Determination of BTEX Compounds by Dispersive Liquid–Liquid Microextraction with GC–FID

Rapid, inexpensive, and efficient sample-preparation by dispersive liquid–liquid microextraction (DLLME) then gas chromatography with flame ionization detection (GC–FID) have been used for extraction and analysis of BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) in water samples. In this extraction method, a mixture of 25.0 μL carbon disulfide (extraction solvent) and 1.00 mL acetonitrile (disperser solvent) is rapidly injected, by means of a syringe, into a 5.00-mL water sample in a conical test tube. A cloudy solution is formed by dispersion of fine droplets of carbon disulfide in the sample solution. During subsequent centrifugation (5,000 rpm for 2.0 min) the fine droplets of carbon disulfide settle at the bottom of the tube. The effect of several conditions (type and volume of disperser solvent, type of extraction solvent, extraction time, etc.) on the performance of the sample-preparation step was carefully evaluated. Under the optimum conditions the enrichment factors and extraction recoveries were high, and ranged from 122–311 to 24.5–66.7%, respectively. A good linear range (0.2–100 μg L⁻¹, i.e., three orders of magnitude; r ² = 0.9991–0.9999) and good limits of detection (0.1–0.2 μg L⁻¹) were obtained for most of the analytes. Relative standard deviations (RSD, %) for analysis of 5.0 μg L⁻¹ BTEX compounds in water were in the range 0.9–6.4% (n = 5). Relative recovery from well and wastewater at spiked levels of 5.0 μg L⁻¹ was 89–101% and 76–98%, respectively. Finally, the method was successfully used for preconcentration and analysis of BTEX compounds in different real water samples.

     

Application of DLLME Based on the Solidification of Floating Organic Droplets for the Determination of Dinitrobenzenes in Aqueous Samples

Dispersive liquid–liquid microextraction (DLLME) based on the solidification of floating organic droplets (DLLME-SFO) combined with gas chromatography-electron-capture detection (GC–ECD) has been developed for extraction and analysis of three dinitrobenzenes. The extraction conditions including extraction solvent, disperser solvent, extraction time, salt effect and temperature were investigated and optimized systematically. The limits of detection were 0.019 μg L^?1 for 1,4-dinitrobenzene, 0.079 μg L^?1 for 1,3-dinitrobenzene and 0.034 μg L^?1 for 1,2-dinitrobenzene. Moreover, it offered good repeatability and high recovery. This method was successfully applied to monitor DNBs in different water samples.     

Optimization of parameters for the alcoholic-assisted dispersive liquid–liquid microextraction of estrogens in water

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L^?1 for E2 and 0.1–100 μg L^?1 for E1. Limits of detection were 0.1 μg L^?1 for E2 and 0.01 μg L^?1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.     

Homogeneous Liquid–Liquid Microextraction for Determination of Organochlorine Pesticides in Water and Fruit Samples

A fast and effective preconcentration method for extraction of organochlorine pesticides (OCPs) was developed using a homogeneous liquid–liquid extraction based on phase separation phenomenon in a ternary solvent (water/methanol/chloroform) system. The phase separation phenomenon occurred by salt addition. After centrifugation, the extraction solvent was sedimented in the bottom of the conical test tube. The OCPs were transferred into the sedimented phase during the phase separation step. The extracted OCPs were determined using gas chromatography–electron capture detector. Several factors influencing the extraction efficiency were investigated and optimized. Optimal results were obtained at the following conditions: volume of the consolute solvent (methanol), 1.0 mL; volume of the extraction solvent (chloroform), 55 μL; volume of the sample, 5 mL; and concentration of NaCl, 5 % (w/v). Under optimal conditions, the preconcentration factors in the range of 486–1,090, the dynamic linear range of 0.01–100 μg L^?1, and the limits of detection of 0.001–0.03 μg L^?1 were obtained for the OCPs. Using internal standard, the relative standard deviations for 1 μg L^?1 of the OCPs in the water samples were obtained in the range of 4.9–8.6 % (n = 5). Finally, the proposed method was successfully applied for extraction and determination of the OCPs in water and fruit samples.     

Determination of Hg(II) in Environmental Water Samples Using DLLME Method Prior to GC-FID

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL^?1. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL^?1. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.     

