Vortex‐ and CO2‐gas‐assisted liquid–liquid microextraction with salt addition for the high‐performance liquid chromatographic determination of furanic compounds in concentrated juices and dried fruits

A novel microextraction method based on vortex‐ and CO₂‐assisted liquid–liquid microextraction with salt addition for the isolation of furanic compounds (5‐hydroxymethyl‐2‐furaldehyde, 5‐methyl‐2‐furaldehyde, 2‐furaldehyde, 3‐furaldehyde, 2‐furoic and 3‐furoic acids) was developed. Purging the sample with CO₂ was applied after vortexing to enhance the phase separation and mass transfer of the analytes. The optimum extraction conditions were: extraction solvent (volume), propyl acetate (125 μL); sample pH, 2.4; vortexing time, 45 s; salt concentration, 25% w/v and purging time, 5 min. The analytes were separated using an ODS Hypersil C₁₈ column (250×4.6 mm i.d, 5 μm) under gradient flow. The proposed method showed good linearities (r² >0.999), low detection limits (0.08–1.9 μg/L) and good recoveries (80.7–122%). The validated method was successfully applied for the determination of the furanic compounds in concentrated juice (mango, date, orange, pomegranate, roselle, mangosteen and soursop) and dried fruit (prune, date and apricot paste) samples.     

Simultaneous determination of caffeine,paracetamol, and ibuprofen in pharmaceutical formulations by high‐performance liquid chromatography with UV detection and by capillary electrophoresis with conductivity detection

Paracetamol, caffeine and ibuprofen are found in over‐the‐counter pharmaceutical formulations. In this work, we propose two new methods for simultaneous determination of paracetamol, caffeine and ibuprofen in pharmaceutical formulations. One method is based on high‐performance liquid chromatography with diode‐array detection and the other on capillary electrophoresis with capacitively coupled contactless conductivity detection. The separation by high‐performance liquid chromatography with diode‐array detection was achieved on a C₁₈ column (250×4.6 mm², 5 μm) with a gradient mobile phase comprising 20–100% acetonitrile in 40 mmol L^?1 phosphate buffer pH 7.0. The separation by capillary electrophoresis with capacitively coupled contactless conductivity detection was achieved on a fused‐silica capillary (40 cm length, 50 μm i.d.) using 10 mmol L^?1 3,4‐dimethoxycinnamate and 10 mmol L^?1 β‐alanine with pH adjustment to 10.4 with lithium hydroxide as background electrolyte. The determination of all three pharmaceuticals was carried out in 9.6 min by liquid chromatography and in 2.2 min by capillary electrophoresis. Detection limits for caffeine, paracetamol and ibuprofen were 4.4, 0.7, and 3.4 μmol L^?1 by liquid chromatography and 39, 32, and 49 μmol L^?1 by capillary electrophoresis, respectively. Recovery values for spiked samples were between 92–107% for both proposed methods.     

Ultrapreconcentration and determination of organophosphorus pesticides in water by solid‐phase extraction combined with dispersive liquid–liquid microextraction and high‐performance liquid chromatography

Solid‐phase extraction coupled with dispersive liquid–liquid microextraction was developed as an ultra‐preconcentration method for the determination of four organophosphorus pesticides (isocarbophos, parathion‐methyl, triazophos and fenitrothion) in water samples. The analytes considered in this study were rapidly extracted and concentrated from large volumes of aqueous solutions (100 mL) by solid‐phase extraction coupled with dispersive liquid–liquid microextraction and then analyzed using high performance liquid chromatography. Experimental variables including type and volume of elution solvent, volume and flow rate of sample solution, salt concentration, type and volume of extraction solvent and sample solution pH were investigated for the solid‐phase extraction coupled with dispersive liquid–liquid microextraction with these analytes, and the best results were obtained using methanol as eluent and ethylene chloride as extraction solvent. Under the optimal conditions, an exhaustive extraction for four analytes (recoveries >86.9%) and high enrichment factors were attained. The limits of detection were between 0.021 and 0.15 μg/L. The relative standard deviations for 0.5 μg/L of the pesticides in water were in the range of 1.9–6.8% (n = 5). The proposed strategy offered the advantages of simple operation, high enrichment factor and sensitivity and was successfully applied to the determination of four organophosphorus pesticides in water samples.     

