Mohammad Rezaee

Determination of polycyclic aromatic hydrocarbons in soil samples using flotation-assisted homogeneous liquid–liquid microextraction

In this study, flotation-assisted homogeneous liquid-liquid microextraction (FA-HLLME) was developed as a fast, simple, and efficient method for extraction of four polycyclic aromatic hydrocarbons (PAHs) in soil samples followed by gas chromatography-flame ionization detector (GC-FID) analysis. A special home-made extraction cell was designed to facilitate collection of the low-density extraction solvent without a need for centrifugation. In this method, PAHs were extracted from soil samples into methanol and water (1:1, v/v) using ultrasound in two steps followed by filtration as a clean-up step. The filtrate was added into the home-made extraction cell contained mixture of 1.0 mL methanol (homogenous solvent) and 150.0 μL toluene (extraction solvent). Using N(2) flotation, the dispersed extraction solvent was transferred to the surface of the mixture and was collected by means of a micro-syringe. Then, 2 μL of the collected organic solvent was injected into the GC-FID for subsequent analysis. Under optimal conditions, linearity of the method was in the range of 40-1000 μg kg(-1) soil (dry weight). The relative standard deviations in real samples varied from 5.9 to 15.2% (n=4). The proposed method was successfully applied to analyze the target PAHs in soil samples, and satisfactory results were obtained.

Homogeneous liquid–liquid microextraction via flotation assistance for rapid and efficient determination of polycyclic aromatic hydrocarbons in water samples

In this work, a rapid, simple and efficient homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) method was developed based on applying low density organic solvents without no centrifugation. For the first time, a special extraction cell was designed to facilitate collection of the low-density solvent extraction in the determination of four polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). The effect of different variables on the extraction efficiency was studied simultaneously using experimental design. The variables of interest in the HLLME-FA were selected as extraction and homogeneous solvent volumes, ionic strength and extraction time. Response surface methodology (RSM) was applied to investigate the optimum conditions of all the variables. Using optimized variables in the extraction process, for all target PAHs, the detection limits, the precisions and the linearity of the method were found in the range of 14-41 μg L(-1), 3.7-10.3% (RSD, n=3) and 50-1000 μg L(-1), respectively. The proposed method has been successfully applied to the analysis of four target PAHs in the water samples, and satisfactory results were obtained.

Application of ultrasound-assisted emulsification microextraction followed by gas chromatography for determination of organophosphorus pesticides in water and soil samples

In the present study a fast, simple and efficient method for determination of organophosphorus pesticides (OPPs) in water and soil samples was developed by using ultrasound assisted emulsification microextraction (USAEME) based on applying low density organic solvents. Fourteen microlitres of toluene was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated toluene (about 4 μL) was injected into a gas chromatographic instrument equipped with a flame ionization detector for analysis. Under the optimum conditions, preconcentration factors of 2390 and 1390 were obtained for diazinon and chlorpyrifos respectively. The method performance was studied in terms of linear dynamic range (LDRs from 0.01 μg L−1 to 100 μg L−1), linearity (r2 ≥ 0.9984), precision (repeatability ≤ 8.7%), and extraction percentage (79.9 and 46.3%). Also, limits of detections of 0.01 and 0.1 μg L−1 were obtained for diazinon and chlorpyrifos respectively. The applicability of the USAEME method was evaluated by the extraction and determination of OPPs from some natural water and soil samples.

A novel method for the high preconcentration of trace amounts of the aflatoxins in pistachios by dispersive liquid–liquid microextraction after solid-phase extraction

In the present study, a new approach which uses solid-phase extraction clean-up combined with dispersive liquid–liquid microextraction is proposed for the preconcentration of trace amounts of aflatoxins (B1, B2, G1 and G2). The aflatoxins were then determined using high-performance liquid chromatography coupled with a fluorescent detector. In this method, pistachio samples were extracted by ultrasound-assisted extraction followed by solid-phase extraction. Then, the solid-phase extract was used as the disperser solvent for the next dispersive liquid–liquid microextraction step for further purification and enrichment of the aflatoxins. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. A good linearity of the aflatoxins was obtained from 0.1 to 50.0 μg kg−1 for B1 and B2, and from 0.2 to 50.0 μg kg−1 for G1 and G2, respectively. The limits of detection (LODs) (S/N = 3) were 0.02 for B1 and B2, and 0.04 μg kg−1 for G1 and G2, respectively. The relative recoveries at the three spiked levels ranged from 85 to 93% with the RSDs less than 13% (n = 3). The method was successfully applied to the determination of aflatoxins in pistachio samples.

Determination of abamectin in citrus fruits using SPE combined with dispersive liquid–liquid microextraction and HPLC–UV detection

A new pretreatment method, SPE combined with dispersive liquid-liquid microextraction, was proposed for the determination of abamectin in citrus fruit samples for the first time. In this method, fruit samples were extracted by ultrasound-assisted extraction followed by SPE. Then, the SPE was used as a disperser solvent in the next dispersive liquid-liquid microextraction step for further purification and enrichment of abamectin. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. Good linearity of abamectin was obtained from 0.005 to 10.0 mg/kg for B1a and from 0.05 to 10.0 mg/kg for B1b with correlation coefficient (r(2)) of 0.998 for B1a and 0.991 for B1b, respectively. The LODs were 0.001 and 0.008 mg/kg (S/N = 3) for B1a and B1b, respectively. The relative recoveries at three spiked levels were ranged from 87 to 96% with the RSD less than 11% (n = 3). The method has been successfully applied to the determination of abamectin in citrus fruit samples.

