Determination of mono- to octachlorobiphenyls in fish oil using florisil adsorption followed by headspace solid-phase microextraction and gas chromatography with time-of-flight mass spectrometric detection | |
| Author | Agustin, Mary Rose R. |
| Call Number | AIT Thesis no.EV-05-36 |
| Subject(s) | Fish oils Gas chromatography--Industrial applications |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science |
| Publisher | Asian Institute of Technology |
| Abstract | Determination of Polychlorinated biphenyls (PCBs) in oily matrices has proven to be technically challenging, this can be attributed to the high affinity of PCBs to lipophilic substances such as fish oil. A simple and reliable method for the determination of Polychlorinated biphenyl from mono- to octachlorobiphenyls in fish oil for dietary supplement is described. The method combines Florisil cleanup and headspace solid-phase microextraction on a 65m polydimethylsiloxane-divinylbenzene (PDMS-DVB). Analyte detection was carried out using GC-time-of-flight mass spectrometry. 53 PCB congeners including the seven indicator PCBs (IUPAC Nos. 28, 52, 101, 118, 138, 153 and 180) were analyzed. Several parameters have been optimized to fully exploit the capability of the proposed method to detect monochlorinated biphenyls up to octachlorinated biphenyls. The adsorption parameters : adsorbent type and adsorbent weight ,vere optimized. Silica gel, alumina and Florisil were used to test for adsorbent type. Although all of them are relatively cheap and of comparable cost, 6 grams of Florisil was chosen to be the adsorbent weight and adsorbent type of choice, since this combination gave the optimum response towards the analytes of concern. Moreover, factors affecting SPME were evaluated. For the extraction time, non-equilibrium condition was used, this is because, it was found out that 60 minutes was not enough to attain equilibrium condition and waiting for the equilibrium time to be achieved would be too long for this specific analytical technique. Thus, for practicality 40 minutes was chosen to be the extraction temperature to be used throughout the experiment. An extraction temperature of 90 °C was chosen over 100 °C since the latter gave poor data precision due to the water that condenses around the SPME fiber. An injection depth of number 3 in the SPME needle auge guide gave an optimal chromatographic response and a desorption time of 260 C was used following the manufacturer's recommendation. A desorption time of 3 minutes gave the minimal carry over and is the shortest time possible to desorb analytes from the fiber completely while allowing quantitative analyte detection and fiber cleaning. Addition of salt, NaCl, was also evaluated. When I gram of salt was added to aqueous PCB solution, the SPME extraction of PCBs was enhanced. However, when this amount of salt was added to the fish oil eluate, non-addition of NaCl gave a better response. This may be due to the change in the ionic strength of the solution, which was brought by the addition of salt. When salt is added to the aqueous solution, the ionic strength of the solution increases, thus, PCBs do not dissolve in the aqueous solution and hence extracted selectively by the non-polar SPME fiber. However, in the fish oil eluate, the addition of salt likewise increases the ionic strength, but in this case, some oil droplets from the fish oil eluate are present. Therefore, PCBs preferentially dissolves their selves in this oily layer, making it difficult for their transfer to the SPME fiber, hence non-addition of NaCI gave a better response. Under optimal conditions, the method detection limit (MDL) of each congener in the range of 0.8 ng/g to 31 ng/g was found. The sum of the 7 indicator PCBs (59 ng/g) was low enough to satisfy the tolerance level set by the European Commission which is 200 ng/g, while the sum of MDLs for the 53 PCB congeners (505 ng/g) satisfied the FDA tolerance level which is 2000 ng/g. In both cases, the proposed method will be highly relevant and useful. A certified reference material (BCR-349) was analyzed and it showed good agreement with the certified data. Furthermore, it can be concluded that this method works well even in the low ng/g level (as low as 2ng./g ) as can be seen in the working linear range and as high as g/kg levels as depicted by the accurate quantification of the PCBs in the certified reference material, BCR-349 (certified values of PCBs in BCR-349 are in the g/kg level). For future studies, the proposed method can be compared to other standard methods such as Soxhlet extraction and other relatively new methods such as Supercritical Fluid Extraction (SFE), Pressurized Liquid Extraction and Microwave Assisted Extraction (MAE) to test how the proposed method fare with other analytical technique in PCBs determination, specifically in fatty matrices |
| Year | 2005 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Lee, Kang-Bong; |
| Examination Committee(s) | Preeda Parkpian;Park, Hyun-Mee; |
| Scholarship Donor(s) | Korea Institute of Science and Technology;Asian Institute of Technology,; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2005 |