Rapid Dispersive Liquid-liquid Microextraction Research Articles

Determination and extraction of acrylamide in processed food samples using alkanol-based supramolecular solvent-assisted dispersive liquid-liquid microextraction coupled with spectrophotometer: Optimization using factorial design

In current study, simple, rapid, sensitive and selective alkanol-based supramolecular solvent-assisted dispersive liquid-liquid microextraction (SSA-DLLME) method was first time developed for the extraction and determination of acrylamide (AA) in coffee, chocolate, roasted nuts, French fries, cereals, biscuits, chips, bread and caramelized fruit using UV–visible spectrophotometer. Different parameters were investigated and optimized to know their effects on the extraction of AA. Studies have shown that effective extraction of AA was achieved at short vortex time (2 min) and acidic pHs. Extraction of AA was inversely proportional to sample volume. The linear range (LR) of the SSA-DLLME method was 0.6–350 ng mL−1. The limit of detection (LOD), and limit of quantification (LOQ) were found to be 0.2 ng mL−1 and 0.6 ng mL−1, respectively. In addition, enhancement factor and preconcentration factor was 114 and 200, respectively. Factorial design was utilized to better understand dual effluents of factors on extraction recovery of the AA. Optimized SSA-DLLME method was successfully applied to process food samples for the determination of AA.

Dispersive Liquid‐Liquid Microextraction (DLLME) Based on Solidification of Switchable Hydrophilicity Solvent Coupled with High‐Performance Liquid Chromatography (HPLC) with Photodiode Array (PDA) Detection for the Determination of Pyrethroid Pesticides in Grains

Rapid dispersive liquid-liquid microextraction (DLLME) based on the solidification of a switchable hydrophilicity solvent (SHS) was established for the preconcentration of pyrethroid pesticides from grain prior to determination using high‐performance liquid chromatography (HPLC) with photodiode array (PDA). Lauric acid was selected to be the switchable hydrophilicity solvent due to its conversion between hydrophobic and hydrophilic forms and solidification at low temperature, thereby avoiding a time-consuming centrifugation step. The results show that the optimal conditions for pyrethroid pesticides included 30 mmol/L lauric acid, hydrochloric acid as the hydrogen donor, a 1:1.8 stoichiometric ratio of sodium laurate and hydrochloric acid, an extraction temperature of 50 °C, an extraction time of 8 min, and a solidification time of 3 min. Under the optimal conditions, this approach provided a high enrichment factor (308.4 to 330.2), a short pretreatment period of less than 15 min, and sensitive detection limits from 5 to 20 ng/g suitable for the analysis of food. The method was employed for the determination of pyrethroid pesticides in grain. The recoveries were 84.3% to 115.7%, and the relative standard deviation was less than 9.9%.

Rapid and Sensitive Determination of Polycyclic Aromatic Hydrocarbons in Green Tea Samples by Dispersive Liquid-Liquid Microextraction Coupled to High-Performance Liquid Chromatography-Diode Array Detection

A rapid and sensitive dispersive liquid-liquid microextraction (DLLME) has been developed for the extraction of selected polycyclic aromatic hydrocarbons (PAHs), namely phenanthrene (PHE) and fluoranthene (FLA) in green tea beverage samples. The extracted PAHs were separated and determined by using high-performance liquid chromatography diode array detection (HPLC-DAD). An experimental design using response surface methodology (RSM) and central composite design (CCD) was performed to evaluate the interactive effects of the 2 most significant parameters, namely extraction time and sample pH. The optimal conditions were sample pH of 6.5 with 1.25 min extraction time. The analysis of variance (ANOVA) showed that the most influential parameter was the extraction time. The predicted values were obtained in good agreement with the actual value (R2 ≥ 0.9086). Under the optimal extraction conditions, the method demonstrated acceptable linearity (R2 ≥ 0.9996) over a concentration range (10 - 1,000 µg L−1) for different PAHs. The limits of detection and quantifications were in the range of (4 - 10 µg L−1) and (18 - 50 µg L−1), respectively. Good analytes recovery (102 - 110 %) and excellent precision level with relative standard deviations (RSD %, n = 3) were obtained between 1.53 and 4.52 %. The method was successfully applied to the analysis of spiked green tea beverage samples. The proposed method is rapid, reliable, sensitive, and environmentally friendly for the detection of PAHs.
 HIGHLIGHTS
 
