A method was validated for the determination of total Hg in fish muscle using continuous flow cold vapour atomic absorption (CVAAS) after microwave digestion in closed vessels. The method was validated according to European Union Regulations 333/2007 and 657/2002, considering the maximum level for the metal in fish, established by European Union regulation 1881/2006. The procedure for determining linear range, selectivity, recovery, precision, trueness, decision limit (CCα), detection capability (CCβ), measurement uncertainty and robustness of the method is reported. The results of the validation process demonstrate the method fulfils the provisions of the Commission Regulation. The selectivity study indicated that there was no matrix effect on the calibration curve between the concentration range of 1.0 and 30.0 µg Hg l(-1). The mean recovery calculated at six levels of fortification was in the range of 94-104%. The limit of detection (LOD) and limit of quantification (LOQ) values were 4.90 and 15.7 µg kg(-1), while the CCα and CCβ values were 0.517 and 0.533 mg kg(-1), respectively, for the maximum contaminant level of 0.500 mg kg(-1). The relative expanded measurement uncertainty of the method was 0.055 mg kg(-1). The method was not affected by slight variations of some critical factors (ruggedness minor changes) as sample mass and volume of the HNO(3) and H(2)O(2) used in the digestion step. The method allowed accurate confirmation analyses of the CRM DORM 3. In fact, the Z-scores attained in a proficiency test round were well below the reference value of 2.0, proving the excellent performance of the laboratory.

From a green chemical point of view, techniques for extracting organic substances employing conventional solvents must be replaced with novel environment-friendly techniques. Dimethyl ether (DME) may be one of such alternative solvents to be used. Rice bran is a co-product of rice milling, which is rich in oil content.Theoretically, around 20-25% of the total weight of rice bran must be oily components known as rice bran oil (RBO). In the present study, liquefied DME was used as a low temperature solvent for extracting RBO.From 10 g of fully dried rice bran used in a single batch extraction with DME, ca. 0.90 g of RBO were recovered (efficiency, 9.0%). Although the efficiency of total RBO extraction by batch extraction with DME was lower than the conventional solvent extraction system using acetone, lipid-pigment complexes potentially beneficial for human health such as ferulic acid-conjugated lipids were efficiently extracted.Fatty acid compositions found in RBO prepared by DME extraction and conventional solvent extraction did not differ. Lastly, improvement of the extraction efficiency was attempted by designing a column-based flow system allowing extraction of RBO with an optimized amount of liquefied DME. By this approach, the efficiency of RBO extraction attained ca. 24% (ca. 0.24 g of RBO extracted and recovered from 1 g of dried rice bran), using 10 to 20 g of liquefied DME applied to 1 g of rice bran packed in the column-type extraction chamber.

Dimethyl ether (DME), the simplest ether with the formula CH 3 OCH 3 , is a low-temperature solvent and extraction agent applicable to specialized laboratory procedures as recently demonstrated for extraction of biologically active, flavoring or pungent organic compounds from some biological materials. Due to its low boiling point, DME facilitates the removal of solvent from the samples after extraction. In the present study, we demonstrated the extraction of proteins from juicy or relatively dry vegetable tissues and the distribution of proteins in the dry phase and separated aqueous phase were compared. It is notable that a series of proteins from carrot roots, sized between 84.7 and 33.1 kDa, were detected in the liquid sample extracted by DME, suggesting that DME could be used as an effective extraction solvent for separating the hydrophilic (water soluble) proteins from the crude protein samples. Extraction of water-soluble proteins largely depends on the de-watering action of DME.

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