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Results and Discussions
The time resolved data from Varian ICP-MS Expert was exported as a .CDF fi le and opened in the Galaxie software, where program data analysis was performed. For reviewing acquired data, Galaxie provides an easy way to view single or multiple chromatograms, and compare results in a single screen.
Elemental speciation
Speciation of the fi ve inorganic and organic arsenic species can be performed using either an isocratic or gradient LC method (see Figures 2 and 3). Using either method, excellent calibrations for each of the arsenic species were obtained with calibration coeffi cients ≥ 0.999 achieved when calibrating on solutions ranging from 0.01 to 50 μg/L. An example calibration curve for MMA is shown in Figure 4. Note the low calibration solution in this calibration is 0.01 μg/L (10 ng/L).
While the gradient method increases the analysis time by approximately 9 minutes (4 minutes increased analysis time and 5 minutes column re-equilibration), it does provide better separation of As(III) from DMA, and improved separation from potential interferences. For example, samples with a high Cl content can result in an additional peak (75ArCl). As shown in Figure 5, the gradient method adequately separates the Cl peak from the neighbouring MMA and AsV peaks.
Typical detection limits
Table 4 shows the typical detection limits (DLs) for the fi ve common organic and inorganic forms of arsenic. All the measurements were made under routine analytical laboratory conditions, not clean-room conditions. This work indicates typ
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