Primaquine Phosphate as a Promising Substitute for N-(1-Naphthyl)ethylenediamine. I. Determination of Nitrite in Natural Waters in Egypt.

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A sensitive and rapid colorimetric method was developed for the determination of nitrite in natural water samples. The method is based on coupling primaquine phosphate (PP) with diazotized p-nitroaniline (PNA) or with diazotized p-aminobenzophenone (PABP) in acid medium. The orange color produced with both amines was stable for more than 24h, and has an absorption maximum at 484nm, and 482 for PNA and PABP, respectively. The calibration graph was linear in the concentration range of 0.025-1.25ppm of nitrite, with a minimum detection limit of 0.015ppm. The molar absorptivities were 8×104mol-1 cm-1 and 7.11×104mol-1 cm-1 for PNA and PABP, respectively. Heavy metals common to natural waters did not interfere. The interference from reducing anions such as I-, S2-, SO32-, and S2O32- was eliminated by precipitation as insoluble lead salts. The excess lead ions did not interfere. Because PP is less liable to self-diazotization-coupling reaction compared with N-(1-naphthyl)ethylenediamine (BMR), the method could be adopted for automated flow-injection analysis of nitrite. In addition, the coupling agent used is safe; a promising substitute for the so-long used Bratton-Marshal reagent which was reported to be carcinogenic. The proposed method is very sensitive and selective.
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