A simplified analysis of dimethylarsinic acid by wavelength dispersive X-ray fluorescence spectrometry combined with a strong cation exchange disk

Formation of dimethyldithioarsinic acid in a simulated landfill leachate in relation to hydrosulfide concentration

Dimethyldithioarsinic acid (DMDTA(V)), present in such intense sources as municipal landfill leachate, has drawn a great deal of attention due to its abundant occurrence and different aspect of toxicity. The hydrosulfide (HS(-)) concentration in leachate was studied as a major variable affecting the formation of DMDTA(V). To this end, the HPLC-ICPMS system equipped with the reversed-phase C18 column was used to determine DMDTA(V). Simulated landfill leachates (SLLs) were prepared to cover a mature landfill condition with the addition of sodium sulfate and sulfide at varying concentrations in the presence of dimethylarsinic acid (DMA(V)). The concentration of sodium sulfide added in the SLLs generally exhibited a strong positive correlation with the concentration of DMDTA(V). As such, the formation of DMDTA(V) in the SLLs is demonstrated to be controlled by the interactive relationship between DMA(V) and the HS(-).

Effectiveness of activated carbon disk for the analysis of iodine in water samples using wavelength dispersive X-ray fluorescence spectrometry

A novel approach using wavelength dispersive X-ray fluorescence (WDXRF) spectrometry combined with an activated carbon (AC) disk was developed for the determination of total iodine concentrations in water samples. Dissolved iodine species (i.e., I(-) and IO3(-)) in water samples were preconcentrated on the AC disk and directly analyzed by WDXRF spectrometry. The adsorption behavior of I(-) and IO3(-) on the AC disk was assessed at varying pH levels (4, 6, and 8). The AC disks completely retained the I(-) and IO3(-) for all the pH levels tested. The calibration curve obtained from the iodine concentrations (i.e., 0, 20, 200, and 400 μg) of AC disks and the measured X-ray intensity from the WDXRF analysis showed a good linearity (R(2)=0.9960), with a relatively low limit of detection (0.575 μg). The durability of the AC disk for repeatable measurements was also assessed to validate the sustainability of the proposed method and consequently the measured X-ray intensity for the AC disks was constant until 8d of analysis time. The accuracy of the proposed AC-WDXRF method was confirmed by measuring iodine concentration spiked in drinking water using inductively coupled plasma-mass spectrometry (ICP-MS). The proposed method is simple, rapid, efficient, and environmental friendly for iodine analysis in water samples. As a precursor of disinfection by products (DBPs), it is important to determine the total iodine concentrations in raw water.