Microwave Digestion of Food Materials

By

Abstract

CEM has developed a method for the simultaneous and rapid preparation of vastly different food sample types for trace metal analysis.

Introduction

The recent passage of the food safety act has resulted in additional required testing by food manufacturers. The CEM MARSXpress Digestion System is well suited to meet this need. In this study, four different sample types that include milk powder, sliced cheese, sausage and a frozen meat topping pizza were prepared in duplicate. The samples were prepared in the CEM MARSXpress System and analyzed by ICP-OES. The accuracy and precision of the analyses are discussed.

Experimental Conditions

The MARSXpress System can process up to 40 samples simultaneously. The system offers a three part vessel with self-regulating pressure control that is simple to use and requires no tools to assemble. In addition, the Contactless All-Vessel IR Temperature Control system monitors and controls all samples being digested. This system allows for vastly different sample types to be prepared simultaneously.

The sausage and pizza were ground in a blender to ensure uniformity. The sliced cheese and milk powder were used without any preparation. The samples were prepared in duplicate. For this work, a 1.0 gram sample was weighed and 10 mL of concentrated nitric acid was added to a CEM 75- mL MARSXpress vessel. The system was ramped to 210°C in 20 minutes and held for 15 minutes. Vessels were allowed to cool for 15 minutes prior to uncapping and dilution. All samples, spikes, and blanks were diluted to 50 mL for analysis.

Results

The ICP results of the digestion are shown in Table I.

All of the samples were completely digested in the CEM MARSXpress vessels. This can be noted as the results show there is a good agreement between the duplicate samples for all analyzed metals.

Conclusions

The MARSXpress System was able to prepare very different food sample types. The system offers significant time savings as up to 40 samples can prepared at one time. In addition, the system operates unattended once started, thus freeing the analyst to do other tasks. The MARSXpress was able to prepare larger one gram samples, which has not been possible until now. The fact that these digests are carried out in sealed vessels reduces the possibility of contamination, as well as potentially reducing blank values. These advantages are noted by our reproducible ICP results.

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