Automated, continuous, and dynamic speciation of urinary arsenic in the bladder of living organisms using microdialysis sampling coupled on-line with high performance liquid chromatography and hydride generation atomic absorption spectrometry

摘要

An on-line and fully automated method was developed for the continuous and dynamic in vivo monitoring of four arsenic species [arsenite (As-III), arsenate (As-V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)] in urine of living organisms. In this method a microdialysis sampling technique was employed to couple on-line with high performance liquid chromatography (HPLC) and hydride generation atomic absorption spectrometry (HGAAS). Dialysates perfused through implanted microdialysis probes were collected with a sample loop of an on-line injector for direct and automated injection into HPLC system hyphenated with HGAAS. The saline (0.9% NaCl) solution was perfused at the rate of 1 mul min(-1) through the microdialysis probe and the dialysate was loaded into 50 m l of sample loop. The separation conditions were optimally selected to be in phosphate buffer solution at a pH 5.2 with a flow rate of 1.2 ml min(-1). The effluent from the HPLC was first mixed on-line at the exit of the column with HCl (1 M) solution and then mixed with a NaBH4 (0.2% m/v) solution. Based on the optimal conditions obtained, linear ranges of 2.5-50 ng ml(-1) for As-III and 6.75-100 ng ml 2 1 for the other three arsenic species were obtained. Detection limits of 1.00, 2.18, 1.03 and 2.17 ng ml 2 1 were obtained for As-III, DMA, MMA and As-V, respectively. Typical precision values of 3.4% (As-III), 5.4% (DMA), 3.6% (MMA) and 7.5% (As-V) were obtained, respectively, at a 25 ng ml 2 1 level. Recoveries close to 100%, relative to an aqueous standard, were observed for each species. The average in vivo recoveries of As-III, DMA, MMA and As-V in rat bladder urine were 56 +/- 5%, 60 +/- 9%, 49 +/- 3% and 55 +/- 7%, respectively. The use of an on-line microdialysis-HPLC-HGAAS system permitted the determination of four urinary arsenic species in the bladder of an anesthetized rat with a temporal resolution of 50 min sampling. [References: 32]