Sources of Organic Contaminants in Solvents and Implications for Geochemistry and Environmental Forensics: An Example from Local Vendors in Nigeria

Two solvents, n-hexane and petroleum ether, commonly used for extract analysis of geological and environmental samples and purchased from chemical suppliers in Nigeria, were analyzed using gas chromatography-mass spectrometry for quantitative determination of organic background contaminants. Series of n-alkanes and n-alk-1-enes in the carbon number range of nC(16)-nC(26), the latter with an even predominance (C-max 16 and 18) were observed. Such alkanes, previously and exclusively assigned a biogenic origin in sediments from the Calabar and Cross River Estuary, are considered here to be derived as distillation residues (n-alkanes) and from leaching of by-products from the production of polyethylene/polyvinyl chloride plastic containers (n-alkenes) where these solvents were stored. Significant concentrations of low molecular weight parent and alkyl polycyclic aromatic hydrocarbons were detected (mainly naphthalene series) and most likely reached the solvents as production residues (crude distillation) and/or cross contamination during storage/laboratory transfer. Plastic additives such as DEHP and DOA(plasticizers) and tris(2,6-di-tert-butyl) phenylphosphate (anti-oxidant derivative) were detected at high levels, also most likely leached from the plastic storage containers by the solvents.