This International Standard specifies two methods for the spectrometric determination of alkaloid retention by filters of cigarettes: — the direct method; — the indirect method. The methods are applicable to filter cigarettes. The direct method shall be used unless it is not applicable owing to incomplete recovery of the retained alkaloids from the filter material (for example, with some types of charcoal filters). The indirect method is not applicable to cigarettes with perforated or porous filter tipping wraps. This International Standard is not applicable in the case of filters having an irreversible nicotine retention and equipped with perforated or porous wrapping. NOTE 1 These methods determine the retention only of alkaloids of tobacco smoke, expressed as nicotine. The retention of other substances present in the mainstream smoke is not necessarily related to the alkaloid retention.