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Garlic peel, an agriculture by-product, was modified using nitric acid as a simple method. Therefore, this study aims to remove and/or minimize of Cr(VI) ions from aqueous media using HNO3 modified garlic peel (HNO3-GP). Scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy analysis of the HNO3-GP, as a solid phase extractor, were performed. The operational parameters of the adsorption such as solution pH, initial concentration of analyte, adsorbent dose, temperature and shaking time were performed. The equilibrium data of Cr(VI) showed a better fit with Langmuir isotherm model with R² = 0.9956 and adsorption capacity equals to 31.7 mg/g. Moreover, the kinetic data of analyte retained revealed that the present system fitted well with pseudo-second-order kinetic model (R² = 0.9918). Thermodynamic studies indicated that the retention step was endothermic and spontaneous in nature depending on the value of ΔH° (118.292 J/mol) and ΔG° (–117.41 kJ/mol). The positive value of ΔS° (394.39 J/mol·K) confirmed that the biosorption process was carried out with high randomness on the surface of HNO3-GP. The results showed that the proposed adsorbent (HNO3-GP) provides an effective and economical approach in highly minimization or almost removal of Cr(VI) ions from the aqueous solution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The study reports a simple and highly selective spectrofluorometric method for trace determination and speciation of chromium(iii & vi) species in water using 10-(3-dimethylaminopropyl) phenothiazine hydrochloride, namely, promazine hydrochloride (PMH) as a fluorescence tagging reagent. The method is based on the redox reaction between PMH and chromium(vi) in aqueous H3PO4, resulting in the formation of complex [Cr(iii)–PMH] followed by fluorescence quenching at λex/em = 300/449 nm. An exceptional value for the limit of detection (LOD = 0.03 μg L−1) is attained with a linear range of 0.1–1.0 μg L−1 under the optimized conditions. A coefficient of variation (CV) of ±2.05% (n = 5) is obtained at 2.0 μg L−1 level of chromium(vi). Chemical speciation of the chromium(iii & vi) species is successfully accomplished after the oxidation of chromium(iii) to chromium(vi) with H2O2 in KOH solution at pH 9.0. The method is validated in environmental water samples with satisfactory recovery percentages (＞97.7%) using inductively coupled plasma-optical emission spectrometry (ICP-OES). The proposed and reference methods are subjected to statistical treatment (student's t and F tests) at 95% confidence with no significant difference, indicating the precision and accuracy of the proposed optical probe. [ABSTRACT FROM AUTHOR]

The current study explores the use of quercetin for developing a highly selective spectrofluorimetric methodology for trace determination, speciation and thermodynamic characterization of tungstate (WO 4 2 - ) species in water. The study relies on the principle of chelate formation between WO 4 2 - 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 λ ex/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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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 β-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 (R 2 ) 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 β-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., (Copyright © 2017 Elsevier B.V. All rights reserved.)