Frontal elutionpaper chromatography for ambient ionization mass spectrometry: analyzing powder samples

Abstract

We developed a convenient method by coupling frontal elution paper chromatography with desorption corona beam ionization mass spectrometry (FEPC/DCBI-MS) for rapid analysis of powder samples. In this method, the powder was deposited directly onto a coarse strip near the base of a triangular paper sheet, and then a strong elution solvent was pipetted onto the base of the paper sheet in the open air for developing. The sample zone migrated at the solvent front under strong elution conditions. Target analytes were finally condensed at the V-shaped tip which was then placed under the visible plasma beam of DCBI for ionization. Steps of solvent extraction and developing were performed on a paper sheet simultaneously. The overall procedure requires less than two minutes. Signal intensities of target analytes were improved significantly due to analyte condensation at the tip and matrix effect reduction. Fundamentals and applications of FEPC/DCBI-MS were demonstrated by analysis of chlorphenamine in herbal medicines, clenbuterol in pig feed powder and nicotine in house-hold dust. The limits of detection ranged from 0.35 μg g⁻¹ to 1.5 μg g⁻¹ (0.52–2.2 ng, absolute) in full-scan positive-ion mode. The linear range was 5.0 μg g⁻¹ to 5.0 × 10² μg g⁻¹ with satisfactory linear coefficient (R² = 0.885–0.956). Good reproducibility was achieved with relative standard deviations (RSDs) less than 20% and the recoveries ranged from 70 to 90%. The results demonstrate that the improved FEPC-DCBI-MS method is satisfactory for semi-quantitative evaluation of analytes in powder samples.