臺灣博碩士論文加值系統

植物營養元素中最重要且需求量最多的是氮、磷及鉀三元素，土壤有機質一般被視為土壤肥力的指標，因此對於有機質肥料中氮、磷、鉀三種主成分含量之分析方法加以評估與研究是非常重要的。
有機質肥料中氮、磷酐及氧化鉀含量的測定方法甚多，惟各有其優缺點而影響其正確性。本研究之主要目的在於(1)評估以元素分析法測定有機質肥料中全氮含量之適宜性，同時並探討有機態氮含量之分析方法；(2)探討鉬釩磷酸銨比色法之最佳吸收波長範圍；及(3)比較並評估以感應耦合電漿原子發射光譜法同步測定有機質肥料中之全磷酐、全氧化鉀含量之適宜性。
凱氏法測定有機質肥料中之氮含量時，由於取樣量大，凱氏法確為測定有機質肥料中氮含量之最適宜方法，利用元素分析法測定有機質肥料中之全氮含量時，由於取樣量極低而不均，致測值之變異性相對加大，且當利用元素分析儀測定全氮時，會觀察到一個微小的系統誤差，故某些元素分析儀之操作條件並不適宜用來測定有機質肥料中之全氮含量。有機態氮含量可利用全氮含量減去無機態氮含量之總和間接估算而得，但亦可利用硫酸法全氮測值減去銨態氮含量來估算純天然有機質肥料中之有機態氮含量將更為適宜，即此間接估算法可推薦作為有機質肥料中有機態氮含量的測定方法。利用釩磷酸銨比色法以紫外光/可見光分子吸收光譜儀在波長400∼420 nm範圍內測定有機質肥料中之全磷酐含量與□□容量法的結果均甚為相近。原子吸收光譜法不適宜用於測定高鉀含量肥料中之氧化鉀含量，但無論待測樣品中之鉀含量高或低，火焰光測定法均適宜用於測定肥料中之氧化鉀含量。利用感應耦合電漿原子發射光譜儀同步測有機質肥料中全磷酐、全氧化鉀含量與□□容量法、鉬釩磷酸銨比色法及火焰光測定法之結果均非常接近，且相關顯著，惟需注意基質干擾之影響，試驗結果亦顯示，感應耦合電漿原子發射光譜法不適宜用於同步測定高磷、鉀含量之肥料樣品，由於純天然有機質肥料中之磷、鉀含量均不高，故感應耦合電漿原子發射光譜法適宜用於同步測定有機質肥料中全磷酐、全氧化鉀含量，即感應耦合電漿原子發射光譜法可推薦作為有機質肥料中全磷酐、全氧化鉀含量的同步測定方法。
將來若能更進一步探討出元素分析儀的最佳操作條件，對本身均勻之有機質肥料樣品而言，元素分析法將會是一種快速之自動全氮分析方法。

Nitrogen, phosphorus, and potassium are the most important and widely used three elements of plant nutrition. The organic matter can be regarded as the index of soil fertility. Therefore the studies and evaluation of the analysis methods on the contents of three main components in organic fertilizers are very important.
Several methods have been used to measure the nitrogen, phosphorus pentoxide, and potassium oxide contents in organic fertilizers, however, all of them still have some disadvantages and them affect the accuracy of measurement. The objectives of this study were to (1) evaluate the suitability of elemental analysis method in determining the content of total nitrogen of organic fertilizers and confer the analysis method of organic nitrogen content; (2) confer the best absorbable wavelength range by using the ammonium vanadomolybdate colorimetric method; and (3) compare and evaluate the suitability of inductively coupled plasma-atomic emission spectrometer method in determining the contents of total phosphorus pentoxide and total potassium oxide simultaneously in organic fertilizers.
