An efficient sample preparation method based on dispersive liquid�liquid microextraction associated with back extraction for trace determination of acidic pharmaceuticals

Reduction of matrix effect seems to be a great challenge for the development of a practical method in bioanalysis. In this regard, a simple and efficient DLLME procedure along with a back-extraction step (DLLME-BE) was developed for the preconcentration of four common non-steroidal anti-inflammatory drugs (NSAIDs) in various biological fluid samples. Briefly, the analytes of interest were initially transferred into the extraction solvent followed by the back-extraction into an immiscible basic methanol (as an acceptor phase) for further preconcentration and clean-up. The main purpose of the work is reducing the matrix effect and sensitive determination of target molecules in the complex matrices. Following on, the separation and determination of the analytes were carried out using GC�MS (in-port derivatization) and HPLC-DAD instrument. The influential parameters affecting the DLLME-BE method were evaluated in detail and the best extraction conditions were established. Under the optimum conditions, low method detection limits in the range of 0.1�1.0 and 0.1�6.0 µg L�1 were obtained for GC�MS and HPLC-DAD analysis, respectively. Additionally, fair intra-day precisions of 2.7�14.5 and 2.8�7.8 as well as inter-day precisions of 3.9�14.5 and 3.5�8.1 were achieved for the GC�MS and HPLC-DAD analysis, respectively. Finally, the method was successfully applied for the determination of four common NSAIDs in different biological fluid samples. © 2018 King Saud Universit

An efficient sample preparation method based on dispersive liquid�liquid microextraction associated with back extraction for trace determination of acidic pharmaceuticals

Reduction of matrix effect seems to be a great challenge for the development of a practical method in bioanalysis. In this regard, a simple and efficient DLLME procedure along with a back-extraction step (DLLME-BE) was developed for the preconcentration of four common non-steroidal anti-inflammatory drugs (NSAIDs) in various biological fluid samples. Briefly, the analytes of interest were initially transferred into the extraction solvent followed by the back-extraction into an immiscible basic methanol (as an acceptor phase) for further preconcentration and clean-up. The main purpose of the work is reducing the matrix effect and sensitive determination of target molecules in the complex matrices. Following on, the separation and determination of the analytes were carried out using GC�MS (in-port derivatization) and HPLC-DAD instrument. The influential parameters affecting the DLLME-BE method were evaluated in detail and the best extraction conditions were established. Under the optimum conditions, low method detection limits in the range of 0.1�1.0 and 0.1�6.0 µg L�1 were obtained for GC�MS and HPLC-DAD analysis, respectively. Additionally, fair intra-day precisions of 2.7�14.5 and 2.8�7.8 as well as inter-day precisions of 3.9�14.5 and 3.5�8.1 were achieved for the GC�MS and HPLC-DAD analysis, respectively. Finally, the method was successfully applied for the determination of four common NSAIDs in different biological fluid samples. © 2018 King Saud Universit

Implementation of an ultrasonic assisted dispersive μ-solid phase extraction method for trace analysis of lead in aqueous and urine samples

Herein, an ultrasonic assisted dispersive micro-solid phase extraction (d-μSPE) method along with a graphite furnace atomic absorption spectrometry (GF-AAS) for the measurement of lead at trace levels in water and urine samples was developed. In this regard, a silica-based amino-tagged nanosorbent (MCM-41@NH 2 ) was successfully synthesized via a hydrothermal method. The surface properties of the synthesized nanosorbent was characterized by FT-IR, XRD, TEM, TGA and BET analytical techniques. Briefly, the nanosorbent was ultrasonically dispersed in the sample of interest for the adsorption of lead ions. Following the adsorption, the nanosorbent was removed off the sample and underwent the desorption process using a tiny volume of HCl, later on to be introduced to the GF-AAS for final lead determination. Meanwhile, to assess the efficiency of the adsorption and desorption processes, the influential variables such as pH, sorbent content, ionic strength and sonication time and desorption solvent features were all investigated and optimized in sequence. Subsequently, under the optimal conditions the calibration curve was found out to be linear over the concentration range of 0.1�1.0 μg/L. In the meantime, the obtained assay accuracy in the analysis of real samples fell within the span of 92�110, whilst the precision varied in the range of 4.8�9.2. Finally, the applied method was successfully applied for the measurement of the trace levels of lead ions in various water and urine samples. © 201

Littered cigarette butt as a well-known hazardous waste: A comprehensive systematic review

