Microanalyzer for biomonitoring lead (Pb) in blood and urine

Biomonitoring of lead (Pb) in blood and urine enables quantitative evaluation of human occupational and environmental exposures to Pb. State-of-the-art ICP-MS instruments can only analyze metals in laboratories, resulting in lengthy turnaround times, and they are expensive. In response to the growing need for a metal analyzer capable of on-site, real-time monitoring of trace toxic metals in individuals, we developed a portable microanalyzer based on flow-injection/stripping voltammetry (ASV), and validated the system using rat blood and urine spiked with known amounts of Pb. Fouling of electrodes by proteins often prevents the effective use of electrochemical sensors in biological matrices. Minimization of such fouling was accomplished with suitable sample pretreatment and by establishing turbulent flow of blood and urine containing Pb onto the electrode inside the microanalyzer, which resulted in no apparent electrode fouling even when the samples contained 50% urine or 10% blood by volume. No matrix effect was observed for the voltammetric Pb signals, even when the samples contained 10% blood or 10% urine. The microanalyzer offered linear concentration ranges relevant to Pb exposure levels in humans (0-20 ppb in 10% blood samples, 0-50 ppb in 50% urine samples). The device showed excellent sensitivity and reproducibility; Pb detection limits were 0.44 ppb and 0.46 ppb, and % R.S.D. was 4.9 and 2.4 in 50% urine and 10% blood samples, respectively. It gave similar Pb concentrations in blood and urine to those measured by ICP-MS. It offered high throughput (3 min per sample) and economical use of samples (60 μL per measurement) as well as low reagent consumption (1 μg of Hg per measurement), thus minimizing environmental concerns associated with mercury use. Since it is miniaturized, the microanalyzer is portable and field-deployable. Thus, it shows much promise as the next-generation analyzer for the biomonitoring of toxic metals.