Sub-pg levels of carbon monoxide (CO) have been determined by the use of the gas chromatograph equipped with a flame ionization detector and a catalytic reduction unit. This unit for conversion of CO to methane consists of the catalyst tube packed with Shimalite-nickel powder, a thermocouple and an electric heater. The catalytic reduction unit was attached between the separation column and the detector of the gas chromatograph. The specification and optimum operating conditions were as follows: catalyst, Shimalite-Ni, (80˜100) mseh, 3 mm Ø×35 cm(0.81 g); catalyst temperature, (340˜350)°C; carrier gas, hydrogen, (30˜40) ml/min. The quantity of 18 pg of CO was the determination limit which could be actually determined under these conditions. The calibration curve for CO was linear up to the determination limit and the coefficient of variation for mesurements was within 5% on sub-pg levels of CO.
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