Dispersive Liquid-liquid Microextraction Process Research Articles

A Cyanoalkyl Silicone GC Stationary-Phase Polymer as an Extractant for Dispersive Liquid–Liquid Microextraction

In this work, three cyanoalkyl silicone GC stationary-phase polymers, namely OV-105, OV-225, and OV-275, were investigated as potential extractants for dispersive liquid–liquid microextraction (DLLME). The OV-225 polymer (cyanopropylmethyl-phenylmethylsilicone) exhibited the cleanest chromatographic background and was extensively studied. The proposed polymer was tested through the DLLME of four non-steroidal anti-inflammatory drugs from aqueous samples, followed by HPLC separation with UV detection at 230 nm. To achieve the maximum enrichment, the experimental conditions that influence the DLLME process were optimized using one-factor-at-a-time and design-of-experiment (DoE) approaches. The extraction variables (polymer mass, dispersive solvent volume, buffer pH, and mixing time) were screened by implementing a two-level full factorial design (FFD). Significant variables were fine-tuned using response surface methodology based on a face-centered central composite design (CCD). The optimum conditions were 10 mg of polymer (extraction medium); 50 µL of tetrahydrofuran (dispersive solvent); 100 µL of phosphate buffer pH 2.75 ([PO43−] = 100 mM); and 3 min of vortex mixing. The addition of salt had a minimal effect on the enrichment factors. In the optimum conditions, enrichment factors up to 46 were achieved using 1.5 mL samples. Calibration curves exhibited correlation coefficients > 0.999 using 4-pentylbenzoic acid as an internal standard. The limits of quantitation were 5 ng/mL for naproxen, 10 ng/mL for diflunisal, 25 ng/mL for indomethacin, and 75 ng/mL for ibuprofen. The analysis of spiked tap water samples showed adequate relative recoveries and precision. In conclusion, the proposed polymer (OV-225) is a potential greener alternative to traditional organic extractants used in DLLME.

A new method based on dispersive liquid-liquid microextraction for fat-soluble vitamin determination in serum by LC-MS/MS.

A green and inexpensive pretreatment known as dispersive liquid-liquid microextraction (DLLME) was developed in this assay coupled with the LC-MS/MS method for routine analysis of fat soluble vitamins (FSVs). The technique was performed with methanol as the dispersive solvent and dichloromethane as the extraction solvent. The extraction phase containing FSVs was evaporated to dryness and reconstituted in a mixture of acetonitrile and water. The influence variables concerning the DLLME procedure were optimized. After that, the method was investigated for its applicability in LC-MS/MS analysis. As a result, the parameters were settled for the optimal conditions during the DLLME process. A cheap and lipid-free substance was found as an alternative to serum to eliminate the matrix effect while preparing the calibrators. The method validation indicated that it was suitable for determining FSVs in serum. Moreover, this method was applied successfully to determine serum samples, which was consistent with the literature. In summary, the DLLME method developed in this report was reliable and more cost-effective than the traditional LC-MS/MS method, and could be applied in the future.

The Measurement of Hazardous Biogenic Amines in Non-Alcoholic Beers: Efficient and Applicable Miniaturized Electro-Membrane Extraction Joined to Gas Chromatography-Mass Spectrometry.

The determination of biogenic amines (BAs) as serious food contaminants and chemical indicators of unwanted microbial contamination or deficient processing conditions in non-alcoholic beers is of great interest for the beverage industries. In the present investigation, the combination of hollow fiber-electro-membrane extraction (HF-EME) and dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography-mass spectrometry (GC/MS) was applied for the analysis of histamine, putrescine, tyramine, cadaverine in non-alcoholic beers. EME is fundamentally based on the electrostatic attraction, diffusion and solvability of analytes in a selected acceptor phase. This membrane-based extraction technique promoted selectivity and the enrichment factor. The DLLME process reduced the volumes of organic solvents and make the coupling of HF-EME to the CG/MS conceivable. The leading variables, which have a great effect on extraction recovery, were optimized. The relative standard deviation was achieved between 4.9 and 7.0%. The recoveries were between 94% and 98%. The limit of detection and limit of quantification were found to be 0.92-0.98 ng mL-1 and 3.03-3.23 ng mL-1, respectively. The enrichment factor was calculated in the range 36-41. The achievements revealed that putrescine and tyramine, with concentrations of 3.87 and 2.33 µg g-1, were at the highest concentration in non-alcoholic beers. This offered method with great benefits could help beverage industries to monitor the concentration of BAs in beers and control them.

