膜渗透与离子色谱联用技术测定蔬菜中亚硝酸盐和硝酸盐

Application of On-line Dialysis in the Determination of Nitrite and Nitrate in Vegetables by Ion Chromatography

建立了膜渗析与离子色谱联用技术分析蔬菜等复杂基体中亚硝酸盐和硝酸盐的方法。蔬菜样品经沸水浴后，试样液通过膜渗析除去水溶性大分子杂质和颗粒，直接进入离子色谱分析。渗析池采用0．20μm的醋酸纤维为渗析膜，以水为接收液，分析柱为Metrosep A Supp4-250阴离子交换柱，以1．8mmol／L Na2CO3＋1．7mmol／L NaHCO3为流动相，采用化学抑制电导检测。以20g称样计量，方法中No^-2、NO^-3的检出限分别为0．075mg／kg和0．105mg／kg；实际样品的加标回收率分别为80．6％-98．7％和90．5％-114％；相对标准偏差（RSD）≤10％。本方法前处理简单，重现性好，准确度高。

An on-line dialysis coupling with ion chromatographic method for the simultaneous determination of nitrite and nitrate in vegetables using suppressed conductivity detection was reported. The nitrite and nitrate were extracted from the vegetable by mixing and diluting the samples with boiled water. The water-soluble giant molecule, impurity and pigment etc. were removed by on-line dialysis with dialysis cellulose acetate membrane of pore size 0.20 μm. A standard or sample containing the anions was separated on an anionexchange column （250 mm × 4 mm） with 1.8 mmol/L Na2 CO3 ＋ 1.7 mmol/L NaHCO3 as eluent and was detected by suppressed conductivity detector. Parameters such as linearity, limit of detection, precision and accuracy of the method were investigated. The relative standard deviation for the proposed method was lower than 10% and considering a sample of 20.0 g （n = 6）, the detection limit of the method was 0. 075 mg/kg and 0. 105 mg/kg of nitrite and nitrate, respectively. The recoveries of nitrite and nitrate in vegetable matrices were 80. 6% -98.7% and 90.5% - 114%, respectively. The proposed method was compared with a reference method （ official AOAC reference method for the determination of nitrite and nitrate in foodstuffs）. These results demonstrated that the proposed method is simple, sensitive and reliable for the determination of nitrite and nitrate in vegetables, despite the presence of the particularly complex matrix.