PCBs DETERMINATION IN TRANSFORMER OIL BY SPE AND GAS CHROMATOGRAPHY ANALYSIS

PCBs DETERMINATION IN TRANSFORMER OIL BY SPE AND GAS CHROMATOGRAPHY ANALYSIS Bogdevich O.P. *, Cadocinicov O.P. * Institute of Geophysics and Geology, Laboratory of Geochemistry GEOLAB Academiei str. 3, of. 133, Chisinau, MD2028, Moldova, Tel: 373-22-739636; Fax: 373-22-739663; e-mail: bogdevicholeg@yahoo.com Keywords: Gas Chromatography, Polychlorinated biphenyl s (PCBs), Solid Phase Extraction (SPE), transformer oil. Summary The aim of this work is the development of the PCBs determination method in the transformer oil by the SPE and Gas Chromatograph analysis. The proposed method was used for the cleanup of modeling solutions of transformer oil polluted by PCBs congeners and Aroclor1254. PCB 209 was used as internal standard for quantitation purposes. Octadecyl bonded silica phase AccuBOND C18 100mg/1ml cartridge was chosen for extraction performing. This technology has shown a very good recovery (84 109 %) and accuracy for investigated samples. The following advantages can be indicated for this method in comparison with others: a little solvent amount, a short labor time, a low analysis cost, a good recovery and accuracy. By this case this method can be recommended for PCBs determination in the complex oil matrix. 1. Introduction Polychlorinated biphenyl s (PCBs) are a subset of the synthetic organic chemicals known as chlorinated hydrocarbons. PCBs have been produced in high volume by the chemical industry and used as additives to oils in electrical equipment, hydraulic machinery, and other applications where chemical stability has been required. These organic compounds can be transported for long distances, and have been detected in the furthest corners of the globe, including places far from where they were manufactured or used. Since PCBs exhibit a high degree of chemical and biological stability and also lipid solubility, they tend to accumulate in the food chains and have been detected in animal and human tissues [2,6,17]. Protection of human health and the environment requires that PCBs be disposed of in such a way that they do not enter the environment. The important step in the environmental management of PCBs is to identify their sources and develop strategies for reducing or eliminating their release into the environment. The chemical formula for PCBs is C 12 H (10-n) Cl n, where n is a number of chlorine atoms within the range of 1-10. Theoretically, a total of 209 possible PCBs congeners exist, but only about 130 of these are likely to occur in commercial products [4]. These compounds were widely used as dielectric fluids: transformer oil, capacitors. The example of the total PCBs application is characterized as follows [4]: Germany dielectric fluids - 56 %; dissapative uses 28,7 %; hydraulic fluids 14,3 %. Japan dielectric fluids 66 %; copying paper 18 %; heat transfer fluids 11 %; other 5 %. USA dielectric fluids - 70 % of total application. 226