Rapid monitoring of carvacrol in plants and herbal medicines using matrix solid-phase dispersion and gas chromatography flame ionisation detector

Matrix solid-phase dispersion (MSPD) method coupled with gas chromatography flame ionisation detector as a quick and easy extraction technique has been developed to extract carvacrol from plants and herbal medicines. Influence of important parameters on the MSPD method efficiency, such as the sorbent material, the ratio of sample to sorbent material, elution solvent and volume of the elution solvent has been evaluated and optimised. Carvacrol was successfully extracted by diatomaceous earth as sorbent with 350 μL of dichloromethane as elution solvent. The calibration curve showed good linearity (r² = 0.9965) and precision (RSD < 8.16%) in the concentration range of 0.5–100 μg mL^? 1 for carvacrol. The limit of detection and limit of quantification were 0.1 and 0.5 μg mL^? 1, respectively. The recoveries were in the range of 74.4–80.5% with relative standard deviation (RSD) values ranging from 8.4% to 9.8%. The reported MSPD extraction method revealed to be simpler and faster than conventional methods used to quantify carvacrol from plants and herbal medicines.     

Determination of Estrone and 17β-Estradiol in Water Samples Using Dispersive Liquid–Liquid Microextraction Followed by LC

A new method, termed dispersive liquid–liquid microextraction (DLLME), was developed for the extraction and pre-concentration of estrone (E1) and 17β-estradiol (E2) in water samples. The samples were extracted by 0.50 mL methanol (disperser solvent) containing 25.0 μL tetrachloroethane (extraction solvent). Important factors such as the volume and type of extraction and disperser solvent, extraction time and salt effect were studied. Under optimum conditions, the enrichment factors and the limits of detection were 347 and 0.2 ng mL^?1 for E1, and 203 and 0.1 ng mL^?1 for E2, respectively. The linear range was 0.5–5,000 ng mL^?1. Compared to other methods, DLLME–LC–VWD has advantages for E1 and E2 analysis in water: high enrichment factor, low cost, simplicity, quick and easy operation.     

Capillary GC Analysis of Glyoxal and Methylglyoxal in the Serum and Urine of Diabetic Patients After Use of 2,3-Diamino-2,3-dimethylbutane as Derivatizing Reagent

The dicarbonyl compounds glyoxal, methylglyoxal, and dimethylglyoxal have been separated by capillary GC on a 30 m × 0.32 mm i.d. HP-5 column after precolumn derivatization with 2,3-diamino-2,3-dimethylbutane at pH 4. Chromatographic separation was complete in 6 min. Nitrogen was used as carrier gas at a flow rate of 2 mL min^?1. Split injection was performed with a split ratio of 10:1 (v/v). The derivatives were monitored by flame-ionization detection, and linear calibration plots were obtained in the ranges 0.06–0.69, 0.05–1.01, and 0.07–1.33 μg mL^?1 for glyoxal, methylglyoxal, and dimethylglyoxal, respectively; the respective detection limits were 20, 10, and 10 ng mL^?1. Glyoxal and methylglyoxal were analyzed in serum and urine from diabetics and from healthy volunteers. Amounts of glyoxal and methylglyoxal in serum from diabetic patients were 0.19–0.33 and 0.20–0.29 μg mL^?1, respectively, with respective relative standard deviations (RSD) of 0.8–1.0 and 0.8–1.1%. Amounts of glyoxal and methylglyoxal in serum from healthy volunteers were 0.05–0.08 and 0.04–0.10 μg mL^?1, respectively, with respective RSD of 0.9–1.2 and 1.0–1.2%. Levels of glyoxal and methylglyoxal in urine from diabetic patients were 0.18–0.40 and 0.25–0.36 μg mL^?1, respectively.     

Analysis of PAHs in Water and Fruit Juice Samples by DLLME Combined with LC-Fluorescence Detection

A simple, rapid and efficient method termed dispersive liquid–liquid microextraction combined with liquid chromatography-fluorescence detection, has been developed for the extraction and determination of polycyclic aromatic hydrocarbons (PAHs) in water and fruit juice samples. Parameters such as the kind and volume of extraction solvent and dispersive solvent, extraction time and salt effect were optimized. Under optimum conditions, the enrichment factors ranged from 296 to 462. The linear range was 0.01–100 μg L^?1 and limits of detection were 0.001–0.01 μg L^?1. The relative standard deviations (RSDs, for 5 μg L^?1 of PAHs) varied from 1.0 to 11.5% (n = 3). The relative recoveries of PAHs from tap, river, well and sea water samples at spiking level of 5 μg L^?1 were 82.6–117.1, 74.9–113.9, 77.0–122.4 and 86.1–119.3%, respectively. The relative recoveries of PAHs from grape and apple juice samples at spiking levels of 2.5 and 5 μg L^?1 were 80.8–114.7 and 88.9–123.0%, respectively. It is concluded that the proposed method can be successfully applied for determination of PAHs in water and fruit juice samples.     

