A comparison of flow injection methods for sulfide determination based on phenothiazine dyes produced from diverse aromatic amines

Synthesis optimization of rich-urea carbon-dots and application in the determination of H2S in rich- and barren-liquids of desulphurizing solutions

In the research of carbon dots (CDs) containing various nitrogen sources, it was first found that urea/citric acid-CDs showed a selective discolouration reaction with sulphide ions. Therefore, by optimizing various synthesis and detection conditions of the CDs determining sulfur ions, such as the raw material ratio, temperature, time, pH, and oxidation atmosphere in the CD synthesis, a discolour CD-probe method for trace-level sulphide ions was developed. The method is environmentally friendly, shows two linear-response ranges in 0.050-1.0 mg L^-1 (A = -0.0827c + 0.8366) and 1.0-15 mg L^-1 S^2- (A = -0.0209c + 0.7587) and can be used for the high and low concentration quantification of sulphide in various wastewaters. Subsequently, in order to realize the separation and detection of sulphide ions in wastewaters or rich- and barren-liquids containing N-methyldiethanolamine and other substances in desulphurizing solutions, an automatic pretreatment system was also established.

Spectrophotometric determination of sulfide based on peroxidase inhibition by detection of purpurogallin formation

This paper presents a new method for spectrophotometirc detection of sulfide applying fungal peroxidase immobilized on sodium alginate. The sensing scheme was based on decrease of the absorbance of the orange compound, purpurogallin produced from pyrogallol and H2O2 as substrates, due to the inhibition of peroxidase by sulfide. Absorbance of purpurogallin was detected at 420nm by using a spectrophotometer. The proposed method could successfully detect the sulfide in the concentration range of 0.6-7.0μM with a detection limit of 0.4μM. The kinetic parameters of Michaelis-Menten with and without sulfide were also calculated. Possible inhibition mechanism of peroxidase by sulfide was deduced according to the variation of parameters and uncompetitive mechanism was observed with respect to hydrogen peroxide. The current method provides an easy to use method for sulfide detection in water samples.

Micelle mediated trace level sulfide quantification through cloud point extraction

A simple cloud point extraction protocol has been proposed for the quantification of sulfide at trace level. The method is based on the reduction of iron (III) to iron (II) by the sulfide and the subsequent complexation of metal ion with nitroso-R salt in alkaline medium. The resulting green-colored complex was extracted through cloud point formation using cationic surfactant, that is, cetylpyridinium chloride, and the obtained surfactant phase was homogenized by ethanol before its absorbance measurement at 710 nm. The reaction variables like metal ion, ligand, surfactant concentration, and medium pH on the cloud point extraction of the metal-ligand complex have been optimized. The interference effect of the common anions and cations was studied. The proposed method has been successfully applied to quantify the trace level sulfide in the leachate samples of the landfill and water samples from bore wells and ponds. The validity of the proposed method has been studied by spiking the samples with known quantities of sulfide as well as comparing with the results obtained by the standard method.

Direct introduction of water sample in multisegmented flow-injection analysis for sulfide determination

The present paper describes an inline flow-injection analysis system for the determination of sulfide in water samples, exploiting the Fischer reaction. Water samples were collected and introduced into a reactor of the FIA system. The sulfide released, after sample acidification, was carried out with a nitrogen gas flow and mixed with N,N diethyl-p-phenylenediamine (DEPD) solution in the presence of Fe(III). The blue dye formed was measured in the wavelength range between 672-679 nm. An evaluation of the effects of chemical and flow factors was performed using the factorial design of two levels, while optimization was accomplished by a Doehlert matrix. The system presented two linear-response ranges: the first of 0.433 to 400 µg L(-1) and the second of 400 to 3500 µg L(-1). The detection and quantification limit were found to be 0.130 and 0.433 µg L(-1), respectively, while the sample throughput was 12 h(-1). The precision was evaluated as the relative standard deviation (n = 10); for 50 and 100 µg L(-1) sulfide it was found to be 1.9 and 2.3%, respectively. The method showed satisfactory selectivity regarding the main interference present in environmental samples. The accuracy of the method was successfully evaluated in environmental water samples after a comparison with a literature reference method.