Principal Research Results

Development of Simple Analytical Method for Trace Chemical
Substances such as PCB Using High Temperature Thermal Degradation
BackgroundIn 2002, The Japan Electrical Manufacturers’ Association (JEMA) announced that trace PCB was contaminated in the insulating oil, in which it had been considered that PCB was not contained. Insulating oil containing PCB is required to be processing fornon-toxicity in Japan. Therefore, the organizations such as the electric power industries, which use and keep insulating oil, are driven
by necessity to check that PCB is contained or not in the oil that they are possessing. It is considered that the insulating oil samples
which are needed to be analyzed are up to a few hundred thousands, so the analytical method is required to be simple and rapid. On
the contrary, measurement demand of trace heavy metals in coal and heavy oil are increased according to the surge of concern to therecent environmental problems. However, the measurement procedure is usually complex and must take much time. Accordingly, theneeds for a simple and rapid analytical method for trace heavy metals are high.

Objectives
To develop a simple and rapid analytical method for the chemical substances in insulating oil, and to evaluate the performances of the developed method.

Principal Results
1. Planning and manufacture of the high temperature thermal degradation system
The author planned and manufactured the high temperature thermal degradation system to analyze PCB in insulating oil andheavy metals in fuels simply and rapidly. (Fig. 1)1) In this system, the sample is thermally degraded immediately in closed and oxygen pressurized container, and then the target chemicals are recovered by trapping the combustion gas in absorbent solution.
Measuring time for PCB in insulating oil with this system is 20-30 minutes, being much shorter than the usual analytical method (-3hours).
2. Simple analysis of PCB in insulating oil by the high temperature thermal degradation system
PCB standard samples, in which PCB concentrations were known, were applied to the system, resulting that almost all PCB
in samples were recovered as hydrogen chloride (Fig. 2). In addition it was confirmed that 0.5ppm of PCB, which is processing standard value of PCB waste in Japan, could be analyzed using this system. Furthermore, several old insulating oil samples, in which PCB
concentrations were known, were analyzed using this system, resulting that PCB were measured almost quantitatively (Table 1).
Slight overestimation of chloride is considered to result from trichlorobenzene in insulating oil.
3. Simple analysis of trace heavy metals in fuels by the high temperature thermal degradation system
Heavy oil and coal samples, in which heavy metal concentrations were known, were applied to the system. As a result, Asand Se in heavy oil were almost recovered, whereas As and Se in coal were measured only 50-60 % of original samples. Required
time to measure heavy metals in fuels with this system is 2 days, being much shorter than the usual analytical method (-10 days).
Accordingly, the high temperature thermal degradation system established in this study was evaluated to have potency as
simple and rapid analytical method for PCB in insulating oil and heavy metals in fuels.

Future Developments
Examining the new thermal degradation system for coal samples, and trying instrumentation of this system.
Main Researcher: Nobuyuki Tanaka,
Research Scientist, Atmospheric Environment Sector, Environmental Science Research Laboratory
Reference
N. Tanaka, 2004, “Development of simple analytical method for trace chemical substances such as PCB using high temperature thermal degradation”, CRIEPI Report, T03034.

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2. Environment - Measures to regional environmental problems

Fig.1 An overview of thermal degration system examined in this study.
The system is divided into gas supply part, thermal degradation part and sample collection part. The procedureis following:Sample is put on a sample plate. After a pressure container is closed, O 2 is filled in the container to30MPa. The sample isthermally degraded by high voltage using insulating electrode. After degradation,sample gas is collected in absorbentsolution.

15Table 1 Analytical result of Cl in usedinsulating oil.
Cl（μg）

105

PCB: 0.5ppm1)

005
10
15
Cl（in PCB:μg）
Fig.2 Relationship between Cl in PCB and Cl
measured by thermal degradation.
Almost 100% of Cl in analyzed PCB samples weredegraded to hydrogen chloride by thermaldegradation and were recovered.

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Input

Measuredoil 115.5

20.0

oil 2

15.7

18.7

oil 3

16.3

20.7

blank1)0

0.20

Insulating oil without PCB.