Disposable Pipette Extraction Research Articles

Miniaturized Salting-Out Assisted Liquid-Liquid Extraction Combined with Disposable Pipette Extraction for Fast Sample Preparation of Neonicotinoid Pesticides in Bee Pollen.

As the main source of nutrients for the important pollinator honeybee, bee pollen is crucial for the health of the honeybee and the agro-ecosystem. In the present study, a new sample preparation procedure has been developed for the determination of neonicotinoid pesticides in bee pollen. The neonicotinoid pesticides were extracted using miniaturized salting-out assisted liquid-liquid extraction (mini-SALLE), followed by disposable pipette extraction (DPX) for the clean-up of analytes. Effects of DPX parameters on the clean-up performance were systematically investigated, including sorbent types (PSA, C18, and silica gel), mass of sorbent, loading modes, and elution conditions. In addition, the clean-up effect of classical dispersive solid-phase extraction (d-SPE) was compared with that of the DPX method. Results indicated that PSA-based DPX showed excellent clean-up ability for the high performance liquid chromatography (HPLC) analysis of neonicotinoid pesticides in bee pollen. The proposed DPX method was fully validated and demonstrated to provide the advantage of simple and rapid clean-up with low consumption of solvent. This is the first report of DPX method applied in bee pollen matrix, and would be valuable for the development of a fast sample preparation method for this challenging and important matrix.

Highly sensitive determination of Cu(II) ions in hemodialysis water by F AAS after disposable pipette extraction (DPX) using Moringa oleifera as solid phase

Clinical samples, such as hemodialysis water, require constant monitoring, since inappropriate processing can lead to copper intoxication even at low concentrations. Sensitive, inexpensive and environmental friendly sample preparation procedures are desirable. For this proposal, an extraction and preconcentration procedure by Disposable Pipette Extraction (DPX) was developed using an homemade device with Moringa oleifera seeds powder as a solid phase for the determination of Cu(II) ions in hemodialysis water at levels of µg L−1 by flame atomic absorption spectrometry (F AAS). The proposed DPX device consists of a conventional micropipette tip, syringe, adapter and glass wool as a filter, being easy to operate, simple and low cost. The optimized extraction and preconcentration conditions allowed the use of 10 mg solid phase with particle size of 250 µm, 6 extraction cycles of sample aliquots at pH 6 and elution with 0.5 mol L−1 hydrochloric acid solution (250 µL). The working concentration range showed satisfactory linearity between 10 and 100 µg L−1 (r2 = 0.9992), assessed by the Mandel test (DS2/Sy22 < F). The preconcentration factor, detection limit and recovery were 50, 0.64 µg L−1 and 96.8–100.4%, respectively. The precision (RSD) was 6.2% (80.0 µg L−1; n = 6). The performance results showed that the extraction and preconcentration procedure with the adapted DPX device is promising for Cu(II) determination in hemodialysis water.

Ultrasound-assisted and disposable pipette extraction for the determination of faecal contaminants in sediment samples by GC-MS

ABSTRACT Given the amount of untreated sewage released into the environment and possible consequences, new methodologies are required for the detection and quantification of potential pollutants found in sediment samples, including faecal contamination. Solid matrix extraction methodologies (e.g. Soxhlet extraction) are generally laborious and require the use of large amounts of solvents, which is inconsistent with the principles of green chemistry. In this study,a simple, robust and efficient analytical method for the determination of faecal sterols in sediment samples using ultrasound-assisted extraction (UAE) followed by pre-concentration with disposable pipette extraction (DPX) was developed. Multivariate experimental designs were used for the optimisation of the extraction parameters for the UAE and DPX procedures. The separation and detection of the analytes were conducted by GC-MS. Dichloromethane was used as the extraction solvent in the UAE. The DPX procedure was conducted applying 5 cycles of extraction with 700 µL of sample (10 s each) and 2 cycles of desorption with 200 µL of solvent (20 s each). The optimised desorption solvent was a mixture composed of ethyl acetate:acetonitrile (60:40 v/v). The limits of detection were 7.6 µg kg−1 for cholesterol and 75 µg kg−1 for cholestanol, coprostanol and stigmasterol and the limits of quantification were 25 µg kg−1 for cholesterol and 250 µg kg−1 for the other analytes. Relative recovery was evaluated for 3 levels of concentration and the results ranged from 78% to 114%. The precision was evaluated through intra-day (n = 3) and inter-day (n = 9) tests, and the ranges observed were 0.5–10%and 2–16%, respectively. The results demonstrate that this effective and fast method shows potential for the determination of faecal contaminants in sediments.

