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One of the most frequently used methods for determining total mercury content in biological samples is cold vapour atomic absorption spectrometry (CV-AAS), which is extensively used in the biomonitoring of environmental pollution. Seabirds are often used as bioindicators of metal contamination because of their specific feeding habits, wide geographical ranges and long lifespan. This paper describes the validation of CV-AAS for determining the total mercury content in biological samples (whole fish, cormorant tissues). The development and optimization of the procedure is outlined, and the main objective of this study was to calculate its validation parameters. The selectivity of the method was documented; linearity (r>0.993) ranged from 0.29 to 100 ng of total mercury per sample mass. For a total Hg content of 80-1,000 ng, a polynomial calibration curve derived directly the Lambert-Beer law was used. The method showed good recoveries (average 98.0%) and a relative standard deviation for repeatability of < 10%. The limit of detection was calculated at 0.096 ng of total Hg per sample mass. The uncertainty budget was evaluated according to the ‘Guide to the Expression of Uncertainty in Measurement’ (GUM) [1]; the relative expanded uncertainty was estimated at < 13%.
Introduction. The Total Antioxidant Capacity (TAC) of human milk reflects the concentration and the activity of many components which prevent oxidative degradation of fats and proteins. This study compares the effectiveness of ABTS and DPPH tests with regard to the recovery, precision and sensitivity (detection and quantification limit) of (TAC) values in human milk. Material and methods. TAC values were determined in twenty five samples of human milk obtained from healthy mothers, residents of Gdańsk, on the 14,h day postpartum. Results. The average TAC of human milk determined by ABTS assay was 19.61 ±3.311 mg TE (Trolox Equivalents)/100 cm3, the average values obtained by the DPPH assay reached 9.95 ±4.36 mg TE/100 cm3. For each milk sample the TAC determined by the ABTS test was significantly higher than the values produced by the DPPH test. The above findings can be attributed to the presence of substances whose spectra overlap with DPPH’ spectra. ABTS test was characterised by a higher sensitivity and repeatability of the determination of TAC in human milk compared to the DPPH test. Conclusions. Comparing the calculated values for the validation parameters of both methods and taking into account the solubility of DPPH only in polar matrices, slower reaction of selected antioxidants with DPPH radical, and the presence in human milk constituents absorbing electromagnetic radiation in the absorption of DPPH be assumed that the ABTS test is more appropriate method of determining of TAC in breast milk.
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