The Kjeldahl method was found to be the most appropriate method to measure the nitrogen content in organic fertilizers due to the amount of sample is large. For the elemental analysis method, the variance of measurement tends to increase because of the amount of sample is very small. However, a small systematic error was observed in elemental analyzer determination of total nitrogen. Therefore some operating conditions of elemental analyzer were not suitable to be used to measure the total nitrogen content in organic fertilizers. The content of organic nitrogen of pure organic fertilizer can be indirectly estimated by using the total amount of inorganic nitrogen contents subtracted from the total nitrogen content, or it can be estimated more appropriately by using the content of ammoniacal nitrogen subtracted from the test value of total nitrogen with sulfuric acid method as well. So the indirectly estimated method should be suggested to be used to measure the contents of organic nitrogen in organic fertilizers. The results of using ammonium vanadomolybdate colorimetric method to measure the total phosphorus pentoxide contents by UV/VIS at 400-420 nm were similar to those of using volumetric quinoline method. Atomic absorption spectrophotometer method was not suitable to be used to measure the total potassium oxide content in the fertilizer of high potassium content. But regardless of high or low potassium content of samples, flame photometric method was found to be the most appropriate method to measure the total potassium oxide content in fertilizers. The results of using inductively coupled plasma-atomic emission spectrometer method to simultaneously measure the total phosphorus pentoxide and total potassium oxide contents were similar to those of using volumetric quinoline method, ammonium vanadomolybdate colorimetric method and the flame photometric method. Their relationships were also very significant when the matrix interference was controlled well. The results also showed that inductively coupled plasma-atomic emission spectrometer method was not suitable to be used to measure the sample of high phosphorus and potassium contents in fertilizers. Because of low phosphorus and potassium contents of pure organic fertilizers, the inductively coupled plasma-atomic emission spectrometer method was suitable to be used to simultaneously measure the total phosphorus pentoxide and the total potassium oxide contents in organic fertilizers. So the inductively coupled plasma-atomic emission spectrometer method should be suggested to be used to simultaneously measure the contents of total phosphorus pentoxide and total potassium oxide in organic fertilizers.
In the future, the research may focus on how to create the best operating condition when elemental analyzer is used to measure the content of total nitrogen in homogenius organic compound

目 錄
頁次
中文摘要I
英文摘要III
目錄VI
圖目錄IX
表目錄XIII
附表目錄XV
壹、前言1
貳、前人研究3
一、氮肥分析原理及相關研究3
二、磷肥分析原理及相關研究18
三、鉀肥分析原理及相關研究28
參、材料與方法33
試驗一、有機質肥料中氮含量分析方法之適宜
性評估33
試驗二、有機質肥料中全磷酐、全氧化鉀含量
分析方法之適宜性評估43
肆、結果與討論68
一、以凱氏法、紫外光/可見光分子吸收光譜法
及元素分析法測定標準品氮含量的準確性68
二、以凱氏法、紫外光/可見光分子吸收光譜法
及元素分析法測定有機質肥料中之氮含量
的適宜性評估78
三、以□□容量法、鉬酸銨容量法及紫外光/
可見光分子吸收光譜法測定標準品之磷酐
含量的準確性90
四、以□□容量法、鉬酸銨容量法及紫外光/
可見光分子吸收光譜法測定有機質肥料中
之全磷酐含量的適宜性評估100
五、以火焰光測定法、原子吸收光譜法測定標
準品之氧化鉀含量的準確性109
六、以火焰光測定法、原子吸收光譜法測定有
機質肥料中之全氧化鉀含量的適宜性評估114
七、以感應耦合電漿原子發射光譜法同步測定
標準品之磷、鉀含量的準確性118
八、以感應耦合電漿原子發射光譜法同步測定
有機質肥料中之全磷酐、全氧化鉀含量的
適宜性評估123
伍、結論133
陸、參考文獻136
附錄148

(1) Yang, S.L., Chemical process industries, Gao Li, Taipei, pp. 105-124
(1990).
(2) Young, C.C., Soil and fertilizer, Nong Shi, Taichung, pp. 62-102 (1997).
(3) Gregorich, G., Carter, M.R., Angers, D.A., Monreal, C.M., and Ellist, P.H.,“Towards a minimum data set to assess soil organic matter quality in agricultural soils,”Can. J. Soil Sci., 74:367-385 (1994).
(4) Bauer, A., and Black, A.L.,“Quantification of the effect of soil organic matter content on soil productivity,”Soil Sci. Soc. Am. J., 58:185-193 (1994).
(5) John, A.E.,“Significance of organic matter in agricultural soils,”In A.J. Beck, et al. (ed.) Organic substances in soil and water: Natural constituents and their influences on contaminant behavior. Royal Society of Chemistry, p.3-17 (1993).
(6) Smith, S.R., and Hadley, P.,“A comparison of organic and inorganic nitrogen fertilizers : Their nitrate-N and ammonium-N release characteristics and effects on the growth response of lettuce,”Plant Soil, 115:135-144 (1989).
