| Food, cosmetic, drinking water are important human health related consumer products ,all consumers concerned about their security quality,this is also the focus of international community in recent years . Measuring nitrite, nitrate and thiocyanate exactly and rapidly in our consumer products can let us master the content of these inorganic nitric toxic compounds in Food Hygiene, this is the power technical support of security quality monitoring and dealing public health instant events. Ion chromatography is one of modes of High performance liquid chromatography , Ion chromatography has been widely used in environment measuring, electronic industry medicine, food analysis and other fields, with a good selectivity and sensitivity, simple and fast, low detection limit[1]. When analysis complex compounds, Ion chromatography always need different sample preparation techniques. This thesis use combined technology of on-line dialysis and ion chromatography(MISP) , it make analysis procedure efficient and automation[2].Nitrite and nitrate are food additives by way of colour former reagent and antiseptic, if we ingest too much, it will harm our health[3]. Ion chromatography is the central method of simultaneous determination NO2- and NO3- at present, In order to eliminate interference, literature articles used solid extraction method, UV detection and LED detection. [4-6] Although Solid extraction method can remove some of impurity, but off-line operation and wasting time; UV detection and LED detection are expensive and not widespread. This article eatablished a method of determination nitrite and nitrate in complex base samples using combined technology of on-line dialysis and ion chromatography. For example, cooked meat was extracted by mixing , ultrasonic and centrifuge, the supernatant liquid was then on-line treated with dialysis after through the Ag column, especially for the salt preserved ham and sausage. By optimizing condition of dialysis and ion chromatography, DL of the NO2- and NO3- in this method were 0.13and 017mg·kg-1. The recoveries were in the range of 88%105%.'Hygienic Standard for Cosmetics'(2007) definite prescripting sodium nitrite is a limited material in cosmetics, limiting dosage is 0.2%. Cosmetics were extracted by mixing and ultrasonic 15min using pure water, after centrifuge the supernatant liquid was then on-line treated with ultrafilter. We use Metrosep A Supp4 as Anion Exchanger Column,a mix solution of 1.8 mmol·L-1Na2CO3 and 1.7 mmol·L-1NaHCO3was used as eluent and was detected by suppressed conductivity detector. Cosmetics are simple base samples,so we rather use on-line ultrafilter than on-line dialysis, this can reduce experiment cost. DL of NO2- in this method is 0.004mg·L-1. This method,which is fast ,sensitive, extract and automation, can simultaneous determine nitrite and nitrate in cosmetics.Since happened event of adding melamine in milk illegally, everyone pay much attention about the quality of milk and dairy products. Thiocyanate(SCN-) can keep milk fresh, use as bacteriostats. Since 12th,Dec,2008, China government forbid adding SCN- in milk and other foods.A method was established of IC detecting thiocyanate. Macro analysis of SCN- usually are Titration and Colorimetry, they are easy to obtain,quickly,but lower sensitivity. The chromatography is a common method of microanalysis, suitable for detecting SCN- from mixed ion. We add 3.5% acetone as organic improver in 2.5 mmol·L-1Na2CO3 and 2.0 mmol·L-1NaHC3. it can shorten retention time and improve chromatography peak. The samples were deal with on-line dialysis technology, which predigest purification course easily. This method was fast ,sensitive,highly selectivity, low detection limit(0.23mg/kg) and worth promotion.
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