Dma 80

Samples (100 mg) were analyzed for Hg concentration using an DMA-80 (Milestone, Shelton, CT, USA) by thermal decomposition (from 60 to 650 °C for about 5–6 min), in oxygen or air atmosphere according to US EPA 7473 method [28 (link)].
Prior to the analysis, the calibration curve was constructed using Hg 1000 mg/L certified standard (CZECH Metrology Institute Analytika). The calibration standard solutions were prepared in glass flasks at 5 concentration points, in the range between 0.05 and 10 mg/L. Each standard solution was injected six times. The method was validated according to the EURACHEM guidelines (EURACHEM 2014). The evaluation of the linearity was based on the determination of the coefficient of determination (r²). Good linearity was observed, achieving a r² = 0.9996. The detection limit (LOD) and quantification limit (LOQ) were counted as 3 times and 6 times the standard deviation for blanks and were 0.29 µg/kg and 0.58 µg/kg, respectively. For seawater matrix LOD and LOQ were 0.05 and 0.16 µg/L respectively. The accuracy of the Hg analysis was tested using spearfish sample (TB 149) and coastal seawater (IRMM BCR-579) certified reference material (CRM). Recoveries were 93% and 95%, respectively.

Total mercury concentrations in blood were analyzed by the gold amalgamation method using a direct mercury analyzer (DMA-80; Milestone Inc., Shelton, CT, USA). For the accuracy of analysis, the mercury standard solution was made stepwise by 1 to 10 mL according to the required concentrations using a 1000 mg/L standard solution (Sigma-Aldrich Inc., St. Louis, MO, USA). The mercury standard solution was diluted with a 0.001% L-cysteine solution to make 100 mL solution, which was then used for preparing the calibration curves and measuring the absorbance of mercury. A 100 μl of sample from each participant was injected into the sample container of the analyzer. The absorbance of samples was measured at 253.7 nm wavelength, and the concentration of mercury in these samples (mg/mL) was determined using a calibration curve [21 ]. For the quality control of the laboratory, we participated in German External Quality Assessment Scheme (G-EQUAS) of the Friedrich Alexander University, Erlangen for occupational-medical and environmental medical toxicological analyses.

For salt samples, a determination of Hg content was also carried out with a direct mercury analyzer (DMA-80, Milestone S.r.l., Sorisole, Italy), an instrument based on the thermal decomposition amalgamation-atomic absorption spectrophotometry (TDA-AAS). The DMA-80 is a more versatile analytical instrumentation compared to ICP-MS: it permits the direct analysis of the sample without the need for pre-treatment and it is a more environmentally friendly analytical method than ICP-MS due to the use of a minimal amount of reagent for instrument cleaning and the safety of operators who are not exposed to mercury. The guidance reported by the EPA Method 7473 (SW-846) [18 ] was referred to in developing the method of analysis of DMA-80. Precisely, ~100 mg of every homogenized sample was initially dried at 230 °C for 3 min and then thermally decomposed at 650 °C for 3 min. The Hg content was determined by working at its typical wavelength, i.e., 253.7.