Selectivity in the sample preparation for the analysis of drug residues in products of animal origin using LC-MS

Quantification of 37 glucocorticoids in chicken muscle by UHPLC-Q-Orbitrap-MS with parallel reaction monitoring

The quantification capability of high-resolution mass spectrometry (HRMS) has received increasing interest from analysts. In this study, we present a method for analyzing 37 glucocorticoids in chicken muscle using UHPLC-Q-Orbitrap MS with parallel reaction monitoring (PRM). The analytes were extracted using acetonitrile (ACN) containing 0.1% formic acid and subjected to commercial PRiME HLB solid-phase extraction (SPE) cartridge clean-up. Under optimized conditions, the analytes were separated on an analytical column and subsequently detected using a high-resolution hybrid quadrupole/Orbitrap mass spectrometer coupled with PRM scan mode. The Q-Orbitrap with PRM exhibited remarkable sensitivity, with limits of quantification (LOQs) ranging from 0.08 μg kg-1 to 7.59 μg kg-1. To validate the method, we conducted intra- and inter-day tests using a blank matrix sample at different spiking levels. The achieved results demonstrated satisfactory recovery values (74.1-97.5%) and precise results (RSDs < 15%) for all the studied analytes. In application, we found dexamethasone with 6.5 μg kg-1 and fluorometholone with 3.9 μg kg-1 in two chicken samples. These findings suggest that the UHPLC-Q-Orbitrap system, in conjunction with the SPE sample preparation method, has great potential as a routine quantification approach for multiple glucocorticoid residues in chicken samples.

Quantifying Antibiotic Distribution in Solid and Liquid Fractions of Manure Using a Two-Step, Multi-Residue Antibiotic Extraction

Antibiotic distribution and analysis within liquid and solid fractions of manure are highly variable due to each compound’s respective physiochemical properties. This study developed and evaluated a uniform method extracting 10 antibiotics from 4 antibiotic classes (tetracycline, sulfonamides, macrolides, and β-lactam) from unprocessed manure, solid−liquid separated manure, and composted solids. Through systematic manipulation of previously published liquid chromatography tandem mass spectrometry methods; this study developed an extraction protocol with optimized recovery efficiencies for varied manure substrates. The method includes a two-step, liquid-solid extraction using 10 mL of 0.1 M EDTA-McIlviane buffer followed by 10 mL of methanol. Antibiotics recoveries from unprocessed manure, separated liquids, separated solids, and heat-treated solids using the two-step extraction method had relative standard deviations < 30% for all but ceftiofur. Total antibiotic recoveries were 67−131% for tetracyclines, 56% for sulfonamide, 49−53% for macrolides, and 1.3−66% for β-lactams. This is the first study to use one protocol to assess four classes of antibiotics in liquid and solid manure fractions. This study allowed for more precise risk assessment of antibiotic transport in manure waste stream applied to fields as a liquid or solid compost.

Sample preparation techniques for suspect and non-target screening of emerging contaminants

The progress in sensitivity and resolution in mass spectrometers in recent years provides the possibility to detect a broad range of organic compounds in a single procedure. For this reason, suspect and non-target screening techniques are gaining attention since they enable the detection of hundreds of known and unknown emerging contaminants in various matrices of environmental, food and human sources. Sample preparation is a critical step before analysis as it can significantly affect selectivity, sensitivity and reproducibility. The lack of generic sample preparation protocols is obvious in this fast-growing analytical field, and most studies use those of traditional targeted analysis methods. Among them, solvent extraction and solid phase extraction (SPE) are widely used to extract emerging contaminants from solid and liquid sample types, respectively. Sequential solvent extraction and a combination of different SPE sorbents can cover a broad range of chemicals in the samples. Gel permeation chromatography (GPC) and adsorption chromatography, including acidification, are typically used to remove matrix components such as lipids from complex matrices, but usually at the expense of compound losses. Ideally, the purification of samples intended for non-target analysis should be selective of matrix interferences. Recent studies have suggested quality assurance/quality control measures for suspect and non-target screening, based on expansion and extrapolation of target compound lists, but method validations remain challenging in the absence of analytical standards and harmonized sample preparation approaches.

