6 Reagents

- HPLC grade acetonitrile;

- HPLC grade methanol;

- HPLC grade water;

- HPLC grade acetic acid;

- Analytical grade n-pentane;

- Analytical grade analytes listed in clause 8.

7 Symbols and units

Fi Detector response factor for each of the analytes

Ris Detector response for each analyte in the calibration standards (the response may be expressed by peak area or peak height).

Ri Detector response for each of the detected analytes.

Cis (mg.kg-1) Concentration of each analyte in the calibration standards.

Ci (mg.kg-1) Concentration of each of the analytes in the mineral insulating oil sample.

8 Analytes

Analytical conditions shall be suitable for the determination of the following furan derivatives:

5-hydroxymethyl-2-furfural (5HMF)

2-furfurylalcohol (2FOL)

2-furfural (2FAL)

2-acetylfuran (2ACF)

5-methyl-2-furfural (5MEF)

For the purpose of this standard, the determination of furoic acids is optional as it is often difficult to resolve them from other organic acids that may be present in aged mineral insulating oil samples.