Combustion analysis apparatus and method

A method and apparatus for combustion analysing a sample in a combustion analyser (120,160,180), where the sample comprises a proportion of sulphur. The sample is supplied to the combustion analyser and combusted to produce combustion products, comprising a yield of sulphur dioxide for detection (150). Nitrogen monoxide or a source of nitrogen monoxide is supplied (140) to the combustion analyser to improve the yield of sulphur dioxide in the combustion products. The yield improver may be supplied before and/or during the combusting step. A proportion of yield improver is preferably greater than the (expected) proportion of sulphur. Ozone may be supplied (170) to the combustion products to convert at least a proportion of any nitrogen monoxide in the combustion products to nitrogen dioxide, before detection.