食品和饲料、粮食、谷物中汞含量、总汞、重金属检测方案(测汞仪)

DIRECT AA MERCURY DETERMINATION IN FOODSTUFF AND MIXED FEED INTRODUCTION Direct atomic absorption mercury determination (without any pre-treatment procedures) in food is complicated by its organic matrix. That is the reason why almost all AAS methods of mercury determination in foodstuff include sample digestion by acids. This stage extends analysis time, increases detection limit and becomes the main source of errors. Using a RA-915M mercury analyzer with Zeeman background correction and a PYRO-915+ pyrolytic attachment allows direct mercury determination in foodstuff, food/feed products and similar samples at ppb level that saves time due to elimination of the sample preparation stage. MEASUREMENT METHOD The measuring method is based on thermal atomization of mercury from a sample using a PYRO-915+ attachment and its consequent determination by flameless AAS with Zeeman background correction using a RA-915M mercury analyzer. A sample is placed into the sample boat, which is inserted into the first chamber of the atomizer, where the sample is heated at a temperature of 200–800°C (depending on the selected operation mode). The mercury compounds are evaporated and partially dissociated, forming elemental mercury. All the gaseous products formed are transported into the second chamber of the atomizer by a carrier gas (ambient air). Mercury compounds are totally dissociated and the organic matrix of the sample is burnt out. Downstream from the atomizer the air flow enters the analytical cell heated up to 700°C, and the mercury atoms are detected by RA-915M analyzer. This approach does not involve preconcentration on a gold trap and “cooling step”, thereby eliminating ensuing problems. The use of ZAAS combined with a “dry” converter provides the highest sensitivity with no interferences from the sample matrix. Purified ambient air is used for combustion, so that no cylinders with oxidizer or compressed gases and “clean room” environment are required. Total time needed for determination of mercury is not longer than 2 minutes. MEASUREMENT RANGE The measurement range of the mass concentration of total mercury is 2.5–5000 µg/kg (mass of homogenized sample is 30–400 mg). Sample Detection limit, ppb Sample Detection limit, ppb Bread 0.5 Milk 0.5 Dry milk and condensed milk 1 Sugar 5 Fruits 0.5 Tea 2 Fish 0.5 Vegetables 0.5 ANALYSIS FEATURES Sample homogenization and weighting is enough as sample preparation. Control of non-selective absorption during the measurement process allows optimizing of sample weight and reduces analysis errors. Rapid analysis. SRMs with any matrix (both liquid and solid) can be used for calibration. Low running cost (Needs no chemical reagent). EQUIPMENT AND REAGENTS The following equipment and materials are used for analysis: Mercury analyzer RА-915М with PYRO-915+ attachment; PC with Windows® ХР/Vista/7/8 and RAPID software; СRM of mercury. EXAMPLES OF ANALYSIS The validity of the LUMEX method is proved by the agreement between the measured and certified concentrations in various standard complex-matrix samples. Reference material Мass, mg Measured value, ppb Certificate value, ppb Deviation, % BCR-150 (Dry milk) 52 / 96 / 109 8.4 / 7.9 / 7.9 9.41.7 -14 DORM-1 (Fish) 50 / 100 860 / 780 79874 +4 BCR-184 (Beef) 29 / 59 100 2.3 / 2.5 / 3.1 2.60.6 0 The information in this leaflet is supplemental. To get more specific information on this method, please contact the developer of this method LUMEX INSTRUMENT Group. NORTH AMERICA Lumex Instruments Canada 0890278 B.C. Ltd. E-mail: info@lumexinstruments.com www.lumexinstruments.com EUROPE Lumex Analytics GmbH E-mail: info@lumexanalytics.de www.lumexanalytics.de RUSSIA Lumex-Marketing LLC E-mail: sales@lumex.ru www.lumexinstruments.com CHINA Beijing Lumex Analytical Equipment Co. Ltd. E-mail: lumex@lumex.com.cn www.lumexcn.com 2        现有食品和饲料中总汞的检测方法主要是原子荧光法，由于其复杂的有机基质，都需要进行酸解等前处理步骤，而前处理过程复杂、耗时长、易污染、易挥发，以及原子荧光法本身存在汞漂移、易污染等问题。使用塞曼扣背景效应汞分析仪和热解附件相结合的方法，由于消除了样品制备阶段，大大提高了检测极限，直接测定食品和饲料产品中的汞含量均在PPB水平以下，而且省却了酸解步骤，可以节省大量的前处理时间。         原子荧光光谱分析法：检出限0.15μg/kg，标准曲线最佳线性范围0μg/L～60μg/L；        冷原子吸收法的检出限：压力消解法为0.4μg/kg，其他消解法为10μg/kg；        比色法为25μg/kg。直接汞测定法为0.5μg/kg。