Direct Determination Of Metals In Alcoholic Samples By Inductively Coupled Plasma Mass Spectrometry With Chip-based Microflow Injection Systerm

The determination of elements in alcoholic samples is closely related to the health of the drinkers. Currently, inductively coupled plasma mass spectrometry (]CP-MS) is one of the most used techniques for the determination of trace elements in wines, due to the high sensitivity together with multi-elemental capabilities. Alcoholic sample is a complex matrix which contains, in addition to ethanol, a variety of inorganic and organic substances. For elemental analysis, samples could undergo some pre-treatment steps such as vaporization, ashing or acid digestion,. However, these methodologies suffer from several drawbacks including complex and time consuming procedure, high risk of contamination and/or loss of analyte. The goal of this work is to fabricate a microfluidic chip to introduce variable-volume sample in the sub-microlitre level for direct determination of metals in alcoholic samples by inductively coupled plasma mass spectrometry.In the first chapter, the methods of routine multi-element analysis of alcoholic samples, the matrix effect of ICP-MS, and flow injection hyphenated with ICP-MS techniques coupling to flow injection were reviewed.In the second chapter, a microfluidic chip for introducing variable-volume sample was fabricated. Combined with the8-way multifunctional valve used in flow injection analysis, the introduction of sub-microlitre sample in inductively coupled plasma mass spectrometry (ICP-MS) was realized.52%ethanol was used to simulate the distilled spirit. The effects of the volume of the52%ethanol introduced into ICP-MS on ICP stability and the spectral interference from the spirit matrix were studied. The relationship between the sampling volume and sensitivity was evaluated. The carrier flow rate was optimized. The experimental results showed that neither alteration of plasma stability nor carbon deposition was observed when the sampling volume of52%ethanol reduced down to0.8μL. Further reducing the sampling volume to0.3μL, the interference from carbon was eliminated. Based on these observations, a microflow injection method for the determination of lead and cadmium in distilled spirits by ICP-MS using external aqueous calibration was developed.