Homogenizer assisted dispersive liquid-phase microextraction for the extraction-enrichment of phenols from aqueous samples and determination by gas chromatography.

In this research, dispersive liquid-phase microextraction has been used for the extraction of some phenols including phenol, 3-methylphenol, 4-nitrophenol, 2-chlorophenol, tert-buthylphenol from aqueous samples, and then the analysis was done by the gas chromatography-flame ionization detector technique. For the first time, a laboratory homogenizer has been applied for dispersing of extracting organic solvent. To improve the chromatographic behavior, acetic anhydride was used as a derivatization reagent of the analytes. The effective parameters on the extraction and derivation process such as extraction solvent type and volume, amount and time of derivatization, sample pH and ionic strength, homogenization time and speed were investigated and optimized. The analytical performances of the method, such as linear dynamic range, repeatability, and detection limit were evaluated under the optimum condition. Under the optimal experimental conditions, the calibration plots were linear the range of 1-500 µg L-1 with the detection limits between 0.1-0.9 µg L-1, and the repeatability in the range of 2.6 to 10.0%. These values vary depend on the compounds. The proposed method was evaluated for the determination of the studied phenolic compounds in different real samples such as river water, tap water and industrial wastewater. The relative recoveries were between 90 and 111%.

A Paper-Based Analytical Device Based on Combination of Thin Film Microextraction and Reflection Scanometry for Sensitive Colorimetric Determination of Ni(II) in Aqueous Matrix.

In this research, the thin film microextraction method was applied for the extraction of Ni(II) ion from aqueous matrixes. Chemically modified cellulosic filter paper with phosphorus was used as a thin film extractor. After extraction, the thin film was treated with a solution of dimethylglyoxime. The colored film was captured by flatbed scanner and the absorbance of the images was extracted by some suitable software. Under the optimum conditions and at the pH 7.0, with the sample volume of 100 mL, the stirring rate of 800 rpm, and the extraction time of 50 min, the calibration curve was obtained in the range of 0.05-5 mg/L Ni(II) (R2 = 0.989). Limit and relative standard deviation were achieved to be 18 µg/L and less than 6.7%, respectively. Relative recoveries were obtained in the range of 87%-105%. Finally, the proposed method was found to be simple and cost-effective, with adequate analytical performance for the rapid detection of Ni(II) in river and wastewater samples.

Reversed-phase single drop microextraction followed by high-performance liquid chromatography with fluorescence detection for the quantification of synthetic phenolic antioxidants in edible oil samples.

The reversed-phase mode of single drop microextraction has been used as a preparation method for the extraction of some phenolic antioxidants from edible oil samples. Butylated hydroxyl anisole, tert-butylhydroquinone and butylated hydroxytoluene were employed as target compounds for this study. High-performance liquid chromatography followed by fluorescence detection was applied for final determination of target compounds. The most interesting feature of this study is the application of a disposable insulin syringe with some modification for microextraction procedure that efficiently improved the volume and stability of the solvent microdrop. Different parameters such as the type and volume of solvent, sample stirring rate, extraction temperature, and time were investigated and optimized. Analytical performances of the method were evaluated under optimized conditions. Under the optimal conditions, relative standard deviations were between 4.4 and 10.2%. Linear dynamic ranges were 20-10 000 to 2-1000 µg/g (depending on the analytes). Detection limits were 5-670 ng/g. Finally, the proposed method was successfully used for quantification of the antioxidants in some edible oil samples prepared from market. Relative recoveries were achieved from 88 to 111%. The proposed method had a simplicity of operation, low cost, and successful application for real samples.

Chemically modified cellulose paper as a thin film microextraction phase.

In this paper, chemically modified cellulose paper was introduced as a novel extracting phase for thin film microextraction (TFME). Different reagents (Octadecyltrichlorosilane, diphenyldichlorosilane, cyclohexyl isocyanate and phenyl isocyanate) were used to modify the cellulose papers. The modified papers were evaluated as a sorbent for the extraction of some synthetic and natural estrogenic hormones (17α-ethynylestradiol, estriol and estradiol) from aqueous samples. Liquid chromatography-fluorescence detection was used for the quantification of the extracted compounds. The cellulose paper modified with phenyl isocyanate showed the best affinity to the target compounds. TEME parameters such as desorption condition, shaking rate, sample ionic strength and extraction time were investigated and optimized. Limit of detections were between 0.05 and 0.23µgL(-1) and relative standard deviations were less than 11.1% under the optimized condition. The calibration curves were obtained in the range of 0.2-100µgL(-1) with a good linearity (r(2)>0.9935). Wastewater, human urine, pool and river water samples were studied as real samples for the evaluation of the method. Relative recoveries were found to be between 75% and 101%.

Combined hollow fiber-based liquid-liquid-liquid microextraction and in-situ differential pulse voltammetry to improve selectivity, sensitivity, and interference elimination in electrochemical analysis.

In this paper, a combined hollow fiber-based liquid three-phase microextraction and voltammetric method are applied for the first time as a highly selective and sensitive method of electrochemical analysis. Desipramine, used as a model compound was extracted from 8 mL aqueous solution (donor phase, 0.10 mol L(-1) NaOH) through a thin phase of propyl benzoate inside the pores of a polypropylene hollow fiber and finally into a 10 microL acidic acceptor solution inside the hollow fiber. Three microelectrodes designed and constructed for the purposes of this study were placed into the two ends of the hollow fiber inside the acceptor solution, and voltammetric analysis was performed in-situ during the extraction. After 15 min, the final stable signal was used for analytical applications. Under the optimized conditions, an enrichment factor of 301 was achieved and the relative standard deviation (R.S.D.) of the method was 6.2% (n=5). The calibration curve was obtained in the range of 5-5000 nmol L(-1) with a reasonable linearity (R(2)>0.988) and the limit of detection (LOD) was found to be 0.8 nmol L(-1). Finally, the applicability of the proposed method was evaluated by extraction and determination of desipramine in plasma and urine samples without any dilutions.

Application of single-drop microextraction combined with in-microvial derivatization for determination of acidic herbicides in water samples by gas chromatography-mass spectrometry.

A single-drop microextraction (SDME) method and gas chromatography with mass spectrometry detection have been developed for the determination of acidic herbicides in water. The analytes were extracted from a 3 mL sample solution using 4 microL of hexyl acetate. After extraction, derivatization was carried out inside a glass microvial (1.1mm i.d.) using pentafluorobenzyl bromide (PFBBr). Triethylamine (TEA) was used as the reaction catalyst. The influence of derivatization reagent volume, catalyst amount, derivatization time and temperature on the yield of the in-microvial derivatization was investigated. Derivatization reaction was performed using 0.3 microL of PFBBr and 0.4 microL of TEA (10%, v/v in toluene) at 100 degrees C during 5 min. Also, the effects of different experimental SDME parameters such as selection of organic solvent, sample pH, addition of salt, extraction time and temperature of extraction were studied. Analytical parameters such as enrichment factor, precision, linearity and detection limits were also determined. The enrichment factors were between 83 and 157. The limits of detection (LOD) were in the range 1.2-7 ng/L (S/N=3). The relative standard deviations obtained were below 10.1% (n=5).