Rapid determination of nitrite in foods in acidic conditions by high‐performance liquid chromatography with fluorescence detection

In this study, a simple, rapid, and sensitive method for the determination of nitrite (NO₂^?) in food samples by high‐performance liquid chromatography with fluorescence detection in acidic conditions had been developed. The derivatization of the nitrite with 2,3‐diaminonaphthalene was performed in acidic conditions to yield the highly fluorescent 2,3‐naphthotriazole, which was directly analyzed by high‐performance liquid chromatography with fluorescence detection without adjusting the solution to alkaline. The analysis column was reversed‐phase C₈ column. A constant flow rate of 1.0 mL/min was employed using water/acetonitrile as the mobile phase in isocratic mode (70:30, v/v). Fluorescence was monitored with excitation at 375 nm and emission at 415 nm. The standard calibration curves were linear for nitrite in different matrixes in the concentration range of 0–100 μg/L, and the correlation coefficients ranged from 0.9978 to 0.9998. The limits of detection and quantification were in the ranges of 0.012–0.060 and 0.040–0.20 mg/kg, respectively. The recoveries of nitrite from samples spiked at three different concentrations were 74.0–113.2%, and the relative standard deviations of the recovery results (n = 6) were 1.67–10.8%. The proposed method has good repeatability and is very sensitive and simple. It has been successfully used to determine nitrite in foods.     

Validated liquid chromatographic method for quantitative determination of allicin in garlic powder and tablets

In the present study, an RP high performance liquid chromatographic method was developed and validated for the determination of allicin in garlic powder and tablets. Chromatographic separation was carried out on an RP-18(e )column (125 mm x 4 mm), using a mobile phase, consisting of methanol-water (50:50 v/v), at a flow rate of 0.5 mL/min and UV detection at 220 nm. Ethylparaben was used as the internal standard. The assay was linear for allicin concentrations of 5.0-60.0 microg/mL. The RSD for precision was <6.14%. The accuracy was above 89.11%. The detection and quantification limits were 0.27 and 0.81 microg/mL, respectively. This method was used to quantify allicin in garlic powder samples. The results showed that the method described here is useful for the determination of allicin in garlic powder and tablets.     

Matrix solid‐phase dispersion coupled with homogeneous ionic liquid microextraction for the determination of sulfonamides in animal tissues using high‐performance liquid chromatography

Matrix solid‐phase dispersion coupled with homogeneous ionic liquid microextraction was developed and applied to the extraction of some sulfonamides, including sulfamerazine, sulfamethazine, sulfathiazole, sulfachloropyridazine, sulfadoxine, sulfisoxazole, and sulfaphenazole, in animal tissues. High‐performance liquid chromatography was applied to the separation and determination of the target analytes. The solid sample was directly treated by matrix solid‐phase dispersion and the eluate obtained was treated by homogeneous ionic liquid microextraction. The ionic liquid was used as the extraction solvent in this method, which may result in the improvement of the recoveries of the target analytes. To avoid using organic solvent and reduce environmental pollution, water was used as the elution solvent of matrix solid‐phase dispersion. The effects of the experimental parameters on recoveries, including the type and volume of ionic liquid, type of dispersant, ratio of sample to dispersant, pH value of elution solvent, volume of elution solvent, amount of salt in eluate, amount of ion‐pairing agent (NH₄PF₆), and centrifuging time, were evaluated. When the present method was applied to the analysis of animal tissues, the recoveries of the analytes ranged from 85.4 to 118.0%, and the relative standard deviations were lower than 9.30%. The detection limits for the analytes were 4.3–13.4 μg/kg.     

