The aim of this work was to validate two methods for methylmercury (CH₃Hg⁺) determination in sediments and cyanobacteria and their application to the Hg methylation study of planktonic organisms in water from a contaminated site in Brazil. Analytical methods for the determination of CH₃Hg⁺ include many steps, and the necessity of adaptation to different matrices is very common and not always easy. In addition, these adaptations require new optimization and validation, which are found in a few articles using the matrix sediments but in none with planktonic organisms. The methods presented here were based on the extraction of CH₃Hg⁺ from these matrices, derivatization, trapping, thermal desorption, GC separation, pyrolysis and detection by AFS (GC-pyro-AFS). The results showed good linearity (0.994) in the range of 0 to 400 pg CH₃Hg⁺ with a repeatability of 3%, an intermediate precision of 8%, a recovery in spiked sample tests in the range of 93 to 129%, and detection limits of 0.04 μg kg⁻¹ for sediments and 1.3 μg kg⁻¹ for cyanobacteria. Certified reference materials showed good recoveries. The method for the cyanobacteria matrix was used for the Hg²⁺ methylation assay with cultures of cyanobacteria and microalgae isolated from water samples collected in an ancient Hg-contaminated gold mining area in Brazil. The production of CH₃Hg⁺ was detected only in the culture of the microalga Stichococcus species (0.23% of total Hg), indicating its participation in the biotransformation of Hg. The methods can be used as important tools in routine analysis and/or studies of the biogeochemical cycle of Hg.

中文翻译：

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沉积物和蓝细菌样品中甲基汞的测定：方法验证及在甲基化研究中的应用

这项工作的目的是验证两种测定沉积物和蓝细菌中甲基汞（CH ₃ Hg ⁺）的方法，并将其应用于巴西受污染场地水中浮游生物的Hg甲基化研究。测定CH ₃ Hg ^+的分析方法包括许多步骤，适应不同基质的必要性非常普遍，而且并不总是那么容易。此外，这些改编还需要进行新的优化和验证，在一些使用基质沉积物的文章中找到了这些，但是对于浮游生物却没有发现。此处介绍的方法基于CH ₃ Hg ⁺的萃取从这些基质中衍生化，捕集，热脱附，GC分离，热解和AFS（GC-pyro-AFS）检测。结果显示，在0到400 pg CH ₃ Hg ⁺的范围内具有良好的线性（0.994），重复性为3％，中间精度为8％，加标样品测试的回收率在93％至129％范围内，并且0.04微克公斤的检测限^-1对沉积物和1.3微克千克^-1蓝藻。经认证的参考物质具有良好的回收率。蓝细菌基质的方法用于Hg ²⁺甲基化测定，该方法是从巴西一个受Hg污染的古老金矿开采区收集的水样中分离出的蓝细菌和微藻培养物。CH的生产仅在微藻链球菌种的培养物中检测到₃ Hg ⁺（占总Hg的0.23％），表明其参与了Hg的生物转化。该方法可用作常规分析和/或研究汞生物地球化学循环的重要工具。