Sulfur speciation by capillary zone electrophoresis

Fast detection of sodium dithionite in sugar using a xanthylium-based fluorescent probe

Dithionite remained in the foodstuff may pose a great threat to the health of consumers. Three xanthylium-based probes were synthesized and their responses to dithionite were explored. Probe SH-1 could respond to dithionite selectively in PBS buffer (15% DMSO, 10 mM, pH = 7.4). Upon the addition of dithionite, the fluorescent emission of SH-1 at 684 nm dropped quickly (within 10 s) and the fluorescence decline was proportional to the concentration of dithionite (0-7.0 μM). The limit of detection was determined to be 0.139 μM. Then, the sensing mechanism was tentatively presented and the structure of resulted adduct (SH-1-SO3-) which was the reaction product of SH-1 and dithionite via a Micheal addition reaction followed by an oxidation reaction was verified. Moreover, white granulated sugar was subjected to the standard spike experiments and the results demonstrated a great potential of SH-1 for the quantitative monitoring of dithionite in foodstuffs.

A Rapid Fluorescence Sensor for the Direct Quantification of Rongalite in Foodstuffs

Rongalite was reported illegally used as a food additive for bleaching purposes and improving the tenderness of foodstuffs, which may endanger public health. At present, rongalite was mostly detected by indirect methods via derivatization or determining its decomposition products. In this study, we developed a new fluorescence sensor for the direct quantification of rongalite based on the principles: (1) dopamine reacts with resorcinol and generates strong fluorophore (azamonardine); (2) rongalite could inhibit the production of fluorophores and then result in lower fluorescence intensity. Hence, the rongalite concentration was inversely proportional to fluorescence intensity of fluorophore. Several crucial reaction conditions of fluorescence sensor were further optimized, such as dopamine and resorcinol concentration, pH values, and reaction time. Under the optimal conditions, the limit of detection of fluorescence sensor was 0.28–0.38 μg/g in vermicelli, wheat and rice powder samples, exhibiting almost 3.5-fold improvement compared to that of lateral flow immunoassay. Moreover, the detection time was substantially decreased to 20 min. The recoveries in spiked samples were 80.7–102.1% with a coefficient of variation of less than 12.6%. In summary, we developed a direct, high throughput, selective and accurate fluorescence sensor that poses a promising application for the rapid detection of rongalite in foodstuffs.

Decolorization of dark-colored waste cotton fabric using redox decoloring agents

A huge quantity of dark-colored waste cotton fabrics with a high content of dye powder is dumped in landfills and incinerated, which is a waste of resources and pollutes the land and atmosphere. Also, it is meaningful to effectively strip the color from these dark-colored waste cotton fabrics with minimal damage to the strength of the textiles. In this study, a dark-colored waste cotton fabric dyed with reactive dyes was subjected to chemical treatment with redox decoloring agents. The effects of various treatments on the coloration and mechanical properties of the fabric were compared. This work developed an effective Na₂S₂O₄–H₂O₂ system for decolorizing waste cotton fabric, with numerous advantages over conventional physicochemical approaches including achieving a CIE whiteness index of 74.1, tensile strength loss of 24.0%, weight loss of 1.2%, decoloration rate of 97.8%, and a degree of polymerization of 735.3. Furthermore, a mechanism was proposed to explain the two-step synergistic decolorization process.

Decolorization of dark-colored waste cotton fabric using redox decoloring agents.

Low consumption and portable technology for dithionite detection based on potassium ferricyanide differential spectrophotometry method in related advanced oxidation processes

Carbon neutrality has been received more attention and emerged in wastewater treatment processes. Due to the development of treating technologies with the rising of new-emerging pollutants, the coupled chemical processes also should remain current for the goal of carbon-neutral operation. Among of those updated strategies, several advanced oxidation processes (AOPs) based on dithionite (DTN, S₂O₄^2-), a common water treatment agent, have been established for refractory organic contaminations removal. However, in terms of DTN detection, the traditional formol-titration method has several application limits including the low detection sensitivity and high consumption of formaldehyde. In this study, compared with traditional method, a low energy consumption technology has been developed based on the potassium ferricyanide with the carbon consumption decreasing by about 5 times. Moreover, detection limit of DTN (mmol/L level) also was lower than the titration method. The method was established based on the fact that every 1 mol of DTN can react with 2 mol [Fe(CN)₆]^3- under alkaline condition. According to that potassium ferricyanide (K₃ [Fe(CN)₆]) has the maximum absorption at 419 nm wavelength, a fitting equation based on the linear relationship between the absorbance variation of K₃ [Fe(CN)₆] and DTN amount in the ranges of 0-30 μmol with the detection limit of 0.6 μmol was established with the determination coefficient of 0.99935. It was found that there was no obvious influence of the ubiquitous foreign species with the amount lower than 6 mM, 4 mM, 6 mM, 4 mM and 1 mg/L for Cl^-, HCO₃^-, NO₃^-, SO₄^2- and NOM, respectively. Moreover, methanol and tert-butanol were employed to verify the influence of the presence of organic matters on the determination of DTN and no impact was observed in this study. The proposed method provides a new way for DTN detection with stable and countable performance in the related AOPs with the low electric energy and carbon source consumption and high detection efficiency.