 A more efficient sample preparation method is required to measure interferences and enrich target analysis of PAHs residues in green tea, as existing methods are time-consuming, significant tendency to form emulsions, consume large volumes of solvents, and involve disposal of toxic or flammable chemicals
 Dispersive liquid-liquid microextraction (DLLME) method coupled with a high-performance liquid chromatography diode array detector (HPLC-DAD) was developed for the analysis of selective PAHs, namely fluoranthene (FLA) and phenanthrene (PHE) in green tea beverage samples
 RSM optimized DLLME parameters based on CCD, and the optimal conditions used during the analysis of PHE and FLA in the green tea samples extracted the non-polar PHE and FLA with good sensitivity. The procedure was simple, rapid, sensitive, and minimized the consumption of organic solvent
 
 GRAPHICAL ABSTRACT

Analysis of persistent contaminants and personal care products by dispersive liquid-liquid microextraction using hydrophobic magnetic deep eutectic solvents

In this work, hydrophobic magnetic deep eutectic solvents (HMDESs) were used in the development of a simple and rapid dispersive liquid-liquid microextraction (DLLME) approach coupled to high performance liquid chromatography with UV detection (HPLC-UV) for the determination of ten organic contaminants including five polycyclic aromatic hydrocarbons, four UV filters, and a pesticide from water at trace levels. The HMDESs were prepared by mixing a hydrogen bond acceptor, metal halide salt, and hydrogen bond donor in suitable molar ratios. Two HMDESs, 2 tetraoctylammonium bromide ([N8888+][Br−]): cobalt chloride (CoCl2): 4 octanoic acid (OA) and 3 trioctylphosphine oxide (TOPO): neodymium chloride (NdCl3): 3 OA, offered the highest analyte extraction efficiency overall and were chosen as suitable solvents for validation of the microextraction method. Under optimized extraction conditions, the method required 30 µL of HMDES as extraction solvent, acetone (87.5 µL) as disperser solvent, a NaCl concentration of 30% (w/v), and an extraction time of 120 s at 20°C. Enrichment factors of the analytes ranged from 44.6 for 3-(4-methylbenzylindene) camphor to 66.0 for 2-ethylhexyl-4-(dimethyl)aminobenzoate. The method provided low limits of detection (LODs) ranging from 0.5 to 4.5 µg L−1, and acceptable precision, with RSD values lower than 9.6%. Furthermore, the validated method was successfully applied for tap and lake water analysis, resulting in relative recoveries of spiked samples ranging between 94.7 and 119.2%.

Simultaneous preconcentration and determination of zirconium in environmental samples using ultrasound-assisted ionic liquid based dispersive liquid-liquid microextraction combined with spectrophotometry

ABSTRACT The Green, delicate and rapid ultrasound-assisted ionic liquid-based dispersive liquid-liquid microextraction technique was developed to preconcentrate trace quantities of zirconium Zr(IV) ion in real samples prior to spectrophotometric detection. The proposed method uses (1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) ionic liquid (IL) as an extraction solvent for Zr(IV) ions after the complexation with quinalizarin at pH 5.0. The effect of various analytical parameters has been investigated. The calibration graph was linear in the range of 2.0–400 µg L − 1 and the limit of detection was 0.6 µg L-1. The preconcentration factor was 100. Relative standard deviation (RSD%) at 200 µg L-1 of Zr(IV)for intra-day and inter-day precisionwere 2.0 and 2.7%, respectively (n = 10). Certified reference materialswere used to verify the accuracy.The proposed method was applied to preconcentrate and determine the content of Zr(IV) in real environmental (water, soil and plants) samples with satisfactory results.

