Articles by Youn-Tae Kim in JoVE
Preparation of DMMTAV and DMDTAV Using DMAV for Environmental Applications: Synthesis, Purification, and Confirmation Hosub Lee1, Youn-Tae Kim2, Seulki Jeong1, Hye-On Yoon1 1Korea Basic Science Institute, Seoul Center, 2Natural Science Research Institute, Yonsei University This article presents modified experimental protocols for dimethylmonothioarsinic acid (DMMTAV) and dimethyldithioarsinic acid (DMDTAV) synthesis, inducing dimethylarsinic acid (DMAV) thiolation through mixing of DMAV, Na2S, and H2SO4. The modified protocol provides an experimental guideline, thereby overcoming limitations of the synthesis steps that could have caused experimental failures in quantitative analysis.
Other articles by Youn-Tae Kim on PubMed
An Assessment of Sampling, Preservation, and Analytical Procedures for Arsenic Speciation in Potentially Contaminated Waters Environmental Geochemistry and Health. | Pubmed ID: 17505895 This study was undertaken to ascertain optimal methods of sampling, preserving, separating, and analyzing arsenic species in potentially contaminated waters. Arsenic species are readily transformed in nature by slight changes in conditions. Each species has a different toxicity and mobility. The conventional field sampling method using filters of 0.45 microm in size could overestimate the dissolved arsenic concentrations, as passing suspended particles that can act as a sink or source of arsenic depending on the site condition. For arsenic species in neutral pH and iron-poor waters, the precipitation can be stable for up to 3 days without any treatment, but for longer periods, a preservative, such as phosphoric acid, is required. Also, the analytical procedure must be selected carefully because the levels and hydride generation efficiencies of arsenic in different species can vary, even for the same amount of arsenic. For arsenic speciation in samples that also include organic species, a hybrid high-performance liquid chromatography (HPLC) column and inductively coupled plasma mass spectrometry (ICP-MS) gave the best resolution and lowest detection limits. However, the procedure using a solid phase extraction (SPE) cartridge can be used economically and conveniently for analyzing samples containing only inorganic arsenic species, such as groundwater, especially that related to mine activity.
Kinetics of Dimethylated Thioarsenicals and the Formation of Highly Toxic Dimethylmonothioarsinic Acid in Environment Environmental Science & Technology. | Pubmed ID: 27701855 Dimethylmonothioarsinic acid (DMMTA) is a highly toxic, thiolated analogue of dimethylarsinic acid (DMA). In comparison, a further thiolated analogue, dimethyldithioarsinic acid (DMDTA), and DMAboth exhibit lower toxicity. To understand the environmental conditions responsible for forming DMMTA, the kinetics of DMAthiolation are examined. The thiolation of DMAis pH-dependent and consists of two consecutive first-order reactions under excess sulfide conditions. The first thiolation of DMAto form DMMTAis faster than the second one to DMDTA. DMMTAis therefore an intermediate. The first reaction is first-order in HS at pH 6.0 and 20 °C; therefore, the overall reaction is second-order and the rate coefficient in this condition is 0.0780 Ms. The rate coefficient significantly decreases at pH 8.0, indicating that HS(aq) triggers the thiolation of DMA. The second reaction rate is significantly decreased at pH 2.5; therefore, reaction under strongly acidic conditions leads to accumulation of highly toxic DMMTAin the early stages of thiolation. The transformation of DMDTAto DMMTAis catalyzed in the presence of ferric iron. Formation of DMMTAshould be considered when assessing risk posed by arsenic under sulfidic or sulfate reducing conditions.