From this data we can see that transformer oil is a principal pollution source of PCBs in the environment. The US Department of Health and Human Services as well as the International Agency for Research on Cancer (IARC) consider PCBs to be probable carcinogens in humans (ATSDR 1997; IARC 1987). Many countries have developed classification for PCB-containing fluids and materials. The benchmark level for PCBs is considered as 50 mg kg -1 (or 50 ppm) in many countries [4]. The analytical determination is very important task for the control of PCBs concentration in the environment. Some Screening Test and Gas Chromatography methods are used for the determination of PCBs in different media [1,15,16]. Gas Chromatography with ECD detector is more accurate for this purpose. The matrix impact is very strong for this determination by the case of close chemical properties of oil and our interested substances (PCBs). Different methods for sample preparation and cleanup exist [5, 7-14,19,20]. These methods are needed in the detail development for the specific analyses. This paper presents the procedure for determination of PCBs in the transformer oil with the utilization of Solid Phase Extraction (SPE) for the sample preparation. With SPE, many of the problems associated with liquid/liquid extraction can be prevented, such as incomplete phase separations, less-than-quantitative recoveries, use of expensive, breakable specialty glassware, and disposal of large quantities of organic solvents. SPE is more efficient than liquid/liquid extraction, yields quantitative extractions that are easy to perform, is rapid, and can be automated. Solvent use and laboratory time is reduced. 2. Experimental 2.1 Chemicals All solvents were GC-pure quality and were purchased from Supelco and Sigma-Aldrich Inc. (Germany). A working stock solution was prepared from PCBs congener mix standard (IUPAC Nos. 18, 29, 31, 52, 44, 101, 118, 138, 149, 180, 194) containing 10 µg of each in 1 ml of heptane, and from Aroclor 1254 1000 µg in 1 ml of hexane. These standard solutions were purchased from Supelco Inc. (Germany). PCB 209 was used as an internal standard. Octadecyl bonded silica phase AccuBOND C18 100mg/1ml cartridge was chosen for extraction performing. Reversed phase separations involve a polar or moderately polar sample matrix (mobile phase) and a nonpolar stationary phase. C18 SPE cartridge has following characteristics: surface area 546 m 2 g -1 ; average pore size 60 ; Surface ph 7; carbon loading 18,8%; surface coverage 1,6 µmol m -2. Compounds are retained in C18 by nonpolarnonpolar interactions and van der Waals or dispersion forces. This cartridge is used usually for reversed phase extraction of nonpolar to moderately polar compound [3]. 2.2 Instrumentation GC 6890 (Agilent, Germany) gas chromatograph equipped with µecd detector, split/splitless injection system, and capillary columns HP-5MS. Parameters of the gas chromatograph system are characterized in Table 1. 227

Table 1. Experimental Conditions Equipment and system elements Method parameters Gas chromatograph: Agilent 6890 Injection ports: Split/splitless inlet; injection - Splitless 1 µl, inlet temperature of 300 C Column HP-5MS 30 m Length, 0,25 mm I.D., 0,25 µm Film; Part number Carrier gas H 2, 1,5 ml min -1, or Average Velocity 46 cm sec -1, Constant Flow Oven First ramp: 100 C (hold 1 min) to 190 C at 30 C min -1 Second ramp: 190 C to 280 C (hold 1 min) at 6 C/min Detector µecd, 320 0 C, N2 makeup, 60 ml min -1 Data collection ChemStation GC was calibrated with five calibration standard solutions in the concentration range 0,05 0,70 µg ml -1 for PCBs, and 0,5 7,0 µg ml -1 for Aroclor1254. The calibration standards were prepared on pure oil matrix passed through cartridges C18 for the removal of the matrix impact. The quantitative calculation was based on the area count obtained for the merged peaks. The area obtained for interested peaks in the chromatograms was compared to the standard and calibration curve to quantify the PCBs concentration. The analysis control and quatitation were performed by ChemStation software version C 00-01 (Agilent). 