For several decades ago, dried blood spot (DBS) was presented as an alternative matrix for measurement of drug concentrations but up today there is no one have used dried saliva spot (DSS) as an alternative sampling technique in bioanalysis. Dried saliva spot (DSS) was used for first time by my group as new sampling technique for saliva samples.
The DSS technique contains placement of a small amount of saliva (50 µL) onto filter paper by micro syringe, the liquid saliva was let for drying at room temperature in a few minutes; then the analyte was extracted from filter paper by adding 100-150 µL acetonitrile contained the internal standard and then vortex for 30 seconds. The last step is transferring the organic phase to the autosampler for injection (30 µL was injected). DSS format offers a simple and rapid method of handling saliva and is suitable for a quantitative and qualitative analysis.
A new sampling technique for saliva using dried saliva spot (DSS) was developed by my group. The use of the DSS technique with LC-MS/MS as a tool for the screening and determination of lidocaine in saliva samples was established. The method is very easy, has a low cost and is convenient in terms of storage. The DSS technique provides speed and the simplicity to the sample-preparation process. The present method is the first application of DSS to handle human saliva. DSS has potential advantages over other sampling methods as it is requiring a micro sample volume (50 μL) and has the potential to overcome difficulties associated with plasma or blood. It does not need special storage; lidocaine is stable within DSS samples at room temperature for many days. In addition DSS can be used for the screening of drugs, metabolites and hormones. Further, DSS in combination with direct analysis in real time (DART) mass spectrometry should be useful for drugs of abuse testing. DSS can open a new dimension in drug analysis since it eases the bioanalysis process in terms of sampling, storing and transport.