Most of cigarettes used in the world have filters. Following smoking, the cigarette butts (CBs) are often littered as wastes in the environment. CBs generally contain several toxic substances that are trapped in the cigarette filter. Filters are made of non-biodegradable materials and remain in the environment for a long time. Within this study, it is attempted to systematically review the articles on CBs and find out the answers to the problems associated with the factors including quantity, distribution, origin and toxicity of CBs in the environment. It is estimated that approximately 5.5 trillion cigarettes are being produced annually in the world and the CB wastes would reach 1.2 million tons and increase by 50 until 2025. CBs contain thousands of dangerous chemicals such as arsenic, benzene, hydrogen cyanide, PAHs, pyridine, heavy metals and so forth. It is also believed that eachCB can pollute 1000 liters of water. Given the inadequacy of mechanical equipment as well as the cost of collecting these wastes, there should be a special focus on these items as follows: producing cigarettes with degradable filters, reducing the rate of smoking in the world, reducing the toxic and chemical substances in the process of plant growth, processing and production of cigarettes, training people to discard CBs properly, putting legal and financial pressures on cigarettes production, and the last but not least, providing effective solutions for collecting CBs. © 2019 Elsevier B.V

Tandem use of solid-phase extraction and dispersive liquid-liquid microextraction for the determination of mononitrotoluenes in aquatic environment.

Solid-phase extraction (SPE) in tandem with dispersive liquid-liquid microextraction (DLLME) has been developed for the determination of mononitrotoluenes (MNTs) in several aquatic samples using gas chromatography-flame ionization (GC-FID) detection system. In the hyphenated SPE-DLLME, initially MNTs were extracted from a large volume of aqueous samples (100 mL) into a 500-mg octadecyl silane (C(18) ) sorbent. After the elution of analytes from the sorbent with acetonitrile, the obtained solution was put under the DLLME procedure, so that the extra preconcentration factors could be achieved. The parameters influencing the extraction efficiency such as breakthrough volume, type and volume of the elution solvent (disperser solvent) and extracting solvent, as well as the salt addition, were studied and optimized. The calibration curves were linear in the range of 0.5-500 μg/L and the limit of detection for all analytes was found to be 0.2 μg/L. The relative standard deviations (for 0.75 μg/L of MNTs) without internal standard varied from 2.0 to 6.4% (n=5). The relative recoveries of the well, river and sea water samples, spiked at the concentration level of 0.75 μg/L of the analytes, were in the range of 85-118%

Extraction of carbonyl derivatives from ozonated wastewater samples using hollow fiber liquid phase microextraction followed by gas chromatography-electron capture detection

Herein, a simple and sensitive method was successfully developed for the extraction and quantification of seven carbonyl compounds (acetaldehyde, propanal, butanal, pentanal, hexanal, glyoxal, methylglyoxal) in a number of wastewater samples previously treated by ozonation process. The compounds were initially derivatized (derivatizing reagent (PFBHA)) and then extracted by a hollow-fiber liquid-phase microextraction method (HF-LPME) in the aqueous sample solution. Afterwards, the extraction solvent was withdrawn from the fiber and injected to a gas chromatograph equipped with electron capture detection (GC�ECD). Factors affecting the extraction efficiency of the whole procedure were optimized using a univariate approach. Under the optimal conditions obtained (sample solution pH, 4; organic extraction solvent, dihexylether; stirring rate, 1000 rpm; no salt addition; and extraction time of 40 min), limits of quantification were 0.5�0.8 μg/l for the studied carbonyl compounds. Dynamic linear ranges were 0.5�100 μg/l for five targets (acetaldehyde, propanal, butanal, pentanal and hexanal) and 0.8�80 μg/l for two targets (glyoxal and methylglyoxal). The relative standard deviations (RSDs ) representing the precision of the method were in the range of 6.4�11.9 based on the average of three measurements. Accuracy of the method was also tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 113. Finally, the method could be used for routine screening of carbonyl compounds in complex matrices. © 201

Synthesis and evaluation of the performance of g-C3N4/Fe3O4/Ag photocatalyst for the efficient removal of diazinon: Kinetic studies

