Determination of normal saturated- and polycyclic aromatic hydrocarbons in the river water of Bangladesh by liquid-liquid extraction and gas chromatography

A liquid-liquid extraction followed by evaporative concentration method was used to determine the concentration of normal, or straight chain, saturated hydrocarbons (NSH) (C₁₀ to C₂₄) and polycyclic aromatic hydrocarbons (PAH) here defined as: fluorene, anthracene, pyrene, chrysene and perylene, in the Buriganga River water of Bangladesh. Samples were collected from 5 and 25 cm depth of water at the southern, middle and northern parts of the river at Postogolla, Sadarghat and Sowarighat stations. Hydrocarbons were extracted from 450 mL of water into 75 mL n-hexane and then concentrated into 1 or 2 mL solution by evaporation. These solutions were analyzed by gas chromatography. The highest and lowest concentrations were determined as 257 μg L^-1 for C₁₃ and 0.24 μg L^-1 for C₂₂ at 5 cm depth of water, at the northern part of the Sowarighat and southern part of the Postogolla, respectively. This method could allow the analysis of water for C₂₂ as low as 0.24 μg L^-1.