2.3 Study of the matrix removal by SPE cartridges The pure transformer oil sample without PCBs was chosen for the preparation of experimental modeling solutions. This sample was diluted in 10 times with hexane by EPA method 3580. PCBs congener mix and Aroclor1254 were added to the diluted oil sample to final concentrations of 0,2 and 0,5 µg ml -1 for each compounds for PCBs and to the total concentrations of 2,0 and 5,0 µg ml -1 for Aroclor1254. Then an internal standard (PCB 209) was added to samples. Samples were shaken for 10 min for the better dissolution. These concentrations were considered by the reason of PCBs limit concentration of 50,0 mg kg -1 in PCBs containing materials. Thereby four modeling samples were prepared for the experiment. The extraction is performed in three steps. First is a disk cleaning by dichlormethane 5 ml under vacuum near 50 kpa, and drying under vacuum 5 min. Second is a conditioning by hexane 10 ml (the functional groups of the sorbent bed are solvated in order to make them interact with the sample). Third is a matrix removal. This step was started right after hexane conditioning by the sample addition to the cartridge (1 ml) and the elution by 2 ml of hexane under vacuum. PCBs were extracted in this eluate. The total time of extraction procedure was near 10 min. This procedure was repeated three times for every concentration and for blank solution. The sample volume was striped to 1 ml under Argon stream. Then 1 µl aliquots of hexane extract is injected into chromatographic column. The same procedure was used for the sample preparation of real transformer oil samples. The vacuum was controlled by Supelco Vacuum Manifold, which has a solvent resistant main vacuum gauge and valve used to monitor the vacuum and release the vacuum during processing. 228

Results and discussion Chromatograms of PCBs mix standard solutions with the concentration of 0,5 µg ml -1 and Aroclor1254 with the concentration of 5,0 µg ml -1 are presented in Fig. 1. Column HP-5MS showed a good chromatographic separation, resolution and reproducibility. The calibration database of Gas Chromatography System was created for 12 PCB congeners and 45 compounds for Aroclor1254. The correlation coefficient for all calibration compounds was in the interval of 0,990 to 1,000. Table 2 Results of PCBs determination in modeling solutions of 0,2 µg ml -1 Nr IUPAC Repetitions Recovery Average St. dev. No 1 2 3 % 1) PCB 31 0,222 0,185 0,194 0,2003 0,01937 100,13 2) PCB 29 0,221 0,183 0,192 0,1986 0,02023 99,30 3) PCB 18 0,218 0,184 0,193 0,1983 0,01740 99,14 4) PCB 52 0,197 0,191 0,188 0,1920 0,00469 95,99 5) PCB 44 0,211 0,177 0,186 0,1914 0,01780 95,70 6) PCB 101 0,214 0,181 0,188 0,1943 0,01759 97,15 7) PCB 149 0,212 0,180 0,187 0,1932 0,01688 96,58 8) PCB 118 0,209 0,177 0,184 0,1902 0,01665 95,10 9) PCB 167 0,211 0,180 0,186 0,1926 0,01666 96,30 10) PCB 138 0,209 0,179 0,185 0,1909 0,01622 95,46 11) PCB 180 0,210 0,180 0,186 0,1922 0,01580 96,11 12) PCB 194 0,215 0,185 