ABSTRACT
Expression of concern for 'Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 2643-2655, DOI: https://doi.org/10.1039/D0RA09298C.
ABSTRACT
Expression of concern for 'Synthesis and characterization of a new ZIF-67@MgAl2O4 nanocomposite and its adsorption behaviour' by Mehdi Davoodi et al., RSC Adv., 2021, 11, 13245-13255, https://doi.org/10.1039/D1RA01056E.
ABSTRACT
In this work, dispersive liquid-liquid microextraction (DLLME) based on high-density extraction solvent was applied as a simple, fast and sensitive method for extraction and preconcentration of methamphetamine from human plasma and urine samples. The efficiency of positive corona discharge ionization ion mobility spectrometry was investigated for direct analysis of the extracted analyte. Effective parameters on the extraction efficiency, such as type and volume of the extraction and disperser solvents, centrifugation time, and sample solution pH were optimized. Trichloromethane and isopropanol were selected as the extracting and disperser solvents, respectively. Under the optimized conditions, the linear dynamic range (R2 = 0.9969) was found to be 0.5-18 µg/L, and 0.15 µg/L was calculated as the limit of detection. The relative standard deviations of intra- and inter-day were obtained 4 and 10%, respectively, and finally, in the analysis of human plasma and urine samples, the extraction recovery was obtained 104%.
Subject(s)
Liquid Phase Microextraction , Methamphetamine , Humans , Liquid Phase Microextraction/methods , Ion Mobility Spectrometry , Limit of Detection , Solvents/chemistryABSTRACT
[This corrects the article DOI: 10.1039/D1RA01056E.].
ABSTRACT
Fabricating suitable adsorbents with low-cost and high efficiency extraction for measurement of very small amounts of agricultural pesticides in food and water is playing a vital key role in personal and environmental health. Here, a new composite of zeolitic imidazolate framework-67@magnesium aluminate spinel (ZIF-67@MgAl2O4) has been fabricated by a simple method at room temperature with different weight ratios. Several techniques such as FE-SEM, BET, XRD, and TGA have been used to confirm the structural characterization of the obtained materials. The obtained ZIF-67@MgAl2O4 was utilized as an adsorbent in the solid phase microextraction technique to extract and preconcentrate the herbicide molinate (as an analyte) in aqueous solution. Corona discharge ionization-ion mobility spectrometry (CD-IMS) was applied for quantification of the analyte molecules. Extraction temperature, extraction time, stirring rate, and sample pH as the main parameters that affected the extraction proficiency were chosen and considered. Under optimal conditions, the linear dynamic range (LDR) of the various concentrations of the molinate and correlation coefficient were 10.0-100.0 µg L-1 and 0.9961, respectively. The limit of quantification (LOQ) and method detection limit (MDL) were 10.0 µg L-1 and 3.0 µg L-1, respectively. The relative standard deviation (RSD) of the ZIF-67@MgAl2O4 for extracting the molinate molecules (molinate concentration; 50 µg L-1) was calculated to be 4% and the enrichment factor (EF) was â¼5.
ABSTRACT
Co-MOF-based zeolitic imidazolate frameworks (ZIF-67) with various morphologies were prepared via an innovative way under distinct reaction conditions. By changing the reaction conditions, including the cobalt source, solvent, time, temperature, and linking agent to the cobalt ions, the morphological evolution of Co-MOF-based ZIF-67 was investigated. The Co-MOF-based ZIF-67 was applied as an adsorbent fiber in the solid-phase microextraction (SPME) technique for extracting a herbicide, namely molinate (as a test compound), in aqueous samples. For recognizing the molinate molecules, drift tube ion mobility spectrometry (IMS) was employed as a sensitive, rapid, and simple detection technique. Two essential parameters, namely extraction temperature and extraction time, influenced the extraction efficiency, and these parameters were also analyzed and optimized. The linear dynamic range (LDR) and the determination coefficient were found to be 0.5-20.0 µg L-1 and 0.9990, respectively. In this regard, the limit of quantification (LOQ) and the detection limit (LOD) were calculated and found to be 0.5 µg L-1 and 0.15 µg L-1, respectively. Finally, the effect of the adsorbent with different morphologies on the extraction efficiency was compared.
ABSTRACT
Thin film nanofibers containing ZnTiO3 nanoparticles were used for rapid and efficient evaporation of solvents as used to extract analytes by dispersive liquid-liquid microextraction (DLLME). The method is referred to as thin film evaporation (TFE). A combination of DLLME and TFE was applied to the extraction and preconcentration of the pesticide chlorpyrifos (as a model compound) prior to analysis by ion mobility spectrometry. The ZnTiO3 nanoparticles were placed on polyacrylonitrile nanofibers which increases the porosity and surface area in the TFE process, thus causing fast and complete evaporation of solvents. The effects of sample pH value, extraction solvent and its volume, disperser solvent and volume, centrifugation time, evaporation time, and desorption temperature were optimized. The relative standard deviations of intra- and inter-day analyses were found to be 3% and 7%, respectively. The method has a linear dynamic range that covers the 0.10-3.0 µg.L-1 chlorpyrifos concentration range, the limit of detection is 0.04 µg.L-1, and the enrichment factor is up to 5400 in case of spiked samples. Some spiked field samples were analyzed and the relative recoveries ranged between 99 and 111%. When applied along with ion mobility spectrometry, the interferences caused by solvent are found to be reduced in the ionization source. This makes it possible to select a variety of solvents as needed for sample extraction. Graphical abstract Schematic presentation of dispersive liquid-liquid microextraction (DLLME) combined with thin film evaporation (TFE) for rapid vaporization of extraction solvent: Application to the pre-concentration of chlorpyrifos prior to its quantification by corona discharge-ion mobility spectrometry (CD-IMS).
ABSTRACT
An appropriate injection port was designed and constructed for direct analysis of stir-bar sorptive extractions using an ion mobility spectrometry (IMS). The novel design of the port offers great simplicity in use, high sensitivity, and high thermal and mechanical stability. The sol-gel technique was applied to prepare polydimethylsiloxane absorbent on a stir-bar. The parameters affecting extraction efficiency including stirring rate, extraction temperature, extraction time, salt addition and desorption temperature were optimized. The detection limit of the method was calculated to be 1.5µgL-1, for diazinon, an organophosphorus pesticide selected as a test compound. The linear dynamic range was obtained to be 5.0-200.0µgL-1 with a determination coefficient of 0.9991 for the test compound. The intra- and inter-day relative standard deviations were calculated to be 4% and 5%, respectively. Agricultural wastewater, well water, and apple were selected as real samples. The detection limit was calculated to be 1.5µgL-1 and 7.5µgkg-1 for the real water samples and the apple sample, respectively. The recovery values (%) were 105 ± 6, 107 ± 3 and 96 ± 6 for the spiked agricultural wastewater, well water and apple samples, respectively. The results revealed that the injection port can be used for direct analysis of samples extracted by any sorbent support, without any further sample preparation.
