(655) Wenninger, J. A., Yates, R. L., Dolinsky, U.,Proc. Sci. Sect. Toilet 1966 (46), p 44. Goods ASSOC., (656) Westfelt, L., Acta Chem. Seand., 20, 2852 11966). (657) Ibid., 21, 152 (1967). (658) Ibid., p 159. (659) Westfelt, L., Svensk Kem. Tidskr., 79, 441 (1967). (660) Westfelt, L., Wickberg, B., Arkiv Kemi, 26, 545 (1967).
(661) Wichtl, M., Planta Med., 11, 53 1963). (662) (Vitte, K., Dissinger, O., Fresenius’ 2. Anal. Chem., 236, 119 (1968). (663) Wolford, R. W., Attaway, J. A., J. Agr. Food Chem., 15, 369 (1967). (664) Wright. R. H.. Perfum. Essent. Oil Rec., 58;648 (1967). ’ (665) Yamada, Iibid., 40, 456 (1966). (668) Yoshida,T., Endo, K., Ito, S., Xozoe, T.. Yakuaaku Zasshi. 87. 434 11967). (669) ZacsGo-Szasz, AI., Siasz, G., Herba Hung., 5 (2-3), 91 (1966). (6iO) Zologtovich, G., ibid., ( l ) ,p 89. (671) Zwaving, J. H., Pharm. Weekblad, 103 (11),273 (1968).
Fertilizers Charles W. Gehrke and lames P. Ussary, Department of Agricultural Chemistry, University o f Missouri, Columbia, Mo. 65201
T
HIS REVIEW covers the literature reported from Jan 1, 1967, to Dec 31, 1968, and includes procedures recorded in readily available journals, in Chemical Abstracts, and in Analytical Abstracts. Some selectivity has been exercised to include only those procedures especially pertinent or those which, in the authors’ judgment, could be adapted easily to fertilizer analytical problems. Quackenbush et. a1 (60) determined the variations in results within and among 23 laboratories on the analysis of nitrogen, phosphorus, and potassium. In addition to the data on variation within and among laboratories, the observations provided information on bias, both in the analysis and in the reporting of data. Details were given of methods of analysis, including modifications of known methods, of plant nutrient solutions specifically for use in connection with hydroponic culture, and also for plant tissue tests for assessment of uptake (60). Methods include those for measuring pH (5 to 8) by using mixed indicators and for determining nitrate, ammonium, phosphate, calcium, magnesium, potassium, sulfate, iron, boron, chloride, copper, zinc, and manganese.
OFFICIAL METHODS
The Association of Official Analytical Chemists (AOAC) in 1966 gave “official” status to a n atomic absorption procedure for copper, iron, magnesium, manganese, zinc, and calcium in fertilizers. The between-laboratory precision ranged from 4 to 7y0 for copper, iron, magnesium, manganese, and zinc. The presence of phosphate interfered in the determination of calcium. Strontium and lanthanum salts or a high temperature acetylene-nitrous oxide flame eliminated the interference. A dichromate method for iron was adopted as official, A method for sampling bulk 58 R
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ANALYTICAL CHEMISTRY
fertilizers was given official status (66, 66). The Japanese National Institute of Agricultural Sciences published, in English and Japanese, a compilation of the Japanese official analytical methods for fertilizers. These methods include sampling, moisture, and 30 elemental and radical determinations (46). SAMPLING
Gehrke et al. (19) designed a study t o investigate the sampling of bulk loads of semigranular, granular, pulverized and, blended fertilizers. An accurate fertilizer sample could be secured by passing a stream sampling cup through the entire flow of material at equally timespaced intervals during the loading of a truck; this stream sample was used as the reference point. The AOAC double and single tube triers did not secure accurate samples of bulk loads. Two compartmented triers and the stream sampler were recommended as official sampling instruments. A concentric sampling pattern for taking samples was recommended. These same investigators evaluated possible mechanisms of sampler bias on dry mixed fertilizers in a n effort to develop better AOAC official sampling instruments and procedures (2). Three 1 ton lots of dry mixed fertilizer with known physical and chemical composition were prepared in the laboratory. Twelve vertical and 12 horizontal cores, arranged in a latin square sampling pattern, were secured from each lot with three triers: the AOAC double tube trier, a double tube compartmented trier, and a n experimental double halftube trier wherein the core was encompassed in place rather than being required to flow into a compartment as with conventional triers. Individual cores were analyzed physically and chemically. Only marginally significant differences were found be-
tween cores on the basis of tube opening size. The experimental double halftube trier was less selective to particle shape than either the compartmented or AOAC triers, but differences were not statistically significant. All triers produced more representative samples from vertical cores than from horizontal cores. Cores drawn at a 60” to 70’ angle from horizontal were not consistently different from vertical cores. Results of chemical analysis confirmed the sieve analysis findings quite closely. Horizontal cores secured with the experimental double half-tube trier confirmed that the bias observed in horizontal cores was due to downward drifting of small particles when the core area was disturbed by sampler insertion. Cores secured with the sample-retaining face upward contained an excess of fines, while cores secured with the sampleretaining face to the side or downward more nearly resembled vertical cores in composition. The experimental double half-tube sampler and a powered auger sampler were compared with the AOAC official compartmented probe and stream samplers on dry mixed fertilizer from three types of blending plants in six states (20). Standard deviations reflecting variability and precision of the experimental tube indicated performance comparable or superior to the official samplers in both chemical and mechanical analysis. The powered auger compared favorably to the official samplers in chemical analysis, but comparison as t o mechanical analysis could not be made because particle size reduction occurred. The official stream sampler failed to secure representative samples from baffle-type mixers when the discharge time was unusually short. Improved indices of sampling accuracy and precision were secured for all samplers used. Docherty devised a n automatic analytical system for analyzing nitrate, am-
