Thomas Richards and Michael J. Shifflet Merck & Co.s Danville, PA.

In pharmaceutical manufacturing one reaction vessel can be used for several products or a reaction vessel may employ a special solvent for cleaning purposes. It is imperative to the integrity of the next product that is produced in that reaction vessel, that the reaction vessel be free from prior contamination. The cleaning process involves filling the reaction vessel with a solvent, in this case water, and drained. A reaction vessel is considered to be free of a contaminating solvent, if the concentration of that solvent in the wash water is less than 10 ppm. Our lab has developed a GC assay that can detect 1,2-dichloroethane, methanol and toluene at the 10 ppm level.

The assay employs an HP 5890 series II gas chromatographic unit with an HP 7673A auto injector. A 30 m wide bore (0.53 mm diameter, 1 mm stationary phase) DB-1 gas chromatographic column was used with He (7 mL/min) as the mobile phase. The analytes were detected by flame ionization and the signal was processed using an SP4400 integrator.

The assay is linear in the range of interest (0 to 100 ppm). All four analytes are reproducible at 10 ppm. The total analysis time is short (8 min).