A simple and fast method for assessment of the nitrogen–phosphorus–potassium rating of fertilizers using high-resolution continuum source atomic and molecular absorption spectrometry

Abstract

The determination of N, P, and K in fertilizers by high-resolution continuum source flame atomic and molecular absorption spectrometry is proposed. Under optimized conditions, measurements of the diatomic molecules NO and PO at 215.360 and 247.620nm, respectively, and K using the wing of the alternative line at 404.722nm allowed calibration curves to be constructed in the ranges 500–5000mgL−1 N (r=0.9994), 100–2000mgL−1 P (r=0.9946), and 100–2500mgL−1 K (r=0.9995). Commercial fertilizers were analyzed by the proposed method and the concentrations of N, P, and K were found to be in agreement with those obtained by Kjeldahl, spectrophotometric, and flame atomic emission spectrometry methods, respectively, at a 95% confidence level (paired t-test). A phosphate rock certified reference material (CRM) was analyzed and the results for P and K were in agreement with the reference values. Recoveries from spiked CRM were in the ranges 97–105% (NO3−-N), 95–103% (NH4+-N), 93–103% (urea-N), 99–108% (P), and 99–102% (K). The relative standard deviations (n=12) for N, P, and K were 6, 4, and 2%, respectively.