Determination of Methadone and Tramadol in Vitreous Humor Specimens Using Dispersive LiquidLiquidMicroextractionandUltraHighPerformance Liquid Chromatography

Background: Drug abuse is spreading rapidly all over the world. Methadone and tramadol are among not only the most abused opioids but also important from the forensic point of view. Therefore, we need to devise a simple and sensitive method for the sample preparation and identification of abused drugs in postmortem specimens. Methods: A simple and rapid Dispersive Liquid-Liquid Microextraction (DLLME) technique coupled with Ultrahigh Performance Liquid Chromatography (UHPLC) was developed for the extraction and analysis of methadone and tramadol from postmortem vitreous humor samples. Different parameters affecting the extraction recovery, such as the type and volume of extraction and dispersion solvents, pH value, sensitivity, and specificity, were optimized and studied. Results: Under optimized conditions, the recovery ranges were 82.3%-89.6% and 85.4%-87.1% for methadone and tramadol, respectively. The linear range was 25-100 ng/mL for both methadone and tramadol with a correlation coefficient (R2) of more than 0.98. Limit of Detection (LoD) and Limit of Quantification (LoQ) were 3 and 8 ng/mL for methadone and 6 and 16 ng/mL for tramadol. The accuracy level of the methods for methadone and tramadol detection were 99.4%-100% and 99.7%-99.9%, respectively. The method was specific enough for the qualitative and quantitative determination of methadone and tramadol. Conclusion: The obtained results showed that DLLME combined with UHPLC is a fast and straightforward method for determining methadone and tramadol in postmortem vitreous humor specimens.

Determination of bisphenol a migration from food packaging by dispersive liquid-liquid microextraction

In the current work, a rapid and simple dispersive liquid-liquid microextraction method (DLLME) was used to determine Bisphenol A (BPA). High performance liquid chromatography with the photodiode-array detector (HPLC-DAD) coupled DLLME method was employed to analyze BPA in food samples packaged including cans, paper boxes, and glass jars. The calibration curve was obtained to be in the linear range 0.009–25 ngg−1 with a correlation coefficient of R2 = 0.9981. The mean relative standard deviations (RSDs) was of 5.2% (n = 3). The limit of detection (LOD) and the limit of quantification (LOQ) of the method were obtained to be 0.001 ngg−1 and 0.08 ng.g−1, respectively.In sum, this method presents:•A rapid, simple and efficient modified DLLME method was used to measure BPA in packaged foods.•The advantages of this method were low detection limit, fast preparation, and high BPA recovery.•The DLLME-HPLC method consists of low detection limit and high recoveries to determine BPA in samples.•The results indicated that DLLME –HPLC-DAD was an applied method to measure BPA in food samples.

Ultra-trace Extraction of Two Bactericides Via Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction.

A simple, rapid and sensitive method coupling ultrasound-assisted dispersive liquid-liquid microextraction (DLLME) with ultra-high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of malachite green (MG) and crystal violet (CV) in different water samples. In ultrasound-assisted DLLME procedure, several parameters affecting the extraction efficiency, including pH, type and volume of the extraction and dispersive solvents, extraction time, ionic strength, were optimized to improve the accuracy and precision of this method. MG and CV were extracted and preconcentrated using dichloromethane and acetonitrile as the extraction and dispersive solvents, respectively. Under the optimum conditions, the proposed method affords good linearity in the range of 0.40-20.0ng/L, and the limit of detections were 0.21 and 0.32ng/L for MG and CV, respectively. The recoveries of the method at three spiked levels were in the range of 83.4-94.2% with relative standard deviations lower than 4.7% (n=3). Satisfactorily, no significant matrix effect has been found as the data ranged between 68% and 102%.

