جستجوی مقالات مرتبط با کلیدواژه "sample preparation" در نشریات گروه "شیمی"

Organochlorine pesticides (OCPs) have been extensively used in agriculture to boost crop yields, creating a significant and enduring global contaminant with adverse effects on the environment and human well-being. These pesticides are characterized by their bioaccumulative and persistent nature, capable of long-distance dispersion. To address this challenge, efforts are ongoing to develop advanced technologies for effectively removing OCPs from the environment, thereby mitigating their impact through appropriate treatment methods in soil and other environmental matrices. Specifically, extensive research has been conducted on the utilization of nanomaterials, including TiO2, Fe2O3, graphene, and graphene oxide, as sorbents in sample preparation and degradation techniques. Graphene (G) and graphene oxide (GO) exhibit unique combination of outstanding characteristics derived from carbon materials (such as exceptional physical, chemical properties, mechanical, and electronic features), deep eutectic solvents (DES) (acting as a functionalization agent), and nanomaterials (including an ultrahigh surface area, abundant functional groups, and a nanometer-scale structure). This review focuses on the adsorption and degradation of OCPS and their metabolites using the remarkable attributes of a mixed graphene-based sorbent, deep eutectic solvents (DES) and MNPs. The combination of these materials, with features such as an expansive surface area (2630 m² g-¹), hydrophilicity, inherent adsorption sites on both sides for molecules, hydrophobicity, double-sided polyaromatic scaffold, adaptable surface modification, hydrogen-bonding, and extensive π-electron structure, positions them as excellent advanced adsorbents and efficient photocatalysts for Magnetic Solid Phase Extraction (MSPE) and Solid Phase Extraction (SPE). These characteristics make them suitable for extracting OCPs from different environmental matrices such as food, environment water, medicine, and biological samples.

Preparing the sample is a vital procedure involving liquid and solid handling approaches toward extracting, enriching, and identifying target analytes from complex environmental matrices. Thus, there is a need for more effective quantitative investigation and green evaluation procedures better than the conventional techniques for the accurate assessment, optimum selection, and testing of analytical techniques. To achieve greenness in analytical methodology, performance criteria such as design procedures, quantities of safe solvent (ionic liquids (IL), deep eutectic solvents (DES)) /toxic reagents consumed, utilization of renewable, reusable and recyclable materials/ biomolecules were evaluated. In this review, economical and eco-friendly approaches are proposed towards an agreement with the novel principles of Green Analytical Chemistry (GAC) using the combination of figures, colorations, unified 0–1 scale, and graphical illustrations: these include National Environmental Methods Index (NEMI), Analytical Greenness Calculator (AGREE), Analytical Eco-Scale (AES), Green Analytical Procedure Index (GAPI) and Pictograms like Hexagon (H) amongst others. These metric tools were proposed and generally adopted to directly assess a systematic and comprehensive improvement of green sample pretreatment, preparation for different extraction, and recovery methods from various modes. These tools are also aimed at evaluating the sustainability of the methods through figures of merits, carbon footprint, and other GAC tools by assigning penalty points (0 to 4) for each block and hexagonal pictograms that provide an easy comparison between analytical procedures

The proposed analytical method tries to illustrate a new approach for the extraction of some pesticides from different fruit beverages (orange, pineapple, cherry, and mango) using UiO-66 as a capable adsorbent. Further preconcentration for heightening enrichment factors of the analytes was accomplished using a dispersive liquid-liquid microextraction. The synthesized adsorbent was carefully characterized using nitrogen adsorption/desorption, X-ray diffraction, MAP, Fourier transform infrared spectrophotometry, energy dispersive X-ray, and scanning electron microscopy analyses. The performed analyses proved the successful formation of the desired compound. After the sorption of the target compounds onto UiO-66 particles by vortexing, the adsorbent was separated by centrifugation. The analyte-loaded adsorbent was treated with 1.0 mL of acetonitrile for the aim of desorption. The obtained eluate containing the desorbed pesticides was mixed with 38 µL of 1,1,1-trichloroethane and hastily injected into sodium chloride solution. After the centrifugation, an aliquot of the sedimented phase was injected into a gas chromatograph equipped with a flame ionization detector. Satisfactory figures of merit obtained in this survey consisted of high enrichment factors (215-275), acceptable extraction recoveries (43-55%), low limits of detection (1.10-2.35 µg L-1) and quantification (3.66-7.82 µg L-1), low relative standard deviations (≤ 7.8%), and wide linear ranges. Also, the proposed method benefits from the high surface area of the adsorbent and low matrix effect.

