, to high organic materials, and to combinations of these. A comparative study of commercial iron powders revealed no common property, such as reduction type, mesh size, manufacturing process, was related to their efficiency in reducing nitrate (SO). Of the 36 commercial brands tested, 13 yielded complete recovery of added nitrogen. A collaborative study of the official AOAC reduced iron and the improved Kjeldahl methods with the chromous ion reduction and the modified reduced iron methods failed t o show clear-cut superiority of any of the four methods (20).
Further collaborative study of the determination of the nitrogen activity index (AI) of urea-formaldehyde compounds by a two-step procedure in IThich the solubility in hot and cold phosphate buffer solutions was utilized indicated the method yielded satisfactory results if reasonable care was exercised in its use (19). A gasometric technique similar to the automated Dumas nitrogen procedure was applied for the determination of total nitrogen in complete fertilizers (61). Samples in which the nitrogen nas present as “4x03, NH4C1, KNO, and (SH4)2HP04 were handled successfully. Samples (0.1 gram) n-ere pyrolyzed in a silica tube and the resultant nitrogen oxides reduced by passing over a mixture of copper and copper oxide heated to $50” C. The nitrogen was measured in a nitrometer in the usual manner. I n a titrimetric procedure, ammonium salts in 50y0ethanol were titrated lvith 0.5A- alcoholic NaOH t o a thynolphthalein end point; potentiometric or conductometric titrations were also applicable (52). Soluble salts, such as XH4C1 or NH4N03, can be titrated directly but insoluble salts, such as (SH4)2S04 and (xH4j2HPO4, require precipitation with calcium nitrate before titration. The technique was found applicable to most intermediate bolutions and to nearly all final products in the fertilizer industry. Ammoniacal nitiogen in mixed fertilizers was also determined titrimetrically with sodium hypochlorite (62). The dead-stop mrthod was preferred for the end point detection in this technique. Conductivity measurements of an aqueous solution of ammonium nitrate and of a n aqueous extract of ammonium nilrate fused with limestone gave results in estimating the nitrogen content which agreed well with chemical methods. -4simple conduetometer sufficed (43). Urea was determined in fertilizers b y a hypochlorite or a hypobromite oxidation procedure (27, 50). Several anions (Cos, so4, Pod) interfered and 11ere removed by conventional techniques. anamide was extracted from mixed izers with acetic acid and determined by adding a n excess of standard silver nitrate; titration of the excess silver n i t h 0.1N KSCK followed in the usual manner (81). The analysis of anhvdrous ammonia is u.ually carried out in the field by the evaporative technique; the Imhoff cone was recommended as the most convenient container for this purpose (70). PHOSPHORUS
Comparative studies of the efficiency of neutral and alkaline (ammoniacal) ammonium citrate as extractants for
“available” PZOS indicated the latter t o be superior even though the neutral solution is used most widely in the United States and has been adopted b y the European Common Market (57). The water-insoluble phosphorus in fertilizer is present mainly as C a H P 0 4 and hydroxyapatite, and the AOAC official method (neutral ammonium citrate) dissolves both, although the latter is much less effective as a plant nutrient, Alkaline ammonium citrate dissolves C a H P 0 4 but not the hydroxyapatite (8). Additional supporting evidence mas also obtained in pot experiments with wheat Ivhich indicated that extraction with neutral ammonium citrate tended to overestimate the fertilizing value of superphosphate, as compared with the alkaline reagent, but vastly underestimated this value for Phosphal (.41P04 and CaO) (28). The values for water- and citratesoluble phosphates, as determined by standard methods, tend t o be increased b y the presence of XH4HSO4 and K H S 0 4 in the sample (46). The p H of the solution must be adjusted t o 3-4 b y the addition of XaOH or K O H to determine the amount of water-soluble P205accurately. I n the precise determination of the citrate-soluble PzOs,it is preferable to extract the sample directly with alkaline ammonium citrate without prior water extraction. Interest continued in the direct determination of available P205through the analysis of the combined watersoluble and citrate-soluble extracts. The suspended matter present in