Principal Research Results

A Biosensor for Detection of PCBs in Transformer Oil

BackgroundThe use of polychlorinated biphenyls in transformer oil was discontinued in the late 1970’s due to its toxicity. Currently, inthe developed countries, the degradation programs for PCB contaminants are operated with environmental monitoring. Several methods including an extraction followed by gas chromatography (GC) with electron capture or mass spectrum (MS) were used to monitor
PCB in oil, but more rapid and cheaper methods are coming to be focused and desired. Immunoassay using antibody and antigen reaction is expected to be a rapid and cheap detection method for PCB in oil. However, the multiple detection of PCB congeners and/or thedisruption of antibody reaction by the oil content are thought to be difficult problems facing immunoassay for PCB in oil. A little information is available for effective immunoassay with simple extraction.

Objectives
Development of a simple and rapid immunoassay to detect PCB in transformer oil.

Principal Results.
1. A simple extraction method of PCB in oil.
To evaluate immunoassay for PCB in oil, a simple extraction method to extract PCB from oil is necessary. In extraction
process, the oil contents preventing antibody reaction must be removed as rapidly and simply as possible. A liquid extraction by HClDMSO(dimethyl sulfoxide) followed by secondary liquid extraction by DMSO could extract PCB from oil. This less complicated 2
step liquid-liquid extraction was suitable for the developed immunoassay (Fig-1). 50% of PCB in oil could be recovered as the extractwith this method.
2. Measurement of the imitated oil by spiking kanechlorFour kinds of Kanechlor (KC300 - 600) are a mixture of PCB congeners. Thus, the contaminated oil was imitated by spiking
each Kanechlor to PCB free transformer oil. The spiked PCB to the oil was extracted by the method described above. The extract wasdiluted 1000 fold with the solution containing anti-PCB antibody. The diluted mixture was subjected to PCB detection with ourbiosensor(FIg-1). PCB congeners could be detected at ppb level within 5 minutes on the sensor.(Fig-2)。The final dynamic range oftotal PCB congeners in the oil was calculated from the dilution factor as 10 - 1400ppm for KC300, 6 - 600ppm for KC400, 2 - 100ppm
for KC500 and 2 - 100ppm for KC600.
3. Measurement of the real contaminated oil from transformer
Total concentrations of PCB in 11 of real contaminated oils from the transformer (0.3~32ppm) were measured with a highresolution mass spectrum (GC-HRMS) and this biosensor. A high correlation was observed between output signals from the biosensor
and the determined PCB concentrations by GC-HRMS (Fig -3). From this correlation, the dynamic range of total PCB congeners in oilon the biosensor was calculated as the range from 5 to 120ppm. A simple two steps liquid-liquid extraction in conjunction with an immunoassay for detecting PCBs in transformer oil was successfully achieved.

Future Developments
We will improve the sensitivity of biosensor with the extraction method.
Main Researcher: Naoya Ohmura, Ph.D.,
Senior Research Scientist, Solution Center for Environmental Issues, Environmental Science Research Laboratory
Reference
Naoya Ohmura. Application of biological function to sensing part 5 (in Japanese). CRIEPI report:U02032 (2004)112

10. Advanced Basic Technologies - Bio-scienceMix 2minPCB Oil

HCl酸
DMSO
DMSO
wash洗PCB Oil
DMSO
DMSO
washPCB抽Extract
出antibodysolution
at 1000 fold
抗 Dilute
体 with1000倍希釈し，バイオFig.1 The extraction and measurement
The PCB congener was extracted from oil by
HCl-DMSO followed by neutral DMSO. The
extract was diluted at 1000 fold with theSignal, volts

66

信号

anti-PCB antibody solution and the mixture
was subjected to the biosensor to detect PCB.
In the absence of PCB in the extract, theresultant signal on the biosensor was large.
In the presence of PCB, the signal wasappeared to be small.

油 -PCB
PCBな44油 PCB多+PCB

22000100

200

300

400Time,sec時間，

100KC300Signal, %

8060

KC500

Fig.2 PCB measurement in the imitatedoil. Four kinds of KC (300〜600)
were spiked to PCB free oil. The
spiked concentrations of PCB ineach KC could be determined fromthe signal.

KC400
40KC600
20010−210−1100

101102103

104

PCB conc. in oil on Biosensor., ppm

KC concentration, ppb
1086Fig.3 The relationship in total PCB
concentrations in real transformeroils between biosensor and GC-

4200HRMS. The relation coefficient was0.96.

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PCB conc. in oil on GC-HRMS, ppm113