monium, phosphate, and potassium based on commercially available samplers, dividers, balances, and the Technicon AutoAnalyzer (16). The sampling and dissolution process were fully automatic, Relative standard deviations of 1to 2y0 were achieved. WATER
Thorpe (63) conducted an AOAC collaborative study on two techniques for determining moisture in peat samples. One method involved drying a 10-g sample at 105 "C for 16 hr in a convection oven. The other method specified air-drying for a t least 24 hr, followed by grinding and finally drying a t 105 "C for 16 hr. Both methods gave the same average results. The relative standard deviations were less than 20/, by each method. Moisture was determined in ammonium bicarbonate by measuring the capacitance with a high frequency titrator (46). Methanol-dioxane (14: 11) was used as an extractant. The standard curve was prepared from NH4HC03, the moisture content of which was determined indirectly from an analysis of all other ingredients, and to which further known amounts of water were added. The calibration curve was linear up to 301, water. The moisture content of mineral fertilizers was determined by measuring the reflection spectra from 1.43 to 1.55 fi (54). I t was simple, convenient, and rapid for moisture contents of 1 to 10% by weight. The time required for one analysis was less than 2 min with an absolute error of less than 0.3% by weight. NITROGEN
The AOAC continued studies in 1967 on methods for determining nitrogen in fertilizers. -4three-laboratory collaborative study was made of the comprehensive nitrogen method, using untreated chromium powder as a reductant (22) and a Raney catalyst powder reduction method ( 7 ) . The report showed that both method worked quite well and, with minor modifications, they should provide the basis for a broader collaborative study to provide an official method for total nitrogen in fertilizer (52). Both methods are applicable to fertilizers containing ammonium, nitrate, organic, and organic plus nitrate nitrogen materials. Further, nitrate could be reduced to ammonium in the presence of high chloride concentrations. The data indicate that digestion conditions that are rugged for less than 0.4 g of nicotinic acid are not rugged for 1-g samples of materials such as blood meal. Both methods foamed excessively during the digestion step. The limitations of AOAC method 2.045 (44) were reviewed and a rephrasing of the
official applications of the method was recommended. In a further study of the Raney catalyst powder method (8), conditions were established in which the commercial alloy containing 50% Ni and 50Tc A1 was a more efficient reductant for nitrates than the alloy used in the three-laboratory collaborative study (50% Ni, 40% Al, 10% Co) described above. The method was more convenient to use when part of the potassium sulfate and all of the sulfuric acid were added as a single dilute solution, Changes in the amounts of reagents, including use of the contents of a Kel-Pak without the polyethylene envelope] resulted in smoother and more effective Kjeldahl digestions. The method was rugged (68) and applicable to inorganic fertilizers, mixtures of nitrates and organic materials, and to the refractory compound nicotinic acid. It was also stated that the time required for analysis could be shortened by using Autopettes for dispensing the standard acid and a Titralyzer for backtitrations. An automated spectrophotometric method utilizing the Technicon AutoAnalyzer was developed by the Missouri Experiment Station Chemical Laboratories (21). Fertilizers were reduced and digested according to the comprehensive nitrogen method and read on the AutoAnalyzer in the range from 5 to 15 ppm nitrogen at a rate of 40 analyses per hr. Ammonium ion was determined by reacting it with alkaline phenol and hypochlorite to form a blue compound closely related to indophenol. Optimum reagent concentrations for the colored reaction were determined, and several ions were investigated to determine if they interfere with the reaction. Mercuric ion, from the digestion catalyst, interfered, but the effect of this interference was eliminated by digesting the standards in the same manner as the samples. Comparisons of results obtained by the automated method and the comprehensive nitrogen method on primary standard grade (NH&SOd and KNOa, Magruder check samples, and several commercial fertilizers showed that the automated method is accurate and precise, and results in a considerable saving of analytical time. Niedermaier (43) reported an automated method using the Autodnalyzer. Kitrate in the dilute HC1-soluble sample was reduced with hypovanadous ion and the resulting ammonium ion was determined colorimetrically using the phenate-hypochlorite reaction. When analyses were made a t the rate of 10 per hr with samples containing 10 to 13y0 nitrogen, a difference of less than =k0.15% absolute was obtained between the automated method and the classical Kjeldahl method.
