Application of a surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for micro-volume based spectrophotometric determination of low level of Cr(VI) ions in aquatic samples

Magnetic nanofluid based on hydrophobic deep eutectic solvent for efficient and rapid enrichment and subsequent determination of cinnamic acid in juice samples: Vortex-assisted liquid-phase microextraction

A quick, environmentally friendly and easy approach for the determination of cinnamic acid in juice samples based on the creation and usage of a novel magnetic nanofluid (mixture of hydrophobic deep eutectic solvent and magnetic nanoparticles) has been reported. Response surface methodology was applied to justify the contribution of the efficient factors including pH, nanofluid volume, ionic strength and vortex time. Cinnamic acid concentrations were monitored and quantified based on their HPLC peak representing linear correlations under the best operational circumstances showing linearity between 3 and 550 ng mL^-1. The LOD, LOQ, and enrichment factor for cinnamic acid were 0.8 ng mL^-1, 2.7 ng mL^-1 and 57.2, respectively. The proposed method was used for enrichment and subsequent determination of cinnamic acid from juice samples which suggests a potential alternative approach for cinnamic acid analysis in complicated food samples.

Preconcentration and Separation of Gold Nanoparticles from Environmental Waters Using Extraction Techniques Followed by Spectrometric Quantification

The quantification of gold nanoparticles (AuNP) in environmental samples at ultratrace concentrations can be accurately performed by sophisticated and pricey analytical methods. This paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods. We discuss several combinations of techniques that are suitable for separation/preconcentration and quantification of AuNP in complex and challenging aqueous matrices, such as tap, river, lake, brook, mineral, and sea waters, as well as wastewaters. Cloud point extraction (CPE) has been successfully combined with electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICP-MS), chemiluminescence (CL), and total reflection X-ray fluorescence spectrometry (TXRF). The major advantage of this approach is the ability to quantify AuNP of different sizes and coatings in a sample with a volume in the order of milliliters. Small volumes of sample (5 mL), dispersive solvent (50 µL), and extraction agent (70 µL) were reported also for surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) coupled with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The limits of detection (LOD) achieved using different combinations of methods as well as enrichment factors (EF) varied greatly, being 0.004–200 ng L−1 and 8–250, respectively.

Extraction and Purification of Inulin from Jerusalem Artichoke with Response Surface Method and Ion Exchange Resins

Inulin is used as an important food ingredient, widely used for its fiber content. In this study the operational extraction variables to obtain higher yields of inulin from Jerusalem artichoke tubers, as well as the optimal conditions, were studied. Response surface methodology and Box-Behnken design were used for optimization of extraction steps. The optimal extraction conditions were as follows: extraction temperature 74 °C, extraction time 65 min, and ratio of liquid to solid 4 mL/g. Furthermore, series connection of ion-exchange resins were used to purify the extraction solution where the optimal resin combinations were D202 strongly alkaline anion resin, HD-8 strongly acidic cation resin, and D315 weakly alkaline resin while the decolorization rate and decreased salinity reached 99.76 and 93.68, respectively. Under these conditions, the yield of inulin was 85.4 ± 0.5%.

A highly sensitive colorimetric assessment of hexavalent chromium using a digital camera

Simple, low-cost, and sensitive methods for the assessment of hexavalent chromium as an important environmental pollutant are highly desirable, especially under resource-limited settings. Therefore, herein we propose an original approach for the simple, low-cost, selective, and extremely sensitive assessment of Cr(VI) utilizing its catalysis of the micellar sensitized o-dianisidine (DA)-hydrogen peroxide reaction. The initial rate of the amended reaction is monitored by tracing the oxidation product, either by a digital camera video recording or spectrophotometrically at 440 nm, for 120 s from mixing the reactants. The optimized reaction conditions were 5 mmol L^-1 DA, 0.6 mol L^-1 H₂O₂, 2.0 v/v% Tween 20, and 10 mmol L^-1 chloroacetate buffer (pH 4.5 ± 0.1), at 30 °C. The linear calibration graph extends to 90.0 ng mL^-1 Cr(VI) with detection limits (3S_b) of 0.8 and 1.0 ng mL^-1, for the video recording and spectrophotometric procedures, respectively. The amended method was successfully applied to the assessment of Cr(IV) in natural and polluted industrial wastewaters. The analytical data were in excellent statistical harmony with those of the standard ETAAS method. The proposed method is two orders of magnitude more sensitive than the diphenylcarbazide standard spectrophotometric method.Graphical abstract.

