Abstract
Conditions are given for the most efficient operation of the microcoulometric gas chromatograph as a multiple detection technique for residues of chlorinated pesticides. Conditions are as follows: Column, aluminum, 6’ long by 4.5 mm i.d., packed with 10% DC 200 silicone fluid (12,500 est) on 80/90 mesh Anakrom ABS (conditioned 1—5 days at 250°C), 210°C column temperature, and 120 ml/min. N2 flow.
Chromatography of certain pesticides is improved by injection of cleaned up crop extracts. Columns with a minimum number of bends are superior to coiled columns. Chromatography is not improved by using glass columns. Relative retention times and instrument sensitivity are tabulated for 87 chlorinated and 26 thio pesticide chemicals. Theoretical chloride recoveries are given for 14 compounds and sulfur recoveries for 3 compounds. Theoretical recoveries indicate that the MCGC system is linear for a particular pesticide when it is present above some minimum quantity. Sample cleanup is essential for consistently accurate and reproducible results. The general level of "maximum sensitivity" of this multiple detection technique is approximately 0.01 ppm. The specificity of the detection system (for CI-, Br-, I- or sulfur) is the instrument's greatest virtue.
High-throughput fabrication and calibration of compact high-sensitivity plasmonic lab-on-chip for biosensing
