Salt-Assisted Graphene Oxide Dispersive Solid Phase Microextraction for Sensitive Detection of Malachite Green and Crystal Violet by HPLC

A ratiometric fluorescent sensor based on S-doped BCNO quantum dots and Au nanoclusters combined with 3D-printing portable device for the detection of malachite green

Sulfur-doped BCNO quantum dots (S-BCNO QDs) emitting green fluorescence were prepared by elemental doping method. The ratiometric fluorescence probe with dual emissions was simply established by mixed S-BCNO QDs with gold nanoclusters (GSH-Au NCs). Because the emission spectrum of Au NCs (donor) at 615 nm overlapped well with the ultraviolet absorption of malachite green (MG), fluorescence resonance energy transfer (FRET) can be achieved. When the concentration of MG increased, the fluorescence intensity (F495) of S-BCNO QDs decreased slowly, while the fluorescence intensity (F615) of Au NCs decreased sharply. The fluorescence intensity ratio of F615/F495 decreased with the increase of MG. By plotting the F615/F495 values against MG concentration, a sensitive and rapid detection of MG was possible with a wide detection range (0.1-50 µM) and a low detection limit of 10 nM. Due to the accompanying fluorescence color change from pink to blue-green, it can be used for visual detection. A three dimensional-printing device utilizing digital image colorimetry to capture color changes through the built-in camera, enables quantitative detection of MG with a good linearity between the values of red/green ratio and MG concentrations at the range 1-50 µM. This sensing platform had a range of advantages, including high cost-effectiveness, portability, ease of operation, and high sensitivity. Furthermore, the sensing platform was successfully applied to the detection of MG in real water sample and fish samples, thereby verifying the reliability and effectiveness of this sensing platform in water quality monitoring and food safety.

Carboxyl-functionalized covalent organic frameworks for the extraction of malachite green and crystal violet in environmental water samples prior to quantification by high-performance liquid chromatography

In this study, monodisperse, uniform, and spherical covalent organic frameworks (COFs) were synthesized using 1,3,5-tris (4-aminophenyl) benzene and 1,3,5-tricarboxaldehyde benzene at room temperature. Post-modification of 6-aminocaproic acid on the COFs yielded carboxyl-modified COFs (COFs-COOH). The modification enhanced the hydrophilicity and adsorption efficiencies of COFs-COOH for malachite green (MG) and crystal violet (CV). A COFs-COOH-based dispersive solid-phase extraction coupled with high-performance liquid chromatography was developed for the analysis of MG and CV. The method showed a linear range from 10 to 1000 ng/mL with detection limits of 1.82 and 0.70 ng/mL for MG and CV detection, respectively. The recoveries of MG and CV from water samples collected from fish farms and markets ranged from 91.63% to 107.10% with relative standard deviations below 5%. Reproducibility tests demonstrated that the adsorption efficiencies of COFs-COOH were maintained at above 85.86% over 15 cycles. The study verified the potential of COFs-COOH as sorbents for the enrichment and separation of triphenylmethane dyes from complex samples.

Electrophoretically deposited sulfonated poly(styrene-co-divinylbenzene) on a screw for microextraction of cationic dyes from aqueous solutions

In the present work, a novel solid-phase microextraction on a screw (MES) was employed to extract cationic dyes (malachite green, methylene blue, and rhodamine B) from food samples and fish breeding pool water. The sulfonated poly(styrene-co-divinylbenzene) was electrophoretically deposited on the surface of the grooves of a screw. Then the screw was placed inside a silicon tube as a holder to create a channel to run a test solution through it. The extracted dyes on the coated screw were eluted by a suitable eluent. High-performance liquid chromatography with an ultraviolet/visible detector was utilized for the separation and analysis of the analytes. The effective parameters of the analyte extraction efficiency were optimized. Under optimum conditions, the limits of detection were 0.15 μg/L, and calibration curves were linear in the range of 0.50-250.00 μg/L, with coefficients of determination > 0.989 for all studied dyes. The relative standard deviations of intra and inter-day (n = 3) were in the range of 2.8%-7.0% and 7.0%-9.5%, respectively. The MES was applied as a simple and repeatable method with acceptable relative recoveries (82.0%-103.0%) for the determination of cationic dyes in grape nectar, ice pop, jelly powder, and fish breeding pool water.

Development of Fe3O4/reduced graphene oxide nanocomposite-based dispersive solid-phase extraction for the quantification of five steroid hormones

Aim: An accurate and sensitive analytical method was proposed to detect some steroid hormones in biological samples. Materials & methods: An Fe₃O₄/reduced graphene oxide nanocomposite-based dispersive solid-phase extraction was developed for the effective and simple preconcentration of steroid hormones from human serum samples. Results & conclusion: The nanocomposite was firstly used as adsorbent to simultaneously extract the selected hormones. Limit of detection values for the selected hormones were calculated between 5.5 and 39.2 ng/kg (mass based). An artificial serum sample was used to test the applicability and accuracy of the developed method; percentage recovery results obtained from two different spiked concentrations were found to be in the range of 80.5-99.9%.

Ultra-trace Extraction of Two Bactericides Via Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction

BACKGROUND

A simple, rapid and sensitive method coupling ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of malachite green (MG) and crystal violet (CV) in different water samples.

OBJECTIVE

In ultrasound-assisted DLLME procedure, several parameters affecting the extraction efficiency, including pH, type and volume of the extraction and dispersive solvents, extraction time, ionic strength, were optimized to improve the accuracy and precision of this method.

METHODS

MG and CV were extracted and preconcentrated using dichloromethane and acetonitrile as the extraction and dispersive solvents, respectively.

RESULTS

Under the optimum conditions, the proposed method affords good linearity in the range of 0.40-20.0 ng/L, and the limit of detections were 0.21 and 0.32 ng/L for MG and CV, respectively. The recoveries of the method at three spiked levels were in the range of 83.4-94.2% with relative standard deviations lower than 4.7% (n = 3).

CONCLUSIONS

Satisfactorily, no significant matrix effect has been found as the data ranged between 68% and 102%.

Supplementary evaluation of retention and physicochemical data involving multivariate analysis approach

This commentary highlights the issue of real differences between stationary phases that were studied in an experimental paper entitled "Novel stationary phases based on asphaltenes for gas chromatography" prepared by Grzegorz Boczkaj and co-authors (J. Sep. Sci. 2016, 39, 2527-2536). Particularly, a chemometric study has revealed relatively small differences between stationary phases investigated. Moreover, simple principle component analysis calculations enabled the identification of the outlier points within large raw dataset and to find the parameters (variables) that may carry equal information.