0,190 0,1963 0,01606 98,15 Integration result for IS IS PCB 209 48110207 47467063 46632829 47403366 740745,7 94,14 Table 3 Results of PCBs determination in modeling solutions of 0,5 µg ml -1 Nr IUPAC Repetitions Recovery Average St. dev. No 1 2 3 % 1) PCB 31 0,495 0,469 0,475 0,4799 0,01371 95,97 2) PCB 29 0,501 0,469 0,482 0,4843 0,01613 96,86 3) PCB 18 0,495 0,474 0,484 0,4843 0,01037 96,87 4) PCB 52 0,498 0,501 0,497 0,4988 0,00192 99,77 5) PCB 44 0,487 0,462 0,474 0,4741 0,01281 94,83 6) PCB 101 0,483 0,460 0,476 0,4731 0,01171 94,63 7) PCB 149 0,479 0,458 0,473 0,4702 0,01089 94,04 8) PCB 118 0,484 0,462 0,473 0,4730 0,01094 94,59 9) PCB 167 0,478 0,458 0,471 0,4690 0,00985 93,81 10) PCB 138 0,480 0,460 0,473 0,4710 0,01000 94,20 11) PCB 180 0 479 0 461 0 475 0 4719 0 00933 94 38 229

Table 4 Results of Aroclor1254 determination in modeling solutions of 2,0 µg ml -1 Peak Ret. Repetitions 2,0 µg ml -1 St Average No time 1 2 3 deviation Recovery % 1 8,02 0,0693 0,0307 0,0685 0,0562 0,02208 98,8 2 8,11 0,0161 0,0158 0,0168 0,0162 0,00052 99,2 3 8,43 0,0332 0,0311 0,0338 0,0327 0,00140 95,0 4 8,50 0,0032 0,0030 0,0031 0,0031 0,00010 90,1 5 8,68 0,0135 0,0131 0,0138 0,0135 0,00034 84,0 6 8,84 0,0031 0,0031 0,0032 0,0031 0,00008 102,1 7 9,15 0,0139 0,0134 0,0143 0,0139 0,00044 94,9 8 9,24 0,0439 0,0416 0,0486 0,0447 0,00357 84,9 9 9,31 0,1033 0,1004 0,1059 0,1032 0,00275 94,9 10 9,45 0,0168 0,0161 0,0171 0,0167 0,00053 94,3 11 9,67 0,0352 0,0348 0,0367 0,0356 0,00103 96,1 12 9,80 0,1501 0,1469 0,1548 0,1506 0,00395 94,8 13 9,92 0,0509 0,0495 0,0523 0,0509 0,00145 94,0 14 10,17 0,0089 0,0088 0,0092 0,0089 0,00021 93,7 15 10,29 0,0463 0,0452 0,0477 0,0464 0,00121 94,6 16 10,40 0,0951 0,0928 0,0980 0,0953 0,00258 94,6 17 10,51 0,0302 0,0298 0,0312 0,0304 0,00077 91,1 18 10,57 0,0132 0,0132 0,0137 0,0134 0,00030 95,0 19 10,63 0,1694 0,1660 0,1747 0,1700 0,00438 96,6 20 10,91 0,0394 0,0384 0,0406 0,0395 0,00112 95,5 21 11,02 0,0291 0,0285 0,0298 0,0291 0,00067 99,0 22 11,19 0,0143 0,0138 0,0147 0,0143 0,00041 97,0 23 11,19 0,0596 0,0577 0,0614 0,0596 0,00187 87,5 24 11,24 0,1256 0,1218 0,1297 0,1257 0,00391 95,4 25 11,45 0,0115 0,0110 0,0123 0,0116 0,00065 87,8 26 11,51 0,0048 0,0045 0,0048 0,0047 0,00017 81,6 27 11,56 0,0055 0,0053 0,0057 0,0055 0,00019 91,3 28 11,63 0,0178 0,0172 0,0184 0,0178 0,00059 94,6 29 11,78 0,0798 0,0774 0,0823 0,0798 0,00244 92,3 30 11,88 0,0733 0,1265 0,1341 0,1113 0,03318 83,8 31 12,09 0,0260 0,0269 0,0287 0,0272 0,00136 89,2 32 12,26 0,0150 0,0142 0,0155 0,0149 0,00066 88,9 33 12,32 0,0154 0,0148 0,0159 0,0154 0,00058 93,4 34 12,46 0,1628 0,1579 0,1682 0,1630 0,00518 94,1 35 12,52 0,0286 0,0278 0,0295 0,0286 0,00086 92,9 36 13,01 0,0165 0,0161 0,0168 0,0165 0,00039 91,2 37 12,88 0,0073 0,0101 0,0108 0,0094 0,00187 81,9 38 13,01 0,0075 0,0073 0,0077 0,0075 0,00018 92,5 39 13,15 0,0563 0,0544 0,0585 0,0564 0,00207 93,2 40 13,47 0,0123 0,0117 0,0127 0,0122 0,00052 89,5 41 13,61 0,0074 0,0070 0,0078 0,0074 0,00042 90,0 42 13,75 0,0377 0,0362 0,0389 0,0376 0,00133 93,7 43 13,89 0,0080 0,0077 0,0083 0,0080 0,00031 90,6 44 14,18 0,0257 0,0249 0,0270 0,0259 0,00105 92,5 45 14 94 0 0274 0 0267 0 0293 0 0278 0 00132 91 6 230