(7) Hendrix, P.F., Colema, D.C., and Crossley, D.A.,“Using knowledge of soil nutrient cycling processes to design sustainable agriculture,” Integrating Sustainable Agriculture, Ecology, and Envionmental Policy., 2:63-82 (1992).
(8) CNS 8449 N4085,“Method of test for fertilizers:Determination of nitrogen content,”Chinese National Standants, Bureau of Stands, Metrology and Inspection, Ministry of Economic Affairs, Taiwan, R.O.C. (2001).
(9) CNS 8450 N4086,“Method of test for fertilizers:Determination of phosphorus content,”Chinese National Standants, Bureau of Stands, Metrology and Inspection, Ministry of Economic Affairs, Taiwan, R.O.C. (1992).
(10) CNS 8451 N4087,“Method of test for fertilizers:Determination of potassium content,”Chinese National Standants, Bureau of Stands, Metrology and Inspection, Ministry of Economic Affairs, Taiwan, R.O.C. (1992).
(11) Zhong, R.L.,“The conversion of nitrogen between soil and plant,”In a study group of the nitrate nitrogen content in organic planting crop, National Chung-Hsing university, department of soil and environmental sciences, Taichung, pp. 9-17 (2000).
(12) Bremner, J. M.,“Total nitrogen,”In Black, C. A. et al. (ed.) Methods of soil analysis, part 2, Agronomy, Am. Soc. of Argon., Madison, WI, 9: 1149-1255 (1965).
(13) Guo, K.S., Soil science, China, Taipei, pp. 321-380 (1997).
(14) Stevenson, F. J.,“Origin and distribution of nitrogen in soil,”In Frank J. Stevenson (ed.) Nitrogen in agricultural soils. Agronomy, American Society of Agronomy, Madison, Wisconsin, U.S.A. 22: 1-42 (1982).
(15) Sheng, C.Y., Fertilizer science, Cheng Chung, Taipei, pp. 65-112 (1988).
(16) Wu, J.T., Fertilizer handbook, The Chinese society of soil and fertilizer sciences, Taichung, pp. 48-68 (2001).
(17) Wright, M., and Davison, K.L.,“Nitrate accumulation in crop and nitrate poisoning of animals,”Adv. Agron., 16:197-247 (1964).
(18) Kowl, J.J., and Barker, A.V.,“Growth and composition of cabbage as influenced by nitrogen nutrient,”Commum. Soil Sci. Plant Anal., 12:979-995 (1981).
(19) Bitzer, C.C., and Sims, J. T.,“Estmating the availability of nitrogen in poultry manure through laboratory and field studies,”J. Environ, Qual., 17:47-54 (1988).
(20) Gale, P.M., and Gilmour, J.T.,“Carbon and nitrogen mineralization kinetics for poultry litter,”J. Environ, Qual., 15:423-426 (1986).
(21) Castellanos, J.Z., and Pratt, P.F.,“Mineralization of manure nitrogen-correlation with laboratory indexes,”Soil Sci. Soc.Am.J., 45:354-357 (1981).
(22) Chae, Y.M., and Tabatabai, M. A.,“Mineralization of nitrogen in soil amended with organic wastes,”J. Environ, Qual., 15:193-198 (1986).
(23) Follett, R.H., Murphy, L.S., and Donahue, R.O., Fertilizers and soil amendments, Prentice-Hall, London, pp. 23-82 (1981).
(24) Nelson, D.W., and Bremner, J.M.,“Presevation of soil samples for inorganic inorganic nitrogen analyses,”Agronomy Journal,Vol. 64, March-April, pp. 196-199 (1972).
(25) Official methods of analysis of fertilizers. The National Institute of Agro-Environmental Sciences Ministry of Agriculture, Japan. pp. 6-63 (1987).
(26) Keeney, D.R., and Nelson, D.W.,“Nitrogen-Inorganic Forms,”In Page., A.L. et al. (ed.) Methods of soil analysis. Part 2. Agron. Monogr. 9. ASA and SSSA, Madison, WI, pp. 643-698 (1982).
(27) Fang, Y.J., Soil analysis manual, The Chinese society of soil and fertilizer sciences, Taichung, pp. 219-250 (1995).
