Pre-illumination of Chlorella cells at room temperature with light primarily absorbed by PSII (650 nm) produces a state called state II. This is characterized by high fluorescence at 715 nm (high F715/F685) at liquid nitrogen temperature. Alternately if the cells are pre-illuminated by light primarily absorbed by PSI (710 nm) then state I with high fluorescence at 685 nm (low F715/ F685) at 77K is produced. We have investigated the role of photophosphorylation in the development of state I/II in chlorella cells using uncoupler and energy transfer inhibitors. The results suggested that the development of state I depends upon the energization of the membrane. Both DCCD and TPTC which permit build up of proton gradient block the adaptation to state I in­ dicating that proton gradient formation alone is not sufficient to develop state I. The data obtain­ ed by us as also published in the literature indicate that redox states o f the electron transport carriers are responsible for the development of state II.

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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.

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