Multi-energy calibration for the determination of non-metals by high-resolution continuum source molecular absorption spectrometry

Spectra of diatomic molecules are rich in fine structures which may be used for different analytical applications in high-resolution continuum source molecular absorption spectrometry (HR-CS MAS). If several bands of a given diatomic molecule are simultaneously measured, they may be used in multi-energy calibration (MEC), a method based on the use of several wavelengths of the same absorbing/emitting entity to improve the accuracy in analytical atomic spectrometry. In this work, MEC is used for the first time as a calibration method for HR-CS MAS using flame (F) and graphite furnace (GF) atomizers. Methods were developed and applied for the determination of N, P and S in fertilizers by HR-CS F MAS and Cl in milk by HR-CS GF MAS. Chlorine, N, P and S were measured via CaCl (10 band heads), NO (13 band heads), PO (13 band heads) and CS (14 band heads), respectively. No statistically significant differences were observed between Cl, N, P and S concentrations determined by MEC and by the conventional external standard calibration (paired t-test at a 95% confidence level, n = 3). Recoveries were in the 97-109% (Cl), 97-103% (P), 99-109% (S) and 98-99% (N) intervals, and the relative standard deviations (n = 12) for Cl, N, P, and S were typically 6%, 3%, 2% and 2%, respectively.