Peak No Table 5 Results of Aroclor1254 determination in modeling solutions of 5,0 µg ml -1 Ret. Repetitions 5,0 µg ml -1 time 1 2 3 Average St deviation Recovery % 1 8,02 0,1591 0,1349 0,1654 0,1531 0,01608 109,2 2 8,11 0,0420 0,0356 0,0418 0,0398 0,00368 96,0 3 8,43 0,0847 0,0709 0,0835 0,0797 0,00761 94,1 4 8,50 0,0076 0,0076 0,0076 0,0076 0,00002 84,3 5 8,68 0,0377 0,0320 0,0410 0,0369 0,00452 90,4 6 8,84 0,0084 0,0069 0,0083 0,0079 0,00083 96,3 7 9,15 0,0370 0,0316 0,0365 0,0350 0,00299 95,8 8 9,24 0,1308 0,0949 0,1427 0,1228 0,02485 94,5 9 9,31 0,2704 0,2278 0,2668 0,2550 0,02360 93,5 10 9,45 0,0439 0,0374 0,0433 0,0415 0,00356 95,5 11 9,67 0,0920 0,0775 0,0910 0,0868 0,00808 95,7 12 9,80 0,4006 0,3360 0,3955 0,3774 0,03591 94,6 13 9,92 0,1329 0,1130 0,1320 0,1260 0,01125 95,3 14 10,17 0,0250 0,0208 0,0243 0,0234 0,00224 95,7 15 10,29 0,1205 0,1020 0,1189 0,1138 0,01023 95,7 16 10,40 0,2553 0,2142 0,2518 0,2404 0,02276 94,7 17 10,51 0,0812 0,0684 0,0801 0,0766 0,00710 95,6 18 10,57 0,0354 0,0303 0,0354 0,0337 0,00295 98,2 19 10,63 0,4585 0,3845 0,4531 0,4320 0,04121 95,0 20 10,91 0,1023 0,0865 0,1007 0,0965 0,00869 95,8 21 11,02 0,0738 0,0630 0,0730 0,0699 0,00602 98,8 22 11,19 0,0375 0,0320 0,0372 0,0356 0,00312 95,1 23 11,19 0,1654 0,1402 0,1642 0,1566 0,01423 94,6 24 11,24 0,3400 0,2851 0,3337 0,3196 0,03003 95,1 25 11,45 0,0336 0,0284 0,0331 0,0317 0,00283 97,7 26 11,51 0,0150 0,0119 0,0149 0,0140 0,00176 90,9 27 11,56 0,0157 0,0133 0,0153 0,0148 0,00126 95,4 28 11,63 0,0467 0,0403 0,0462 0,0444 0,00356 97,1 29 11,78 0,2126 0,1805 0,2091 0,2007 0,01759 95,5 30 11,88 0,3388 0,2888 0,2084 0,2787 0,06581 83,9 31 12,09 0,0786 0,0673 0,0777 0,0746 0,00628 100,4 32 12,26 0,0415 0,0348 0,0416 0,0393 0,00386 96,3 33 12,32 0,0412 0,0355 0,0408 0,0391 0,00320 96,3 34 12,46 0,4392 0,3720 0,4334 0,4149 0,03728 94,8 35 12,52 0,0749 0,0651 0,0748 0,0716 0,00562 96,8 36 13,01 0,0464 0,0390 0,0456 0,0437 0,00403 97,0 37 12,88 0,0278 0,0233 0,0274 0,0262 0,00248 91,4 38 13,01 0,0211 0,0178 0,0208 0,0199 0,00184 97,0 39 13,15 0,1488 0,1272 0,1465 0,1408 0,01184 95,8 40 13,47 0,0349 0,0296 0,0341 0,0329 0,00287 96,7 41 13,61 0,0214 0,0181 0,0209 0,0201 0,00176 96,4 42 13,75 0,0996 0,0858 0,0982 0,0945 0,00761 96,1 43 13,89 0,0233 0,0201 0,0230 0,0221 0,00179 97,2 44 14,18 0,0671 0,0576 0,0661 0,0636 0,00525 96,6 231

Response_ 2.2e+07 2e+07 Signal: PCB05.D\ECD1B.CH PCB180 14.16 PCB194 16.60 1.8e+07 PCB138 12.45 1.6e+07 PCB18 PCB118 PCB149 PCB167 1.4e+07 7.40 PCB44 PCB101 11.23 PCB29 11.76 8.41 11.18 1.2e+07 9.78 7.37 PCB52 1e+07 8.01 PCB31 8000000 6.64 6000000 4000000 a) IS DCB 18.37 2000000 Time Response_ 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 1.4e+07 1.2e+07 1e+07 8000000 6000000 4000000 2000000 1 2 3 5 4 6 9 12 16 19 8 13 15 11 1720 31 35 21 7 10 18 28 22 32 25 33 14 26 27 Signal: AR545.D\ECD1B.CH 24 23 29 30 34 39 42 44 37 38 36 40 4143 45 b) IS DCB Time 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Fig. 1 Chromatograms of PCBs (a) and Aroclor1254 (b) standard solutions with concentrations of 0,5 and 5,0 µg ml -1 respectively 232

Response_ 2.2e+07 Signal: PCBOIL51.D\ECD1B.CH PCB194 16.59 2e+07 PCB180 14.16 1.8e+07 1.6e+07 1.4e+07 1.2e+07 1e+07 8000000 PCB18 PCB118 7.41 PCB167 PCB44 11.23 PCB29 11.76 PCB101 PCB149 8.42 11.18 7.38 9.79 PCB52 PCB31 6.64 8.02 PCB138 12.45 6000000 9.23 4000000 2000000 7.95 7.89 7.64 14.86 IS DCB 18.37 17.22 Time Response_ 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Signal: OIL545_1.D\ECD1B.CH 1.4e+07 19 1.3e+07 1.2e+07 34 1.1e+07 12 1e+07 24 9000000 9 8000000 16 7000000 6000000 1 8 23 29 30 5000000 13 15 39 4000000 3000000 2000000 2 3 4 5 6 11 10 7 17 20 21 28 18 22 14 25 26 27 31 35 32 33 42 44 40 37 38 36 4143 45 IS DCB Time 8.00 9.00 10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 Fig. 2 Chromatograms of PCBs (a) and Aroclor1254 (b) modeling solutions with concentrations of 0,5 and 5,0 µg ml -1 respectively 233