Novel strategy for disposable pipette extraction (DPX): Low-cost Parallel-DPX for determination of phthalate migration from common plastic materials to saliva simulant with GC-MS

In widespread use in commercial products as plasticizers, phthalic acid esters (phthalates) have worried researchers and society in general, given the negative impacts on living organisms, especially human health. Since they are not chemically linked to the polymeric matrix, their migration is evident for samples that come into contact with plastics that contain them, such as water, food and saliva. In this work, a new strategy is described, named parallel-disposable pipette extraction (Pa-DPX), in a fast, efficient and robust analytical method using five simultaneous extractions for the determination of migration of 6 phthalates from common plastic materials (children's toys, school supplies, dog toys and oral contact items) to saliva simulant, using gas chromatography-mass spectrometry (GC-MS). The optimized conditions were 5 extraction cycles with 1600 μL of saliva simulant and desorption with 200 μL of ethyl acetate using 5 cycles with the same aliquot. The calibration curves resulted in determination coefficients higher than 0.9915, limits of detection at 1.5 μg L−1, and the quantification limits were 5.0 μg L−1. Excellent results were obtained for repeatability (relative standard deviation ranging from 8.7% to 20.1% for 5 μg L−1) and intermediate precision, varying the day of analyses (7.9%–16.2%). The analyte recovery ranged from 75% to 114% for two different samples, in four different levels of concentration. The Pa-DPX-GC-MS method was successfully applied to determine the migration of PAE from 21 samples. At least one PAE was detected in 81% of samples, and di-n-octyl phthalate was found in higher concentration, achieving the migration of almost 30 μg per g of sample.

Estrogens determination through disposable pipette extraction coupled to ultraviolet spectroscopy and nonlinear pseudo‐univariate calibration: Solving rank deficiency problems

AbstractIn this study, the disposable pipette extraction (DPX) approach was employed to prepare water samples containing the hormones 17‐β‐estradiol (beta‐EST), estrone (ETR), estriol (EST), and 17‐α‐ethinylestradiol (17‐EE). Both multivariate and univariate experimental designs were used to optimize the DPX procedure through ultraviolet (UV) and high‐performance liquid chromatography (HPLC). The determination of estrogens in water through UV spectroscopy exhibited rank deficiency, and after trying several strategies, it was possible to suggest that the rank deficiency in the spectra was solved by column augmented matrix strategy afterward complexing the hormones with β‐cyclodextrin, in which the relative concentration recovered by the multivariate curve resolution with alternating least squares (MCR‐ALS) to each hormone was employed in the development of nonlinear pseudo‐univariate calibration models based on support vector machine (SVM) approach. The models were validated through parameters of merit determination and by comparing the models results with those obtained by HPLC. The alternative methodology for the determination of estrogens in water through UV spectroscopy is an environmentally friendly analytical methodology employing less solvent and with high throughput. Moreover, it is not possible to determinate these hormones without using the chemometric approaches, mainly due to the rank deficiency, which needs to be broken to allow for the differentiation between the substances and later modeling.