Three-dimensional (3D) thermal controlled polymer for simplified dispersive liquid-liquid microextraction in phthalic acid easters detection of straw

In this paper, a three-dimensional (3D) polyfunctional group and thermal controlled polymer p(POSS-co-DMAEMA) was prepared based on the chemical structure of the phthalic acid easters (PAEs) and applied as an extractant for dispersive liquid–liquid microextraction (DLLME) in combination with HPLC-UV. The polymer with good biocompatibility can be dispersed and aggregated by shaking and heating based on the thermal controlled properties without the assistance of instruments, which shortened the DLLME process as low as 5 min. The feasibility of the developed method was verified using 5 PAEs as targets in simulated water samples, which showed good precision (RSD%, 1.3–10.0, n = 3) and low detection limit (0.19–0.52 ng mL−1) under the optimal extraction conditions. This proposed method was successfully applied in analyzing four straws and good spiked recoveries over the range of 91.60–128.00% were obtained. Furthermore, molecular docking was employed to explore the molecular interactions and calculate binding energies between the polymer and organic pollutants, ensuring the synthesized polymer has a strong extraction ability for PAEs. The satisfied extraction efficiency can be attributed to the fact that the p(POSS-co-DMAEMA) is water-soluble at room temperature but hydrophobic at high temperature, and the high extraction ability can be achieved by the strong intermolecular forces between the polymer and PAEs. The experimental results suggest that the proposed method holds good promise for the trace analysis of PAEs.

In-a-syringe surfactant-assisted dispersive liquid-liquid microextraction of polycyclic aromatic hydrocarbons in supramolecular solvent from tea infusion

In this work, an automated surfactant-assisted dispersive liquid-liquid microextraction approach based on in-a-syringe concept was developed for the first time. The procedure assumed mixing aqueous sample phase and hydrophilic emulsion containing hexanoic acid and sodium hexanoate in a syringe of flow system. Sodium hexanoate acted as an emulsifier in dispersive liquid-liquid microextraction process and it was required for the formation of supramolecular solvent phase. After spontaneous separation of phases in the syringe, the upper supramolecular solvent phase containing target analytes was withdrawn and analyzed. The procedure was applied to the determination of 13 polycyclic aromatic hydrocarbons in tea infusion by high performance liquid chromatography with fluorescence detection. It was shown that the supramolecular solvent provided effective extraction of polycyclic aromatic hydrocarbons and fast phase separation in the syringe without centrifugation. The enrichment factors were in the range of 38–46. The automated microextraction procedure lasted 4 min including syringe cleaning. Under optimal experimental conditions the linear detection ranges were found to be 0.05–50.00 μg L−1 with limits of detection calculated from a blank test, based on 3σ, 0.02–0.04 μg L−1. Recovery values in the range of 85–105% were achieved for tea infusion with a reproducibility expressed as RSD less than 4.1%.

