Assay of nicotine in biological materials: sources of contamination and their elimination

A previous method for the measurement of nicotine in biological samples was subject to occasional interference from a contaminant which eluted simultaneously with the internal standard (quinoline). This has been rectified by substituting isoquinoline as the internal standard and modifying the operating conditions of gas chromatography. Other source of contamination in nicotine assays such as the analytical reagents, the atmosphere and the sample itself are discussed in detail.