Residue analysis of fungicides fenpicoxamid, isofetamid, and mandestrobin in cereals using zirconium oxide disposable pipette extraction clean-up and ultrahigh-performance liquid chromatography-tandem mass spectrometry

In the present study, a fast multiresidue method determining three novel fungicides fenpicoxamid, isofetamid, and mandestrobin in cereals was developed and validated for the first time using ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Samples were extracted by QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) methodology, and cleaned up using the disposable pipette extraction (DPX) tips containing primary secondary amine (PSA) and silica gel modified with zirconium oxide (Z-Sep) in less than 1 min. Linearity (r > 0.99) of three fungicides in the calibration range of 0.001–0.1 µg mL−1 was satisfactory. Mean recoveries (n = 15) from all matrices were between 84.8% and 100.3% as the corresponding intra-day and inter-day relative standard deviations (RSDs) were less than 10.6%. Limits of quantitation (LOQs) of all analytes in different matrices were defined at 0.01 mg kg−1. The results indicate this method can serve as a sensitive and rapid approach to monitoring contents of fenpicoxamid, isofetamid, and mandestrobin in cereals.

Graphitic carbon nitride as sorbent for the emulsification-enhanced disposable pipette extraction of eight organochlorine pesticides prior to GC-MS analysis.

Graphitic carbon nitride (g-C3N4) was explored as a sorbent for the emulsification-enhanced (EE) disposable pipette extraction (DPX) of eight organochlorine pesticides (OCPs) from environmental waters. The OCPs, including α-hexachlorocyclohexane, Aldrin, α-Chlordane, Dieldrin, 4,4'-dichlorodiphenyldichloroethylene, 4,4'-dichlorodiphenyldichloroethane, Heptachlor and Heptachlor epoxide (Isomer A), were analyzed by gas chromatography-mass spectrometry. The sorbentg-C3N4 was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, g-C3N4 exhibits good water dispersibility and allows easy analyte recovery - a characteristic not commonly observed in carbon-based materials. When applied to DPX, g-C3N4 rapidly establishes strong interactions with the OCPs. Consequently, g-C3N4 displays superior extraction capability in comparison to six other commercial sorbents. An emulsification step prior to DPX was found to enhance the overall extraction efficiency by pre-concentrating the OCPs into the microdroplets of an organic solvent. The microdroplets were then adsorbed onto g-C3N4. Under the most favorable conditions, wide linear responses spanning over two to four orders of magnitudes are established. The limits of detection range between 2.4ng·L-1 and 46.2ng·L-1. The method is reproducible (relative standard deviations ≤ 7.4%) and enrichment factors are between 42 and 57. When applied to the analysis of lake and river water samples, EE-DPX-gas chromatography-mass spectrometry exhibits good resilience against matrix interferences. The relative recoveries range between 77.7% and 106.3%. In comparison to other sorbent-based extraction techniques reported for the analysis of OCPs in aqueous samples, EE-DPX utilizes the minimal amount of sample and solvent, and requires the shortest sample preparation time. Graphical abstractSchematic representation of the emulsification-enhanced disposable pipette extraction (DPX) of organochlorine pesticides (OCPs) using graphitic carbon nitride (g-C3N4) as sorbent. Emulsification and DPX work synergistically, thus allowing rapid dissolution of analytes into microdroplets of organic solvent, before being extracted by g-C3N4.

Exploring Polypyrrole as Extraction Phase for Disposable Pipette Extraction Method for Multiclass Organic Micro-Pollutant Determination in River and Tap Water Using Gas Chromatography-Mass Spectrometry

The use of a polypyrrole (PPy) is described as an efficient extraction phase for disposable pipette extraction (DPX), in a fast and ruggedized analytical method for simultaneous determination of 18 organic micro-pollutants in water using gas chromatography-mass spectrometry (GC-MS). The DPX-blank pipettes were filled with PPy, a material produced through the chemical polymerization of PPy using iron(III) chloride hexahydrate. The optimized conditions were 5 extraction cycles with 600 µL of sample, adjusted to pH 9, and desorption with 150 µL of ethyl acetate using 7 cycles with the same aliquot. The calibration curves resulted in determination coefficient (R2) higher than 0.9963, the limit of detection (LOD) ranged from 0.4 to 1.5 µg L−1, and the limit of quantification (LOQ) were from 1.4 to 5.0 µg L−1. Excellent results were obtained for repeatability (2.3 to 15%, for 5 µg L−1) and intermediate precision, varying the day of analyses (3.9 to 15.5%) and the pipette tip (3.4 to 22.4%). The analyte recovery ranged from 75.4 to 115.0% for river water, and from 74.9 to 116.2% for tap water, in three different levels of concentration. The DPX-GC-MS method with PPy was successfully applied to determine the 18 analytes in river and tap water from the cities of Joinville and Florianopolis, Santa Catarina, Brazil.