Improving the steric hindrance effect of linear sulfonated acetone–formaldehyde dispersant and its performance in coal–water slurry

PSAF gains a significant steric hindrance effect from the introduction of phenol groups into its molecular structure. It exhibits stand-up adsorption rather than lie-down adsorption on SAF, resulting in a stronger steric hindrance effect and improved rheological properties.

OPTIMIZATION OF DITHIONITE BLEACHING OF HIGH YIELD BAGASSE PULP

Non-wood raw materials are an essential fiber source in regions where forest resources are limited. Therefore, chemi-mechanical high-yield bagasse pulp was prepared and then bleached with a dithionite bleaching agent. One- and two-stage bleaching of the pulp was carried out by using sodium dithionite (Y) as a sole bleaching agent, or after bleaching with hydrogen peroxide to achieve high brightness for the prepared pulp. Different parameters, such as consistency, concentration, temperature, time and pH were investigated. The effect of various additives, such as diethylenetriaminepentaacetic acid (DTPA) as chelating agent or Zn compounds and hexamethylenetetramine to stabilize the bleaching solution, was studied. The effect of dissolved oxygen in liquor was also considered.

A near-infrared fluorogenic probe with fast response for detecting sodium dithionite in living cells

Developing a reliable fluorescence probe is crucial for accurately monitoring sodium dithionite (Na₂S₂O₄, SDT) in biosystems, but the current reported azo-based ones suffers from short excitation/emission wavelengths and relative slow response speed. To address this issue, we herein present a novel near-infrared emissive fluorescence probe for SDT, namely DCM-MQ, consisting of a dicyanomethylene-benzopyran fluorogenic reporter and a 1-methylquinolinium as recognition moiety. On the basis of the specific reduction mechanism, DCM-MQ exhibited a rapid colorimetric and fluorescent recognition for SDT (less than 3 s) with large Stokes shift (112 nm) and high sensitivity (detection limit was 19 nM). The fluorescence imaging results demonstrate that DCM-MQ is competent for monitoring SDT in living systems.

Tracing the 'ninth sulfur' of the nitrogenase cofactor via a semi-synthetic approach

The M-cluster is the [(homocitrate)MoFe₇S₉C] active site of nitrogenase that is derived from an 8Fe core assembled via coupling and rearrangement of two [Fe₄S₄] clusters concomitant with the insertion of an interstitial carbon and a ‘9^th sulfur’. Combining synthetic [Fe₄S₄] clusters with an assembly protein template, here we show that sulfite can give rise to the ‘9^th sulfur’ that is incorporated in the catalytically important belt region of the cofactor after the radical SAM-dependent carbide insertion and the concurrent 8Fe-core rearrangement have already taken place. Based on the differential reactivity of the formed cluster species, we also propose a new [Fe₈S₈C] cluster intermediate, the L*-cluster, that is similar to the [Fe₈S₉C] L- cluster but lacks the ‘9^th S’ from sulfite. This work provides a semi-synthetic tool for protein reconstitution that could be widely applicable for the functional analysis of other FeS systems.

Recent trends in CE of inorganic ions: From individual to multiple elemental species analysis

The major methodological developments in CE related to inorganic analysis are overviewed. This is an update to a previous review article by the author (Timerbaev, A. R., Electrophoresis 2004, 25, 4008-4031) and it covers the review work and innovative research papers published between January 2004 and the first part of 2006. As was underlined in that review, a growing interest of analytical community in providing elemental speciation information found a sound response of the CE method developers. Presently, almost every second research paper in the field of interest deals with element species analysis, the use of inductively coupled plasma MS detection and biochemical applications being the topics of utmost research efforts. On the other hand, advances in general methodology traditionally centered on a CE system modernization for improvements in sensitivity and separation selectivity have attracted less attention over the review period. While there is no indication that inorganic ion applications would surpass by the developmental rate the more matured analysis of organic analytes, CE can now be seen as an analytical technique to be before long customary in a number of inorganic analysis arenas.