Polymethylpentene test tube

The arsenic species (iAs, MMA, and DMA) in urine were determined using an atomic absorption spectrophotometer (AA-6800) with an arsenic speciation pretreatment system (ASA-2SP, Shimadzu Co., Kyoto, Japan). The speciation analysis involved the well-established hydride generation of volatile arsines, followed by cryogenic separation in liquid nitrogen. The detection limit of 1 ng( ± < 5%) for all three arsenic species was determined by hydride generation-atomic absorption spectrometry (HGAAS). Brie y, 1 mL urine that was stored at-80°Cwas thawed at room temperature and digested with a 1 N NaOH solution at 100°C for 3 h in a 15 mL polymethylpentene test tube (Sarstedt), followed by dilution with Milli-Q water (Millipore, Yonezawa, Japan). Yamauchi and Yamamura, 1984 found that the digestion procedure did not alter the distribution of iAs or methylated arsenicals.
The absorbance of arsenic in the digested urine samples was recorded at 193.7 nm.

We determined As species (iAs, MMA and DMA) in the urine and liver using atomic absorption spectrophotometer (AA-6800) with an As speciation pretreatment system (ASA-2SP; Shimadzu Co., Kyoto, Japan) as we reported previously (Sun et al., 2007) . Total As species (tAs) were calculated as sum of iAs, MMA and DMA. Briefly, 1 mL of urine that had been stored at -80°C was thawed at room temperature and digested with 2 M NaOH solutions at 100°C for 3 hr in a 15-mL polymethylpentene test tube (Sarstedt) followed by dilution with deionized water. The assay samples were stirred once every 60 min. The concentrations of arsenicals in urine were corrected by individual urinary concentration of creatinine (Cr). The calculation formula of As species in the urine is tAs*N/Cr (μg As/g Cr), where N is the dilution ratio. A 50-mg liver sample was homogenized by adding 2.0 mL of deionized water, and then mixed with 1.0 mL of 3 M H 2 SO 4 . The samples were digested in a focused microwave field during a period of 10 min in a 10-mL polymethylpentene test tube. The calculation formula of As species in the liv-er is tAs*3/50 (μg As/g wet wt). Two indices, the first methylation ratio (FMR) and secondary methylation ratio (SMR) were introduced to evaluate methylation capacity, which were calculated as (MMA+ DMA)/tAs and DMA/ (MMA+DMA), respectively.