Disposable pipette extraction phase based on styrene–divinylbenzene/pernigraniline composite, applied for dexamethasone determination in synovial fluid by HPLC with UV detector

A reliable method using disposable pipette extraction (DPX) based on composite of pernigraniline and styrene–divinylbenzene (Sty–DVB) copolymer was applied to the analysis of dexamethasone in synovial fluid using high-performance liquid chromatography and ultraviolet (UV) detector (HPLC–UV). DPX variables, namely, number of draw/eject cycles for extraction or desorption, sample pH, volume, and desorption solvent, were optimized to establish the best sorption equilibrium and analysis time. The highest extraction efficiency value was obtained with 50 μL of synovial fluid mixed with 1950 μL of water, in five cycles of 300 μL of sampling, followed by liquid desorption of the drug with 300 μL of methanol in three cycles. The developed method demonstrated a linear response over the range from 10 to 100 ng/mL, with R2 = 0.993. The limit of quantification (LOQ) was 10 ng/mL. Based on the validation results, the proposed method can be a useful tool to detect dexamethasone levels in synovial fluid.

Disposable pipette extraction using a selective sorbent for carbendazim residues in orange juice

In this work, a selective sorbent for carbendazim was prepared by the thermal immobilization of the poly(glycidoxypropylmethyl-co-dimethylsiloxane), PGDMS, on silica. The lab-made Si(PGDMS) sorbent was physicochemically and morphologically characterized and was used into the pipette tip for the disposable pipette extraction (DPX) of carbendazim residues of orange juice. The DPX method was optimized from a central composite design and validated according to the SANTE/11813/2017 document recommended by the European Union. The proposed method presented recoveries between 93 and 110% with RSD <16% and the limit of quantification below the MRL for carbendazim in citrus. The whole sample preparation process was carried out at less than 3 min, with good accuracy and precision without the need of any cleanup step or electrical equipment, allowing its portability for the extraction of carbendazim residues in orange juice.

Determination of anandamide in cerebrospinal fluid samples by disposable pipette extraction and ultra-high performance liquid chromatography tandem mass spectrometry

This work describes the development and validation of an ultra-high performance liquid chromatography tandem mass spectrometry method that uses disposable pipette extraction (DPX-UHPLC-MS/MS) to determine the endocannabinoid anandamide (AEA) in cerebrospinal fluid samples (CSF). The DPX parameters sorption equilibrium time, sample volume, number of draw-eject cycles, washing solvent volume, and elution solvent volume were optimized by design of experiments (DOE) techniques. The simple DPX protocol proposed herein required a reduced amount of CSF sample and organic solvent. The DPX-UHPLC-MS/MS method presented linear range from 0.10 ng mL−1 (LLOQ) to 3.0 ng mL−1, inter- and intra-assay accuracy with EPR values varying from −8.2% to 9.6%, inter- and intra-assay precision with CV values ranging from 1.3% to 14.8% (except for the LLOQ), and no significant matrix effect. The innovative DPX-UHPLC-MS/MS method was successfully applied to determine AEA in CSF samples from Parkinson’s disease (PD) patients and should therefore be used in clinical studies.