Colorimetric Probe Coupled to Dispersive Liquid–Liquid Microextraction for Determination of Dopamine in Serum

In this work, a highly sensitive method using a colorimetric probe coupled to dispersive liquid–liquid microextraction (DLLME) was developed for the quantitative determination of dopamine (DA) in serum. The DA in serum was concentrated by DLLME to increase the detection sensitivity and reduce the matrix effects. After the DLLME process, a colorimetric probe of silver triangular nanoparticles (AgTNPs) was used to detect DA, which was based on the plasma transformation of AgTNPs caused by strong interactions with melamine (MA). The results showed that DA could inhibit the aggregation of AgTNPs induced by MA, resulting in the recovery of the surface plasmon resonance (SPR) peak of AgTNPs. Thus, the DLLME method followed by colorimetric probe detection of DA can be achieved. The parameters affecting the proposed method were optimized, under the optimal conditions, a linear calibration curve was obtained over a concentration range of 5 to 250 nM with a recovery from 94.4 to 101.3%. The detection limit was 1.6 nM (at an S/N ratio of 3). The present method was successfully applied to determine DA in human serum.

A Novel Ionic Liquid of [BeMIM] [Tf2N] for Extracting Pesticides Residues in Tea Sample by Dispersive Liquid–Liquid Microextraction

In this work, a novel 1-benzyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BeMIM][Tf2N]) ionic liquid (IL) was used for extracting three organophosphorus pesticides (OPPs) (ethoprophos, fenitrothion, and phoxim) from tea samples by dispersive liquid–liquid microextraction (DLLME). The OPPs were detected by high-performance liquid chromatography (HPLC) with UV detector. Four [Tf2N]-based ILs were compared during the extraction process, and [BeMIM][Tf2N] showed the best performance. Acetonitrile was used as an extracting solvent in the extracting process and as a dispersant solvent in the DLLME process. Several parameters affecting the performance of the method including the selection of extraction solvent type, dispersant type, pH, extraction time, extraction temperature, salt addition, and centrifugation time were optimized. Under the optimal conditions, the enrichment factors of the analytes were in the range of 242.8–266.0, and the limit of detection was 0.1 μg/kg. The optimized method was also used for testing tea samples from different brands. The recoveries of the analytes were between 78.8 and 102.2%, with the RSDs were in the range of 0.9–4.5. The developed method is low-cost, time-saving, and reagent-saving; it is a promising and efficient sample technique for solid-sample preparation.

Application of response surface modeling and chemometrics methods for the determination of Atenolol, Metoprolol and Propranolol in blood sample using dispersive liquid–liquid microextraction combined with HPLC-DAD

A novel dispersive liquid–liquid microextraction (DLLME) method using ionic liquids (ILs) followed by high-performance liquid chromatography-diode array detector (HPLC-DAD) has been devised to specify Atenolol, Atenolol, Metoprolol and Propranolol in blood real samples. Fourteen effective parameters in DLLME process, including pH of aqueous sample, volume of the dispersion and extraction solvents and ionic strength of donor phase, etc.; were screened using fractional factorial screening methodology (FFSM) based on Placket-Burman design (PBD) and subsequently were optimized by response surface methodology using central composite design (CCD). A mixture of IL (1-butyl-3-methyl imidazolium hexa fluoro phosphate) and disperser solvent (methanol) was quickly injected into the sample solution leading to the formation of the semi cloudy solution. Afterwards, HPLC-DAD was applied to examine the sedimented IL drop. The detection limits (LOD) for all analytes ranges were 0.00268–0.00300 µg L−1. The relative standard deviations (RSDs) for seven experiments were between 3.832% and 4.432% for three target analytes. The proposed method illustrated wide dynamic linear range (DLR, 0.009–1 µg L−1), desirable linearity (R2 ≈ 0.997), high enrichment factors (EF, 313–330) and good relative recoveries (RR, 96–104%). Clear separation and desirable chromatogram was quickly reached without the intervention of the matrix. Besides, a comparison of this method with previous methods indicated that the suggested method is a reproducible, quick and dependable sample pretreatment technique for extraction and determination of pharmaceuticals in blood sample.

Synthesis and characterization of deep eutectic solvents (five hydrophilic and three hydrophobic), and hydrophobic application for microextraction of environmental water samples.