the combined solutions can be filtered or allo\ved t o settle before aliquoting (31, 34). Comparison of the two techniques showed both to give equally precise results, and a considerable saving in time resulted from the settling procedure where a large number of samples n-ere handled. The colorimetric phosphomolybdorariadate method was applied to a wide variety of phosphate materials as well as to mixed fertilizers and was found t o be satisfactory (67). It was also applied to the direct available measurement following the destruction of citrate by the ternary acid (HKOs, HC104, and H2S04) or the chlorate (KaC1o3, HS03, HC104, and HC1) procedures (7, 39). Further study of these methods indicated that each resulted in complete citrate destruction but both left varying amounts of acids which also interfered (16). This could be minimized b y protecting the flask during the digestion to reduce fume condensation and the interference eliminated by neutralizing the residual acid after the addition of the molybdovanadate reagent. The AOAC official volumetric method was reported t o be applicable t o the direct determination of available Pz05
provided the nonortho phosphate was hydrolyzed to the ortho form. Kitric acid sufficed for the hydrolysis of inorganic forms, but HCI04 was required where organic phosphorus compounds were present (40). A significant contribution to phosphorus methodology was made b y a group of industry, state, and federal laboratories in a collaborative study comparing the volumetric and gravimetric forms of the quinolinium and the ammonium phosphomolybdate procedures w. the photometric method on samples prepared from a single crystal of NH4H2P04. The results of this study, using this highest purity sample, confirmed the accuracy of the photometric and of both forms of the quinolinium phosphomolybdate methods, and again pointed out the positive bias of the ammonium phosphomolybdate method
(38). The precipitation of the quinolinium phosphomolybdate from acid solution was preferable t o precipitating from a neutralized solution since a significantly lower blank resulted ( 6 1 ) . Following collaborative study, this procedure was adopted as “first action” by the BOAC for the determination of total and of citrate-insoluble PzOS. The quinolinium modification was also recommended for use as a referee method in International trade (11). The addition of acetone t o the quinoline-molybdate reagent eliminated interference from the ammonium citrate present in direct available extracts (16). It also improved the physical properties of the precipitate and simplified the precipitation step in the method. A ternary acid solution (10:4:2 mixture of H K 0 3 , HClO4, &Soh) was recommended for the preparation of sample solutions for total phosphorus b y the molybdovanadate spectrophotometric method. It was found to be applicable t o all types of samples including organic Iihosphorus compounds (32). The extremely low solubility of BiP04 continues t o hold the interest of the phosphorus analyst. I n a complexometric approach, the phosphate was precipitated n i t h an excess of Bi(K03)a and, following filtration, the excess bismuth was titrated with E D T A in the presence of xylenol orange (37). I n a related procedure the BiPOl was dissolved in HXOs and the bismuth determined polarographically. However, a number of ions interfered and clean-up was required prior to polarography (21). The total P20sin superphosphate was determined by a titrimetric procedure after dissolution of the sample in dilute HCl. An aliquot was treated n i t h a cation exchange resin, adjusted t o p H 4.63, and titrated n i t h 0.1S S a O H VOL. 35, NO. 5 , APRIL 1963
59R
t o a p H of 8.98 (69). Superphosphates were also analyzed by direct titration with magnesium chloride in the presence of Eriochrome Black T ( 3 ) . The sulfate content could be determined in the same solution by titration with BaC12 following precipitation of the SIgXH4PO4. POTASSIUM