Alternative solvent‐based methyl benzoate vortex‐assisted dispersive liquid–liquid microextraction for the high‐performance liquid chromatographic determination of benzimidazole fungicides in environmental water samples

Vortex‐assisted dispersive liquid–liquid microextraction using methyl benzoate as an alternative extraction solvent for extracting and preconcentrating three benzimidazole fungicides (i.e., carbendazim, thiabendazole, and fluberidazole) in environmental water samples before high‐performance liquid chromatographic analysis has been developed. The selected microextraction conditions were 250 μL of methyl benzoate containing 300 μL of ethanol, 1.0% w/v sodium acetate, and vortex agitation speed of 2100 rpm for 30 s. Under optimum conditions, preconcentration factors were 14.5–39.0 for the target fungicides. Limits of detection were obtained in the range of 0.01–0.05 μg/L. The proposed method was then applied to surface water samples and the recovery evaluations at three spiked concentration levels of 5, 30, and 50 μg/L were obtained in the range of 77.4–110.9% with the relative standard deviation <7.4%. The present method was simple, rapid, low cost, sensitive, environmentally friendly, and suitable for the trace analysis of the studied fungicides in environmental water samples.     

Ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction for the separation and determination of estrogens in water samples by high‐performance liquid chromatography with fluorescence detection

An ionic liquid foam floatation coupled with ionic liquid dispersive liquid–liquid microextraction method was proposed for the extraction and concentration of 17‐α‐estradiol, 17‐β‐estradiol‐benzoate, and quinestrol in environmental water samples by high‐performance liquid chromatography with fluorescence detection. 1‐Hexyl‐3‐methylimidazolium tetrafluoroborate was applied as foaming agent in the foam flotation process and dispersive solvent in microextraction. The introduction of the ion‐pairing and salting‐out agent NH₄PF₆ was beneficial to the improvement of recoveries for the hydrophobic ionic liquid phase and analytes. Parameters of the proposed method including concentration of 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, flow rate of carrier gas, floatation time, types and concentration of ionic liquids, salt concentration in samples, extraction time, and centrifugation time were evaluated. The recoveries were between 98 and 105% with relative standard deviations lower than 7% for lake water and well water samples. The isolation of the target compounds from the water was found to be efficient, and the enrichment factors ranged from 4445 to 4632. This developing method is free of volatile organic solvents compared with regular extraction. Based on the unique properties of ionic liquids, the application of foam floatation, and dispersive liquid–liquid microextraction was widened.     

Ultrasound‐assisted emulsification microextraction coupled with high‐performance liquid chromatography for the simultaneous determination of fragrance allergens in cosmetics and water

A simple, inexpensive, and environmentally friendly method based on ultrasound‐assisted emulsification microextraction followed by solidification of floating organic drop and high‐performance liquid chromatography coupled to diode array detection was developed for the simultaneous determination of 18 potentially allergenic fragrance substances. Several parameters affecting the microextraction process were investigated in detail by the “one‐variable‐at‐a‐time” approach. Optimal conditions were the following: 50 μL of 2‐dodecanol as extraction solvent, 10 mL of sample containing 150 g/L of salt, and 5 min of sonication at 35°C. Under the optimized conditions, method showed good linearity in the selected ranges, with squared correlation coefficients ranging from 0.948 to 0.999. Limits of detection ranged from 0.001 to 0.154 μg/mL and enrichment factors from 9 to 237. Precision of the method, expressed as relative standard deviation, was checked at two levels obtaining good results (3.3–14.4%). Recovery studies were made in baby bath water and in eau de cologne showing acceptable accuracy. Finally, the developed method was successfully applied to different commercial cosmetic and water samples. The most commonly found analyte was linalool followed by cinnamal and lilial. Most of the analyzed samples contained at least one of the target compounds.     