The AOAC conducted a collaborative comparison of the Dumas and Kjeldahl methods for total nitrogen in feeds (17). By use of the Coleman nitrogen analyzer 11, it was found that the mean values of the six feed materials studied showed good agreement between the two methods. The standard deviation was 10.18 to 10.39 for the Dumas method and k0.6 to 10.40 for the Kjeldahl method. For two organic standard materials, the Dumas method gave better accuracy but poorer precision. Makarevich and Koyander (37) developed a volumetric method for total nitrogen in fertilizers using the chloramine method. An aliquot of a sulfuricsalicylic acid Kjeldahl reduction and digestion was adjusted to pH 6.7 with phosphate buffer containing KBr. To this was added chloramine, KI, and oxalic acid. The released iodine was titrated with sodium thiosulfate solution using starch indicator. The determination takes 30 to 40 min to complete after digestion and has a relative error Of
1.50/,.
A method was devised by Goulden and Manning (25) with which ammonium, nitrate, sulfate, and phosphate in water-soluble fertilizers can be determined by infrared spectrometry. The I R absorption spectra of suitable prepared aqueous fertilizer extracts were recorded and the absorbance measured a t the appropriate four wavelengths. Results calculated from these absorbances gave dmmonium concentrations which agreed with those obtained by chemical analyses to a relative accuracy of 1% a t the 10% nitrogen level. The other determinations agreed to within approximately 3y0 relative. Glintic and biaksimovic (24) found that ammonium ions could be satisfactorily determined gravimetrically after precipitation with sodium tetraphenylborate. The results were in good agreement with the classical Kjeldahl results. The AOAC collaboratively compared a slow-release nitrogen method and a water-insoluble nitrogen method (4,28). Precision of the water-insoluble nitrogen results was improved over an earlier collaborative study from an among laboratory standard deviation of 6.16 to 1.03%. The two methods gave significantly different results with urea-formaldehyde samples. This difference gives a significant change in the activity index. Because both methods can be useful for testing specific types of slowrelease nitrogen or water-insoluble nitrogen, it was recommended that both methods be retained as official AOAC methods. Katz and Fassbender (33) developed a system for the determination of the potential biodegradability of ureaaldehyde condensates used as fertilizers. The system was based upon the biochemical oxygen demand principle]
VOL. 41, NO. 5, APRIL 1969
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narrower fractionation of materials, and use of microbial cultures adapted to these individual fractions. Samples were fractionated into five fractions according to their solubility in water a t 25, 50, 75, and 100 "C. Mixed microbial cultures were developed to utilize the nitrogen in these fractions. Degradation studies of these urea-formaldehyde fractions showed that 90 to 100% of the theoretical amount of nitrogen in each fraction was used. When this system was applied to the urea-crotonaldehyde condensate used as fertilizer, results showed that 90 to 1057, of the nitrogen was utilizable. It was concluded that biodegradable methods are applicable in determining the potential biodegradability of any urea-aldehyde condensate showing agronomic potential. A new method has been developed for the determination of biuret in urea, based on the separation of the copperbiuret complex with an anion exchanger, followed by titration of the bound copper with EDTA (23). The method may be used directly for the determination of biuret in solutions and in end products of a urea factory, with biuret contents as low as 0.0017,. Beals et al. (5) developed an automated colorimetric method for determination of biuret in low biuret urea. The method was based on the AOAC official colorimetric method (44). Color is developed with cupric sulfate in alkaline tartrate buffer and measurement of the absorbance a t 550 mfi. The overall average relative standard deviation was 3.17,; the relative standard deviation for samples containing from 0.227, to 0.026% biuret was 2.1%. PHOSPHORUS
A study was made by the AOAC to determine the stoichiometry of the volumetric ammonium phosphomolybdate method for PzOs with particular reference to solubility losses and ammonia content of the precipitate (3). This investigation showed that the recovery of ammonia by distillation from a caustic solution was depressed by the presence of molybdic acid. Recovery was reduced to 98.67, a t the stoichiometric ratio of MoOs to N of 4 : l . The mechanism of the phenomenon was not explained. However, after the method was standardized for ammonia in the presence of molybdic acid, the yellow precipitate was found to contain 99.5Y0 of the theoretical ammonia according to the formula ("4) 3PO4:12Mo03. Guerrant et al. (26) reported a quick extraction technique for available phosphorus in fertilizer. Samples were extracted in a Gooch crucible with a jet of 65 "C neutral ammonium citrate in 10 to 20 min. A single direct determination of available phosphorus was 60
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ANALYTICAL CHEMISTRY
