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RESEARCH PRODUCT

Determination of Sulfur in Fertilizers by Inductively Coupled Plasma-Atomic Emission Spectrometry: Spectral and Interelement Effects at Various Wavelengths

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Abstract Three analytical wavelengths (180.731,182.037, and 182.625 nm) were tested for determination of sulfur in 2 fertilizers by inductively coupled plasmaatomic emission spectrometry (ICP-AES). Variable S results at 182.037 nm were caused by a downward sloping background shift (Fe line at 181.851 nm) during measurement of the sample solutions. At 182.625 nm an emission peak doublet, 182.619/182.635 nm, was observed from which the instrument selected the measurement peak. A shift from calibrated peak 182.619 nm to noncalibrated peak 182.635 nm occurred when the S/B ratios were ≤22-31 in the fertilizer samples examined. For the 3 wavelengths of S investigated, the pattern of spectral and interelement interference changed at the same wavelength according to the composition of the fertilizer. K, P, and Mg typically caused interelement effects and Ca and B caused spectral effects during S determination. In the interference studies, 180.731 nm proved the best wavelength for the ICP-AES determination of S in fertilizers. Interlaboratory studies showed the accuracy of the method to be ± 6.2% for both water- and acid-soluble S, independent of the measurement wavelength, instrument, and operator.