This International Standard specifies a method for determining e-caprolactam and ?-laurolactam in polyamides by gas chromatography. It is suitable particularly for the determination of e-caprolactam in polyamide 6 and ?-laurolactam in polyamide 12. Bearing in mind that gas chromatography offers a wide range of possible conditions, the method specified is that shown to have been suitable in practice. Two variants of the basic method are specified: - Method A is an extraction method with boiling methanol, and the extract is injected into a gas chromatograph. - Method B is a method using a solvent, and the solution is injected into a gas chromatograph.