Polychlorinated biphenyls (PCB), chlorobenzenes (CB) and organochlorine pesticides (OC) data from rivers [LOIS]

Prior to analysis the samples were stored in the dark at 4 degreesC. The sample (500ml) was transferred to a volumetric flask and extracted with 5 x 10ml aliquots of hexane. The hexane extract was transferred to a to a Kuderna-danish flask via a funnel containing anhydrous sodium sulphate and reduced to approx. 1.5ml at 80 degreesC. The extract was adjusted to exactly 1.0ml under a stream of nitrogen. The whole of the reduced extract was cleaned up on a glass column containing 0.8g of alumina deactivated with 5% water. The cleaned up extract was then reduced to 0.5ml under a stream of nitrogen. An internal standard was added (Dichlobenyl) and each extract split equally into two chromatography vials. Chlorobenzenes were analysed by GC-MS in select ion mode. Organochlorine pesticides and PCB congeners were analysed by GC-ECD. A spiked recovery and a sample blank were included with each batch of samples. The results were not corrected for recovery losses. Limits of detection were defined as the concentration of analyte that gives a signal twice that of the baseline noise. Blank sample bottles were taken into the field during sample collection and opened and closed on site. The blank bottles were extracted with 5 x 10ml of hexane and the hexane extracts analysed by the procedure used for the samples. Spiked recovery samples (hexane washed HPLC grade water, containing 0.5g of clean clay particles, spiked with all the analytes) were included in each batch. OCs and PCBs were identified by relative retention time. CBs were identified by relative retention time and ion ratios (3 ions). Calibration was by the internal standard method. A zip file of box-and-whisker plots for each determinand is available, showing the range of values (median, inter-quartile range, 1.5 * inter-quartile range, outliers) recorded at each site to enable prospective users to understand data quality.