Effects of desolvation on line emission intensities and analyte transport in inductively coupled plasma atomic emission spectrometry using ultrasonic nebulization

The influence of HCl, KCl, KBr, KI and Ca in a nitric acid matrix on the emission signals and transport rates in inductively coupled plasma atomic emission spectrometry using ultrasonic nebulization with desolvation is studied. In general, a depression in the analyte emission signals in the presence of nitric acid is observed compared to that in solutions containing matrix elements in a nitric acid solution. This difference arises from the reduced analyte transport efficiencies. The greatest depressions in the analyte transport efficiency (by a factor of about 7 compared to the analyte transport efficiency for Mn) are observed for As-III and Se-IV in a nitric acid solution. The presence of KBr, KI, KCl and Ca in a concentration as low as 0.001 M has a large enhancement effect on the emission signals for Cu, As-III and Se-IV. The exceptions are Sb species in the presence of KBr, where a 50% depression in the analyte transport efficiency and the emission signal is observed in comparison to a nitric acid solution. Calcium and potassium bromide are the most efficient at eliminating the different valence state responses for As and Se. The transport efficiency for Cu is comparable to that of Mn in the presence of KI and Ca; however, KI is less suitable because it causes large memory effects. The present study shows that during the nebulization of the analyte solutions the adsorption of the analytes on the walls of the desolvating tubes and the rejection of the analytes to the drain solutions may occur. The former process is dominant for copper, whereas during the nebulization of As-III and Se-IV in nitric acid, the amount of the analytes in the drain increases. The depressions in the sensitivity for copper can be improved by decreasing the heating temperature of the desolvator and increasing the carrier gas flow rate.