Determination of Gemfibrozil in Drug Matrix and Human Biological Fluid by Dispersive Liquid-Liquid Microextraction with High Performance Liquid Chromatography

A simple and rapid dispersive liquid-liquid microextraction technique coupled with high performance liquid chromatography (HPLC) was developed for the extraction and analysis of gemfibrozil in drug matrix and biological fluids like human plasma and urine samples. In this method, carbon tetrachloride at microliter volume level and methanol were used as extraction and disperser solvents, respectively. The effects of factors including the type and volume of disperser and extraction solvents, pH and extraction time on the performance of the sample preparation were carefully evaluated. Under optimum conditions, the obtained enrichment factors were between 9.2 - 9.3 and extraction recoveries were high and ranged between 91.2 - 93.2%. The calibration curve was linear in the range of 0.1 - 100 mg/L with a detection limit of 12.3 µg/L. The relative standard deviation (RSD) for ten replicate measurements of gemfibrozil was 1.3%. The performance of the method was checked by the analysis of the gemfibrozil in presence of other drugs in water samples.

Dispersive Liquid-Liquid Microextraction Method for the Simultaneous Determination of Four Isomers of Hexachlorocyclohexane and Six Pyrethroid Pesticides in Milk by Gas Chromatography Electron Capture Detector

In this study, a simple and rapid dispersive liquid-liquid microextraction method was established, and the residuals of four isomers of hexachlorocyclohexane and six kinds of pyrethroid pesticides in milk were simultaneously determined by gas chromatography electron capture detector (GC-ECD). The milk sample was first extracted with acetonitrile and cleaned with primary secondary amine (PSA). Then 0.5 mL of acetonitrile was mixed with 140 μL of cyclohexane and rapidly injected into 3 mL of pure water. After vortexing and centrifugation, the floating phase was removed with a 0.1-mL pipette into the GC-ECD. The type and volume of extraction solvent, volume of disperser solvent, volume of water, vortex time, and amount of salt were optimized. Under optimal extraction conditions, the ten pesticides showed a good linear relationship in a certain concentration range in milk matrix, and the correlation coefficients were greater than 0.99. The limits of detection ranged from 0.07 to 2 μg/kg, and the limits of quantitation ranged from 0.2 to 5 μg/kg. The average recovery rates were between 70.1% and 106.3%, and the relative standard deviations were less than 15.2%. This method can be used for the determination of hexachlorocyclohexane and pyrethroid pesticides in milk and for subsequent research.

Development of a dispersive liquid-liquid microextraction method based on a ternary deep eutectic solvent as chelating agent and extraction solvent for preconcentration of heavy metals from milk samples

A simple, green, rapid, and efficient ligandless dispersive liquid-liquid microextraction procedure based on solidification of a ternary deep eutectic solvent has been proposed for the extraction of trace amounts of Cd(II), Cu(II), and Pb(II) ions in milk samples prior to their determination by flame atomic absorption spectrometry. Initially, a suitable mole ratio of sorbitol, menthol, and mandelic acid are mixed in a test tube, and after heating, a deep eutectic solvent with low density compared to water is formed. The synthesized solvent is used as a chelating agent and an extraction solvent in the extraction of some heavy metal ions from milk samples. The influence of several effective parameters on the responses and extraction recoveries of the analytes was investigated. Under the optimum experimental conditions, the linear ranges were in the ranges of 1.0–40 μg L−1 for Cd(II) and Pb(II), and 1.0–25 μg L−1 for Cu(II). The obtained relative standard deviations (n = 6, C = 2.5 μg L−1 of each cation) and detection limits were in the ranges of 3.4–4.1% and 0.38–0.42 μg L−1, respectively. Finally, the developed method was successfully applied for the determination of Cd(II), Cu(II), and Pb(II) ions in different milk samples.