Herein, a well-known pesticide named diazinon was successfully removed from aqueous solutions by the UV photocatalytic process in which g-C3N4/Fe3O4/Ag was applied as a nanocomposite. Initially, g-C3N4/Fe3O4/Ag nanocomposite was synthesized by a hydrothermal method and XRD, FT-IR, SEM, EDX and PL analyses were employed to identify the nanocomposite structure. The best conditions for the complete removal of diazinon (DZN) (i.e., 100 ) were obtained after 60 min under the following conditions: pH = 7, catalyst dosage of 0.5 g/L and DZN concentration of 5 mg/L. The removal reaction followed the first order kinetic model (k, 0.067; R2, 0.9982). Furthermore, the effects of several scavengers such as ammonium oxalate (AO), tert-butanol (TB) and benzoquinone (BQ) on the performance of the removal reaction were investigated revealing that the hydroxyl ions played an active role in the reaction. Finally, the photocatalytic process using the nanocomposite g-C3N4/Fe3O4/Ag proved to be promising for the removal of DZN pesticide from aqueous media. © 201

Generic approach for the sensitive absolute quantification of large undigested peptides in plasma using a particular liquid chromatography-mass spectrometry setup.

A generic LC-MS approach for the absolute quantification of undigested peptides in plasma at mid-picomolar levels is described. Nine human peptides namely, brain natriuretic peptide (BNP), substance P (SubP), parathyroid hormone 1-34 (PTH), C-peptide, orexines A and B (Orex-A and -B), oxytocin (Oxy), gonadoliberin-1 (gonadothropin releasing-hormone or luteinizing hormone-releasing hormone, LHRH) and α-melanotropin (α-MSH) were targeted. Plasma samples were extracted via a 2-step procedure: protein precipitation using 1vol of acetonitrile followed by ultrafiltration of supernatants on membranes with a MW cut-off of 30 kDa. By applying a specific LC-MS setup, large volumes of filtrates (e.g., 2×750 μL) were injected and the peptides were trapped on a 1mm i.d.×10 mm length C8 column using a 10× on-line dilution. Then, the peptides were back-flushed and a second on-line dilution (2×) was applied during the transfer step. The refocalized peptides were resolved on a 0.3mm i.d. C18 analytical column. Extraction recovery, matrix effect and limits of detection were evaluated. Our comprehensive protocol demonstrates a simple and efficient sample preparation procedure followed by the analysis of peptides with limits of detection in the mid-picomolar range. This generic approach can be applied for the determination of most therapeutic peptides and possibly for endogenous peptides with latest state-of-the-art instruments

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

A fast, simple, low cost surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for the determination of low level of Cr(VI) ions in several aquatic samples has been developed. Initially, Cr(VI) ions present in the aqueous sample were readily reacted with 1,5�diphenylcarbazide (DPC) in acidic medium through complexation. Sodium dodecyl sulfate (SDS), as an anionic surfactant, was then employed as an ion-pair agent to convert the cationic complex into the neutral one. Following on, the whole aqueous phase underwent a dispersive liquid-liquid microextraction (DLLME) leading to the transfer of the neutral complex into the fine droplet of organic extraction phase. A micro-volume spectrophotometer was used to determine Cr(VI) concentrations. Under the optimized conditions predicted by the statistical design, the limit of quantification (LOQ) obtained was reported to be 5.0 μg/L, and the calibration curve was linear over the concentration range of 5�100 μg/L. Finally, the method was successfully implemented for the determination of low levels of Cr(VI) ions in various real aquatic samples and the accuracies fell within the range of 83�102, while the precision varied in the span of 1.7�5.2. © 201

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

A fast, simple, low cost surfactant-assisted dispersive liquid-liquid microextraction method along with central composite design for the determination of low level of Cr(VI) ions in several aquatic samples has been developed. Initially, Cr(VI) ions present in the aqueous sample were readily reacted with 1,5�diphenylcarbazide (DPC) in acidic medium through complexation. Sodium dodecyl sulfate (SDS), as an anionic surfactant, was then employed as an ion-pair agent to convert the cationic complex into the neutral one. Following on, the whole aqueous phase underwent a dispersive liquid-liquid microextraction (DLLME) leading to the transfer of the neutral complex into the fine droplet of organic extraction phase. A micro-volume spectrophotometer was used to determine Cr(VI) concentrations. Under the optimized conditions predicted by the statistical design, the limit of quantification (LOQ) obtained was reported to be 5.0 μg/L, and the calibration curve was linear over the concentration range of 5�100 μg/L. Finally, the method was successfully implemented for the determination of low levels of Cr(VI) ions in various real aquatic samples and the accuracies fell within the range of 83�102, while the precision varied in the span of 1.7�5.2. © 201