Pipette vial dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the determination of benzoylurea insecticide in fruit juice

A simple, sensitive, and efficient method of using a pipette vial to perform dispersive liquid–liquid microextraction based on the solidification of floating organic droplets was coupled with high‐performance liquid chromatography (HPLC) and a diode array detector for the preconcentration and analysis of four benzoylurea insecticides in fruit juice. In this method, 1‐dodecanol was used as an extractant, and a snipped pipette was used as an experimental vial to simplify the procedure of collecting and separating solidified extractant. The experimental parameters were optimized using a Plackett–Burman design and one‐factor‐at‐a‐time method. Under the optimal conditions in the water model, the limits of detection for analytes varied from 0.03 to 0.28 μg/L, and the enrichment factors ranged from 147 to 206. Linearity was achieved for diflubenzuron and flufenoxuron in a range of 0.5–500 μg/L, for hexaflumuron in a range of 1–500 μg/L, and for triflumuron in a range of 5–500 μg/L. The correlation coefficients for the analytes ranged from 0.9986 to 0.9994 with recoveries of 91.4–110.9%. Finally, the developed technique was successfully applied to fruit juice samples with acceptable results. The relative standard deviations of the analytes at two spiking levels (50 and 200 μg/L) varied between 0.2 and 4.5%.     

Optimized determination of polybrominated diphenyl ethers by ultrasound‐assisted liquid–liquid extraction and high‐performance liquid chromatography

A method based on ultrasound‐assisted liquid–liquid extraction and high‐performance liquid chromatography has been optimized for the determination of six polybrominated diphenyl ether congeners. The optimal condition relevant to the extraction was first investigated, more than 98.7 ± 0.7% recovery was achieved with dichloromethane as extractant, 5 min extraction time, and three cycles of ultrasound‐assisted liquid–liquid extraction. Then multiple function was employed to optimize polybrominated diphenyl ether detection conditions with overall resolution and chromatography signal area as the responses. The condition chosen in this experiment was methanol/water 93:7 v/v, flow rate 0.80 mL/min, column temperature 30.0°C. The optimized technique revealed good linearity (R² > 0.9962 over a concentration range of 1–100 μg/L) and repeatability (relative standard deviation < 6.3%). Furthermore, the detection limit (S/N = 3) of the method were ranged from 0.02 to 0.13 μg/L and the quantification limit (S/N = 10) ranged from 0.07 to 0.35 μg/L. Finally, the proposed method was applied to spiked samples and satisfactory results were achieved. These results indicate that ultrasound‐assisted liquid–liquid extraction coupled with high‐performance liquid chromatography was effective to identify and quantify the complex polybrominated diphenyl ethers in effluent samples.     

Ionic‐liquid‐based dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the determination of multiclass pesticide residues in water samples

Ionic‐liquid‐based dispersive liquid–liquid microextraction in combination with high‐performance liquid chromatography and diode array detection has been proposed for the simultaneous analysis of four multiclass pesticide residues including carbaryl, methidathion, chlorothalonil, and ametryn from water samples. The major experimental parameters including the type and volume of ionic liquid, sample pH, type, and volume of disperser solvent and cooling time were investigated and optimum conditions were established. Under the optimum experimental conditions, limits of detection and quantification of the method were in the range of 0.1–1.8 and 0.4–5.9 μg/L, respectively, with satisfactory enrichment factors ranging from 10–20. The matrix‐matched calibration curves, which were constructed for lake water, as a representative matrix were linear over wide range with coefficients of determination of 0.996 or better. Intra‐ and interday precisions, expressed as relative standard deviations, were in the range of 1.1–9.7 and 3.1–7.8%, respectively. The relative recoveries of the spiked environmental water samples at one concentration level were in the range of 77–102%. The results of the present study revealed that the proposed method is simple, fast, and uses environmentally friendly extraction solvent for the analysis of the target pesticide residues in environmental water samples.     

Automated online pretreatment and cleanup recycle coupled with high‐performance liquid chromatography‐mass spectrometry for determination of deca‐bromodiphenyl ether in human serum

Automated online SPE‐HPLC‐MS was established for the determination of deca‐bromodiphenyl ether in human serum. The online SPE with large volume injection was utilized to enhance the sensitivity. Online SPE with dilution line greatly decreased matrices effect, which enabled serum samples to be injected directly into pre‐column. Washing line was designed for the system to solve the serious residual phenomenon and reduce the risk of sample wastage and contamination. Under the optimized conditions, the linear of the method was in the range 0.1–10 ng/mL with the LOD of 0.026 ng/mL. The recoveries of serum samples spiked with deca‐bromodiphenyl ether at 0.5 ng/mL was in the range from 83.30 to 102.7% with RSD in interday less than 8.67%. The satisfactory results demonstrated that the method of online sample pretreatment and cleanup recycle were reliable for human serum analysis.     

