重力分相器用于流动注射-液-液萃取-原子吸收光谱法间接测定硝酸根

A Gravitational Phase Separator for Use in Flow Injection / Liquid -Liquid Extraction /Indirect Atomic Absorption Spectrometric Determination of Nitrate and Nitrite

应用一种新型的四通道重力分相器，通过实验，选定了流动注射－液－液萃取－原子吸收间接测定硝酸根的最佳化学条件和仪器参数，方法的精密度（ＲＳＤ）和检出限分别为１．９％（０．２５ ｍｇ／Ｌ，ｎ＝１０）和 ０．０２８ ｍｇ／Ｌ，测定速度为 ２５样／ｈ，用本系统测定水样中的硝酸根和亚硝酸根，标准加入回收率为１００％～１１０％。

Nitrate reacts with bis (2, 9-dimethyl-1, 10-phenanthrolinato) copper (I) to form an ion-pair which is subsequently extracted into 4-methyl-2-pentanone. By measuring the atomic absorption signal of copper in the organic phase, a mixture of NO3 and NO2 can be sequentially determined. In one aliquot of sample, nitrite is oxidised by Ce (Ⅳ). so total ni- trate can be determined. In another aliquot, nitrite is converted to nitrogen with sulfamic acid, for the determination of original nitrate. A versatile phase separator has been designed and is connected to the extraction manifold. Experimental conditions and manifold parame- ters have been investigated in detail. The proposed method is effective, with a detection limit of 0. 028 mg/L of NO3-. The RSD is 1.9% for 0.25 mg/L of NO3 (n=10) and a sampling rate of 25 samples/h can be achieved. Recoveries of NO3 in water samples are 100-110%.