Non-chromatographic separation and determination of thimerosal and inorganic mercury in vaccines by Fe3+-induced degradation with cold vapor atomic fluorescence spectrometry

Abstract

An effective, rapid and inexpensive method without chromatographic separation was proposed for the determination of thimerosal (THM) and inorganic mercury (IHg) in vaccine samples, based on Fe³⁺-induced degradation of THM in a commercially available atomic fluorescence spectrometer (AFS). In the proposed method, inorganic mercury was measured at a low concentration of KBH₄ (0.005%, m/v) in the absence of Fe³⁺, while the total mercury (THg) was determined by measuring the same fluorescence signals of IHg and THM, which was effectively degraded and reduced in the presence of 10 mg L⁻¹ Fe³⁺ and a relatively high concentration of KBH₄ (1.0%, m/v). Then, the concentration of THM can be obtained by subtracting IHg concentration determined in the absence of Fe³⁺ from THg concentration in the presence of Fe³⁺. The parameters influencing mercury determination were optimized in detail, including Fe³⁺ concentration, the concentration of the KBH₄ reductant and HCl carrier, and the carrier gas flow rate. Under the optimized conditions, the limits of detection for THM and IHg were 0.03 μg L⁻¹ and 0.02 μg L⁻¹, respectively. Spiked commercial vaccine samples including hepatitis-B and rabies vaccines were analyzed. Satisfactory recoveries were obtained for both THM and IHg.