Benzyl alcohol interference from heparin lock flush solutions in a high pressure liquid chromatographic procedure for...

During the course of a pharmacokinetic study of the antibiotic mezlocillin, we observed an interfering peak in the high pressure liquid chromatographic analytical procedure that was identified as benzyl alcohol. The benzyl alcohol interferent was traced to a preservative in heparin and saline solutions used to flush heparin locks and indicated that the heparin lock purge volume was inadequate to clean the flushing solution. The present study uses this as a model to study the amount of dilution and contamination interference observed in a controlled study where the purge volume was varied for two "real situation" concentrations of benzyl alcohol in the flush solution. It was found that only 0.5 ml of purge must be drawn to avoid significant contamination interference if benzyl alcohol-free saline is used for dilutions. Contamination interference from benzyl alcohol can also be avoided by spectroscopic or chromatographic resolution if the interference is identified and the particular analyte in question can be resolved. The results of this study provide valuable information for any study in which heparin locks are used and especially in procedures where benzyl alcohol may interfere with the method of analysis. If saline containing benzyl alcohol is used for the dilution of heparin solutions, 1.0 ml of purge must be drawn.