Lanthanum as a matrix modifier to eliminate interference in molybdenum analysis of feedstuffs by graphite furnace atomic absorption spectroscopy
Titel:
Lanthanum as a matrix modifier to eliminate interference in molybdenum analysis of feedstuffs by graphite furnace atomic absorption spectroscopy
Auteur:
Brown, T. F. Zeringue, L. K.
Verschenen in:
Communications in soil science and plant analysis
Paginering:
Jaargang 19 (1988) nr. 2 pagina's 167-181
Jaar:
1988-02
Inhoud:
Phosphate and sulfate were shown to interfere in the analysis of aqueous molybdenum (Mo) standards by graphite furnace atomic absorption spectroscopy (GFAAS) when either peak area or peak height was used to measure absorption signals. Lanthanum (La) addition to the standards eliminated interferences from PO4= and SO4= when absorption signals were measured as peak area but not when measured as peak height. Adding La (2.4 mM) to Mo-spiked plant tissue digests improved Mo recovery, especially in samples with molar Ca/P and Ca/P+S ratios less than 1.0. Mo spike recoveries (%) from meat/bone meal, dry milk replacer, whole soybean, alfalfa hay, cottonseed meal, and National Bureau of Standards citrus leaves were 76.5, 67.0, 55.0, 93.5, 35.5, and 94.0, respectively, without La in the digest. When La (2.4 mM) was added, percentage recoveries were 95.0, 97.0, 95.0, 99.5, 83.0, and 99.9, respectively. Poor recovery of Mo spikes in the absence of La appeared to be related more to Ca/P and Ca/P+S ratios than to absolute P or S content, with poorest spike recovery occurring in samples with Ca/P and Ca/P+S ratios less than 1.0. Based on the low standard deviations for repeated analyses of a variety of feedstuffs and plant tissues and the good recovery of Mo spikes from digests of these materials, it is recommended that lanthanum be used as a matrix modifier for analysis of Mo in aqueous plant tissue digests by GFAAS.
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