Solid-phase Extraction Clean-up Procedure Research Articles

Occurrence of polycyclic aromatic compounds in guarana (Paullinia cupana) seeds subjected to different drying processes

In this study, the levels of polycyclic aromatic compounds (PACs), such as polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (oxy-PAHs) were investigated in guarana seeds (Paullinia cupana) subjected to different drying methodologies. An innovative extraction method combined with a miniaturized dispersive solid-phase extraction cleanup procedure was developed for the determination of PACs concentration. Thirteen-eight guarana seed samples subjected to three different drying methodologies (sun drying, greenhouse drying, and alguidar furnace drying) were collected from different rural producers in the South Region of the State of Bahia, Brazil. Principal component analysis and diagnostic ratios were used to evaluate the correlation between samples and the PACs and the main sources of contamination. According to the results, the average concentration of PACs found in sun-dried, greenhouse-dried, and alguidar-dried ranged from 1.30 µg kg−1 (coronene) to 114 µg kg−1 (fluorene), from 0.48 µg kg−1 (dibenzo[a,h]anthracene) to 128 µg kg−1 (fluorene), and from 6.0 µg kg−1 (anthracene) to 422 µg kg−1 (phenanthrene). Oxy-PAHs, such as 1,4-NQ was detected predominantly in sun-dried and greenhouse-dried samples at concentrations ranging from 30.7 µg kg−1 to 83.9 µg kg−1. Low molecular weight PAHs, such as naphthalene, acenaphthylene, and fluorene were found in most of the samples independently of drying methodology. However, high molecular weight PAHs, including the carcinogenic benzo[a]pyrene was found predominately in alguidar-dried samples in concentrations higher than 20 µg kg−1.

Development of SPE clean-up procedure for acrylamide determination from potato-based products by GC-MS/MS

Abstract The aim of this work was to develop an analytical method for determining acrylamide in potato-based products by gas chromatography and tandem mass spectrometry analysis (GC-MS/MS) using solid-phase extraction (SPE) clean-up. Different conditions for extraction and clean-up of AA extracts were studied on a potato crisps reference material (RM) with the value of 625 ± 45 μg/kg: the solvent volume used for AA elution, the extraction water temperature, the volume of hexane used, and also the addition of Carrez solutions. The SPE cartridge sorbents contain silica-based C-18 groups (anion and cation exchangers) and polymers (polystyrene-divinylbenzene). After SPE clean-up, extracts were derivatized with bromine compounds. A good efficiency for AA extraction and a cleaned-up extract from this matrix were obtained when the SPE procedure was carried out with water at room temperature, simultaneous with hexane, without Carrez solutions, by using two types of SPE cartridges (Isolute Multimode; Isolute ENV+), and 5 mL of elution solvent. The SPE clean-up procedure functionality was demonstrated by the results obtained in the Food Analysis Performance Assessment Scheme proficiency test (z-score: −0.8) on French fries (precooked) matrix and also by comparative analysis with a laboratory procedure, validated and accredited on cereal-based food matrices, in which liquid–liquid extraction and clean-up through a florisil column were realized (RSD(R) = 2.23–5.10%).

Determination of 5-HT3 Receptor Antagonists in Human Urine by Porous Graphitic Carbon (PGC) Solid Phase Extraction (SPE) Coupled with High Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS)

The quantitative determination of drugs in urine by high performance liquid chromatography electrospray-ionization mass spectrometry (HPLC-ESI-MS) is challenging due to complex matrix interferences and the relatively low concentrations of analytes in urine. In this study, porous graphitic carbon (PGC) was investigated as solid phase extraction (SPE) sorbent before HPLC-ESI-MS determination of three 5-hydroxytryptamine (3) (5-HT3) receptor antagonists from human urine. The factors affecting extraction of the target antagonists were investigated and optimized systematically by using single-factor tests. The optimized SPE procedure was developed for the simultaneous extraction and sample pretreatment of tropisetron, ondansetron, and granisetron in urine by HPLC-ESI-MS/MS. Using the optimized conditions, the matrix effects were reduced by the PGC-based SPE clean-up procedure, with acceptable matrix effects for tropisetron, ondansetron, and granisetron from 96.53% to 98.42%, 93.19% to 94.36%, and 94.48% to 95.60%, respectively. The reported method significantly removes matrix interferences from the urine samples and exhibited satisfactory recovery and process efficiency for the determination of tropisetron, ondansetron, and granisetron. The established pretreatment method provides a promising strategy for the removal of interferences from hydrophilic basic drugs in biological fluids.

