Effect of water vapour on the determination of trace substances trapped on activated carbon

Abstract

The effect is studied of the activated carbon moisture on the recovery (R) of some organic substances, viz. benzene, acetone, tetrahydrofuran, ethanol, 2-methyl-1-propanol, and 1-butanol, trapped from air of different humidity and desorbed with carbon disulphide to equilibrium. If the weight fraction of water in the activated carbon is w = 0.02, the variations of R lie within the limits of error (for 0.3 g of activated carbon and 5 ml of CS2), whereas if w = 0.15, the variations of R, if disregarded, can result in errors as high as -45% for ethanol and -6 to -12% for butanol and acetone. In the case of benzene and tetrahydrofuran, the increase in the water content in the carbon does not affect the R value. The error increases as the activated carbon-to-carbon disulphide weight ratio is raised. For the standard addition method, the relative error was in average 18% (largely negative) for ethanol and -4.5 to -13% for the remaining substances.