made by the alkalimetric quimociac method, modified for speed and for use in high citrate concentrations. The results compared favorably in accuracy to the gravimetric quimociac results reported on 20 Magruder check samples. The method is useful for screening or quality control purposes. Jordan (31) developed an automated high precision determination for P205 in fertilizers using the phosphomolybdovanadate color reaction. Both precision and accuracy were well within 0.5% relative for determining total phosphorus on 35y0 Pz06 rock phosphate samples. A similar high precision automated method was reported by Longert and Martin (36). They found that an absolute precision of better than 3=0.05% P205 was obtained for phosphoric acid samples containing from 45 to 53% PzOa. Clements and Marten (14 ) developed an automated technique for determining Pz05 in phosphoric acid. The average relative standard deviation was 0.247, for samples containing 477, P205. Total analytical time was less than 5 min. An automated technique was developed to measure continuously the soluble Pzo5 in the effluents from phosphoric acid manufacturing plants, and also to measure intermittently the PzOb concentration in the product acid (1). Woodis (66) suggested using Amberlite IR-120 cation exchange resin to remove interfering cations before the determination of the various forms of phosphorus in wet-process phosphoric acid by paper chromatography. The sample was treated with sodium peroxide to oxidize ferrous iron to the ferric form. A comparison of a gravimetric method, a volumetric method, and a colorimetric method was made by Weiser and Riedel in Germany (65). It was concluded that the gravimetric method using precipitation as MgNH4PO4 and conversion to Mg9P207 is accurate enough to be used as a reference method, Direct precipitation and weighing as molybdophosphate, precipitation as MgTu"4PO4 in the presence of citric acid, and (for up to 30% of Pz06) colorimetry are also generally satisfactory. Titration with alkali in the presence of CaCh or complexometric titration after precipitation as quinolinium phosphomolybdate was less satisfactory. In a greenhouse study designed to correlate the solubility of Thomas phosphate in 27, citric acid to plant response, there appeared to be a distinct dependence on the 2Y0 citric acid-soluble phate rather than on total phosphate (42). The noncitric acid-soluble residue was not available to the plants. Buzas and Vigh (10) reviewed gravi-
metric, volumetric, and photometric methods for phosphorus in fertilizers. It was recommended that the colorimetric phosphomolybdovanadate method be used for routine determinations. In a similar evaluation, Cantini et al. (12) found good agreement between spectrophotometric and volumetric methods. For determining phosphates in superphosphates, an ion exchange method and a photometric method are simpler and quicker, while the accuracy was equally as good as a classical method (34). An amperometric titration method for phosphorus in liquid fertilizers was reported (62). Ten to 15 ml of buffer solution (prepared by adding 350 ml of a solution containing 7.5 g of glycine and 5.85 g of NaN03 per liter to 650 ml of W "01) were added to the sample solution, and the mixture was titrated amperometrically (rotating platinum electrode) with Bi(NO3)3. Phosphorus in products of double superphosphate manufacturing was analyzed by differential colorimetry using the molybdenum blue method (57). Good agreement was obtained with a gravimetric method on samples containing less than 337, P&. Determinations of phosphate, sulfate, and fluorosilicate in wet process phosphoric acid were made by high frequency titrations (47). The total time for two analyses was 30 to 45 min. POTASSIUM
Rexroad and Gehrke (51) observed that the AOAC official ammonium carbonate extraction method for potassium in fertilizers (2.079) gave consistently lower results than the AOAC official ammonium oxalate extraction method (2.070). An average lower absolute difference of 0.47, K20 was found on 17 typical commercial fertilizers by the carbonate method. Studies showed that this difference was associated with the impurities in fertilizer grade phosphate raw materials, particularly the varying solubility of the (Fe, Al) (NH4,K, H) phosphates. Because of this significant observation, the AOAC associate referee for potassium recommended that the ammonium carbonate extraction procedure be deleted as an official method (27). Investigation of the assumed interference of Hap04 in the analysis of alkalies showed that the presence of the acid had little effect on the determination of potassium (59). Concentrations of HC1 as low as 0.02M gave significant negative interferences. A group of Russian scientists (9) designed an ethanol-fueled burner for the determination of potassium by flame photometry. The burner was tested on a large number of samples and was
made available for the state farm workshops. McCracken et a2. (40) compared the atomic absorption method to the sodium tetraphenylborate method for potassium in 1190 fertilizers. Triplicate analyses of 101 samples by each method showed standard deviations of 0.229% by STPB and 0.424y0 by atomic absorption. The standard deviation of the difference between the two pairs was 0.50%. Other elements normally found in fertilizers did not interfere at 4038 A. Compounds and acids found by the Japanese chemists, Miwa and Yamazoe (41), to interfere with the determination of potassium by atomic absorption were categorized: compounds and acids lowering the absorbance 10 to 15'%-i.e., HzS04, ("&SO4, "01, and NH4N03; those lowering the absorbance 30%-i.e., HCl and NH4C1; those lowering the absorbance 70 to 80%-i.e., H3P04, NH4H2P04, and (NH&HP04. Phosphate interference was suppressed by the addition of tetraphenylborate, Sr, La, or Ca. The other interferences were greatly reduced by maintaining the HC1 concentration at 0.10N. It was concluded that the atomic absorption method was superior to the flame emission method but inferior to the STPB method. I n the development of an atomic absorption method for the analysis of potassium in fertilizers, several interfering materials were found that