The analysis of acidic and basic non-steroidal anti-inflammatory drugs in milk and muscle samples: a comprehensive analytical approach using UHPLC-MS/MS

In animal husbandry for food production, the administration of non-steroidal anti-inflammatory drugs (NSAIDs) as anti-inflammatory, analgesic, and antipyretic agents, has seen an increase due to raised awareness of animal welfare issues. Residues of NSAIDs may be present in animal products that are intended for human consumption, and since some may pose a certain risk to human health, there is a need to monitor NSAID residues at low levels via routine and targeted surveillance. In analytical chemistry, NSAIDs are usually differentiated using their acid-base properties. Within this study, a method for simultaneous analysis of 27 NSAIDs, including both groups, in milk and muscle samples in 12.5 min is described. Sample processing consisted of enzymatic hydrolysis and acetonitrile extraction, followed by a clean-up of the extract by SPE, and measurement by UHPLC-MS/MS. The in-house validation study (alternative approach), covering trueness, precision, sensitivity, decision limit (CCα), detection capability (CCβ) and matrix effect, was designed and evaluated with the help of validation software to meet the demands of regulatory compliance. The method recovery for milk and muscle matrix was in the range of 98.1% to 106.5% and 98.8% to 102.7%, whereas the CCβ as the parameter for screening analysis, ranged from 0.07 to 46.7 µg/kg and 1.19 to 69.7 µg/kg, and the CCα, as the parameter for confirmatory analysis, from 0.11 to 56.7 µg/kg and 1.12 to 518.6 µg/kg, respectively. The occurrence of NSAID residues in milk and muscle samples was assessed using the developed method within the Croatian National Residue Control Plan, revealing quantifiable residues for diclofenac, ketoprofen, and salicylic acid mostly in milk samples. The most abundant NSAID in analysed samples was salicylic acid, which may be introduced into the food chain and be present in various types of matrices due to its natural occurrence in plants as a phytohormone.

Multiclass, Multiresidue Method for the Quantification and Confirmation of 112 Veterinary Drugs in Game Meat (Bison, Deer, Elk, and Rabbit) by Rapid Polarity Switching Liquid Chromatography-Tandem Mass Spectrometry

An analytical program for multiclass, multiresidue residue analysis to qualitatively and quantitatively determine veterinary drug compounds in game meats by LC-MS/MS has been developed and validated. The method was validated for the analysis of muscle from bison, deer, elk, and rabbit to test for 112 veterinary drug residues from the following drug classes: β-agonists, anthelmintics, anti-inflammatory drugs, corticosteroids, fluoroquinolones, β-lactams, macrolides, nitroimidazoles, phenicols, polypeptides, sulfonamides, tetracyclines, thyreostats, and tranquilizers. Muscle was extracted using a simple and quick procedure based on a solvent extraction with 80% ACN/water and sample cleanup with dispersive solid-phase extraction. The compounds of interest were separated using a Waters HSS T3 column and detected by tandem mass spectrometry with rapid polarity switching to detect both negatively and positively charged ions in a single run. Recoveries were calculated using extracted matrix-matched calibration curves for each type of matrix. The average accuracy of fortified compounds ranged from 95.6 to 101% at the target quantitative validation level in the four matrices. The method was also validated as a qualitative screening method where all sample responses were compared with a single extracted matrix-matched calibrant at the target testing level (5 or 25 ng/g). Samples demonstrating a presumptive positive above the threshold value were re-extracted and analyzed with a five-point matrix-matching extracted calibration curve. Since the beginning of this survey program, 360 samples have been analyzed for veterinary drug residues in game meats. Antibiotic or tranquilizer residues have been identified in deer (chlortetracycline, haloperidol, and tulathromycin) and rabbit (sulfadiazine).

Determination of Polypeptide Antibiotic Residues in Food of Animal Origin by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

A novel UHPLC-MS/MS method for the determination of polypeptide antibiotic residues in animal muscle, milk, and eggs was developed and validated. Bacitracin A, colistin A, colistin B, polymyxin B1, and polymyxin B2 were extracted from the samples with a mixture of acetonitrile/water/ammonia solution 25%, 80/10/10 (v/v/v), and put through further evaporation, reconstitution, and filtration steps. The chromatographic separation was performed on a C18 column in gradient elution mode. Mass spectral acquisitions were performed in selective multiple reaction monitoring mode by a triple quadrupole mass spectrometer. The method was validated according to the criteria of Commission Decision 2002/657/EC. The method quantifies polypeptides in a linear range from 10 to 1000 μg kg⁻¹, where the lowest concentration on the calibration curve refers to the limit of quantification (LOQ). The recoveries ranged from 70 to 99%, the repeatability was below 13%, and within-laboratory reproducibility was lower than 15%. The decision limit (CCα) and detection capability (CCβ) values were calculated, and ruggedness and stability studies were performed, to fulfill the criteria for confirmatory methods. Moreover, the developed method may also be used for screening purposes by its labor efficiency.