A pass-through solid-phase extraction clean-up method for the determination of 11 quinolone antibiotics in chicken meat and egg samples using ultra-performance liquid chromatography tandem mass spectrometry

The major challenges in determination of antibiotic residues in foods stem from the complexity of matrix, as well as from polar differences and low concentrations of antibiotics. In this study, an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method has been developed for the determination of 11 quinolone antibiotics in chicken meat and egg samples using a pass-through solid phase extraction (SPE) cleanup procedure. The samples were treated with optimized acetonitrile/water solution to precipitate proteins, release and extract the target antibiotics. Then, fats and phospholipids were removed by a pass-through SPE cleanup procedure. Subsequently, highly sensitive determination and confirmation of 11 quinolones was accomplished by UPLC-MS/MS in the positive ionization mode with multiple reaction monitoring. Through the protocol, recoveries in chicken meat ranging from 70.4 to 98.4%, while in egg samples between 66.9 and 99.0%, with a low limit of detection ranged from 0.1 to 0.16 μg/kg. Finally, the method has been successfully utilized for the screening of eleven quinolones antibiotics residues in 60 chicken meat and 110 eggs samples from the local markets. Enrofloxacin and ciprofloxacin were detected in both chicken meat and eggs samples with the highest concentrations of 44.4 μg/kg and 6.22 μg/kg, respectively.

A Sensitive LC-MS/MS Method for Palytoxin Using Lithium Cationization.

Palytoxin (PlTX) and analogues are produced by certain dinoflagellates, sea anemones, corals and cyanobacteria. PlTX can accumulate in the food chain and when consumed it may cause intoxication with symptoms like myalgia, weakness, fever, nausea, and vomiting. The analysis of PlTXs is challenging, and because of the large molecular structure, it is difficult to develop a sensitive and selective liquid chromatography-mass spectrometry (LC-MS/MS) method. In this work, an LC-MS/MS method was developed to analyse PlTXs with use of lithium iodine and formic acid as additives in the mobile phase. For method development, initially, LC-hrMS was used to accurately determine the elemental composition of the precursor and product ions. The main adduct formed was [M + H + 2Li]3+. Fragments were identified with LC-hrMS and these were incorporated in the LC-MS/MS method. A method of 10 min was developed and a solid phase extraction clean-up procedure was optimised for shellfish matrix. The determined limits of detection were respectively 8 and 22 µg PlTX kg−1 for mussel and oyster matrix. Oysters gave a low recovery of approximately 50% for PlTX during extraction. The method was successfully in-house validated, repeatability had a relative standard deviation less than 20% (n = 5) at 30 µg PlTX kg−1 in mussel, cockle, and ensis, and at 60 µg PlTX kg−1 in oyster.

Simultaneous determination of 35 ultra-trace level organophosphorus pesticide residues in Sanjie Zhentong capsules of traditional Chinese medicine using ultra high performance liquid chromatography with tandem mass spectrometry.