influenced the absorption by potassium at 7664.9 8. The same interfering materials had little effect on the absorption a t 4044.1 A. However, a high concentration of an interfering substance had varyingo amounts of interference a t 4044.1 A, depending on the presence of other ions. The method had a slight negative bias but gave acceptable results and was simple and fast. The English chemists, Skinner and Docherty (61), developed an automatic ultraviolet absorptiometric method for the determination of potassium. The method involved the precipitation of potassium by the addition of a known excess of sodium tetraphenylborate, removal of the potassium tetraphenylborate by filtration, and measurement of the excess sodium tetraphenylborate in the filtrate by its absorbance a t 254 mp. Except for a Uvicord UV absorptiometer, most of the equipment was standard AutoAnalyzer modules. Buildup of precipitate in the system was eliminated by immersing the mixing coils in an ultrasonic bath. The method was developed for use in a production plant where flame photometric results were affected by fertilizer dust in the air. I n addition to satisfactorily analyzing for ammonium nitrogen by sodium tetraphenylborate, Glintic and Maksimovic (24) found that potassium results by
the sodium tetraphenylborate method were in good agreement with the gravimetric perchlorate method. A gravimetric method for determination of potassium found in rocks involves the precipitation of potassium with a solution of sodium tetraphenylborate at pH 2, after removal of iron as Fe(0H)a by the addition of calcined MgO (36). Calcium and magnesium did not interfere with the determination. Catani and Rossetto (IS) precipitated potassium with a slight excess of a standard solution of sodium tetraphenylborate. The precipitate of potassium tetraphenylborate was removed by filtration and the excess tetraphenylborate was backtitrated with alkyldimethylbenzylammonium chloride. Precision and accuracy were good with standard potassium salts and mixed fertilizers. Precipitation of potassium as sodiumpotassium cobaltinitrite was studied as a function of potassium concentration, amounts of cobaltinitrite, acetic acid concentration, and concentration of calcium and magnesium (65). Quantitative measurements were made with the use of radioactive 42K. Optimum precipitation conditions were: potassium concentration greater than 0.2 mol per 1; molar ratio of Na&o(No2)6: KzNaCo(N02)6 between two and 10; and the concentration of acetic acid 0.15 to 0.30M. Calcium concentrations of 0.07 to 0.7M had no effect on the solubility of the K2NaCo(h'02)o and magnesium had no effect a t low concentrations. The relative error was less than 3y0 for solutions containing from 1.00 to 1.04 mg of potassium per ml. A volumetric method using cation exchange chromatography and a nonaqueous solution was developed for the determination of potassium in pure salts or in mixed fertilizers (67). Pure salts were dissolved in methanol, an aliquot of the resulting solution was passed through a cation exchange resin column in the hydrogen form, and the acid was eluted with methanol and titrated potentiometrically (glass and SCE electrodes) with 0.05N tetraethyl ammonium hydroxide in methanol. The relative error was no greater than 1%. For mixtures of salts, acetone was added to the eluted mixture (1:2). This resulted in more distinct breaks in the titration curve. For two-component mixtures, the relative error in determining each salt was no greater than 2.5y0, SECONDARY AND MICRONUTRIENTS
The AOAC atomic absorption method for the determination of secondary and micro plant nutrients (2.08G2.091) was studied collaboratively for a third time and expanded to include calcium, sodium, and potassium (58). Analysis of seven samples by 19 collaborators resulted in between-laboratory relative
precisions of 4 to 7% for Cu, Fe, Mg, Mn, and Zn. The method was recommended for adoption as official first action for Ca. Further study of the method for K and Na was recommended. The K results were inconclusive and the Na results were poor. I n 1968, A h Bride (39) reviewed and recalculated this 1967 study and recommended to the AOAC that this method be adopted as official, final action for calcium, copper, iron, magnesium, manganese, and zinc. Ingram (SO) conducted an AOAC collaborative study on the determination of iron in fertilizer by dichromate titration. Results were quantitative after first oxidizing with perchloric acid. High concentrations of phosphorus, potassium, and ammonium nitrate did not interfere. It was recommended that the method be adopted as official, first action, and that further study be made on methods of sample preparation, particularly for organic samples. A procedure for determining low levels of molybdenum in fertilizers by atomic absorption was proposed by Hoover and Duren (29). With potassium thiocyanate as a complexing agent, molybdenum was extracted with isoamyl alcohol to remove it from interfering substances. The method is not applicable to samples containing high concentrations of iron. The method gave reliable results tolevels as low as 2.5 ppm of molybdenum. A polarographic method for determination of molybdenum and zinc in fertilizers was reported (49). Iron, aluminum, magnesium, manganese, copper, nickel, and chromium did not interfere. The results agreed with those of spectrographic determinations. The method was used to study the solubility of fertilizers and the transfer of molybdenum and zinc from them into the aqueous phase. Curthoys and Simpson (15) determined zinc polarographically in samples of superphosphate and trace element superphosphate. Polarograms were recorded on aliquots a t -0.90 and -1.34 V with a mercury pool anode and an ac potential of 2.87-mV rms. There was no interference from phosphate or iron, nor does the presence of the hydrogen reduction wave have any effect. Results agreed with those obtained by atomic absorption spectrometry. An ion exchange separation technique was described for the separation of copper, zinc, manganese, molybdenum, and cobalt in phosphate fertilizers (64). For the separation, a cation exchange column in the ammonium form, washed with ammonium citrate reagent, was used. Fifty milliliter aliquots of the combined water and citrate reagentsoluble material from a fertilizer were passed through the column. Only copper and zinc were adsorbed. Manganese, cobalt, molybdenum, and iron VOL. 41, NO. 5, APRIL 1969
