Linear alkylbenzenes (LABs) are manufactured for the production of specific surfactants used in commercial detergents. Although most LABs are consumed in the process, small amounts persist and are carried, mainly through household detergent use, into wastewater and ultimately into the environment. LABs consist of a mixture of secondary phenylalkanes with linear alkyl side chains ranging in length from C10 to C14. Because of their unique structure and compositions, they are easily identified and measured in complex environmental samples. Because they are not rapidly degraded, they are useful as waste-specific tracers.

LAB determination is a quantitative technique used for the determination of twenty-four different C10 to C14 LABs in extracts of sediment or water. Quantitation is performed by capillary gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode (SIM). The gas chromatograph is temperature-programmed and operated in splitless mode. The capillary column is a J&W Scientific DB-5MS (30 m long by 0.25 mm ID and 0.25 mm film thickness), or equivalent. The data acquisition system allows continuous acquisition and storage of all data during analysis and is capable of displaying ion abundance versus time or scan number.

A sample batch is analyzed as an analytical set including samples along with the following specified quality control samples: method-blank, matrix-spike, and matrix-spike duplicate.

A calibration curve is established by analyzing each of five calibration standards (analyte concentrations ranging from 0.02 to 1 mg/mL) and determining a relative response factor (RRF) for each analyte. Calibration check standards are interspersed throughout an analytical batch in order to insure the instrument's integrity. LABs not contained in the calibration solution are assigned the same RRF as the most structurally similar compound contained in the calibration solutions. Analyte concentrations are determined using the internal standard method.