The aim of this study was to develop an analytical method for the simultaneous determination of ultra-trace levels of 35 organophosphorus pesticide residues in Sanjie Zhentong capsules, a traditional Chinese medicine prescription. A method based on multiclass and multiresidue sample preparation was developed. First, samples were hydrated with water at 4°C. A ratio of 1:3 sample/water was used for each of the sample amounts. Then, different extraction solvents were screened. This step was followed by a dispersive solid-phase extraction clean-up procedure using both primary secondary amine and polyamide. A comprehensive sensitive multiresidue liquid chromatography tandem mass spectrometry method was investigated and validated. Good linearity was achieved in the range of 10-500 μg/kg for each analyte. The average recovery ranged from 70 to 120%, except for methamidophos, fonophos, diazinon, and chlorpyriphos-ethyl, the recoveries of which ranged from 60-70% at the lower concentration level. The precision values were lower than 10% for all the compounds in three concentration levels. The limits of detection and limits of quantification values were 0.01-2.1 and 0.05-3.4 μg/kg, respectively. The matrix effects were determined, and most of the compounds showed signal suppression. Finally, this optimized procedure was applied for the analysis of real samples.

On-line Enrichment and Measurement of Four Halogenated Phenols in Water Samples Using Pressure-Assisted Electrokinetic Injection–Tandem Mass Spectrometry

A rapid and sensitive method using pressure-assisted electrokinetic injection (PAEKI) as the on-line sample enrichment technique and electrospray-tandem mass spectrometry as the monitor has been developed for the determination of four halogenated phenols, 2,4,6-trichlorophenol, 2,4-dichlorophenol, 2,3,4,6-tetrachlorophenol and tetrabromobisphenol A, in water samples. In 8-min of injection, the four halogenated phenols in water samples were enriched up to several thousand times. With the aid of a solid-phase extraction clean-up procedure, the method achieved a detection limit in the range of 7.4 to 37.1 ng L(-1) for the four phenols by multiple reaction monitoring in a negative mode. The overall recoveries for all four halogenated phenols in water samples were in the range of 68 to 114%. The good method repeatability has been demonstrated by the relative standard deviations (RSDs) of less than 10% for water samples spiked with standard mixtures. The four target phenols in all the water samples were below the detection limits.

Development and validation of HPLC method for the determination of tobramycin in urine samples post-inhalation using pre-column derivatisation with fluorescein isothiocyanate

A reversed-phase liquid chromatography method involving pre-column derivatisation with fluorescein isothiocyanate (FITC, isomer I) for determination of tobramycin in urine samples after inhalation has been developed. FITC reacts with the primary amino groups of tobramycin and other aminoglycosides under mild conditions to form a highly fluorescent and stable derivative. The chromatographic separation was carried out on a Phenomenex Luna C 18 column at ambient temperature using a constant flow rate of 1 ml/min and mobile phase of acetonitrile–methanol–glacial acetic acid–water (420:60:5:515, v/v/v/v). The tobramycin–FITC derivative was monitored by fluorescent detection at an excitation wavelength 490 nm and emission wavelength 518 nm. The linearity of response for tobramycin was demonstrated at 11 different concentrations of tobramycin extracted from spiked urine, ranging from 0.25 to 20 μg/ml. Tobramycin and neomycin were extracted from spiked urine by a solid phase extraction clean-up procedure on a carboxypropyl-bonded phase (CBA) weak cation-exchange cartridge, and the relative recovery was >99% ( n = 5). The limit of detection (LOD) and limit of quantitation (LOQ) in urine were 70 and 250 ng/ml, respectively. The method had an accuracy of <0.2%, and intra-day and inter-day precision (in term of %coefficient of variation) were <4.89% and 8.25%, respectively. This assay was used for urinary pharmacokinetic studies to identify the relative lung deposition of tobramycin post-inhalation of tobramycin inhaled solution 300 mg/5 ml (TOBI ®) by different nebuliser systems.