Interest continues to focus on the tetraphenylborate procedure, and factors influencing the accuracy of this technique were investigated. High ainounts of animal by-products in the sample n ere found to cause low results but this interferenre could be eliminated by treating the sample with potassiumfree carbon during the sample solution preparation (26, 26). The use of freshly prepared 3% reagent n as recominended in the gravimetric method (13). The influence of 15 foreign ions, not previously reported, on the determination of potassium as the tetraphenylborate shoJTed a slight interference only from the persulfate and the periodate ionr (76). Interference from N H 4 + was obviated by XaOBr oxidation; the addition of formic acid reduced the excess bromine (59). The combined nater- and citratesoluble extract prepared for the direct determination of available P z O ~was proposed as a sample solution for the determination of potassium by the tetraphenylborate volumetric method (33). The additional ammonium ion. contributed by the citrate extract N ere handled by increasing the amount H C H O and KaOH as complexing agents. The direct titration of potassium with tetraphenylborate was reported in a technique employing amperonietric equivalence-point detection. A calomel-graphite electrode system as used with +0.55 volt applied to the latter electrode (71). Direct titrations were also possible using a glass indicator electrode sensitive to potassium but insensitive to pH changes over the range of 7 t o 9.5. Calcium tetraphenylborate was recommended as the titrant since the electrode n as nearly insensitive to calcium a t p H 7 (36). I n an indirect approach, the filtered potassium tetraphenylborate was dissolved in acetone and titrated with 0.1A7 AgN03 to a “reversed dead-stop” end point n i t h two identical silver electrodes (60). I n a modification of t h e indirect volumetric method, the excess tetraphenylborate solution n as back titrated ith TINOl in the presence of dimethyl yellow as an adsorption indicator (35). Potassium was titrated conductometrically with HC104 following treatment with an anion exchange resin and
60R
ANALYTICAL CHEMISTRY
other clean-up steps (68). I n an indirect complexometric approach, potassium was precipitated as the perchlorate which nas then reduced to the chloride and precipitated as AgC1. Dissolution of the AgC1 in ammoniacal nickel tetracyanide liberated ? 3 + 2 n hich n as titrated with EDTA ( 7 2 ) . Potassium was precipitated as the orotate from solutions containing ammonium or iubstituted ammonium salts of orotic acid. The potassium salt was less soluble in alcoholic solutions than in water and these were reconimended in the gravimetric procedure proposed (68). Ethanolic solutions were also recommended to reduce the solubility of potassium cobaltinitrite (14). Radiometric methods based on the activity of the Kho were again reported for the determination of potassium in fertilizers (64). An adapter attached to the Geiger-Muller counter facilitated measurement of the JT-eak radiations (75). Two counter tubes connected in parallel also increased the input to the counter (44). CALCIUM AND MAGNESIUM
Attention continues to center on
EDTA titrations and on techniques for obviating interferences from the ions occurring normally with calcium and magnesium. Unithiol (sodium 2:3 diniercaptopropane sulfonate) gave stable coniplexes with mercury, lead, and zinc and was recommended as a masking agent for these ions ( 7 7 ) . The level of iron, manganese, aluminum, and phosphate lvhich can be tolerated in the complexometric determination of calcium was reported to be 2, l, 3, and 6 mg. per 50 nil., respectively (66). Interference from phosphate, aluminum, iron, and silicates was eliminated by masking with citrate, triethanolamine, cyanide, and tartrate, respectively. Hoirever, an exceSs of citrate also interfered (82). The addition of m-nitrophenol, ascorbic acid, and S a C S permitted the titration of total calcium and magnesium with EDT.1 (Eriochrome Black T) in the presence of phosphate ions. Calcium vias then titrated with EDTA (murexide) and the magneqium content calculated by difference ( 7 8 ) . The addition of an excess of standard EDTA followed by a back-titration TTith zinc was proposed as a rapid method of determining calcium in Ca3(P04j2(46). Calcium was determined in the presence of niagnesiuin by titration with E D T L I in a n alkaline solution in the presence of Calcein ( 6 ) or Calcon (23). Magnesium could then be titrated, after adjusting the p H of the solution, with Eriochrome Black T as the indicator. Phosphate was removed
