ISO 18635:2016 specifies a method for the quantitative determination of the sum of short-chain polychlorinated n-alkanes also known as short-chain polychlorinated paraffins (SCCPs) in the carbon bond range, n-C₁₀ to n-C₁₃, inclusive in mixtures with chlorine mass fractions ("contents") between 50 % and 67 %, including approximately 6 000 of approximately 8 000 congeners.

This method is applicable to the determination of the sum of SCCPs in sediment and suspended (particulate) matter, sewage sludge, and soil using gas chromatography-mass spectrometry with electron capture negative ionization (GC-ECNI-MS).

Depending on matrix and the detection capabilities of the GC-ECNI-MS, the method can be applied to samples containing, e.g. 0,03 µg/g to 3 µg/g sum of SCCPs.