Determination of Mercury in Artificial Saliva Extract of Chewing Tobacco by Dispersive Liquid–Liquid Micro-Extraction Using Electrothermal Atomic Absorption Spectrometry (ETAAS)

Abstract

An enrichment method was developed for the determination of inorganic mercury (Hg) in artificial saliva extracts (ASE) of frequently consuming chewing tobacco products (CTP). The artificial saliva extracts of the mainpuri and gutkha chewing tobacco were subjected to dispersive liquid-liquid micro-extraction (DLLµE) based on the ultrasound based back extraction of hydrophobic complex of inorganic mercury (iHg) separately by L-cysteine and hydrochloric acid. The total Hg, extractable Hg (_EHg), and enriched inorganic mercury in artificial saliva extracts of chewing tobacco were determined by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma – optical emission spectrometry (ICP-OES). The results obtained by these techniques were not significantly different (p > 0.05). Factors affecting the extraction efficiency of inorganic mercury such as concentration of the ligand, pH, disperser/extracting solvent, sonication time, and back extracting reagents were optimized by multivariate techniques. The precision and accuracy of total mercury (tHg) was confirmed by analyzing a tobacco certified reference material, while the validity of the proposed method (DLLµE) was ensured by spiking inorganic mercury in artificial saliva extracts of the chewing tobacco products. Using the optimized conditions for developed method, the limit of detection and enrichment factor for inorganic mercury were 0.17 μg/L and 96.2, respectively. The extractable Hg in artificial saliva extracts of chewing tobacco was from 35 to 48% of the total content. However, the concentration of inorganic mercury was between 68 and 80% of the total extractable concentration in artificial saliva extracts of the chewing tobacco.

Keywords:

• dispersive liquid–liquid micro-extraction
• mercury
• electrothermal atomic absorption spectrometry
• multivariate techniques
• chewing tobacco
• artificial saliva extract

Conflict of interest

All authors declare no conflicts of interest.

Acknowledgments

The authors would like to thank the National Centre of Excellence in Analytical Chemistry (NCEAC) at the University of Sindh Jamshoro for providing excellent laboratory facilities to carry out this work.