The PCBs determination in transformer oil by Gas Chromatography has a strong matrix impact. Proposed SPE extraction method has a possibility to clean up investigated modeling samples and reduces this impact very well. Cartridges C18 are a good solution for this matrix impact elimination. After this cleanup 1 µl of the obtained extract was injected in column HP- 5MS. Chromatograms of modeling solutions have a minimal retention time drift (0,02 min) and the close base line in comparison with chromatograms of calibration solutions. The quantitative result of extracted modeling samples of PCBs congeners is presented in tables 2 and 3. The average value of modeling solutions with the concentration of 0,2 and 0,5 µg ml -1 are in intervals 0,1902 0,2003 and 0,4690 0,4988 by Standard Deviation 0,00469 0,0202 and 0,0019 0,0161 respectively. The recovery of congener PCBs for modeling samples was assessed by standard solutions with the same concentration and by internal standard PCB209. The recovery was indicated in the interval of 95,10 100,13 % for modeling solution with the PCBs concentration of 0,2 µg ml -1 and 94,04 99,77 % for modeling solution with the PCBs concentration of 0,5 µg ml -1. (table 2, 3). The better statistic parameters were indicated for samples with higher concentration. The same result was indicated for modeling solutions of Aroclor1254 with concentrations of 2,0 and 5,0 µg ml -1 (table 4, 5). The total concentration of every 45 component can be assessed easy by ChemStation software for this mixture. Maximal 4 peaks with retention times 9,80, 10,63, 11,24, 12,46 min have a good recovery in intervals 94,1 96,6 % for 2,0 µg ml -1 and 94,6 95,0 % for 5,0 µg ml -1 internal standard. The recovery for total Aroclor1254 amount is 93,1 % for 2,0 µg ml -1 and 94,9 % for 5,0 µg ml -1. The internal standard recovery is 94,1 and 93,0 % respectively for the different concentration. These good parameters for every solution are explained by two reasons: first is a good cleanup of modeling samples by SPE procedure on C18 cartridges, and second is a good separation, resolution and accuracy of Chromatographic System by the proposed method. Conclusion The utilization of AccuBOND C18 100mg/1ml cartridges with Octadecyl bonded silica phase showed a good result of the SPE cleanup and PCBs determination by Gas Chromatography in the transformer oil. The proposed method has following principal advantages: reducing a solvent amount, labor time, and so an analysis cost in comparison with other technologies; increasing a labor capacity and number of samples up to 10 times (from 30 40 per month to 300 400 per month for one worker); minimization of the matrix impact on the Gas Chromatography analysis; good recovery and accuracy of PCBs determination in the complex oil matrix. This method can be recommended for the implementation in analytical laboratories for the investigation of the pollutant content in the complex oil matrix. 234

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