by converting to the molybdate-phosphate complex extracted from aqueous solution by a mixture of 1 : l n-butanol and chloroform (23). Interference from manganese n-as eliminated by complexing with potassium ferrocyanide (23) or by precipitating as the diethyldithiocarbamate extracted by a mixture of carbon tetrachloride and iso-amyl alcohol (82). A potentiometric titration employing a mercury indicator electrode was described for the determination of small amounts of calcium (73). Magnesium, if present, was precipitated as MgNH4PO4 prior to the addition of a n excess of standard E D T A solution. The excess was then back-titrated potentiometrically with a standard calcium solution. The naphthalhydroxamate spectrophotometric method n as applied to the determination of calcium in a et process (4). Interference from the relatively large amounts of iron and aluminum normally present was overcome by complexing these ions with tartrate. A flame photometric method for calcium was reported in which strontium was employed as an internal standard and as a buffer (24). I n this technique a small amount of strontium (100 p.p.ni.) was added to all samples. Individual standard curves were prepared for strontium and for calcium. Both elements were determined in the sample solution and any difference between the apparent and known strontium content was applied as a correction factor to the apparent calcium content. The technique was applicable to cements and slags as well as to mixed fertilizers. BORON
The identical p H method of determining added borate in fertilizers continues to find favor among fertilizer analysts. Phosphate ions must be removed prior to the titration and Bi(K03)3 was recommended for this purpose in preference to the usual lead or barium salts (79). Boron in nitrate solutions n a s determined by the colorimetric carminic acid procedure. After the nitrate mas destroyed by refluxing TT-ith H2S04 and HCOOH, the absorbance n a s read a t 585 or 610 mp (63). -1colorimetric procedure n-as also applied in the analysis of porcelain enamel frits ( 6 3 ) . MICRONUTRIENTS
dtomic absorption spectrophotometry has been applied successfully to the determination of molybdenum. The response was greatest in an oxygen poor (reducing) flame (IS). The interference caused by the presence of calcium, strontium, magnesium, iron, and sulfate ions was completely elim-
inated by the addition of an excess of AlCla ( 1 7 ) . Atomic absorption spectrophotometry u as also applied to the determination of copper and zinc. Increased sensitivity nas obtained in each case by complexing the metal R ith ammonium tetramethylenedithiocarbamate and atomizing an isobutyl methyl ketone solution of this complex ( 1 ) . S o n e of the elements present in fertilizers were found to interfere provided the total salt concentration u-as not sufficiently high t o interfere with atomization ( 2 ) . Copper and zinc were determined in biological materials, including manures, by polarographic methods. The metals were concentrated by a dithizone extraction of the ash prior to polarography (61). An acetate buffer containing triethanolamine was recommended for the determination of copper in the presence of iron (47). Care must be taken during the ashing of samples containing zinc t o avoid losses by volatilization. A n-et ashing technique was recommended (6) as was the dry ashing of the sample with Ca(H?P04)?H20 (10). The latter reacts with zinc to form a phosphate polymer stable a t 900' C.; the polyphosphate protective action probably applies to other trace elements as \%-ell (6). Folloning ashing, zinc was measured by reaction with zincon (6)or by a modified dithizone method (10). Cobalt 1%as determined photometrically with 2-nitroso-1-naphthol; interferences were eliminated by extracting the cobalt-dye complex with CHC13 prior to photometric measurement (66). PESTICIDES
A highly selective gas chromatographic method for determining aldrin in fertilizers was reported in which a fixed amount of phenanthrene was added to a lievane extract of the sample. The level of aldrin present was determined from the ratio of the two peak areas (9). *lldrin n a s a150 determined by a total chloride procedure. I n this method the sample was extracted with dilute HSOs until all soluble material was removed, including free chlorides. The sample m a s then burned in the presence of H202, 02, and H20 and the resulting chloride titrated amperometrically with silver nitrate (80). Ai column partition chromatographic method was employed for the separation of acetic, mono-, di-, and trichloroacetic acids and to the determination of sodium trichloroacetate acid in fertilizers (48). The compounds were separated and eluted from a stationary phase consisting of li-k' H2SOa on diatomaceous earth, by a 1: 1 mixture of CH2Cl2 and
CCI,.
LITERATURE CITED
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