Disposable Pipette Extraction (DPX) Coupled with Liquid Chromatography–Tandem Mass Spectrometry for the Simultaneous Determination of Pesticide Residues in Wine Samples

A novel multiresidue analytical method based on disposable pipette extraction (DPX) to determine the trace level of 28 pesticides in wine samples using liquid chromatography–tandem mass spectrometry (LC–MS/MS) has been developed. The DPX method is used for both extraction and purification. After the optimization, targets were eluted with 1% HCl in acetonitrile and the eluent was placed into LC analysis. The developed method exhibited good linearity (R2 > 0.99) for all 28 pesticides. Satisfactory recovery of 28 pesticides was observed ranging from 71 to 109%, with the intraday relative standard deviations (RSDs) and inter-day RSDs of 1–11% and 3–18%, respectively. Limits of detection (LODs) and limits of quantification (LOQs) were found to range from 1.5 to 3 μg/L and 5 to 10 μg/L, respectively. DPX was more suitable as compared with quick, easy, cheap, effective, rugged, and safe (QuEChERS) and solid-phase extraction (SPE) methods. The DPX method was applied to 47 commercial wine samples collected from China, and pesticide residues (0.02–0.09 mg/L) were found. In general, the developed method was highly reliable, selective, and sensitive for analyzing 28 pesticide residues in wine samples and would be applicable to other beverages.

A rapid and environmentally friendly analytical method based on conductive polymer as extraction phase for disposable pipette extraction for the determination of hormones and polycyclic aromatic hydrocarbons in river water samples using high-performance liquid chromatography/diode array detection

In this study, for the first time, an analytical methodology comprised of disposable pipette extraction technique (DPX) based on a conductive polymer (polypyrrole - PPy) was developed for the simultaneous extraction/determination of 14 compounds including two hormones and twelve polycyclic aromatic hydrocarbons in river water samples. Pipette tips of 1 mL were filled with the extraction material, named PPy.CTAB, and the separation/detection was performed HPLC-DAD. The extraction material was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The optimized extraction conditions were comprised of 700 μL of sample using 2 cycles of 15 seconds each, and pH adjusted at 6.00. Regarding the desorption step, a mixture of 200 μL of acetonitrile and methanol (50:50, v/v) was used with 6 cycles of 15 seconds each. The calibration curves were performed in the sample matrix and LODs and LOQs ranged from 1.5 to 6.1 μg L-1 and from 5.0 to 20.0 μg L-1, respectively, with r ≥ 0.9901. The accuracy ranged from 44-139% and intraday precision with values ≤ 8% and interday ≤ 26%. The methodology was applied in three samples collected from Tubarão River located in the city of Orleans - SC and the analytes were not detected in these samples.

Effective and High-Throughput Analytical Methodology for the Determination of Lead and Cadmium in Water Samples by Disposable Pipette Extraction Coupled with High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (HR-CS GF AAS)

A new procedure for the preconcentration of trace amounts of free Pb and Cd by disposable pipette extraction (DPX) is proposed herein. Recycled cork is used as a biosorbent and the procedure is completely free of organic solvents. The cork was reduced to a powder and characterized by scanning electron microscopy. Several parameters that influence the preconcentration of Pb and Cd with DPX-cork, such as the sample pH, number of extraction cycles, biosorbent mass, and percentage of acid in the desorption step, were studied. The tolerance of DPX-cork with respect to 10 potential interfering ions was also evaluated. Coupled with the high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) technique, the sample preparation method allowed the analytical limits required for quality control (according to the permitted limits established by legislation) to be obtained. The limits of detection for the extraction of a 3.5-mL water sample were 200 ng L−1 for Pb and 100 ng L−1 for Cd. The relative standard deviations were around 7.5% for Pb and 8.0% for Cd. The optimized method was successfully applied to the determination of Cd and Pb in two certified reference materials (water and wastewater) and five water samples (collected from a mangrove, a creek, and the sea).

