| 18967191 |
Wang GF, Satake M, Horita K: Spectrophotometric determination of nitrate and nitrite in water and some fruit samples using column preconcentration. Talanta. 1998 Aug;46(4):671-8.
A sensitive analytical method for the simultaneous assay of nitrate and nitrite in water and some fruit samples is presented. The method is based on nitrite determination using the diazotization-coupling reaction by column preconcentration and on the reduction of nitrate to nitrite using the Cd-Cu reductor column. Nitrite is diazotized with sulfanilamide (SAM) in the pH range 2.0-5.0, sulfamethizole (SM) in pH 1.8-5.6 and sulfadimidine (SD) in pH 1.8-4.0 in a hydrochloric acid medium to form water-soluble colourless diazonium cations. These cations were coupled with sodium 1-naphthol-4-sulfonate (NS) in the pH range 9.0-12.0 for the SAM-NS system, pH 8.6-12.0 for the SM-NS system and pH 9.4-12.0 for the SD-NS system to be retained on naphthalene-tetradecyldimethylbenzylammonium (TDBA)-iodide (I) adsorbent packed in a column. The solid mass is dissolved out from the column with 5 ml of dimethylformamide (DMF) and the absorbance is measured by a spectrophotometer at 543 nm for SAM-NS, 537 nm for SM-NS and 530 nm for SD-NS. The calibration graph was linear over 30-600 ng NO (2)-N and 22-450 ng NO (3)-N in 15 ml of final aqueous solution (i.e. 2-40 ng NO (2)-N ml (-1) and 1.5-30 ng NO (3)-N ml (-1) in aqueous sample) for three systems. The detection limits were 1.4 ng NO (2)-N ml (-1) and 1.1 ng NO (3)-N ml (-1) for SAM-NS, 1.2 ng NO (2)-N ml (-1) and 0.89 ng NO (3)-N ml (-1) for SM-NS, 1.0 ng NO (2)-N ml (-1) and 0.75 ng NO (3)-N ml (-1) for SD-NS, respectively. The concentration factor is eight for SAM-NS and SM-NS, and 12 for SD-NS. Interferences from various foreign ions have been examined and the method was successfully applied to the determination of low levels of nitrate and nitrite in water and some fruit samples. |
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