This paper describes the applicability of micellar media instead of extraction steps with toxic solvents for direct determination of copper beta-resorcylate as burning rate catalyst in double base propellant (DB propellant). The method is based on a simple and safe sample preparation of DB propellant, and then complex formation of copper ion with Diethyldithiocarbamate (DDTC) in the presence of sodium dodecyl sulfate (SDS) as a micellar media. Under optimal conditions, at λmax= 445 nm, the calibration graph was linear in the range of 0.25-4.5 µg mL-1 for copper with detection limits 0.125 µg mL-1. The validity of the method was evaluated by means of the data statistical analysis. For this purpose, the method was applied to the determination of copper beta-resorcylate in DB propellant and the results were statistically compared based on t- and F-tests with those obtained by the by ICP-AES. There was no significant difference between the mean values and the precisions of the two methods at the 95% confidence level. The results showed that the proposed method offers an accuracy and reliable approach for the determination of copper β-resorcylate in DB propellant, and can be suggested as a routine method in military quality control laboratories.

A novel molecularly imprinted polymer-coated stir bar has been used to selectively extract diclofenac (DFC) directly from real samples. DFC was used as template molecule for preparation of MIP coating. The effect of different parameters on the extraction efficiency were studied and the optimum conditions were established as: the absorption and desorption times were fixed at 10 min, stirring speed was 600 rpm, pH was adjusted to 5.1, the amount of NaCl was 0.35 mol/L and extraction process was performed at a temperature of 45 °C. Under the optimum conditions, the linear range of method was 0.5- 500.0 µg/L for DFC and the detection limit was calculated to be 0.15 µg/L with an enrichment factor of 242 folds. The technique was successfully applied for the analysis of trace amounts of DFC in seawater and commercial tablet samples. The mean recoveries of spiking real samples with DFC at 10.0 µg/L level were between 94.2-100.0 % with a mean RSD of 0.7-4.6%.

Sample preparation is an important step in chemical analysis. The present article gives an overview about the Stir bar sorptive extraction (SBSE) as a technique for sample preparation for chromatographic analysis. Stir bar extraction, desorption steps and optimization of the extraction conditions like pH, extraction time, addition of an inert salt, addition of an organic modifier and stirring speed have been discussed. Extraction mechanism, advantages, disadvantages and some applications in water, environmental, pharmaceutical and food analysis have been also discussed. The application of SBSE can be considered as an attractive alternative to classical extraction methods by reducing the consumption of and exposure to the solvent, disposal cost, and extraction time.

Foodstuffs analysis is very important due to population growth and increasing consumer demand for safety and nutritional excellence. The Analysis of different compounds in foodstuffs is so difficult without using sample preparation techniques. Traditional techniques require large amounts of toxic organic solvents. As a result, they are not only expensive but also environmentally unfriendly and they generate a considerable amount of waste. Nowadays efforts are being focused on development of microextraction techniques. Different microextraction techniques such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), and liquid phase microextraction (LPME) have found an important place in sample preparation because of their inherent advantages over the conventional procedures. In particular, they have been applied with successfully for the analysis of food samples despite their complexity. The review discusses different microextraction approaches used in analysis of chemical compounds and metal ions in foodstuffs. It summarizes the application of microextraction techniques in food analysis in details as possible.