Separation of thiosulfate and the polythionates in gold thiosulfate leach solutions by capillary electrophoresis

Thiosulfate pretreatment enhancing short-chain fatty acids production from anaerobic fermentation of waste activated sludge: Performance, metabolic activity and microbial community

A novel strategy based on thiosulfate pretreatment for enhancing short-chain fatty acids (SCFAs) from anaerobic fermentation (AF) of waste activated sludge (WAS) was proposed in this study. The results showed that the maximal SCFA yield increased from 206.1 ± 4.7 to 1097.9 ± 17.2 mg COD/L with thiosulfate dosage increasing from 0 to 1000 mg S/L, and sulfur species contribution results revealed that thiosulfate was the leading contributor to improve SCFA yield. Mechanism exploration disclosed that thiosulfate addition largely improved WAS disintegration, due to thiosulfate serving as a cation binder for removing organic-binding cations, especially Ca²⁺ and Mg²⁺, dispersing the extracellular polymeric substance (EPS) structure and further entering into the intracellularly by stimulated carrier protein SoxYZ and subsequently caused cell lysis. Typical enzyme activities and related functional gene abundances indicated that both hydrolysis and acidogenesis were remarkably enhanced while methanogenesis was substantially suppressed, which were further strengthened by the enriched hydrolytic bacteria (e.g. C10-SB1A) and acidogenic bacteria (e.g. Aminicenantales) but severely reduced methanogens (e.g. Methanolates and Methanospirillum). Economic analysis confirmed that thiosulfate pretreatment was a cost-effective and efficient strategy. The findings obtained in this work provide a new thought for recovering resource through thiosulfate-assisted WAS AF for sustainable development.

Sample plug induced peak splitting in capillary electrophoresis studied using dual backscattered interferometry and fluorescence detection

The appearance of unexpected peaks in capillary electrophoresis (CE) is common and can lengthen the time of method development as assay conditions and experimental parameters are varied to understand and mitigate the effects of the additional peaks. Additional peaks can arise when a single-analyte zone is split into multiple zones. Understanding the underlying mechanism of these phenomena, recognizing conditions that favor its presence, and knowing how to confirm and eliminate the effect are important for efficient method optimization. In this study, we examine how the overlap of analyte zones with the sample plug can lead to peak splitting. This is explored experimentally using dual detection CE, which enables both the sample plug and analyte zones to be independently and simultaneously measured from the same detection volume. Simulations performed via COMSOL Multiphysics confirm the origin of the splitting and help guide experiments to reduce and eliminate the effect. Our findings show that this peak splitting mechanism can arise in separations of both small and large molecules but is, especially, prevalent in separations of slowly migrating macromolecules. This effect is also more prevalent when using a short length-to-detector, as is commonly found in microfluidic applications. A simple diffusion-less model is introduced to develop strategies for reducing peak splitting that avoids modifying the apparatus, such as by lengthening the separation length, which can be difficult. Decreasing the sample plug length and slowing the electroosmotic flow can both reduce this effect, which is confirmed experimentally.

Capillary electrophoresis of inorganic ions: An update

This review as a sequel of three earlier similar reports gives a summary of the progress and significant methodological developments, starting from 2002, in the use of capillary electrophoresis (CE) for inorganic ion analysis. As substantiated by the illustrative number of relevant references, improvements in sensitivity achieved both in and outside a CE system, advances in manipulating the separation selectivity, novel hardware configurations, and system performance innovations are continually being reported over the review period. Specifically viewed are the recent advancements in elemental (bio)speciation analysis, which remains one of the most fertile areas of CE research, as well as in three recently booming research topics: contactless conductivity detection, separations on microchips, and transient isotachophoretic preconcentration. A state-of-the-art picture of technique's potentialities within the field of interest presented here demonstrates that CE has become recognized and is growing in acceptance as a reliable alternative to traditional analytical methods such as high-performance liquid chromatography (HPLC).

Investigation of the factors that induce analyte peak splitting in capillary electrophoresis

Peak splitting has a detrimental effect on analyses by capillary electrophoresis. Many papers have reported it and several mechanisms have been proposed to explain the phenomenon. We investigated the electrophoretic behavior of an amphoteric analyte, levodopa, in phosphate buffer and observed a peak splitting phenomenon at moderate sample concentrations and under general analytical conditions, even without organic solvent. The dependence of effective mobility on pH was taken into account and pKa values of 2.30, 8.11, and 9.92 were obtained for levodopa. Then, we constructed pH-dependent distribution diagrams of levodopa and phosphate species present in aqueous solution and proposed that the most relevant factors contributing to peak splitting are the presence of ionizable groups in the analyte molecule and the occurrence of ionization, yielding charged species which interacted with buffer electrolyte species in a definite pH range to form complexes. This result is different from those presented in the literature and broadens our understanding of amphoteric analyte peak splitting.