Determination of arsenic in organic solvents and wines using microscale flow injection inductively coupled plasma mass spectrometry

Abstract

The presence of carbon-containing substances can enhance As signals and elevate background levels observed in inductively coupled plasma mass spectrometry (ICP-MS), thus causing potential errors in the quantification of As. Most approaches for eliminating these interferences are tedious and time consuming and increase the risk of sample contamination and analyte loss. A microscale flow injection (µFI) system employing a microconcentric nebulizer (MCN) for efficient sample introduction into the ICP-MS system was used to reduce signal enhancement effects. Also investigated was the suitability of several elements (Se, Y, In and Sb) to be used as internal standards for As in samples containing organic solvents. The µFI-ICP-MS system developed in this study was shown to reduce the signal enhancement caused by organic solvents by a factor of 2-3 compared with a conventional FI-ICP-MS system. Sample volumes of 0.2, 0.5 or 1.0 µl were injected into the µFI-ICP-MS system at carrier flow rates ranging from 50 to 200 µl min ^–1 . Response profiles obtained following the injection of 1.0 µl solutions containing 20 pg µl ^–1 As at carrier flows of 50, 100 or 200 µl min ^–1 , allowed for throughputs of approximately 80, 140 or 180 samples per hour, respectively. The relative standard deviation (%RSD) of the transient signals, determined over a 20 min period at the previously mentioned flow rates, ranged from 2 to 5%. The calculated absolute limit of detection of the µFI-ICP-MS system, ranging from 25 to 59 fg As, demonstrates the method's potential for determining As at ultratrace levels. The µFI-ICP-MS method was subsequently used to determine As in red and white wines. Diluted wine samples (1+1 dilution in de-ionised water) were analysed without any further sample preparation. When using In as the internal standard the average recovery of As was found to be 100±2%. The concentration of As was determined to be between 7 and 13 pg µl ^–1 for all wines examined. These values are significantly lower than the reported maximum permissible concentration limits for As in wine.`mv-8\