Abstract
The ppb order of total chromium in human urine was determined by graphite furnace atomic absorption spectrometry after the following pretreatments. Water-soluble inorganic salts in human urine such as sodium chloride were removed by a coprecipitation method. Chromium (VI) which is not collected by the ferric hydroxide coprecipitation method was reduced to chromium(III) by L-ascorbic acid and was coprecipitated with ferric hydroxide at pH 10. After aging for 30 min, the precipitate was filtered with a 0.45μm millipore filter. Coprecipitated organic materials such as protein were digested with nitric acid-hydrogen peroxide for 90 min. Since the analytical line of chromium is 357.9 nm, correction of the background absorption by the coprecipitated inorganic salts was made by using a higher-brilliant thermal cathode type deuterium lamp instead of the conventional deuterium lamps even in the measurements in the visible region. The coefficient of variation was 0.97 % at 5 ppb chromium in synthetic urine (n=7) and 3.30 % in 24 h human urine (n=4). The ppb order of total chromium was determined for the urine of 8 people, and satisfactory results were obtained.