Development of a Vortex-Assisted Dispersive Liquid-Liquid Microextraction (VA-DLLME) and LC-MS/MS Procedure for Simultaneous Determination of Fipronil and its Metabolite Fipronil Sulfone in Tomato Fruits

A rapid, simple, inexpensive, and reliable vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) method was developed for the determination of fipronil and its major metabolite, fipronil sulfone, in tomato fruits using liquid chromatography tandem mass spectrometry (LC-MS/MS). No salting-out or cleanup steps were required after extraction. Average recoveries ranged from 89.8 to 96.3% with relative standard deviation (RSD) values below 11.6%. The limit of quantitation (LOQ) of the method was 0.25 μg/kg, which is 20 times below the European Union-defined maximum residue limit (MRL) of 5 μg/kg. Good linearity was achieved, with a correlation coefficient ≥ 0.996 based on matrix-matched calibration. We investigated the dissipation and residue distribution of fipronil in tomato fruits after one application of suspension concentrate (SC) or emulsifiable concentrate (EC) formulations over 28 days under field conditions using the VA-DLLME method. The half-life (t1/2) of fipronil dissipation was 2.4 and 2.8 days, and the estimated pre-harvest interval (PHI) was 23 and 32 days for the SC and EC formulation, respectively. A risk assessment was conducted by evaluating the health risk index (HRI); the estimated PHIs values indicate it is safe to consume tomatoes after the recommended application of fipronil.

A rapid dispersive liquid-liquid microextraction based on hydrophobic deep eutectic solvent for selective and sensitive preconcentration of thorium in water and rock samples: A multivariate study

Thorium [Th(IV)] and its compounds are highly toxic and cause severe damage to bone and kidney through long term exposures. Conventional methods of Th(IV) detection are complicated and costly. In this study, we developed a new dispersive liquid-liquid microextraction (DLLME) based on hydrophobic deep eutectic solvent (HDES) for preconcentration of Th(IV) in water and rock samples prior to UV–Vis. spectrophotometric detection. The microextraction procedure was carried out by applying thorin as a chelating agent, cethyltrimethyl ammonium bromide (CTAB) as an ion pairing agent and a DES consisted of 1-hexyl-3-methylimidazolium and salicylic acid components as an extraction solvent. Central composite design (CCD) was applied to obtain the best condition of the microextraction procedure. The developed method is a green, facile, fast, selective and sensitive that could detect Th(IV) in the concentration range of 10–600 ng mL−1 with a limit of detection (LOD) and preconcentration factor of 2.1 ng mL−1 and 59, respectively. The relative standard deviation of five replicate measurements of Th(IV) at 100 ng mL−1 was 1.7%. Finally, the proposed method was successfully applied to the analysis of Th(IV) in water and rock samples, and desirable results were obtained.

One step rapid dispersive liquid-liquid micro-extraction with in-situ derivatization for determination of aflatoxins in vegetable oils based on high performance liquid chromatography fluorescence detection

A rapid dispersive liquid-liquid micro-extraction (DLLME) with in-situ derivatization method for extraction and purification of aflatoxins (AFs) in vegetable oils was developed and evaluated. Oil extract, dichloromethane and trifluoroacetic acid were mixed and injected into water to form a cloudy solution. AFs in the oil were extracted into the numerous liquid droplets (with diameters from a few microns to dozens of microns) of extractant, where derivatization was carried out in situ. The proposed sample preparation method was coupled with high performance liquid chromatography with fluorescence detection (HPLC-FLD) for determination of four AFs in vegetable oils. The method showed excellent linearity in three orders of magnitude, good relative recoveries, good repeatability and high sensitivity with limits of detection in range of 0.005–0.03 ng/mL. The accuracy of the method was also verified by certified reference sample. Finally, different kinds of vegetable oils from the local supermarket were analyzed.

