Determinación de mercurio en productos alimenticios y la comida mixta usando la absorción atómica directa

INTRODUCTION

Direct atomic absorption mercury determination (without any pre-treatment procedures) in food is complicated by its organic matrix. That is the reas on why almost all AAS methods of mercury determinat ion 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/RA-915+ 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.

MEASURING 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/RA-915+ 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/RA-915+ 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.