Determination of moutan tannins by high‐performance liquid chromatography and capillary electrophoresis

Cortex Moutan (Radicis Cortex Moutan), the dried root bark of Paeonia moutan and P. spp., contains a series of water‐soluble tannins. With the eight components, 1 4,6‐di‐O‐GG (4,6‐di‐O‐galloyl‐D‐glucose), 2 1,2,3,6‐tetra‐O‐GG, 3 1,2,3,4,6‐penta‐O‐GG, 4 1,3,4,6‐tetra‐O‐GG, 5 3,4,6‐tri‐O‐GG, 6 1,3,6‐tri‐O‐GG, 7 3,6‐di‐O‐GG, and 8 1,2,6‐tri‐O‐GG, as marker substances, a rapid and efficient method of analysis based on HPLC and CE was developed. Using a phosphate eluent, a 5C18‐MS separating column, and a detection wavelength of 280 nm, HPLC was successfully used to analyze the eight constituents within 60 min. The analysis can be completed within 50 min, using the MEKC mode with a buffer composed of borate, SDS, and isopropanol, and a detection wavelength of 210 nm. The detection limit for the marker substances varied from 0.04 to 0.93 μg/mL for the HPLC method and 0.02 to 0.36 μg/mL for the CE method.     

Extraction and preconcentration of formaldehyde in water by polypyrrole‐coated magnetic nanoparticles and determination by high‐performance liquid chromatography

In this study, a simple and rapid extraction method based on the application of polypyrrole‐coated Fe₃O₄ nanoparticles as a magnetic solid‐phase extraction sorbent was successfully developed for the extraction and preconcentration of trace amounts of formaldehyde after derivatization with 2,4‐dinitrophenylhydrazine. The analyses were performed by high‐performance liquid chromatography followed by UV detection. Several variables affecting the extraction efficiency of the formaldehyde, i.e., sample pH, amount of sorbent, salt concentration, extraction time and desorption conditions were investigated and optimized. The best working conditions were as follows: sample pH, 5; amount of sorbent, 40 mg; NaCl concentration, 20% w/v; sample volume, 20 mL; extraction time, 12 min; and 100 μL of methanol for desorption of the formaldehyde within 3 min. Under the optimal conditions, the performance of the proposed method was studied in terms of linear dynamic range (10–500 μg/L), correlation coefficient (R² ≥ 0.998), precision (RSD% ≤ 5.5) and limit of detection (4 μg/L). Finally, the developed method was successfully applied for extraction and determination of formaldehyde in tap, rain and tomato water samples, and satisfactory results were obtained.     

Ultrasound‐assisted supramolecular‐solvent‐based microextraction combined with high‐performance liquid chromatography for the analysis of chlorophenols in environmental water samples

An efficient, inexpensive and environmentally benign ultrasound‐assisted supramolecular‐solvent‐based microextraction technique combined with high‐performance liquid chromatography was used for the determination of chlorophenols in environmental water samples. Different factors such as amount of decanoic acid, volume of tetrahydrofuran, pH of the sample, ultrasound time and ionic strength were investigated and optimized. The optimized extraction conditions were 60 mg decanoic acid, 1.5 mL tetrahydrofuran, 3 min ultrasound time, without salt addition. Under this condition, the extraction recoveries were 83.0–89.3 with preconcentration factors of 94–102. The calibration curves were linear from 5.0–400.0 ng/mL with square of the correlation coefficient higher than 0.9998 and the limits of detection were between 1.5–2.0 ng/mL. The values of intra‐ and inter‐day relative standard deviations were 3.2–6.0 and 7.3–8.0%, respectively. Analysis of different samples showed that the concentration of 2,5‐dichlorophenol in Babolrood river water was 80.6 ng/mL.     

Dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography for the enrichment and sensitive determination of Sudan Red pollutants in water samples

Sudan Red pollutants have gained more attention in recent years. The present study described a simple and sensitive determination method for Sudan Red pollutants with dispersive liquid–liquid microextraction coupled to high‐performance liquid chromatography. Chlorobenzene and ethanol were used as the extraction solvent and disperser solvent, respectively. The possible parameters such as the kind of solvents, ionic strength, and sample pH that could affect the enrichment have been optimized. Under the optimal conditions, the pollutants have been well enriched and the linear ranges of Sudan Red I and II were in the range of 0.3–40 μg/L, and the linear ranges of Sudan Red III and IV were in the range of 1.2–160 μg/L. The detection limits were in the range of 0.18–0.46 μg/L, and the precisions were in the range of 3.7–5.9%. All these demonstrated that the proposed method could be a good alternative for the routine analysis of Sudan Red pollutants in water samples.     

Online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry for the determination of five tannins in traditional Chinese medicine injections

A rapid analytical method based on online solid‐phase extraction with high‐performance liquid chromatography and mass spectrometry has been established and applied to the determination of tannin compounds that may cause adverse effects in traditional Chinese medicine injections. Different solid‐phase extraction sorbents have been compared and the elution buffer was optimized. The performance of the method was verified by evaluation of recovery (≥40%), repeatability (RSD ≤ 6%), linearity (r² ≥ 0.993), and limit of quantification (≤0.35 μg/mL). Five tannin compounds, gallic acid, cianidanol, gallocatechin gallate, ellagic acid, and penta‐O‐galloylglucose, were identified with concentrations ranging from 3.1–37.4 μg/mL in the analyzed traditional Chinese medicine injections.     

Glass slides functionalized by 1‐carboxyethyl‐3‐methylimidazolium chloride for the determination of triazine herbicides in rice using high‐performance liquid chromatography

A novel and simple supported ionic‐liquid‐based solid‐phase extraction method for the determination of triazine herbicides in rice was developed. Glass slides were functionalized by an ionic liquid, 1‐carboxyethyl‐3‐methylimidazolium chloride, and were used for the simultaneous extraction of seven triazine herbicides in rice samples. The effects of the type of extraction solvent, the extraction time, the type and volume of loading solvent, and the type of eluting solvent on the extraction efficiency were investigated and optimized. Under the optimum operation conditions, the limits of detection for seven triazine herbicides in rice samples obtained by high‐performance liquid chromatography were 3.16–5.42 ng/g, which were lower than the maximum residue levels established by various organizations. The linear correlation coefficients were higher than 0.9975 in the concentration range of 0.015–1.08 μg/g for the seven triazine herbicides. The recoveries of the seven triazine herbicides at the two concentration levels of 0.15 and 0.45 μg/g are between 82.47 and 104.21%, with relative standard deviations of 0.69–9.19%. The intra‐ and inter‐day (n = 5) precisions for all triazine herbicides at the spiked level of 0.30 μg/g were 1.72–11.71%.     

Simultaneous determination of cyadox and its metabolites in plasma by high‐performance liquid chromatography tandem mass spectrometry

Cyadox is a novel antimicrobial growth‐promoter of the quinoxalines. For food safety and pharmacokinetic studies, a convenient, sensitive and reproducible LC‐ESI‐MS/MS method was developed for the simultaneous determination of cyadox and its major metabolites, quinoxaline‐2‐carboxylic acid, 1,4‐bisdesoxycyadox, cyadox‐1‐monoxide and cyadox‐4‐monoxide in chicken plasma. Plasma sample was subjected to a simple deproteinisation with acetonitrile. Analysis was performed on a C₁₈ column by detection with mass spectrometry in multiple reaction monitoring mode. A gradient elution program with 0.2% formic acid, methanol and acetonitrile was performed at a flow rate of 0.2 mL/min. The decision limits (CCαs) of five analytes in plasma ranged from 1.0 to 4.0 μg/L, and the detection capabilities (CCβs) were <10 μg/L. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The extraction recoveries of five analytes were between 87.4 and 93.9% in plasma at the spiked levels of 5 (10)–200 μg/L with the relative standard deviations <10% for each analyte. The developed method demonstrated a satisfactory applicability in real plasma samples.