Determination of carbamazepine in formulation samples using dispersive liquid–liquid microextraction method followed by ion mobility spectrometry

A simple, sensitive, fast and efficient method based on dispersive liquid–liquid microextraction (DLLME) followed by ion mobility spectrometry (IMS) has been proposed for preconcentration and trace detection of carbamazepine (CBZ) in formulation samples. In this method, 1 mL of methanol (disperser solvent) containing 80 μL of chloroform (extraction solvent) was rapidly injected by a syringe into a sample. After 5 min centrifugation, the preconcentrated carbamazepine in the organic phase was determined by IMS. Development of DLLME procedure includes optimization of parameters influencing the extraction efficiencies such as kind and volume of extraction solvent, disperser solvent and salt addition, centrifugation time and pH of the sample solution. The proposed method presented good linearity in the range of 0.05–10 μg mL^?1 and the detection limit was 0.025 μg mL^?1. The repeatability of the method expressed as relative standard deviation was 6 % (n = 5). This method has been applied to the analysis of carbamazepine formulation samples with satisfactory relative recoveries ≤75 %.     

Composition and antioxidant activity of Senecio nudicaulis Wall. ex DC. (Asteraceae): a medicinal plant growing wild in Himachal Pradesh,India

The composition of essential oil isolated from Senecio nudicaulis Wall. ex DC. growing wild in Himachal Pradesh, India, was analysed, for the first time, by capillary gas chromatography (GC) and GC–mass spectrometry. A total of 30 components representing 95.3% of the total oil were identified. The essential oil was characterised by a high content of oxygenated sesquiterpenes (54.97%) with caryophyllene oxide (24.99%) as the major component. Other significant constituents were humulene epoxide-II (21.25%), α-humulene (18.75%), β-caryophyllene (9.67%), epi-α-cadinol (2.90%), epi-α-muurolol (2.03%), β-cedrene (1.76%), longiborneol (1.76%), 1-tridecene (1.16%) and citronellol (1.13%). The oil was screened for antioxidant activity using DPPH, ABTS and nitric oxide-scavenging assay. The oil was found to exhibit significant antioxidant activity by scavenging DPPH, ABTS and nitric oxide radicals with IC₅₀ values of 10.61 ± 0.14 μg mL^? 1, 11.85 ± 0.28 μg mL^? 1 and 11.29 ± 0.42 μg mL^? 1, respectively.     

Effect of bioclimatic area on the composition and bioactivity of Tunisian Rosmarinus officinalis essential oils

The chemical composition of eight Tunisian Rosmarinus officinalis L. populations (A–H) from different bioclimatic areas has been examined by gas chromatography (GC) and GC-mass spectrometry. The essential oils are characterised by high amounts of oxygenated monoterpenes (58.2–71.7%) followed by monoterpene hydrocabons (15.1–26.7%). 1,8-Cineole, camphor, α-pinene and borneol are the main representative components. The antioxidant activity was investigated by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), ferric reducing ability power assay and β-carotene bleaching test. Samples showed antiradical activity by inhibiting DPPH radical with IC₅₀ values ranging from 375.3 to 592.8 μg mL^? 1 for samples F and A, respectively. Sample A also showed the most promising activity in β-carotene bleaching test (IC₅₀ of 31.9 μg mL^? 1). The essential oils were also screened for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity. Sample G showed the highest activity against AChE (IC₅₀ of 64.7 μg mL^? 1) while sample D (IC₅₀ of 29.5 μg mL^? 1) exhibited the most potent activity against BChE.     

LC Determination of Chloramphenicol in Honey Using Dispersive Liquid–Liquid Microextraction

A novel method, dispersive liquid–liquid microextraction coupled with liquid chromatography-variable wavelength detector (LC-VWD), has been developed for the determination of chloramphenicol (CAP) in honey. A mixture of extraction solvent (30 μL 1,1,2,2-tetrachloroethane) and dispersive solvent (1.00 mL acetonitrile) were rapidly injected by syringe into a 5.0 mL real sample for the formation of cloudy solution, the analyte in the sample was extracted into the fine droplets of C₂H₂Cl₄. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase was determined by LC-VWD. Some important parameters, such as the kind and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 3 to 2,000 μg kg^?1 for target analyte. The enrichment factor for CAP was 68.2, and the limit of detection (S/N = 3) were 0.6 μg kg^?1. The relative standard deviation (RSD) for the extraction of 10 μg kg^?1 of CAP was 4.3% (n = 6). The main advantages of method are high speed, high enrichment factor, high recovery, good repeatability and extraction solvent volume at μL level. Honey samples were successfully analyzed using the proposed method.     

