1 SCOPE
This International Standard specifies two methods for the potentiometric determination of the carbonyl value of essential oils which contain carbonyl compounds, either aldehydes or ketones.
Method I (see clause 5), is based on a cold oximation reaction with hydroxylammonium chloride. It applies to essential oils whose main constituents are easily oximable aldehydes and ketones, with the exception of citronellal which needs a low temperature to avoid cyclization phenomena and acetalization.
NOTE 1 In the case of citronellal the free hydroxylamine method described in ISO 1271 should be used.
NOTE 2 Examples of essential oils concerned are lemongrass, hesperydus and rue.
Method II (see clause 6), is based on a hot oximation reaction with hydroxylammonium chloride. It applies to essential oils whose main constituents are ketones which are in general oximable only with difficulty.
NOTE 3 Examples of essential oils concerned are vetiver, Dalmation sage and white artemisia which contain methylketones oximable only with difficulty.
The International Standard for a specific essential oil will specify the method to be used, whether this is the free hydroxylamine method described in ISO 1271 or another method.