The determination of opioids, cocaine, and metabolites from blood serum is a routine task in forensic laboratories. Typical methods include many manual or semi-automated steps like protein precipitation, dilution, solid phase extraction, evaporation, and derivatization preced¬ing GC/MS or LC/MS analysis. In this study, a validated, semi-automated routine method was completely automated by replicating method parameters on an automation platform that also performs the sample injection step. Only marginal optimization of parameters was necessary. The automation platform utilizes an x-y-z robot with modules to perform solid phase extraction, evaporation of the eluate, derivatization, and injection into a GC/MS.
For the semi-automated method a RapidTrace SPE Workstation using standard SPE cartridges was used. Evaporation of the eluates was performed using a ten vial position heating block where each position was equipped with a nitrogen gas stream.
The automation platform was based on a GERSTEL Dual Head Single Rail (DHSR) MultiPurpose Sampler (MPS), equipped with a solid phase extraction module, solvent filling stations, agitator, solvent evaporation station, wash stations and appropriate vials trays. Two syringes were mounted on the MPS, one (2.5 mL) for sample preparation and one (10 uL) for sample injection. The entire platform was mounted on a 6890 GC/5975 MSD (Agilent Technologies). Injections were made into a GERSTEL Cooled Injection System (CIS) installed into the GC.
Although analyses for the two methods were performed on different systems (7890GC/5975 MSD for semi-automated and 6890GC/5975 MSD for automated), methods parameters were similar and did not contribute to differences in data obtained.
Results and Discussion
Analysis of almost 170 authentic serum samples and more than 50 authentic samples of other matrices like urine, tissue, and blood was conducted. Co¬caine, benzoylecgonine, methadone, morphine, codeine, 6- monoacetylmorphine, dihydrocodeine, and 7- aminoflunitrazepam were determined by both methods and the results were shown to be equivalent – even near the limits of quantification (low ng/ml range).
The method was shown to be robust (no instrument failures), and by using the sample overlapping feature provided by the GERSTEL Maestro software, a sample throughput comparable with the semi-automated method of around 29 samples per day was achieved. To the best of our knowledge, this application is the first one reported in the literature employing this sample automation platform.