(28) Bremner, J.M., and Mulvaney, C.S.,“Nitrogen-Total,”In Page., A.L. et al. (ed.) Methods of soil analysis. Part 2. Agron. Monogr. 9. ASA and SSSA, Madison, WI, pp. 595-624 (1982).
(29) Huang, Y.M., Fertilizer handbook, The Chinese society of soil and fertilizer sciences, Taichung, pp. 97-100 (2001).
(30) Bremner, J.M.,“Determination of nitrogen in soil by the Kjeldahl method,”J. Agric. Sci., 55:11-33 (1960).
(31) Rexroad, P.R.,“Nitrogen in feed and fertilizer,”Journal of the AOAC, Vol. 56, No. 4, pp. 862-863 (1973).
(32) Glowa, W.,“Zirconium dioxide, a new catalyst, in the kjeldahl method for total nitrogen determination,”Journal of the AOAC, Vol. 57, No 5, pp. 1228-1330 (1974).
(33) Wall, L.L., and Gehrke, C.W.,“Technical communications substitution of cupric sulfate for mercuric oxide as catalyst for the kjel-foss instrument,”Journal of the AOAC, Vol. 59, No. 1, pp. 219-220 (1976).
(34) Liao, C.F.,“Tellurium as catalyst in semimicro kjeldahl method for total nitrogen determination,”J. Assoc. Off. Anal. Chem., Vol.65, No. 4, pp.786-790 (1982).
(35) Keeney, D.R., and Bremner, J.M.,“A simple steam distillation method of estimating b-hydroxy-a-amino acids,”Analytical Biochemistry, 18:274-285 (1967).
(36) Rexroad, P.R., and Krause, G.F.,“Total nitrogen methods-applicable to all fertilizers samples,”Journal of the AOAC, Vol. 53, No. 3, pp. 450-456 (1970).
(37) Johnson, F.J., and Miller, D.L.,“Alkaline distillation of ammoniacal and nitrate nitrogen with raney catalyst powder,”Journal of the AOAC, Vol. 57, No. 1, pp. 8-9 (1974).
(38) Liao, C.F.-H.,“Devarda alloy method for total nitrogen determination,”Soil Sci .Soc.Am.J., 45: 852-855 (1981).
(39) Jen, J.F., and Chau, T.Y.,“The introduction of elemental analyzer,”In a seminar of valuable instruments, National Chung-Hsing university, department of chemistry, Taichung, pp. 1-9 (1999).
(40) Sanchez-Monedero, M.A., Roig, A., Martinez-Pardo, J., Cegrarra, J., and Paredes, C.,“A microanalysis method for determining total organic carbon in extracts of humic substances. Relationships between total organic carbon and oxidable carbon,”Bioresource Technology, 57:291-295 (1996).
(41) Fujitake, N., and Kawahigashi, M.,“13 C NMR Spectra and elemental composition of fractions with different particle sizes from an andosol humic acid,”Soil Sci. Plant Anal. Nutr., 45:359-366 (1999).
(42) Fujitake, N., Kusumoto, A., Tsukamoto, M., Noda, Y., Suzuki, T., and Otsuka, H.,“Properties of soil humic substances in fractions obtained by sequential extraction with pyrophosphate solutions at different pHs,”Soil Sci. Plant Anal. Nutr., 45:349-358 (1999).
(43) Tate, D.F.,“Determination of nitrogen in fertilizer by combustion:collaborative study,”Journal of the AOAC, Vol. 77, No. 4, pp. 829-839 (1994).
(44) Sachen, R.W., and Thiex, N.J.,“Effect of sample introduction and atmospheric blank on determibation of nitrogen (crude protein) by combustion,”Journal of the AOAC, Vol. 80, No. 1, pp. 14-19 (1997).
(45) Skoog, D.A., Holler, F.J., and Nieman, T.A., Principles of instrumental analysis, SAUNDERS COLLEGE, U.S.A., pp. 115-844 (1992).
(46) Wu, J.T., and Wang, Y.P.,“Effects of some environmental factors on nitrate content of Chinese cabbage (Brassica chinensis L.),”Journal of the chinese agricultural chemical society, Vol. 33, No. 2, pp. 125-133 (1995).
(47) CNS 12966 N4146,“Method of test for hazardous components in fertilizers:Determination of nitrous acid,”Chinese National Standants, Bureau of Stands, Metrology and Inspection, Ministry of Economic Affairs, Taiwan, R.O.C. (1992).
