Abstract
The new approach to automate stationary techniques to analyze gas using a stepwise injection analysis (SWIA) is revealed and determination of hydrogen sulfide in natural gas using SWIA is described. The determination is based on absorption of hydrogen sulfide into open to the air reaction tube with 2% zinc acetate solution, stepwise injection of the reagents to the reaction tube to form a methylene blue and subsequent measurement of the downstream colored product at 670 nm. The open to the air reaction tube is a part of hydraulic system and has PTFE granules to increase a surface area during the gas sample bubbling. Nitrogen was purged to the reaction tube for enhanced mixing. All experimental manipulations were controlled by software. The absorbing solution has an absorption efficiency of >98% at a sampling flow rate of 0.3 l/min. This method provides a linear working range of 0.5 to 20 mg/m3 with a relative standard deviation of 2.5 % (n=10) at the 5 mg/m3 level for 3 liters of gas sample and concentration time of 10 min. The determination limit of 0.1 mg/m3 was achieved using 3 liters of gas sample and time of one cycle of 18.5 min.