A natural and renewable biosorbent phase as a low‐cost approach in disposable pipette extraction technique for the determination of emerging contaminants in lake water samples

This study proposes an efficient analytical methodology using a biosorbent (cork) as an extraction phase in disposable pipette extraction technique for the rapid determination of the emerging contaminants methyl paraben, ethyl paraben, benzophenone, 3-(4-methylbenzylidene) camphor and 2-(ethylhexyl)-4-(dimethylamino) benzoate in lake water samples using high-performance liquid chromatography with diode array detection. The optimized conditions were comprised of 800 μL of sample, three cycles of 30 s each for the extraction, pH 6, addition of 30% w/v of NaCl. For the desorption step, the optimized desorption conditions were achieved with 100 μL of a mixture comprised of 50% methanol and 50% acetonitrile v/v, using one cycle of 30 s. Excellent analytical performance was achieved with limits of detection of 0.6μg/L for methyl paraben to 1.4μg/L for 3-(4-methylbenzylidene) camphor, and the limit of quantitation varied from 2μg/L for methyl paraben to 4.3μg/L 3-(4-methylbenzylidene) camphor, respectively. The correlation coefficients ranged from 0.9962 for ethyl paraben to 0.9980 for methyl paraben. The method accuracy varied from 71-132%, and the intraday precision ranged from 3 to 23% (n=3) and interday from 9 to 23% (n=9). The robustness was evaluated through Youden and Lenth's methods and indicated no significant variations in the results.

Expanding the applicability of cork as extraction phase for disposable pipette extraction in multiresidue analysis of pharmaceuticals in urine samples

In this paper, cork is proposed as a natural and renewable material for the extraction phase in disposable pipette extraction to be applied in the multiresidue determination of pharmaceuticals in human urine by HPLC with diode array detection. The compounds carbamazepine, losartan, ketoprofen, 17‑β‑estradiol, naproxen, diazepam, 17‑α‑ethinylestradiol, estrone, diclofenac and ibuprofen were studied. A known amount (5 mg) of cork, with a size of 200 mesh, was inserted into a pipette tip. The method optimization was carried out with univariate and multivariate approaches. The optimized conditions were sample pH adjusted to 3, urine dilution factor of 40 (158 μL of urine diluted in 6.142 mL of ultrapure water), 9 extraction cycles each performed with 700 μL of sample, and extraction time of 10 s per cycle. Desorption was performed with 85 μL of methanol applying 6 cycles of 10 s each using the same solvent aliquot. For the clean-up step, 4 cycles were carried out each with 200 μL of methanol. The limits of quantification varied from 5 to 10 μg L−1 with determination coefficients higher than 0.9919 for the calibration curves for all the analytes. Intra-day and inter-day precision and relative recovery from urine samples donated by two volunteers were assessed based on three spiked concentrations. The analyte relative recoveries ranged from 65 to 117% (n = 3) for the two samples. Intra-day precision ranged from 1.2 to 17% (n = 3) and inter-day precision varied from 11 to 21% (n = 9).

An effective and high-throughput analytical methodology for pesticide screening in human urine by disposable pipette extraction and gas chromatography – mass spectrometry

In this paper, the use of disposable pipette extraction (DPX) for the determination of pesticides in human urine in possible cases of poisoning is proposed for the first time. The pesticides studied were oxamyl, propoxur, carbofuran, 3‑hydroxycarbofuran, carbaryl, methiocarb, terbufos, parathion methyl, malathion, chlorpyrifos and endosulfan. The pipette tip used for the extraction of these compounds was commercially acquired. It has a capacity of 5 mL and contains 20 mg of sorbent material (styrene-divinylbenzene). The optimization of the main parameters that can influence the extraction efficiency of this sample preparation technique was performed with univariate and multivariate approaches. The analytes were separated and identified by gas chromatography coupled to mass spectrometry (GC–MS). The optimal extraction conditions were 5 extraction cycles of 30 s and 5 desorption cycles of 15 s with 250 μL of ethyl acetate. Elution of the extract was performed in a vial containing 100 mg of anhydrous sodium sulfate. The method developed was validated, providing correlation coefficients higher than 0.9955 for all analytes, limits of detection (LOD) of 0.76 to 1.52 μg L−1, limits of quantification (LOQ) of 2.5 to 5.0 μg L−1, relative recoveries of 63 to 118%, intra-day precision of 0.7 to 15.3% and inter-day precision of 4.9 to 13.1%. An effective and rapid method for the analysis of human urine for the identification of possible cases of poisoning by pesticides was successful developed.