Hydrophilic and hydrophobic deep eutectic solvents (DESs) as "green" solvents were applied in this study for the microextraction of environmental samples. A series of DESs (five hydrophilic and three hydrophobic) were synthesized and characterized by Fourier transform infrared spectroscopy. Physicochemical property parameters of eight DESs including water solubility, density, conductivity, and freezing point were assessed. Compared with the performance of five hydrophilic DESs in water phase, the three hydrophobic DESs were more suitable for application in dispersive liquid-liquid microextraction for the determination of sulfonamides in water sample. In dispersive liquid-liquid microextraction process, analytical parameters including type and volume of extraction solvent, extraction time, and pH of water sample were investigated. Under optimum conditions, 60μL of hydrophobic DESs was used for extraction for 2min in pH = 7.0 sample. The linear ranges were 0.05-5.0μg/mL for the four sulfonamides with the correlation coefficients in the range of 0.9991-0.9999. The limits of detection were in the range of 0.0005-0.0009μg/mL and the limits of quantification were in the range of 0.0019-0.0033μg/mL. The recoveries of the analytes of the proposed method for the spiked samples were 80.17-93.5%, with the relative standard deviation less than 6.31%. The results indicated that three hydrophobic DESs showed commendable performance for extraction of sulfonamides, and hydrophobic DES-based microextraction method was successfully applied for monitoring sulfonamides in water samples. Graphical abstract.

Determination of Pyrethroids and Phthalate Esters in Radix et Rhizoma Glycyrrhizae by Successive Ultrasonic-assisted Extraction and Dispersive Liquid-Liquid Microextraction Followed by Gas Chromatography-Mass Spectrometry

A rapid, inexpensive and efficient sample preparation method for simultaneous extraction and determination of three pyrethroids and seven phthalate esters in Radix et Rhizoma Glycyrrhizae samples was developed. The target analytes were extracted using a two-step extraction method including ultrasonic-assisted extraction and dispersive liquid-liquid microextraction coupled with gas chromatography-mass spectrometry (GC-MS). In ultrasonic-assisted extraction process, acetone was used as extraction solvent and extraction time was set as 3 min. In dispersive liquid-liquid microextraction process, optimized experimental conditions including 100 μL of CCl4 as extraction solvent and 1.0 mL of acetone as dispersant with 3% (m/V) of NaCl were adopted. The eluents were further quantitatively determined by GC-MS. All ten kinds of analytes were well separated, and the calibration curves showed good linearity, with correlation coefficients greater than 0.9992. Low detection limits of 0.0035 μg kg-1 for DMP to 1.0 μg kg-1 for IMIP were achieved. The method demonstrated good recoveries between the acceptable range of 79.7% for IMIP to 105.7% for TETR at three spiked levels with RSD < 8.2% for most of evaluated analytes. The method was employed for detection of Radix et Rhizoma Glycyrrhizae samples with satisfactory results.

Butan-1-ol as an extractant solvent in dispersive liquid-liquid microextraction in the spectrophotometric determination of aluminium

Determining aluminium ions at μg L−1 scale currently requires either costly analytical techniques such as inductively coupled plasma, and/or graphite furnace atomic absorption spectrometry. Dispersive liquid-liquid microextraction (DLLME) is designed to promote separation and preconcentration, thus making it possible to determine the analyte of interest without significant matrix influence. This study was aimed at the development of a spectrophotometric method to determine Al3+ after microextraction of its complex with quercetin. Butan-1-ol was used as a novel extractant solvent in the DLLME process. The parameters influencing complexation and microextraction, such as the amount of quercetin and volume of extractant were evaluated by univariate analysis. In optimised conditions were estimated for the proposed method: linear range from 7.5 to 165.0 μg L−1, LOD of 2.0 μg L−1, and LOQ of 7.0 μg L−1. The accuracy was checked by applying the proposed method to water (NIST SRM-1643e) and rice flour (NIST SRM-1568c) certified reference materials and spike-and-recovery trials with distinct samples (mineral water, green tea, thermal spring water, contact lens disinfecting solution, saline concentrate for hemodialysis and urine).