(48) Knicker, H., and Ludemann, H.D.,“N-15 and C-13 CPMAS and solution NMR studies of N-15 enriched plant material during 600 days of microbial degradation,”Org. Geochem., 23:329-341 (1995).
(49) Knicker, H., Almendros, G., Gonzalez-Vila, F.J., and Ludemann, H.D.,“13C and 15N NMR analyses of some fungal melanins in comparison with soil organic matter,”Org. Geochem., Vol. 23, No. 11/12, pp.1023-1028 (1995).
(50) Preston, C.M.,“Applications of NMR to soil organic matter analysis: history and prospects,”Soil science, Vol.161, No.3 pp.145-165 (1996).
(51) Wall, L.L., and Gehrke, C.W.,“Semiautomated method for total nitrogen in fertilizers,”Journal of the AOAC, Vol. 60, No. 4 , pp. 881-889 (1977).
(52) Barbera, A.,“Determination of nitrate nitrogen in compound fertilizers,”Journal of the AOAC, Vol. 60, No. 3, pp. 706-708 (1977).
(53) Boy, V.M., and Guijosa, M.,“Ammonia-selective electrode determination of nitrogen in fertilizers,”J. Assoc. Off. Anal. Chem., Vol. 64, No. 5, pp. 1096-1099 (1981).
(54) Mizobuchi, M., Kitada, Y., Tamase, K., Sasaki, K., and Ueda, Y., “Liquid chromatographic determination of ammoniacal and urea nitrogen in fertilizer,”J. Assoc. Off. Anal. Chem., Vol. 67, No. 6, pp. 1132-1134 (1984).
(55) Chen, J.H., Soil analysis manual, The Chinese society of soil and fertilizer sciences, Taichung, pp. 253-273 (1995).
(56) Chen, Z.D., Foundamental soil science, Xu Shi, Taipei, pp. 326-356 (1998).
(57) Wang, Y.P., Plant nutrition science, National Chung Hsing University, Taichung, pp. 62-186 (1997).
(58) Yang, S.L., Quantitative chemical analysis, Gao Li, Taipei, pp. 182-193 (1982).
(59) Twu, H.G., Industries analysis and experiment, Zheng Wen, Taipei, pp.251-275 (1989).
(60) Johnson, F.J., and Farley, J.A.,“Evaluation of methods for determining available P2O5 in fertilizers,”Journal of the AOAC, Vol. 60, No. 3, pp. 702-705 (1977).
(61) Melton, J.R., and Hoover, W.L.,“Microwave oven drying in the gravimetric phosphorus method,”J. Assoc. Off. Anal. Chem., Vol. 64, No. 6, pp. 1319-1321 (1981).
(62) Jones, J.B.,“Simultaneous determination of total boron, calcium, copper, iron, magnesium, phosphorus, potassium, and zine in fertilizers by inductively coupled argon plasma emission spectroscopy,”J. Assoc. Off. Anal. Chem., Vol. 65, No. 4, pp. 781-785 (1982).
(63) Melton, J.R., Hoover, W.L., Howard, P.A., and Green, V.S.,“Atomic absorption adaptation of the quinolinium molybdophosphate method for phosphorus, available P2O5 in fertilizers,”Journal of the AOAC, Vol. 54, No 2, pp. 373-375 (1970).
(64)Trimm, J.R., Stumpe, L.A., Lawrence, J.E., Duncan, R.D., and Johnson, F.J.,“Paper chromatographic determination of phosphorus species,”J. Assoc. Off. Anal. Chem., Vol. 63, No. 4, pp. 859-863 (1980).
(65) Johnson, F.J.,“Automated determination of phosphorus in fertilizers:collaborative study,”J. Assoc. Off. Anal. Chem., Vol. 61, No. 3, pp. 533-536 (1978).
(66) Tan, Z.W., Soil analysis manual, The Chinese society of soil and fertilizer sciences, Taichung, pp. 277-290 (1995).
(67) Neuner, T.E., Pickett, E.E., Gehrke, C.W., and Wippler, J.F., “Automated flame photometric determination of K2O in fertilizers,”Journal of the AOAC, Vol. 58, No. 5, pp. 923-927 (1974).
