Sorption behavior of selected chlorophenols onto polyurethane foam treated with iron(III): kinetics and thermodynamic study.

An efficient, selective, and inexpensive method for complete elimination of chlorophenols (CPs) from water has been established. The proposed procedure was based upon the use of n-tributyl phosphate (TBP)-plasticized iron(III) physically immobilized polyurethane foam (PUF) solid sorbent for complete removal of CPs from aqueous media at pH close to 0. The interaction of the complex ion [Fe(C6H5O)6]3- with protonated ether oxygen of the PUF sorbent forms ternary ion associate on/in the PUFs. The retention of 4-chlorophenol (4-C) and 2,4,6-trichlorophenol (TCP) by the TBP-treated iron(III)-immobilized PUF fitted well with the pseudo-second-order kinetic model with a rate constant (k) of 0.04 and 0.15 g (mg min)-1, respectively. The sorption of 4-CP was endothermic whereas the uptake of TCP was favorable at low temperature approving the exothermic and non-spontaneous characteristics of its uptake. The ΔS value for 4-CP reveals good affinity of the ion [Fe(C6H5O)6]3- towards the PUF sorbent.

A quercetin based fluorescent chemical sensor for ultra-sensitive determination and speciation of tungsten species in water.

The current study explores the use of quercetin for developing a highly selective spectrofluorimetric methodology for trace determination, speciation and thermodynamic characterization of tungstate (WO42-) species in water. The study relies on the principle of chelate formation between WO42- and quercetin with subsequent increase in the emission intensity. The developed method could be applied successfully in a wide linear range (1.0-400.0 µg L-1) with a detection limit of 0.28 µg L-1 and quantification limit of 0.92 µg L-1 at λex/em = 400/492 nm. The developed method was successfully applied in real tap and waste water samples. The suitability of the proposed method was further validated by inductively coupled plasma-optical emission spectrometry (ICP-OES) in terms of student's t and F tests at 95% confidence. Characterization (NMR, FTIR and electronic spectra), stoichiometry, stability constant, fluorescence mechanism and thermodynamic parameters (ΔH, ΔS, and ΔG) of the produced complex species were evaluated and properly assigned. The fluorescence quenching mechanism of tungstate quercetin complex by Triton X-100 was also evaluated for computing Stern-Volmer quenching constant and approximating quenching sphere. The method showed a clear significance over most of the reported methods for tungsten in literature in terms of good accuracy, robustness, ruggedness, short analytical time and cost-effectiveness.

Biogenic Amines Formation Mechanism and Determination Strategies: Future Challenges and Limitations.

The evolution in foodstuff-monitoring processes has increased the number of studies on biogenic amines (BAs), in recent years. This trend with future perspective needs to be assembled to address the associated health risks. Thus, this study aims to cover three main aspects of BAs: (i) occurrence, physiology, and toxicological effects, most probable formation mechanisms and factors controlling their growth; (ii) recent advances, strategies for determination, preconcentration steps, model technique, and nature of the matrix; and (iii) milestone, limitations with existing methodologies, future trends, and detailed expected developments for clinical use and on-site ultra-trace determination. The core of the ongoing review will discuss recent trends in pre-concentration toward miniaturization, automation, and possible coupling with electrochemical techniques, surface-enhanced Raman scattering, spectrofluorimetry, and lateral flow protocols to be exploited for the development of rapid, facile, and sensitive on-site determination strategies for BAs.

A simple and low cost dual-wavelength ß-correction spectrophotometric determination and speciation of mercury(II) in water using chromogenic reagent 4-(2-thiazolylazo) resorcinol.

The most common problems in spectrophotometric determination of various complex species originate from the background spectral interference. Thus, the present study aimed to overcome the spectral matrix interference for the precise analysis and speciation of mercury(II) in water by dual-wavelength ß-correction spectrophotometry using 4-(2-thiazolylazo) resorcinol (TAR) as chromogenic reagent. The principle was based on measuring the correct absorbance for the formed complex of mercury(II) ions with TAR reagent at 547nm (lambda max). Under optimized conditions, a linear dynamic range of 0.1-2.0µgmL-1 with correlation coefficient (R2) of 0.997 were obtained with lower limits of detection (LOD) of 0.024µgmL-1 and limit of quantification (LOQ) of 0.081µgmL-1. The values of RSD and relative error (RE) obtained for ß-correction method and single wavelength spectrophotometry were 1.3, 1.32% and 4.7, 5.9%, respectively. The method was validated in tap and sea water in terms of the data obtained from inductively coupled plasma-optical emission spectrometry (ICP-OES) using student's t and F tests. The developed methodology satisfactorily overcomes the spectral interference in trace determination and speciation of mercury(II) ions in water.