A dispersive liquid-liquid microextraction based on solidification of floating organic droplet followed by injector port silylation coupled with gas chromatography–tandem mass spectrometry for the determination of nine bisphenols in bottled carbonated beverages

In the present study, a method has been efficiently developed for the first time to determine nine bisphenol analogues [bisphenol A (BPA), bisphenol C (BPC), bisphenol AF (BPAF), bisphenol E (BPE), bisphenol F (BPF), bisphenol G (BPG), bisphenol M (BPM), bisphenol S (BPS), and bisphenol Z (BPZ)] together in bottled carbonated beverages (collected from the local market of Lucknow, India) using dispersive liquid-liquid microextraction process. This is based on solidification of floating organic droplet (DLLME-SFO) followed by injector port silylation coupled with gas chromatography–tandem mass spectrometry. The process investigated parameters of DLLME-SFO (including the type of extraction and disperser solvents with their volumes, effect of pH, ionic strength, and the sample volume), factors influencing to injection port derivatization like, collision energy, injector port temperature, derivatizing reagent with sample injection volume, and type of organic solvent. BPA, BPF, BPZ, and BPS were detected in each sample; whereas, other bisphenols were also detected in some carbonated beverage samples. After optimizing the required conditions, good linearity of analytes was achieved in the range of 0.097–100ngmL−1 with coefficients of determination (R2)≥0.995. Intra-day and inter day precision of the method was good, with relative standard deviation (% RSD)≤10.95%. The limits of detection (LOD) and limits of quantification (LOQ) values of all bisphenols were ranged from 0.021 to 0.104ngmL−1 and 0.070 to 0.343ngmL−1, respectively. The recovery of extraction was good (73.15–95.08%) in carbonated beverage samples and good enrichment factors (96.36–117.33) were found. Thus, the developed method of microextraction was highly precise, fast, and reproducible to determine the level of contaminants in bottled carbonated beverages.

Portable kit for high-throughput analysis of polycyclic aromatic hydrocarbons using surface enhanced Raman scattering after dispersive liquid-liquid microextraction

In this work, a portable kit was developed for convenient high-throughput trace analysis of polycyclic aromatic hydrocarbons (PAHs) using surface enhanced Raman scattering (SERS) after dispersive liquid-liquid microextraction (DLLME) process. This portable kit contains three sealed reagent tubes (labeled as T1, T2 and T3), a self-made well plate, and a portable Raman spectrometer. The reagent tube T1 contains a mixture of disperser solvent and extraction solvent, which involved a 2min sample pretreatment of DLLME process. The quick injection of solvents in tube T1 into the sample containing PAHs formed a cloudy solution immediately, which consists of fine droplets of extraction solvent dispersed entirely into aqueous phase. The enrichment factor was found to be 29.6. T2 and T3 contain methanol and 1-propanethiol-modified silver nanoparticles (PTH-Ag NPs), respectively. The liquid in the tube T3 was used to enhance the Raman signal of analytes on the self-made high-throughput micro reactor. A linear relationship between the concentration of pyrene and the relative Raman peak intensity was obtained (R2 = 0.993). The detection limit was 0.50μgL−1 for pyrene. RSD of the high-throughput analysis of 12 samples was calculated as 4.8%. The ability of DLLME-SERS technique in the extraction of PAH isomers from water samples were investigated. The performance of DLLME-SERS in the recovery of pyrene from lake, spring and drinking water was also studied.

Preconcentration and determination of ceftazidime in real samples using dispersive liquid-liquid microextraction and high-performance liquid chromatography with the aid of experimental design.

A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid-liquid microextraction followed by high-performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid-liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001-10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.

Determination of tramadol by dispersive liquid-liquid microextraction combined with GC-MS.

