Developing a method for tracing PCBs in bees and beeswax

Nuura Abshir Yuusuf & Naud Johan Megens

Studenteropgave: Bachelorprojekt

Abstrakt

This project worked on biomonitoring PCB quantities in beeswax collected from beehives from different areas. This is done by replicating methods previously used, these methods are adjusted to get the best results possible. The main focus was developing a useful method, in which PCB quantities can be measured.
Different methods for extracting and quantifying Polychlorinated Biphenyl (PCB) from beeswax were attempted, in order to create an efficient method. The biggest challenge was to remove the wax residues from the samples. Beeswax was extracted with acetonitrile and hexane, the samples were then heated. ASE200 extractor with hexane as solvent was used. This is followed by washing in a separatory funnel. The samples were then washed with sulfuric acid to remove esters, and sodium sodium-carbonate to remove any acids.

Freezing the samples for different durations was attempted for solidification of the remaining waxes in the solvent. Centrifugation is done in order to get rid of any pellet formed. Thereafter the samples were condensed, and washed repeatedly, then the sample was filtered through an SPE column.
The column was eluted and conditioned with PCB mix7, to see which solvents that was best suited. Combinations of acetonitrile and hexane were used. All samples were analysed using a Gas Chromatograph-Mass Spectrometer (GC-MS) to identify PCB congeners in the samples.

To identify the efficiency of the methods applied, all samples had a C13 PCB52 internal standard added during the beeswax extraction. PCB was only observed in the beeswax sample that was extracted with acetonitrile:ethanol (1:1). Calculations of the data obtained by the GC-MS suggest that the sample contained 625.2ppb PCB sum 7 per gram beeswax. Concentrations of the individual PCBs were equal to that found in the literature. This was the amount found in literature. Only the added internal standard could be recovered in the other samples, at a retrieval rate of 10%. PCB seemed to freeze out of the solvent when freezing the sample for longer than an hour, as observed during the ASE200 extraction.

A series of column methods with PCB mix7 as sample was tried with different solvents for the column, conditioning and eluting created different speed of elution, but differences were minor. The PCB mix7 internal standard retrieval rate on the SPE was 53% compared to the PCB mix7 sample that didn't get filtered through the column.

UddannelserBasis - Naturvidenskabelig Bacheloruddannelse, (Bachelor uddannelse) BachelorBasis - International Naturvidenskabelig Bacheloruddannelse, (Bachelor uddannelse) Bachelor
SprogEngelsk
Udgivelsesdato19 dec. 2016
Antal sider49
VejledereJohn Mortensen