A simple, rapid and low cost reversed-phase dispersive liquid-liquid microextraction for the determination of Na, K, Ca and Mg in biodiesel

In this work a method based on reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) as sample preparation for the extraction and preconcentration of Na, K, Ca and Mg in biodiesel samples was developed. The analytes determination was performed by flame atomic absorption spectrometry (FAAS), operating in emission mode for Na and K and in absorption mode for Ca and Mg. The extraction/preconcentration step of the analytes was performed by using a mixture of dispersant and extractant solvents (isopropanol and HNO3, respectively) and the aqueous phase containing the analytes was separated by centrifugation. Some parameters such as sample mass, type and volume of dispersant and extractant solutions, HNO3 concentration (extraction solution), use of ultrasound, centrifugation time and temperature were evaluated. During the optimization of RP-DLLME, biodiesel samples were spiked with a multi-element biodiesel B100 (Conostan®) with final concentration of 1.0 μg g−1 of the analytes. Analytes determination was performed by FAAS using external calibration with aqueous reference solutions. The limits of quantification (LOQ) for Na, K, Ca and Mg were 0.04; 0.02; 0.05 and 0.08 µg kg respectively. The accuracy was evaluated by recovery tests, which ranged from 93.9% to 108.1%, with relative standard deviation lower than 3% for all analytes. Then, the proposed method was applied for analytes determination in five biodiesel samples produced from different raw materials. Comparing to conventional methods for elements determination in biodiesel (e.g., dilution with organic solvent, sample digestion, etc.), RP-DLLME combined to FAAS is simple, low cost, low reagents consumption and provides LOQs values significantly below compared to the limits established in the legislation for these elements in biodiesel.

Determination of glyoxal, methylglyoxal, and diacetyl in red ginseng products using dispersive liquid-liquid microextraction coupled with GC-MS.

A simple and rapid dispersive liquid-liquid microextraction method coupled with gas chromatography and mass spectrometry was applied for the determination of glyoxal as quinoxaline, methylglyoxal as 2-methylquinoxaline, and diacetyl as 2,3-dimethylquinoxaline in red ginseng products. The performance of the proposed method was evaluated under optimum extraction conditions (extraction solvent: chloroform 100μL, disperser solvent: methanol 200μL, derivatizing agent concentration: 5g/L, reaction time: 1 h, and no addition of salt). The limit of detection and limit of quantitation were 1.30 and 4.33μg/L for glyoxal, 1.86 and 6.20μg/L for methylglyoxal, and 1.45 and 4.82μg/L for diacetyl. The intra- and interday relative standard deviations were <4.95 and 5.80%, respectively. The relative recoveries were 92.4-103.9% in red ginseng concentrate and 99.4-110.7% in juice samples. Red ginseng concentrates were found to contain 191-4274μg/kg of glyoxal, 1336-4798μg/kg of methylglyoxal, and 0-830μg/kg of diacetyl, whereas for red ginseng juices, the respective concentrations were 72-865, 69-3613, and 6-344μg/L.

Ultrasound-assisted dispersive liquid-liquid microextraction of tetracycline drugs from egg supplements before flow injection analysis coupled to a liquid waveguide capillary cell.

A simple, rapid, and efficient ultrasound-assisted dispersive liquid-liquid microextraction (US-DLLME) method was developed for extraction of tetracycline residues from egg supplement samples, with subsequent determination by flow injection analysis (FIA) coupled to a liquid waveguide capillary cell (LWCC) and a controlled temperature heating bath. Tetracyclines react with diazotized p-sulfanilic acid, in a slightly alkaline medium, to form azo compounds that can be measured at 435nm. The reaction sensitivity improved substantially (5.12-fold) using an in-line heating temperature of 45°C. Multivariate methodology was used to optimize the factors affecting the extraction efficiency, considering the volumes of extraction and disperser solvents, sonication time, extraction time, and centrifugation time. Good linearity in the range 30-600μgL(-1) was obtained for all the tetracyclines, with regression coefficients (r) higher than 0.9974. The limits of detection ranged from 6.4 to 11.1μgL(-1), and the recoveries were in the range 85.7-96.4%, with relative standard deviation lower than 9.8%. Analyte recovery was improved by approximately 6% when the microextraction was assisted by ultrasound. The results obtained with the proposed US-DLLME-FIA method were confirmed by a reference HPLC method and showed that the egg supplement samples analyzed were suitable for human consumption.