61 R
were washed from the column with 120 (5 ml) portions of citrate reagent and determined photometrically. Molybdenum was determined as the thiocyanate, cobalt as the 0-nitroso-a-naphtholate, and manganese as permanganate. After the column is washed with water, copper and zinc were eluted with 40 and 50 ml, respectively, of 2N HCl and determined photometricelly as the dithizonates. Manganese was determined complexometrically with EDTA and thymolphthalein as the indicator in ammonium hydroxide medium (11). Iron and aluminum were masked with triethanolamine. The sample was dissolved in a mixture of HClOa and HN08. The insoluble silicic acid was removed by filtration and weighed for the determination of silicon. Calcium and magnesium were separated by cation exchange chromatography before titration by EDTA (58). Elution was accomplished with a solution of 0.8M HC1-0.3X KCl. Trivalent iron and aluminum were found in both fractions, but were masked with triethylamine and KCl. Phosphate and citrate were not adsorbed and calcium was eluted ahead of magnesium. A photometric method which employs Nile blue B was described for the determination of 0.01 to 1.30 mg. of boron in fertilizers, soils, plants, and mineral water samples (18). The method measures Nile blue fluoroborate colorimetrically. The average relative standard deviation was 2.4%. The Analytical Committee of The Fertilizer Manufacturers’ Association, a British organization, proposed a potentiometric method for boron in fertilizers (6). Interferences were removed chemically, mannitol was added, and the liberated acid was titrated potentiometrically with 0.05N NaOH. The titer was determined with a n analyzed sample. A phototurbidometric titration of sulfate in wet process phosphoric acid was proposed by Pile and Williams (48). The sample, adjusted to contain from 30 to 35% ethanol, was titrated with 0.01M BaCl?, using mechanical stirring, in an absorptiometer equipped with a green filter. Impurities normally present in the acid did not interfere, the method was accurate, and one sample could be completed in 20 min. A volumetric determination of sulfate in phosphoric acid was reported (4). One or two drops of 3,6-bis-(4-nitro-2sulfophenylazo) - 4,5 - dihydroxynapthalene-2,7-disulfonic acid (Na salt) and a volume of ethanol or acetone equal to the sample solution and the sulfate were titrated with 0.2N BaClz to a color change from violet to blue. Fluorine was determined in fused fertilizer phosphates and phosphorites (32). The fluorine compounds were reacted with silicate glass in H?SOI. 62 R
ANALYTICAL CHEMISTRY
Sodium alizarinsulfonate was added, the pH adjusted, a buffer solution added, and the solution titrated with thorium nitrate solution. Thallium was determined in potassium fertilizers using ac arc spectromMicro amounts of thaletry (69). lium were extracted with 4,4’-methylenediantipyrene in chloroform. T1 (I) was not titrated by this reagent and it was necessary to oxidize it to T1 (111) with saturated bromine water before the extraction step. The T1 (111) was reextracted from the chloroform layer with aqueous EDTA, evaporated in the presence of H2S04, and analyzed. Traces of zinc, cadmium, and iron (111) did not interfere and were determined simultaneously. Zirconium was used as a n internal standard. Sensitivity was a t a level of 1 ppm with a relative error of less than 10%.
(24) Glintic, M., Maksimovic, L., Teknika (Belgrade), 21 ( 1 4 ) , 520 c-520e (1966)
(Croat).
(25) Goulden, J. D. S., Manning, D. J., J . Sci. Food Agr., 18 (lo),466-9 (1967). (26) Guerrant, G. O., Hunter, J. D., McBride, C. H., ibid., (6), pp 1273-9. (27) Hambleton, L. G., J . Ass. Ofic. Anal. Chem., 51 (4), 857-8 (1968). (28) Holt, K. E., ibid., 50 (2), 414-18 (1967). (29) Hoover, W. L., Duren, S. C., ibid., (6), 1269-73 (. (30) Ingram, W. J., ibid. (2), pp 397400. (31) Jordan, D. E., “Automation in Analytical Chemistry,” pp 253-6, Mediad, Inc., White Plains, N. Y., (1968). (32) Kalmykov, S. I., Khon, K. V., Khim. Sel’skae Khozyarstvo, 5 (6), 54-7 (1967). (33) Katz, S. E., Fassbender, C. A., J . Ass. Offic. Anal. Chem., 50 (4), 975-80 11967). (34). Krastavcevic, M., Misovic, J., Teknzka (Belgrade), 21 (9-12), 2164-8 (1966) (Croat). (35) Kurdina, F. F., Il’ina, E. T., Vop. \ - - -
I
Miner. Geokhim. Technol. Miner. Syr’ya,
1966, pp 13942 (Russ). (36) Longert, J. I., Martin, C. J., Jr
LITERATURE CITED
(1) Atkinson, T. W. L. “Automation in Analytical Chemistry,’” pp 180-2, Mediad, Inc., White Plains, N. Y., 1967. (2) Baker, W. L., Gehrke, C. W., Krause, G. F., J . Ass. O$c. Anal. Chem., 50 (2), 407-13 (1967). (3) Barker? J. E., ibid., (3), pp 712-13. (4) Basargin, N. N., Nikitina, N. A., Zavod. Lab., 32 (5), 517-19 (1966) (Russ). (5) Beals, E. G., Garritsen, P. G., Med-
dings, B., “Automation in Analytical Chemistry,” Mediad, Inc., White Plains, N. Y., 1967. (6) Borland, H., Brownlie, I. A,, Godden, P. T., Analyst (London), 92, 47-53 (1967). (7) Brabson, J. A., Burch, W. G., Jr.,
Woodis, Y. C., Jr., unpublished method.