Solid-phase extraction combined with dispersive liquid–liquid microextraction as an efficient and simple method for the determination of carbamazepine in biological samples

An analytical method, solid-phase extraction combined with dispersive liquid–liquid microextraction (SPE-DLLME), is established to determine carbamazepine in biological fluids and water samples. After concentration and purification of the samples in SPE C18 sorbent, 1.5 mL of acetonitrile containing 60.0 μL of chloroform was injected into 5.0 mL pure water. After extraction and centrifuging, the sedimented phase was evaporated and the residue was dissolved in 30 μL methanol and injected into the HPLC system. Some important extraction parameters, such as sample solution flow rate, sample pH, type and volume of extraction and disperser solvents as well as the salt addition, are studied and optimized. The new method (SPE-DLLME) provides detection limits of 0.8 μg L−1 and 1.7 μg L−1 in urine and plasma samples, respectively. The calibration graphs are linear in the range of 2.5–500 μg L−1 and 5.0–500 μg L−1 in urine and plasma, respectively. The results show that SPE-DLLME is a suitable method for the determination of carbamazepine in biological and water samples.

ULTRASOUND-ASSISTED EMULSIFICATION MICROEXTRACTION OF VARIOUS PRESERVATIVES FROM COSMETICS, BEVERAGES, AND WATER SAMPLES

In the present work, an efficient method based on ultrasound-assisted emulsification microextraction was developed for the determination of sodium benzoate (SB), p-hydroxybenzoic acid (PHBA), methyl-paraben (MP), ethyl-paraben (EP), and propyl-paraben (PP) in different samples. In this procedure, 40 μL of (5% w/v) aliquot 336 in 1-octanol was injected slowly into a 12-mL home-designed centrifuge glass vial containing an aqueous sample of the analytes that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and the separated organic solvent was then injected into a 20-μL loop of high performance liquid chromatography coupled with UV detector. Under the optimum conditions, preconcentration factors (PFs) in the range of 109–490 were obtained. The performance of the proposed method was studied in terms of its linear range (LR, 0.6 μg/L up to 10000 μg/L), linearity (R2 ≥ 0.9963), precision [RSD% ≤ 3.6; reproducibility, RSD (%) ≤ 9.8] and extraction recoveries (22.6–102.1%). Limits of detections (LODs) were 8.3, 1.2, 0.60, 0.42, and 0.25 μg/L for SB, PHBA, MP, EP, and PP, respectively. Finally, the applicability of the proposed method was evaluated by the extraction and determination of the target analytes from beverages, cosmetics, and water samples.

Extraction and Separation of Molybdenum by Using Homogeneous Liquid-Liquid Microextraction via Flotation Assistance

Homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) was investigated for the extraction of molybdenum from the water samples. Alizarin Red S and cetyl trimethylammonium bromide (CTAB) were used as a complexing ligand and ion-pairing reagent, respectively. The enriched analyte in the floated organic phase was determined by electrothermal atomic absorption spectrometry (ETAAS). In this work, low density organic solvent was used and no centrifugation was required in this procedure. A special extraction cell was designed to facilitate the collection of the low-density extraction solvent. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Under the optimum conditions, the method performance was studied in terms of linear dynamic range (0.5-200 µg L-1), linearity (r2 > 0.991), precision (repeatability < 10.0 %). Also, the limit of detection (LOD) of 0.1 µg L-1 was obtained for molybdenum. The proposed method has been successfully applied for the determination of the molybdenum in water samples.

HOMOGENEOUS LIQUID–LIQUID MICROEXTRACTION VIA FLOTATION ASSISTANCE FOLLOWED BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AS AN EFFICIENT AND SENSITIVE TECHNIQUE FOR THE DETERMINATION OF ABAMECTIN IN AQUATIC SAMPLES

Homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) and high-performance liquid chromatography-UV detection was presented for the extraction and determination of abamectin in aquatic samples. Toluene at microliter volume level and acetone were used as extraction and homogeneous solvents, respectively. In this research, a special extraction cell was designed to facilitate collection of the low-density extraction solvent. No centrifugation was required in this procedure. The water sample solution was added into the extraction cell, which contained an appropriate mixture of extraction and homogeneous solvents. Using air flotation, extraction solvent was collected at the conical part of the designed cell. The effects of different variables on the efficiency of the extraction such as kind and the volume of extraction and homogeneous solvents, ionic strength, and extraction time were studied and optimized. Under the optimum conditions, the calibration graphs were linear in the range of 2.0–500 µ g L−1 for B1a and 4.0–500 µ g L−1 for B1b with detection limits of 0.5 µ g L−1 for B1a and 1.7 µ g L−1 for B1b. HLLME-FA is a fast, simple, and efficient method for the determination of abamectin in aquatic samples.

A NOVEL METHOD FOR THE DETERMINATION OF TRACE THORIUM BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION BASED ON SOLIDIFICATION OF FLOATING ORGANIC DROP

In this study, dispersive liquid-liquid microextraction based on the solidification of floating organic droplets was used for the preconcentration and determination of thorium in the water samples. In this method, acetone and 1-undecanol were used as disperser and extraction solvents, respectively, and the ligand 1-(2-thenoyl)-3,3,3-trifluoracetone reagent (TTA) and Aliquat 336 was used as a chelating agent and an ion-paring reagent, for the extraction of thorium, respectively. Inductively coupled plasma-optical emission spectrometry was applied for the quantitation of the analyte after preconcentration. The effect of various factors, such as the extraction and disperser solvent, sample pH, concentration of TTA and concentration of aliquat336 were investigated. Under the optimum conditions, the calibration graph was linear within the thorium content range of 1.0-250 µg L-1 with a detection limit of 0.2 µg L-1. The method was also successfully applied for the determination of thorium in the different water samples.