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) has been developed for preconcentration and determination of tramadol, ((±)-cis-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol-HCl), in aqueous and biological samples (urine, blood). DLLME is a simple, rapid and efficient method for determination of drugs in aqueous samples. Efficient factors on the DLLME process has defined and optimized for extraction of tramadol including type of extraction and disperser solvents and their volumes, pH of donor phase, time of extraction and ionic strength of donor phase. Based on the results of this study, under optimal conditions and by using 2-nitro phenol as internal standard, tramadol was determined by GC-MS, and the figures of merit of this work were evaluated. The enrichment factor, relative recovery and limit of detection were obtained 420, 99.2% and 0.08 µg L(-1), respectively. The linear range was between 0.26 and 220.00 µg L(-1) (R(2) = 0.9970). The relative standard deviation for 50.00 µg L(-1) of tramadol in aqueous samples by using 2-nitro phenol as IS was 3.6% (n = 7). Finally, the performance of DLLME was evaluated for analysis of tramadol in urine and blood.

Retrieval of the Extraction Solvent by Magnetic Particles for Dispersive Liquid–Liquid Microextraction of UV Filters

A simple dispersive liquid–liquid microextraction (DLLME) method, based on retrieval of the extraction solvent by magnetic particles and followed by HPLC–UV analysis, was proposed for the determination of UV filters in environmental water samples. The new method uses vortex agitation in the DLLME process to achieve rapid equilibrium. Another feature of the proposed method is that the retrieval of the extraction solvent is accomplished by functionalized magnetic particles rather than by special designed vessels or refrigeration and thawing process associated with DLLME when low-density extraction solvent was used. The parameters that may influence the extraction, including vortex time, volume of extraction solvent, weight of the magnetic particles, volume of desorption solvent, pH, and ionic concentration of the sample solution, were investigated in detail. Under the optimized conditions, the limits of detection for the target UV filters were in range of 0.7–12.3 ng mL−1. The results also demonstrated good linearity and precision, with the regression coefficients above 0.9989 and the RSDs below 4.4%, respectively.

Application of dispersive liquid–liquid microextraction for estrogens׳ quantification by enzyme-linked immunosorbent assay

Estrogens, such as 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), are the major responsible for endocrine-disrupting effects observed in aquatic environments due to their high estrogenic potency, even at concentrations ranging from pgL−1 to ngL−1. Thus, it is essential to develop analytical methodologies suitable for monitoring their presence in water samples. Dispersive liquid–liquid microextraction (DLLME) was used as a pre-concentration step prior to the quantification of E2 and EE2 by enzyme-linked immunosorbent assay (ELISA). First, an evaluation of the effect of DDLME on the E2 and EE2 ELISA calibration curves was performed. Since the extraction procedure itself had an influence on the ELISA optical density (OD), it became necessary to subject, not only the samples, but also all the standards to the DLLME process. Working ranges were determined, being between 1.2 and 8000ngL−1, for E2, and between 0.22 and 1500ngL−1, for EE2. The influence of organic matter, both in the extraction and quantification, was evaluated and it was observed that its presence in the solution did not affect considerably the calibration curve. Recovery rates were also determined, ranging from 77% to 106% for ultrapure water and from 104% to 115% for waste water samples, the most complex ones in what concerns matrix effects. Results obtained when applying the proposed method to real water samples can be considered quite satisfying. Moreover, the obtained working ranges encompass values generally reported in literature, confirming the practical use of the method for environmental samples.

