Flow injection analysis of nitrite by gas phase molecular absorption UV spectrophotometry

A flow injection method on the basis of gas phase molecular absorption is described for the determination of nitrite in the aqueous solution. 200 μl of nitrite solution is introduced into a carrier stream of distilled water. The carrier stream containing nitrite zone is reacted with a stream of hydrochloric acid (2 M). The stream is then segmented by O2 gas. The produced gaseous products are purged into the O2 segments, react with O2 and are carried toward the gas–liquid separator. The gaseous phase is separated from the liquid stream by the use of home-made gas–liquid separator and then is swept into a home-made flow cell. The absorbance of gaseous phase is measured at 205 nm using a UV/VIS spectrophotometer. Under selected conditions, two linear ranges, up to 1000 μg ml−1 and 1000–2000 μg ml−1 of nitrite were obtained. The limit of detection was 7.5 μg ml−1 NO2−. The relative standard deviations of repeated measurements of 100 and 500 μg ml−1 NO2− were 3.7 and 1.0%, respectively. Up to 30 samples h−1 can be analyzed. Interferences in the proposed method were few and were readily overcome. The proposed method was successfully applied to the determination of nitrite in the spiked water samples, a number of meat products and urine.