Solid-phase extraction clean-up procedure for the analysis of PAHs in lichens

A clean-up procedure based on a solid-phase extraction column was optimized for determination of polycyclic aromatic hydrocarbons (PAHs) in lichen extracts to remove co-extracted compounds from the matrix in the final extract. Several kinds of solid phases were evaluated: normal phase (-NH2 and alumina), strong anion exchange and reversed phase. The -NH2 columns were the most effective by using a packed solid bed of 500 mg. The lichen raw extract was loaded on the column previously conditioned with dichloromethane and hexane. Hexane (0.5 mL) was used as rinsing solvent, and PAHs were quantitatively eluted (80–97%) using 2 mL of hexane–dichloromethane (65–35) as eluting solvent. In these conditions, even the heaviest PAHs were quantitatively eluted. The optimized SPE method provides a short time and low-solvent-consumption sample clean-up compared with other conventional methods based on column chromatography. The analytical procedure, dynamic sonication-assisted extraction, followed by the optimized solid-phase extraction clean-up, was used to determine the 16 EPA priority PAHs from native lichens collected from the Aragon valley in central Pyrenees. The PAH concentrations in lichen samples ranged from 352 to 1654 ng g−1, and the minimum concentration value was established as the regional reference PAH levels in the area.

Analysis of Acrylamide in Green Tea by Gas Chromatography−Mass Spectrometry

Optimization of the solid-phase extraction cleanup procedure enabled the GC-MS analysis of acrylamide in tea samples without the interference of bromination by tea catechins. Although polyvinylpolypyrrolidone (PVPP) is available for removing tea catechins from tea extract, the peaks derived from PVPP had the same retention time as brominated acrylamide in mass chromatograms obtained by GC-MS. A considerable amount of acrylamide was formed at roasting temperatures of > or =120 degrees C; the highest acrylamide level was observed when tea samples were roasted at 180 degrees C for 10 min. Higher temperatures and longer processing times caused a decrease in the acrylamide content. Furthermore, an analysis of 82 tea samples showed that rather than the reducing sugar content, the asparagine content in tea leaves was a significant factor related to acrylamide formation in roasted products. The acrylamide level in roasted tea products was controlled by asparagine in the presence of reducing sugars.

Multicommuted fluorescence based optosensor for the screening of bitertanol residues in banana samples

A multicommuted flow through optosensor is developed in order to determine bitertanol in banana samples, by measuring the pesticide native fluorescence at 261/326 nm. The solid support used in the flow-through cell, C 18, allows both high selectivity and sensitivity necessary for the screening of the pesticide at residue levels. These characteristics of optosensing are implemented with low sample consumption and automation intrinsic properties of multicommutation, providing a useful tool for pesticide residue routine determination in foods. An acetonitrile extraction/partitioning and dispersive solid-phase extraction clean-up procedure proved to be useful; an additional cleaning step with C 18 solid phase extraction (SPE) cartridges was carried out, eliminating all matrix limitations. Recovery experiments performed on banana samples at different concentrations provided recoveries between 81% and 115%. A detection limit of 0.014 mg kg −1 was obtained. This makes the method suitable for screening bitertanol in banana samples, fulfilling the maximum residue levels of 3 mg kg −1 established by the European Union.

Combination of TLC and HPLC-MS/MS Methods. Approach to a Rational Quality Control of Chinese Star Anise

In this study, a methodological approach for an effective and reliable quality control of Chinese star anise (Illicium verum Hook. F.) is developed and validated. A combined method of TLC and HPLC-MS/MS was used for differentiation of various Illicium species, especially Chinese and Japanese star anise. Species can be distinguished by their TLC flavonoid pattern. A sensitive and selective HPLC/ESI-MS/MS method was developed for the detection and quantification of lower admixtures of I. anisatum and of further toxic Illicium species at a low concentration range using the sesquiterpene lactone anisatin as a marker. The proposed assay includes a solid-phase extraction cleanup procedure with a high recovery (>90%). Chromatographic separation of anisatin was carried out on a C18 column, followed by MS detection using ESI in negative mode. The precursor/product ion transitions m/z 327 --> 127 (quantifier) and m/z 327 --> 297 (qualifier) were monitored. Statistical evaluation of this multireaction-monitoring procedure reveals good linearity and intra- and interday precision. The limits of detection and quantification are 1.2 and 3.9 microg/kg, respectively.