Rapid analysis of aflatoxin M1 in milk using dispersive liquid–liquid microextraction coupled with ultrahigh pressure liquid chromatography tandem mass spectrometry

A simple, rapid, and sensitive method based on simultaneous protein precipitation and extraction of aflatoxin M1 (AFM1) followed by dispersive liquid-liquid microextraction (DLLME) and ultrahigh pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis was developed for the determination of AFM1 in milk samples. In order to precipitate the proteins and extract AFM1 from milk, a sample pretreatment using acetonitrile and NaCl as the extraction/denaturant solvent and salting-out agent, respectively, was optimised. Subsequently, the acetonitrile (upper) phase, containing AFM1, was used as the disperser solvent in DLLME, and extractant (chloroform) and water were added in turn to the extract to perform the DLLME process. The main parameters affecting the extraction efficiency of the whole analytical procedure, such as acetonitrile volume, amount of salt, type and volume of extractant and water volume, were carefully optimised by experimental design. Under optimum conditions, the developed method provides an enrichment factor of 33 and detection and quantification limits (0.6 and 2.0 ng kg(-1), respectively) below the maximum levels imposed by current regulations for AFM1 in milk and infant milk formulae. Recoveries (61.3-75.3%) and repeatability (RSD < 10, n = 3), tested in different types of milk at four AFM1 levels, met the performance criteria required by EC Regulation No. 401/2006. Moreover, the matrix effect on the signal intensity of the analyte was negligible. The proposed method provides a rapid extraction and an accurate determination of AFM1 in milk and formula milk using a simple and inexpensive sample preparation procedure.

Determination of benzophenone-3 and its main metabolites in human serum by dispersive liquid–liquid microextraction followed by liquid chromatography tandem mass spectrometry

A new analytical method for the determination of benzophenone-3 (2-hydroxy-4-methoxybenzophenone), and its main metabolites (2,4-dihydroxybenzophenone and 2,2’-dihydroxy-4-methoxybenzophenone) in human serum is presented. The method is based on dispersive liquid–liquid microextraction (DLLME) as preconcentration and clean-up technique, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Acidic hydrolysis and protein precipitation with HCl 6M (1:1) (100°C, 1h) were carried out before extraction. The variables involved in the DLLME process were studied. Under the optimized conditions, 70µL of acetone (disperser solvent) and 30µL of chloroform (extraction solvent) were mixed and rapidly injected into 800µL of hydrolyzed serum sample. Sample pH or ionic strength adjustment were not necessary. The method was validated by analyzing spiked human serum samples. No satisfactory recoveries were obtained when aqueous standards or standards prepared in synthetic serum were used, but excellent recoveries were achieved by using matrix-matched calibration standards. Moreover, limits of detection in the low µgL−1 level and good repeatability were obtained. In order to show the applicability of the proposed method in the study of percutaneous absorption processes, it was applied to the analysis of serum samples from two volunteers after topical application of a sunscreen cosmetic product containing 2-hydroxy-4-methoxybenzophenone.

Dispersive liquid–liquid microextraction followed by high-performance liquid chromatography for determination of benzoate and sorbate in yogurt drinks and method optimization by central composite design

A new method based on dispersive liquid–liquid microextraction (DLLME) followed by high-performance liquid chromatography (HPLC) for determination of benzoate and sorbate salts in yogurt drinks was developed. The effective parameters in DLLME process, including volume of extraction and disperser solvents, pH and salt effect, were optimized using response surface methodology (RSM) based on central composite design. The yogurt drink samples were extracted using NaOH and Carrez solutions (potassium hexaferrocyanide and zinc acetate) were used for sedimentation of proteins. For DLLME, a mixture of extraction solvent (1-octanol) and disperser solvent (ethanol) was rapidly injected into the sample solution by syringe and cloudy solution is formed. Subsequently, the upper 1-octanol layer was analyzed by HPLC. The detection limits for benzoate and sorbate were 0.06ngmL−1 and 0.15ngmL−1, respectively. The relative standard deviations (RSD) for seven analyses were 4.96% for benzoate and 4.58% for sorbate. The proposed method demonstrated good linearity and high enrichment factor. A clean separation and good chromatogram is readily achieved without the presence of matrix interference. A comparison of this method with previous methods demonstrated that the proposed method is an accurate, rapid and reliable sample-pretreatment method that gives very good enrichment factors and detection limits for extracting and determining sorbate and benzoate in yogurt drink samples.