An "OR-AND" logic gate based multifunctional colorimetric sensor for the discrimination of Pb2+ and Cd2

Pb²⁺ and Cd²⁺ are the most ubiquitous heavy metal ion pollutants, and they have aroused much attention due to their irreversible and significant damage to human organ. In this work, a new fluorescein-based "OR-AND" logic gate colorimetric probe 3',6'-bis((tert-butyldiphenylsilyl)oxy)-2-(2-((2-hydroxyphenyl)imino)ethylidene)aminspiro[isoindoline-1,9'-xanthen]-3-one (FP) was designed and synthesized via attaching 2-(2-((2-hydroxyphenyl)imino)ethylidene)amino and tert-butyldiphenylsilyl to fluorescein as the specific identification groups. This sensor can rapidly and sensitively discriminate Pb²⁺ and Cd²⁺ by utilizing F^- as an auxiliary reagent. When Pb²⁺ or Cd²⁺ was added into the FP solution, the absorption band at 533 nm increased and the peak at 374 nm decreased, the color changed from colorless to pale-purple, resulting in a ratiometric spectral change. However, adding fluoride ion to the FP solution containing Pb²⁺ or Cd²⁺ resulted in a distinct phenomenon in which the pale purple color fades out to colorless for a Pb²⁺-containing solution and deepen to dark purple for a Cd²⁺-containing solution, which is attributable to the different coordination mechanisms. In aqueous solution, the detection limits of FP can reach 0.42 μM for Pb²⁺ and 0.53 μM for Cd²⁺. The probe exhibited rapid responses for these analytes. Moreover, FP was successfully used to rapidly detect trace amounts of hazardous Pb²⁺ and Cd²⁺ in tap water with good relative recovery and the relative standard deviations (RSD) were 1.8% for Pb²⁺ and 0.3% for Cd²⁺, providing a novel approach for detecting Pb²⁺ and Cd²⁺ in practical application.

Landing microextraction sediment phase onto surface enhanced Raman scattering to enhance sensitivity and selectivity for chromium speciation in food and environmental samples

The current study explores the first full mode liquid microextraction technique coupled with surface-enhanced Raman spectroscopy (SERS), and has been successfully applied for chromium speciation in food and environmental matrices. Herein, chromium as chlorochromate anion [CrO3Cl]- and the cationic rhodamine 6G [RG]+ dye has been extracted in organic phase as a complex ion associate [RG+.CrO3Cl-.nS]org at pH ≤ 1.0. Afterwards, the extracted phase was deposited on the surface of the nano-flower shaped silver nanoparticles substrate and the SERS response was monitored against the reagent blank at 1505 cm-1. Substrate characterizations, reaction mechanism assignment, stoichiometry, speciation, analytical applications, selectivity and validation were performed. The analytical procedure exhibits a detection limit of 0.03 µg L-1 under the optimized experimental conditions. The accuracy of the proposed strategy was validated by inductively coupled plasma optical emission spectrometry method using student's t- and F tests at 95% confidence.

Trace Determination of Iron in Real Waters and Fruit Juice Samples Using Rapid Method: Optimized Dispersive Liquid-Liquid Microextraction with Synthesized Nontoxic Chelating Agent

The purpose of this research was to optimize a new method for preconcentration and determination of trace iron concentrations in aqueous solutions. For this purpose, a newly synthesized ligand, 3-(3-hydroxy-2-methyl-4-oxopyridin-1(4H)-yl) benzoic acid (3-OH-3-MOPBA), was used in the dispersive liquid-liquid microextraction (DLLME) method coupled with UV-vis spectroscopy. The experiments considering input variables of extractant volume, disperser volume, salt concentration, and pH were designed with the aid of central composite design (CCD). The results were analyzed using response surface methodology (RSM). The limit of detection (LOD) was found to be 4.0 μg L^-1 under the optimized conditions. A calibration curve with a good linearity (R² = 0.9986) was obtained over the concentration range of 15-800 μg L^-1. The relative standard deviations (RSD) were found to be around 2.1% (n = 7). The main advantages of the developed method are simple application, environment friendly, short time, and low cost which makes this method to be applied routinely for measuring iron in various water samples.