Determination of small sample volumes in the analysis of drugs at specific sites in the oral cavity.

Two methods for the determination of sample volumes between 0.2 and 0.6 microliters were compared by preparing standard curves for volumes over this range. The first method used a Periotron and the second the sample mass. A linear model was fitted and 95% confidence limits for volumes estimated by each method were calculated. This showed that use of either the maximum Periotron reading or the sample mass allowed estimation of volumes to within +/- 0.056 microliter and +/- 0.047 microliter respectively. It is proposed that measurement of sample mass provides a simple and accurate method to determine sample volume when analysing drug concentrations at specific sites in the oral cavity.