(68) Guo, K.S., Soil and fertilizer, China, Taipei, pp. 22-31 (1988).
(69)Budavari, S., The merck index, MERCK, U.S.A. (1996).
(70)CNS 13027 N4149,“Method of test for fertilizers:Determination of peat and humus,”Chinese National Standants, Bureau of Stands, Metrology and Inspection, Ministry of Economic Affairs, Taiwan, R.O.C. (1992).
(71) Ludwick, A.E., Western fertilizer handbook, Interstate Publishers, California, pp. 130-131 (1995).
(72) Leeman, L., PS series ICP/Echelle spectrometers reference manual, Leeman Labs., Lowell, U.S.A., Rev. 1.0-1.2 (1990).
(73) Wu, J.T.,“The source and decreasing countermeasures of nitrate in drinking water and vegetables,”Soil and fertilizer news, 61:13-16 (1997).
(74) Wu, J.T.,“The determination of nitrate in vegetables,”In a study group of the nitrate nitrogen content in organic planting crop, National Chung-Hsing university, department of soil and environmental sciences, Taichung, pp. 18-27 (2000).
(75) Chanyasak, V., and Kubota, H.,“Carbon / organic nitrogen in water extract as measure of composting degradation,”J. Ferment. Technol.,Vol. 59, No. 3, pp. 215-219 (1981).
(76) Ayuso, M., Pascual, J.A., Garcia, C., and Hernandez, T.,“Evaluation of
urban wastes for agricultural use,”Soil Sci. Plant Nutr., Vol. 42, No. 1,
pp. 105- 110 (1996).
(77) Wang, Y.P., and Huang, Y.M.,“A study on the determination of organic matter content in compound organic fertilizers,”In the end research test report about agricultural synthetic adjusting plan, National Chung-Hsing university, Taichung, pp. 13-14 (1994).
(78) Navarro, A.F., Cegarra, J., Roig, A., and Bernal, M.P.,“An automatic microanalysis method for the determination of organic carbon in wastes,”Commun. Soil Sci. Plant Anal., 22:2137-2144 (1991).
(79) Thorpe, V.A.,“Rapid spectrophotometric method for direct available P2O5 in fertilizer,”Journal of the AOAC, Vol. 57, No. 3, pp. 548-552 (1974).
(80) Wall, L.L., and Gehrke, C.W.,“Automated method for determining direct available P2O5 in fertilizers,”Journal of the AOAC, Vol. 57, No. 4, pp. 785-790 (1974).
(81)Thorpe, V.A.,“Rapid micor screening method for direct available
P2O5 in fertilizers,”Journal of the AOAC, Vol. 59, No 1, pp.
20-22 (1976).
(82) Sweeney, R.A.,“Performance criteria proposed for Automated
determination of direct available P2O5 in fertilizers,”J. Assoc. Off.
Anal. Chem., Vol. 68, No. 3, pp. 466-470 (1985).
(83) Hambleton, L.G.,“Collaborative study of the automated method for K2O in fertilizers,”Journal of the AOAC, Vol. 54, No. 3, pp. 640-650 (1970).
(84) Kane, P.F., and Stringham, R.W.,“Flame photometric determination of K2O in fertilizers:Collaborative study,”J. Assoc. Off. Anal. Chem., Vol. 66, No. 5, pp. 1242-1250 (1983).
(85) Newlon, N.,“Evaluation of new flame photometric instrumentation to meet requirements of AOAC official method for potassium in fertilizers,”Journal of the AOAC, Vol. 76, No. 6, pp. 1182-1186 (1993).
(86) Hamalova, M., Hodslavska, J., and Janos, P.,“Determination of phosphorus, and magnesium in fertilizers by inductively coupled plasma — atomic emission spectroscopy and comparison with other techniques,”Journal of the AOAC, Vol. 80, No. 6, pp. 1151-1155 (1997).
(87) Lin, H.M., and Yang, M.X.,“The introduction of Inductively coupled plasma-atomic emission spectrometer,”Instruments Today, Vol. 4, No. 1, pp. 64-74 (1982).
(88) Matilainen, R., and Tummavuori, J.,“Iron determination in fertilizers by inductively coupled plasma atomic emission spectrometry:study of spectral and interelement effects at different wavelengths,”Journal of the AOAC, Vol. 79, No. 1, pp. 22-28 (1996).