(8) Brabson, J. A,, Woodis, T. C., Jr., J . Ass. Ojic. Anal. Chem., 52 ( l ) , 23-30 (1969). (9) Bur’yanov, Ya. B., Besedina, E. F., Tr. Altai. SeE’.-Khoz. Znst., 10, 74-7 (1966) (Russ). (10) Buzas, I., Vigh, K., Magy. Kem. Lab., 20 (9), 493-8 (1965) (Hung). (11) Cakon, M., Kovarik, M., Hutnicke Listy, 22 (9), 634-5 (1967) (Czech). (12) Cantini, R. A., Pellegrino, D., Jacintho, A. O., An. ESC.Super. Agr., “Luiz Queiroz,” Univ. Sa0 Paula, 23, 41-52 (1966) (Port). (13) Catani, R. A., Rossetto, A. J., ibid., pp 31-9. (14) Clements, J., hIarten, J. F., “4uto-
mation in Analytical Chemistry, 183-6. Mediad, Inc., White Plains, Y., 1967. (15) Curthoys, G., Simpson, J. R., Analyst (London),91,195-8 (1966). (16) Docherty, A. C., Chem. Znd. (London), 7,216-20 (1968). (17) Ebeling, M. E., J . Ass. O j k . Anal.
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Chem., 50 ( l ) , 38-41 (1967). (18) Gagliardi, D., Wolf, E., Mikrochim. Acta, 1, 140-7 (1968) (Ger). (19) Gehrke, C. W., Baker, W. L., Krause, G. F., Russell, C. H., J . Ass. O$c. Anal. Chem., 50 (2) 382-92 (1967). (20) Ibid., 51 (4), 859-65 (1968). (21) Gehrke, C. W., Kaiser, F. E., Ussary, J. P., ibid. ( l ) , pp 200-11. (22) Gehrke, C. W., Ussary, J. P., Perrin, C. H., Rexroad, P. R., Spangler, W. H., ibid., 50 (4), 965-75 (1967). (23) Geurts, J. J., van Stelle, J. E.,
Brinkman, E. G., Anal. Chim. Acta, 41 ( l ) , 113-20 (1968).
“Automation in Analytical Chemistry,;: pp 261-4, Mediad, Inc., White Plains, N. Y., 1968. (37) Makarevich, V. M., Koyander, A. E., Agrokhim., 3,123-6 (1968) (Russ). (38) .McBride, C. H., J . Ass. O$c. Anal.
Chem., 50 (2), 401-7 (1967). (39) Ibid., 51 (4), 847-51 (1968). (40) McCracken, bf. L., Webb, H. J., Hammer, H. E., Loadholt, C. B., ibid., 50 ( l ) , 5-7 (1967). (41) Miwa, E., Yamazo, F., Nippon Dojo-Hiryogaku Zasshi, 38 (12), 469-74 (1967) (Jap). (42) bIunk, H., Phosphorsaeure, 27 (3-6), 198-212 (1967). (43) Niedermaier, T., 2. Anal. Chem., 223 (5), 336-43 (1966) (Ger). (44) “Official Methods of Analysis,” 10th
ed, Association of Official Agricultural Chemists, Washington, D. C., 1965. (45) “Official Methods of Analysis of Fertilizers,” Kogusuri Printing Co., Ltd., Tokyo, Japan, 1967. (46) Pandey, A. D., Roy, A. K., Technology (Sindri), 2 (3), 125-9 (1965). (47) Zbid., 3 (4), 183-8 (1966). (48) Pile, P. C., Williams, A,, J . Agr. FoodChem., 14 (5), 521-2 (1966). (49) Protsenko, G. P., Kovalenko, P. N., Agrokhim., 1 (3), 127-30 (1966) (Russ). (50) Quackenbush, F. W., Rund, R. C., RLiles, S. R., J . Ass. Ojic. Anal. Chem., 49 (5), 9 1 5 4 3 (1966). (51) Rexroad, P. R., Gehrke, C. W., ibid., 50 (3), 714-17 (1967). (52) Rexroad, P. R., Krause, G. F., ibid., 51 (4), 851-7 (1968). (53) Rodziewicz, W., Grzedzicki, K., Chem. Anal. (Warsaw), 12 (2), 273-80 (1967) (Pol). (54) Rud’ko, B. F., Gozhenko, N. A,,
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(12), 1460 (1966) (Russ). (58) Shirarshi, N., Yoshikawa, S., Japan Analyst, 15 (lo), 1083-7 (1966) (Jap). (59) Shupen, V. K., Agrokhim., 1 (lo), 98-100 (1966) (Russ). (60) “Simplified Analysis of Hydroponic
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(66) Woodis, T. C., Jr., J . Ass. Oflc. Anal, Chem,, 52 (I), 30 (1969). (67) Yarovenko, A. N., Komarova, K. A.,
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Zugagina, L. N., Sibiryakov, N. F., Uch. Zap., Permsk. Gos. Univ., 159, 238-42 (1966) (Russ). CONTRIBUTION of.the Missouri Agricultural Experiment station. Journal Series No. 5664, approved by the director.
Food Katherine G. Sloman, Arthur K . Foltz, and James A. Yeransian, General Foods Technical Center, White Plains, N. Y.