Development and Validation of Ultrasound Assisted and Dispersive Liquid-Liquid Microextractions Combined with HPLC-UV Method for Determination of Bosentan in Human Plasma and Urine

A feasible, rapid, sensitive and reliable dispersive liquid-liquid microextraction (DLLME) and ultrasonic assisted liquid-liquid microextraction (USAEME) combined with high-performance liquid chromatography (HPLC) method with UV detection was developed and validated for analysis of bosentan in human plasma and urine samples. All validation tests were reported according to FDA guidelines. Since chromatographic methods are precise, accurate and provide excellent separation are increasingly being used in determination of trace amount of drugs in biological goals. So the optimized experimental extraction factors from our previous work were used to evaluate HPLC-UV method for decreasing the limit of quantifications (LOQs) to cover the therapeutic range. Simple centrifugation of urine samples was sufficient prior to microextraction procedure, while acetonitrile protein precipitation provides sample clean up for plasma samples. The suggested method was linear (correlation coefficient R2 > 0.998) over a range of 0.1-10 µg mL-1 which covers the therapeutic range. Proposed methods are practical for quantitative analysis of bosentan in real samples, and could be used in routine clinical analyses.

Optimized Dispersive Liquid-Liquid Microextraction Method and High Performance Liquid Chromatography with Ultraviolet Detection for Simultaneous Determination of Sorbic and Benzoic Acids and Evaluation of Contamination of These Preservatives in Iranian Foods.

A rapid, simple, and sensitive dispersive liquid-liquid microextraction procedure followed by HPLC-UV was applied to determine the benzoate and sorbate in foods. The method was optimized for some variables including extraction solvent type and volume, dispersing solvent type and volume, and the effects of salt and pH. Optimum conditions were determined as follows: sample volume, 5 mL; extraction solvent (chloroform) volume, 250 μL; disperser solvent (acetone) volume, 1.2 mL; NaCl amount, 0.75 g/5 mL at pH 4. Sixty samples were analyzed, including 15 doogh, 15 fruit juice, 15 cookie, and 15 tomato paste; benzoic acid was detected in 57 samples (95%) at levels up to 448.1 μg/mL and sorbic acid in 31 samples (51.6%) at levels up to 1369 μg/mL. Under the optimum experimental conditions, the LOD and LOQ were determined as 0.1 and 0.5 μg/mL for benzoate and 0.08 and 0.3 μg/mL for sorbate, respectively. The results showed that these preservatives are commonly used at high levels in yogurt drinks (dooghs) and cookies. Also, the concentration of benzoic acid that was detected in the tomato paste and fruit juice samples was low but may affect children and sensitive persons.

Pre-concentration of uranium from water samples by dispersive liquid–liquid micro-extraction

Abstract In this study, a simple and rapid dispersive liquid–liquid microextraction (DLLME) was developed for the determination of uranium in water samples prior to high performance liquid chromatography with diode array detection. 1-(2-pyridylazo)-2-naphthol (PAN) was used as complexing agent. The effect of various parameters on the extraction step including type and volume of extraction and dispersive solvents, pH of solution, concentration of PAN, extraction time, sample volume and ionic strength were studied and optimized. Under the optimum conditions, the limit of detection (LOD) and preconcentration factor were 0.3 μg L−1 and 194, respectively. Furthermore, the relative standard deviation of the ten replicate was &lt;2.6%. The developed procedure was then applied to the extraction and determination of uranium in the water samples.