Determination of polychlorinated dibenzo-p-dioxin and dibenzofuran congeners in air particulate and marine sediment standard reference materials (SRMs)

Due to the limited number of environmental matrix certified reference materials (CRMs) with assigned values for natural levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), an interlaboratory study was undertaken by the National Institute of Standards and Technology (NIST) and Environment Canada to establish reference concentration values for selected PCDD/Fs in two well-characterized NIST Standard Reference Materials (SRMs): SRM 1649a (Urban Dust) and SRM 1944 (New York/New Jersey Waterway Sediment). Results from 14 laboratories were used to provide reference values for the seventeen 2, 3, 7, 8-substituted PCDD/F congeners, the totals for individual tetra- through hepta-substituted PCDD/F homologues, and the total amount of tetra- through hepta-substituted PCDD/Fs. The mass fractions for the individual 2, 3, 7, 8-substituted congeners range from approximately 0.01 microg/kg to 7 microg/kg dry mass.

Use of the Microwave-Assisted Process in extraction of fat from meat, dairy, and egg products under atmospheric pressure conditions

Fat from meat, dairy, and egg products was extracted by using Microwave-Assisted Process (MAP) technology under atmospheric pressure conditions. Fat content was determined gravimetrically after extraction with microwaves and organic solvents that are transparent to microwaves relative to the sample. (In situ hydrolysis was performed for dairy and egg products.) Fat from the food sample migrated completely to the extractant when samples were irradiated with focused microwave for a total of 3 min for meat products, 1 min for dairy products, and 4 min for egg products. Unlike current methods used for determining fat in meat products, the microwave-assisted method does not require a dry sample, because moisture in the sample (around 75%) enhances the efficiency of extraction. No preprocessing was required for meat samples other than homogenization, which is critical, as it is for other current methods. In addition to speed and ease of use, the features of this technology are low solvent consumption, low energy consumption, reproducibility, and recoveries similar to or even better than those of conventional extraction methods.