Isolation of bound residues of nitrofuran drugs from tissue by solid-phase extraction with determination by liquid chromatography with UV and tandem mass spectrometric detection

Use of nitrofuran drugs in food-producing animals has been prohibited within the EU because they may represent a public health risk. Monitoring compliance with the ban has focused on the detection of protein-bound nitrofuran metabolites which, in contrast to the parent compounds, are stable and persist in animal tissues. This paper describes a solid phase extraction clean-up procedure for the protein-bound metabolite of furazolidone, 3-amino-2-oxazolidone (AOZ), allowing detection of the derivatised metabolite, NPAOZ, at residue level. Validation studies for the method on porcine liver samples fortified at 5 and 25 ng g −1 show mean recovery of 84±19.2 and 90±16.3%, respectively. Comparison between liquid chromatography with UV or tandem mass spectrometric detection shows agreement within 10% for incurred porcine liver samples.

Determination of Chlormequat in Fruit Samples by Liquid Chromatography-Electrospray-Mass Spectrometry/Mass Spectrometry

An ion-pair liquid chromatography-mass spectrometry/mass spectrometry method was developed for the determination of chlormequat in fruit samples. A solid-phase extraction cleanup procedure with C18 cartridges was used. Sample preparation was simple and the achieved detection limit (0.03 mg/kg) and quantitation limit (0.08 mg/kg) were below the maximum residue levels legislated by the European Union. The chromatographic separation was performed by using a C8 column and heptafluorobutyric acid as ion pair reagent. The detection was conducted with an electrospray source and an ion trap as a mass analyzer. The reproducibility of the method gave good run-to-run (8-9%) and day-to-day (9-13%) precision values, and its applicability to the determination of chlormequat in pears and grapes, purées, and pear, apple, and grape juices was demonstrated.

Liquid chromatographic method for determining added folic acid in fortified cereal products

Reversed-phase ion-pair high-performance liquid chromatography (HPLC) was coupled with detection by UV absorption (280 nm) for separation and quantitation of added folic acid (FA) in fortified cereal based foods. A simple and rapid liquid–solid extraction method, combined with enzymatic digestion, to recover FA from the sample matrices is also presented. The quantitation of added FA was achieved in products including corn (maize), wheat-, rice- and oat-based cereal breakfastfoods fortified at 25% and 100% of the reference daily intake (RDI). The retention time for FA was ca. 15 min, and the detection limit was 2 ng/20 μl injection for standard FA. When FA was added to unfortified samples of wheat flour at concentrations of 3.08 or 20.0 μg/g, recoveries were 93% and 96%, respectively. Comparison of HPLC results with those of a standard microbiological assay has shown quite good agreement ( r=0.998). A solid-phase extraction clean-up procedure has also been developed for use with samples fortified with low levels of FA, where interferences may otherwise hinder quantitation.

Liquid chromatography-atmospheric-pressure chemical ionization mass spectrometry as a routine method for the analysis of mutagenic amines in beef extracts

A liquid chromatography-mass spectrometry (LC-MS) method using atmospheric-pressure chemical ionisation as interface was developed for the simultaneous determination of 14 heterocyclic aromatic amines and related compounds in beef extracts. The separation was performed on a conventional C 18 column using a binary mobile phase composed of acetonitrile and 50m M ammonium acetate at pH 5.7, and elution was carried out in gradient mode. Several parameters influencing the mass spectra were optimized, and the effect of the variation of cone voltage on the mass spectra was studied. The [M+H] + ions and some fragments produced in the source were observed in the mass spectra when several extraction voltages were applied. Quality parameters (run-to-run and day-to-day reproducibility, intervals of linearity, and limits of detection) were studied in the optimum working conditions. The method was used to analyze the heterocyclic amines present in a commercial beef extract. Therefore, a solid-phase extraction clean-up procedure was performed prior the LC-MS analysis due to the complexity of the sample and the compounds Glu-P-1, Harman, Norharman and AαC were identified in the samples at ppb levels and successfully confirmed using in-source fragmentation.