Inadvertent introduction of squalene, cholesterol, and other skin products into a sample.

Recent developments in analytical techniques permit the chemical ecologist to achieve identification of naturally occurring compounds with relatively small amounts of the products of interest. However, the microanalytical techniques employed frequently require the handling of sample vials and other transferral instruments such as syringes and micropipets, where the analyst's hands come into close contact with the sample. Here we show how inadvertent contamination of a sample with skin lipids can occur simply by catching a 1-ml sample vial by the neck rather than the base or by activating a syringe by holding the plunger extension between the fingers rather than taking it by the head. Squalene, cholesterol, and, to a lesser extent, hydrocarbons and fatty acids from fingers are easily introduced into the sample in this manner. These findings are particularly relevant for a parasitology laboratory such as ours, investigating the function of vertebrate-derived products in hematophagous arthropods.