The first parameter investigated was the delay time. This is the time in seconds which elapses between the probe of the autosampler reaching the fully down position and the absorbance reading becoming stable. For a 0.02 μg/mL mercury standard in 40% v/v nitric acid the delay time required is 55 seconds (Figure 1). The same concentration of mercury in 20%, 30% and 50% v/v nitric acid requires the same delay time, but higher concentrations of mercury take a few seconds longer to reach a steady signal.