A hybrid material as a sorbent phase for the disposable pipette extraction technique enhances efficiency in the determination of phenolic endocrine-disrupting compounds

In this study, the hybrid material 3-n-propyl(3-methylpyridinium) silsesquioxane chloride (Si3Py+Cl−) was synthesized and investigated as a novel sorbent phase for the disposable pipette extraction (DPX) technique coupled to high-performance liquid chromatography-florescence detection. This sorbent phase was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Aqueous samples containing the phenolic endocrine-disrupting compounds bisphenol A (BPA), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (4-t-OP), 4-octylphenol (4-OP) and 4-nonylphenol (4-NP) were subjected to DPX procedures and a series of optimizations was performed to determine the ideal extraction conditions using this approach. The proposed sorbent phase exhibited higher extraction efficiency than DPX-RP (reversed phase tips containing styrene-divinylbenzene), commonly used for the determination of the phenolic endocrine- disrupting-compounds under study. Satisfactory analytical performance was achieved with linear ranges from 2 to 100μgL−1 for 4-t-OP and 1–100μgL−1 for the other analytes. Limits of detection of 0.60μgL−1 for 4-t-OP and 0.30μgL−1 for other analytes, RSDs ranging from 1 to 20% and relative recoveries of 83–116% were obtained. Based on these satisfactory results, this sorbent phase represents a valuable alternative for the extraction of compounds with polar moieties in their structure.

Determination of drugs in plasma samples by disposable pipette extraction with C18-BSA phase and liquid chromatography–tandem mass spectrometry

This work describes restricted access material (RAM) constituted of porous octadecylsilane particles with the outer surface covered with bovine serum albumin (C18-BSA) as a stationary phase to extract drugs from plasma samples by disposable pipette extraction (DPX) for further analysis by liquid chromatography–tandem mass spectrometry (LC–MS/MS). The C18-BSA phase simultaneously excluded macromolecules by chemical diffusion barrier (BSA network) and enrichment of the interior phase (C18) with drug traces by sorption. The hydrophilic barrier of the C18-BSA allows small molecules (drugs) to permeate through the hydrophobic part (C18), while at the same time it excludes the macromolecules by chemical diffusion barrier (BSA network). Optimization of the DPX variables (sorption equilibration time, exclusion of endogenous compounds, and elution step) improved the sensitivity and selectivity of the method, which presented a linear range from the lower limit of quantification (0.5–20.0ngmL−1) to the upper limit of quantification (32.5–10,500ngmL−1), inter- and intra-assay precision with coefficients of variation (CV) lower than 15%, and relative standard error (RSE) of the accuracy ranging from −12% to 11%. The developed method was successfully used to determine five antipsychotics (olanzapine, quetiapine, clozapine, haloperidol, and chlorpromazine) in combination with seven antidepressants (mirtazapine, paroxetine, citalopram, sertraline, imipramine, clomipramine, and fluoxetine), two anticonvulsants (carbamazepine and lamotrigine), and two anxiolytics (diazepam and clonazepam) in plasma samples from schizophrenic patients for therapeutic drug monitoring.

A New Method for the Determination of Creatinine in Urine Samples Based on Disposable Pipette Extraction

A method based on disposable pipette extraction (DPX) was successfully applied to creatinine determination in urine samples analysis using liquid chromatography with ultraviolet spectrophotometric detection (DPX/LC-UV). DPX variables, number of draw/eject cycles, sample pH, and type of the desorption solvent, were employed in a factorial experimental design to optimize the sorption equilibrium and time analysis. Among the evaluated DPX variables, the highest extraction efficiency was obtained with 500 µL of urine sample mixed with 1 mL of borate solution (pH 9) with one draw/eject cycle followed by liquid desorption of 1 mL of methanol in seven draw/eject cycles. The developed DPX/LC-UV method showed a linear response from the limit of quantification of 0.317 to 3.390 g L-1 with r2 = 0.996 and inter-day precision with a coefficient of variation below 8.8%. Based on these results, the proposed method can be a useful tool for determining the creatinine levels in urine samples.