I
N THIS REVIEW the authors have at-
tempted to provide a representative survey of advances, innovations and constructive modifications in food analysis. The publications covered generally appeared in the time span of October 1966, when the preparation of the previous review (1P) was begun, to October 1968. Where dates cited are earlier than this the work had not yet come ta the writers’ attention for past inclusion. As before, for the sake of space, identical work in American and foreign journals led t o the choice of the more familiar domestic publications especially when availability allowed checking the content of papers for applicability. Several texts have appeared which augment the field of food analysis. The subject of quality control in the food industry with a new chapter on flavor measurement is covered by Kramer and Twigg’s work (17P). The American Public Health ilssociation (2OP) has published a book on standard methods for dairy products. The proceedings of the 1966 Technicon automation symposium (2IP) have appeared and contain papers of interest to food analysts. ADDITIVES
The detection and identification of additives in foods becomes more important each year and the number and type of additives used increases steadily, Methods for antioxidants are many and varied. Dilauryl thiodipropionate and other antioxidants have been separated from lard, using a vacuum technique, by Fazio, et al. (18A). Butylated hydroxyanisole (BH.4) has been determined spectrophotometrically by formation of a nitroso derivative by Davidek, et al. (IOA). Photometric measurement of nordihydroguiaretic acid (NDGA) after reaction with molybdophosphoric acid and triethanolamine has been used by Galea, et al. (2SA). Vacuum sublimation and gas-liquid chromatography (GLC) have been proposed by McCaulley, et al. (45A) for determination of several antioxidants in lard. BHA,
butylated hydroxy toluene (BHT), and NDGA have been separated by thinlayer chromatography (IIA). BHT has been extracted from emulsifiers by iMiethke (46A) and detected by TLC or GLC. Takahashi (6SA) has reported the results of B collaborative study of the determination of BHA and BHT in cereals using gas chromatography. The presence of 24 phenolic antioxidants in oats has been shown by Daniels, et al. (9A) using thin-layer and column chromatography. Methods of analysis for preservatives have been reviewed by Schuller and Veen (61A), and a book on “Detection and Determination of Preservatives in Foods” published by Diemair and Postel (17A). Gas chromatography has been used for the determination of alkyl ether derivatives of 4hydroxybenzoates by Wilcox (67A), for the determination of sorbic and benzoic acids in wine by Wurdig (7OA) and investigated for a number of preservatives by Amano, et al. ( 2 A ) . The technique of steam distillation, thin-layer chromatography and UV spectromety has been applied to the analysis of solid foods for benzoates by Lewis (43A). -4 thin-layer chromatographic procedure has been used by Dickes (16A) for the separation and identification of 4-hydroxybenzoic acid and its esters in foods. Monselise (47A) has described an extraction procedure and subsequent spectrophotometric measurement for sodium benzoate and potassium sorbate in preserved fruits and vegetables. Ionexchange chromatography has been used by Ford (21A) to determine benzoic acid in soft drinks. Thin-layer chromatography has been described by Ludwig, et al. (44A) and Roidich, et al. (69A) for the separation and identification of some preservatives. A colorimetric procedure for 4-hydroxybenzoic acid with diazotised nitroaniline has been described by Aoki, et al. (SA). Benzoic acid has been determined polarographically after nitration by Davidek, et al. (13A). Procedures for dehydroacetic acid using separation and coloration on cation exchange resin (69A) and anion
exchange resin (608) have been described by Sakai, et al. Hydrogen peroxide and sorbic acid were detected in fish paste products by Kanno, et al. (36-4) using colorimetry for the peroxide and sorbic acid after steam distillation. A spot test using phloroglucinol in trichloracetic acid-acetic acid has been used for sorbic acid in wine by Alessandro ( 1 A ) . Screening and quantitative methods for sorbic acid in orange juice have been described by Floyd (19A). iln improved procedure for recovering sorbic acid from foods using vacuum steam distillation has been suggested by Kirnura, et al. (S7A), and other preservatives have been recovered by this technique (b2A). Dialysis has been used as a means of separating preservatives for spectrophotometric measurement by Hamaguchi, et al. (28A). Thin-layer chromatography has been proposed by Takeshita, et al. (64A) as a means of determining 2(2-furyl)-3-(5-nitro-2 furyl) acrylamide in foods. Double development on thinlayer plates has been used by Gosseli, et al. (25A) to separate nine common preservatives. Diethylcarbonate has been determined in wine by Brandenburg, et al. (6A) and by Reinhard (54A) using gas chromatography. Diethylpyrocarbonate has been determined by Kanno, et al. (35A) using gas chromatography, and by Pauli, et al. (52.4) by colorimetry. Gas chromatography of their trimethylsilyl derivatives has been used by Sahasrabudhe (57A) as a means of analysis of polyglycerols and their fatty acid esters. Glycol and sorbitan esters have also been analyzed using the silylation technique by Suffis, et al. (62A). Propylene glycol esters of fatty acids have been separated using silicic acid chromatography followed by gas chromatography (58A). A simple method for the detection of sorbitan mono- and triesters has been proposed by Kroeller (4OA) using thin-layer chromatography. A procedure for the presence of fatty acid mono- and diethanolamides uses chromatography on silica gel G (41A). VOL. 41, NO. 5, APRIL 1969
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