Direct analysis of herbicides by paper spray ionization mass spectrometry

Measurement of herbicide residues in environmental matrices is typically performed using liquid or gas chromatography coupled to mass spectrometry, generally with one or more stages of sample processing or purification prior to analysis. Paper spray ionization enables the rapid mass spectrometric analysis of such samples without the use of chromatography or sample cleanup techniques. Samples are applied to a paper strip and dried, after which they may be stored or transported. By applying solvent and a high voltage to the paper strip, the analyte is extracted from the paper and ionized by electrospray from the tip of the paper strip. Qualitative and quantitative measurement of triazine herbicides and the chloroacetanilide herbicide metolachlor are demonstrated using samples spiked into water and crop extracts at part-per-billion concentrations. The linear dynamic range includes the U.S. statutory maxima for atrazine in crops and human health hazard levels in water, as well as E.P.A. levels of concern and regulatory limits for metolachlor in crops and water.