The regression line of peak area ratios of cyanide to the internal standard on concentration using a least-squares fit had a linear relationship with y = 0.7140x + 0.1997 (for working range of 0.07–10.0 mg L1) and r2= 0.9963, where x is the cyanide concen-tration (mg L1) and y is the peak area ratio of cyanide to the internal standard.