IEC 61619 Insulating liquids - Contamination by polychlorinated biphenyls (PCBs) - Method of determination by capillary column gas chromatography
1 Scope and object
This International Standard specifies a method for the determination of polychlorinated biphenyl (PCB) concentration in non-halogenated insulating liquids by high-resolution capillary column gas chromatography using an electron capture detector (ECD).
The method gives the total PCB content and is especially useful when a detailed analysis of PCB congeners is necessary. Other methods, such as IEC 60997, may be used when a less detailed analysis is acceptable.
The method is applicable to unused, reclaimed (including dechlorinated and chemically and/or physically treated), or used insulating liquids contaminated by PCBs.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of this normative document. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative document indicated below. Members of IEC and ISO maintain registers of current valid International Standards.
IEC 60475:1974, Method of sampling liquid dielectrics.
3 Definitions
For the purposes of the International Standard, the following definitions apply:
3.1 polychlorinated biphenyl (PCB)
a biphenyl substituted by one to ten chlorine atoms
NOTE For legal purposes, congeners with one, two or ten chlorine atoms may be excluded from this definition.
3.2 congener
all the chlorine derivatives of biphenyl, irrespective of the number of chlorine atoms, are termed congeners
NOTE There are 209 possible PCB congeners. These are listed in Table B.1. The congener numbers (IUPAC) are for easy identification; they do not represent the order of chromatographic elution.
4 Principle
The PCB congeners are determined by temperature programmed gas chromatography. The chromatograph uses a high-efficiency capillary column to separate the PCBs into single or small groups of overlapping congeners.
The sensitivity of the electron capture detector (ECD) may be reduced by the presence of mineral oil. In this method the sample is diluted 100 times to reduce this effect to a minimum.
A sample preparation (clean-up) procedure is used to remove most of the impurities likely to interfere with the determination.
Reference compounds are included to enable calculation of experimental relative retention times (ERRTs) which are compared to a data file of peak ERRTs to identify individual or groups of unresolved congeners. An internal standard is added for quantification.
Relative response factors (RRF), taken from the data files (9.1), corrected by experimental relative response factors (ERRFs) obtained from reference compounds, are applied to identified peaks to quantify the individual (or groups of) congeners, and the values summed to give total PCB content.