Liquid–Liquid Microextraction of Nitrophenols Using Supramolecular Solvent and Their Determination by HPLC with UV Detection

A novel, efficient, and environmentally friendly method—supramolecular solvent liquid–liquid microextraction (SMS-LLME) combined with high-performance liquid chromatography (HPLC)—was first established for the determination of p-nitrophenol and o-nitrophenol in water samples. Several important parameters influencing extraction efficiency, such as the type and volume of extraction solvent, pH of sample, temperature, salt effect, extraction time, and stirring rate, were optimized in detail. Under the optimal conditions, the enrichment factor was 166 for p-nitrophenol and 160 for o-nitrophenol, and the limits of detection by HPLC were 0.26 and 0.58 μg L^?1, respectively. Excellent linearity with coefficients of correlation from 0.9996 to 0.9997 was observed in the concentration range of 2–1,000 μg L^?1. The ranges of intra- and interday precision (n = 5) at 100 μg L^?1 of nitrophenols were 5.85–7.76 and 10.2–11.9 %, respectively. The SMS-LLME method was successfully applied for preconcentration of nitrophenols in environmental water samples.     

On-line Micro Solid-Phase Extraction of Clodinafop Propargyl from Water,Soil and Wheat Samples Using Electrospun Polyamide Nanofibers

An on-line extraction/determination set up was designed for micro solid-phase extraction of clodinafop propargyl from water, soil and wheat samples using electrospun polyamide nanofiber mats. The prepared mats were packed in a stainless steel tube which conveniently acted as a high-performance liquid chromatography injection loop. Influential parameters affecting the extraction efficiency were optimized using a distilled water sample fortified with 25 μg L^?1 of clodinafop propargyl. An enrichment factor of 440 was achieved for clodinafop propargyl indicating the ability of the whole procedure. Under the optimum conditions, the linearity for the analyte was in the range of 6–700 μg L^?1, while a limit of detection and limit of quantification of 2 and 6 μg L^?1 were achieved, respectively. The intra-day and inter-day RSD% at the concentration level of 25 μg L^?1 were 4.6 and 9.3 %, respectively. To investigate the matrix effect, the developed method was applied to the analysis of real water samples including paddy and river waters as well as the wheat and soil samples. The relative recovery percentages for the spiked samples were in the range of 63–95 %.     

Quantitative Determination of Underivatized α-Tocopherol in Cow Milk, Vitamin and Multivitamin Drugs by GC-FID

A simple and rapid method for direct determination of α-tocopherol (α-T, vitamin E) in pharmaceutical preparations (vitamin and multivitamin tablets) and cow milk obtained from different villages of Erzurum in Turkey was developed and validated by GC-FID. Separation of underivatized α-T in pure substance, milk samples, vitamin and multivitamin tablets was performed in about 8.4 min, using an HP-5 capillary column. The range of quantification for the GC-FID was 1–30 μg mL^?1. Within-day and between-day precision (RSD %) were less than 8.5%, and accuracy (relative error) was less than 11.0% (n = 6). LOQ and LOD values were found to be 0.35 and 0.30 μg mL^?1, respectively. The developed method was applied directly and easily to the analysis of α-T in vitamin and multivitamin preparations and cow milk. RSD values were found to be 6.59% (Grandpherol soft gelatine capsule: 200 I.U.), 0.59% (Megadyn film tablet: 10 mg) and 1.54% (Supradyn drage: 10 I.U.). The developed method was also applied to cow milk samples and mean values of α-T content was found 2.99 μg mL^?1 in cow milk samples. This developed and validated GC–FID method, in conjunction with other methods, could be successfully applied for routine laboratory because of its simplicity, rapidity, sensitivity, precision and accuracy.     

Determination of Hg(II) in Environmental Water Samples Using DLLME Method Prior to GC-FID

Mercury exists in two forms in environment, inorganic salts and organic compounds. Determination of mercury is very important, due to its health effects. In the present research, diphenylation of mercury using phenylboronic acid as a derivatization reagent was used for the determination of Hg(II) in real water samples. A simple, rapid and cheap method named dispersive liquid–liquid microextraction was used for the extraction of analyte under the following conditions: extraction solvent 16 μL of carbon tetrachloride, disperser solvent 1 mL of ethanol and sample volume 5 mL. Under the optimal conditions, the enrichment factor for diphenylmercury was 931 and the limit of detection calculated on the basis of five replicates was 0.004 μg mL⁻¹. The repeatability of the method expresses as relative standard deviation was 5.1 (n = 6). The linear range was between 0.01 and 10 μg mL⁻¹. The performance of the proposed technique was evaluated for the determination of mercury in different environmental water samples.

