Quantitative determination of mercury in blood-based DL-cysteine-modified direct mercury analyzer method

Occupational mercury poisoning is a significant work-related illness due to that mercury vapor and its compounds can enter the human body and cause systemic damage. Therefore, regular blood mercury monitoring is essential for occupationally exposed individuals. Among existing detection methods, mercury analyzers are widely used for direct blood mercury determination. Despite the utility of direct mercury analyser (DMA), their application to blood samples is often compromised by limitations such as method instability and mercury carryover. To address these challenges, this study introduces a DL-cysteine-assisted determination method. It is based on the principle that DL-cysteine forms stable complexes with mercury in blood, thereby mitigating container adsorption and memory effects. Specifically, DL-cysteine solution was incorporated into both the mercury calibration standards and the blood samples within the sample boat prior to analysis using a DMA. The limit of detection was 0.5 μg/L, and the limit of quantification was 1.5 μg/L. Method accuracy, evaluated by spiked recovery, ranged from 99.14% to 99.92%. Experiments demonstrated that the stability, recovery, and repeatability of the direct mercury determination method were improved by introducing DL-cysteine, which offers practical value in enhancing the performance of direct mercury determination methods and is suitable for routine blood mercury monitoring.