Desolvation-induced non-linearity in the analysis of bromine using an ultrasonic nebulizer with membrane desolvation and inductively coupled plasma mass spectrometry

Abstract

Ultrasonic nebulization coupled with a membrane desolvator is used for the introduction of bromine containing samples in inductively coupled plasma mass spectrometry. Severe non-linearity (R² = 0.9317) is observed when ammonium bromide (NH₄Br, 0–100 ng mL⁻¹) solution is nebulized, suggesting the loss of bromide ions at the desolvation stage. It is proposed that the primary reason for this phenomenon is the formation of gaseous HBr and its subsequent removal in the desolvation unit. In order to preserve the linearity in the calibration curve, excess NaCl (1 μg mL⁻¹ of Na) is added to the solutions, resulting in a perfectly linear (R² = 0.9999) calibration curve. However, in the presence of a strong acid (2% HNO₃), no significant improvement in the linearity is observed with the addition of NaCl. Bromine signal enhancement and improved linearity are also observed when 1 μg mL⁻¹ of Na is added to KBr solutions. Also, addition of 2% HNO₃ to KBr solutions results in signal suppression through the formation of HBr.