     

Magnetic Stirring-Assisted Dispersive Suspended Microextraction with Solidification of a Floating Organic Droplet for the Determination of Trace Fungicides in Water and Wine

For the first time, a simple method for magnetic stirring-assisted dispersive suspended microextraction has been developed for the determination of three fungicides (azoxystrobin, diethofencarb, and pyrimethanil) in water and wine samples. The method is based on the solidification of a floating organic droplet coupled with high performance liquid chromatography. In the proposed method, the low toxicity solvent 1-dodecanol was used as the extractant. Both the extraction and phase separation process were performed with magnetic stirring. No centrifugation step was involved. After separating the two phases, the extraction solvent droplet was easily collected through solidification at lower temperature. Important parameters such as the kind and volume of organic extraction solvent, extraction and restoration speed, extraction and restoration time, and salt concentration were optimized. Under the optimal conditions, the limits of detection for the analytes varied from 0.14 to 0.26 µg L^?1. The enrichment factors ranged from 125–200. The linearity ranges were 1–2000 µg L^?1, yielding correlation coefficients (r) higher than 0.9990. The relative standard deviation (n = 6) at two spiked level of 0.2 µg mL^?1 and 4 µg L^?1 varied between 2.2% and 7.8%. Finally, the developed technique was successfully applied to determine target fungicides in real water and wine samples, where the obtained recoveries ranged from 83.8–105.3%     

Ion-Pair LC Method for Simultaneous Determination of Aliskiren Hemifumarate,Amlodipine Besylate and Hydrochlorothiazide in Pharmaceuticals

A rapid and precise LC method was developed for the simultaneous determination of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) using acetonitrile:25 mM octane sulfonic acid sodium salt monohydrate in water (60:40 v/v) as the mobile phase. The flow rate was maintained at 1.2 mL min^?1 on a stationary phase composed of Supelco, Discovery^® HS (C18) column (25 cm × 4.6 mm, 5 μm). Isocratic elution was applied throughout the analysis. Detection was carried out at λ _max (232 nm) at ambient temperature. The method was validated according to ICH guidelines. Linearity, accuracy and precision were satisfactory over the concentration ranges of 32–320, 2–44 and 4–64 μg mL^?1 for ALS, AML and HCZ, respectively. LOD and LOQ were estimated and found to be 0.855 and 2.951 μg mL^?1, respectively, for ALS, 0.061 and 0.202 μg mL^?1, respectively, for AML as well as 0.052 and 0.174 μg mL^?1, respectively, for HCZ. The method was successfully applied for the determination of the three drugs in their co-formulated tablets. The results were compared statistically with reference methods and no significant difference was found. The developed method is specific and accurate for the quality control and routine analysis of the cited drugs in pharmaceutical preparations.     

Determination of Explosives in Water Using Disposable Pipette Extraction and High Performance Liquid Chromatography

The use of disposable pipette extraction was examined for the simple and rapid determination of seven high explosives (cyclotrimethyl-enetrinitramine, cyclotetramethyl-enetetranitramine, 2,4,6-trinitrophenyl-methylnitramine, 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, nitroglycerin, and pentaerythritol tetranitrate) in water. The current study involved the determination of slightly polar and nonpolar explosives in water with a reversed phase sorbent followed by high performance liquid chromatography. The method was based on a styrene divinylbenzene sorbent loosely placed inside a 5-mL pipette tip. Water samples were drawn into the tip and mixed with the sorbent. Air bubbles were also drawn through the tip following sample solution to enhance mixing. Because disposable pipette extraction uses small amounts of sorbent, minimal solvent is required to elute analytes and solvent evaporation is not necessary. The method provided rapid sample preparation, and required less than five minutes to extract 1.0 mL of water sample in the current study. Matrix-matched calibration was performed, and the limits of detection (LOD) were determined to be below 0.1 µg mL^?1 for all targeted explosives in water with an enrichment factor of two. Coefficients of determination (r²) were greater than 0.9990 for all studied explosives, and the recoveries ranged from 69.76% to 87.51%, 83.77% to 91.25%, and 83.62% to 98.99% for samples spiked at 0.25 µg mL^?1, 1.0 µg mL^?1, and 5.0 µg mL^?1, respectively. The relative standard deviations of recoveries at all spiked levels were below 8.97%. These results indicate that the disposable pipette extraction method provided good accuracy and precision for the determination of explosives in water.