The standard specifies two methods for the determination of chromium in water by atomic absorption spectrometry. The two methods are covered in separate clauses as follows: Clause 3: Determination of chromium by flame atomic absorption spectrometry; Clause 4: Determination of chromium by electrothermal atomization atomic absorption spectrometry. Clause 3 is applicable to the analysis of water and waste water when the concentration range is between 0,5 mg/l and 20 mg/l of chromium. When the concentration is below 0,5 mg/l the determination can be carried out after carefully evaporating an acidified sample to small volume, taking care to avoid the formation o