Characterisation of hederacoside C metabolites using ultrahigh-performance liquid chromatography quadrupole Orbitrap mass spectrometry based on automatic fragment ion search

INTRODUCTION

Hederacoside C (HDC) is a bioactive natural triterpenoid saponins constituent originating from traditional Chinese medicines, playing an important role in the treatment of acute respiratory infections and chronic inflammatory bronchitis. Meanwhile, it is recognised by Korea as a botanical drug.

OBJECTIVES

In order to develop an integrated template approach to analysing screening and identification of the metabolites of traditional Chinese medicines. This study will provide available information for further pharmaceutical studies of HDC and other triterpene saponins.

METHODOLOGY

An analysis strategy based on ultrahigh-performance liquid chromatography quadrupole Orbitrap mass spectrometry (UHPLC-Q-Orbitrap-MS) technique combined with automatic fragment ion search (FISh) was firstly exploited for the characterisation metabolites of HDC in vivo and in vitro. Accurate full mass scan combined with an on-line FISh annotations approach was developed to rapidly identify all the potential metabolites of HDC. Furthermore, FISh accurately located the structure of the target compound in a large number of mass spectral data.

RESULTS

A total of 34 metabolites were detected and tentatively identified by analysing comprehensive biological samples. The results clearly demonstrated that HDC underwent general metabolic reactions including dealkylation, reduction, oxidation, desaturation, dehydration, cysteine conjugation, GSH conjugation, taurine conjugation, and glycine conjugation to produce 26 phase I and eight phase II metabolites.

CONCLUSION

In the present study, UHPLC-Q-Exactive Orbitrap MS technique combined with FISh provided a rapid and efficient platform to characterise metabolites of HDC in vivo and in vitro. The proposed method could develop an integrated template approach to screen and identify the constituents and metabolites of traditional Chinese medicines.

Comparison of Solid-Phase Microextraction to Solvent Extraction and QuEChERS for Quantitative Analysis of Veterinary Drug Residues in Chicken and Beef Matrices

A fully automated high-throughput method using solid-phase microextraction (SPME) was developed and validated for quantitative analysis of more than 100 veterinary drugs in chicken and beef tissue. The work also encompassed a comparison of the SPME method to two well-documented sample preparation procedures, solvent extraction (SE) and quick, easy, cheap, effective, rugged, and safe (QuEChERS). SPME showed considerably less matrix effects, with only two compounds showing significant matrix effects in comparison to 30% of analytes in QuEChERS and 42% in SE in beef tissue. Excellent accuracy and precision results were achieved with all methods in the chicken matrix, with more than 91% of analytes falling within the 70-120% range of their true concentrations and relative standard deviation of ≤25% at 0.75X and 1.5X, where X is the maximum residue level. Similar results were achieved in beef tissue. All methods were able to meet regulatory limit of quantitation levels for the majority of target analytes.

QuEChERS extraction coupled to GC-MS for a fast determination of polychlorinated biphenyls in breast milk from Polish women

Polychlorinated biphenyls (PCBs) in breast milk has been determined. Therefore, it was necessary to develop and adapt an analytical method to analyze PCB compounds. The whole procedure was applied to 31 breast milk samples, which were collected from Polish mothers. The QuEChERS method was optimized as a fast and cheap sample preparation method. The procedure allowed us to obtain recovery values between 96.46% and 119.98% with acceptable relative standard deviations (3.36-12.71%). Gas chromatography with mass spectrometry (GC-MS) was used for final determination. The method was validated using parameters such as linearity, limit of detection and quantification, intra-day precision, and reproducibility. The mean concentration of ∑iPCBs in this study was 30.94 ng/g of lipid. Assigned daily intake of PCBs was lower than the tolerable daily intake, which shows that the analyzed milk is safe to the infants. However, the monitoring of PCBs in milk is still important, and the QuEChERS method with GC-MS can be an effective tool for tracking organic impurities in breast milk.

A rapid and reliable assay to determine flumequine, marbofloxacin, difloxacin, and sarafloxacin in commonly consumed meat by micellar liquid chromatography

BACKGROUND

Micellar liquid chromatography - fluorescence detection was used to determine the antibiotics flumequine, marbofloxacin, difloxacin, and sarafloxacin in porcine, bovine, poultry, ovine, caprine, rabbit, and equine meat, to verify compliance with EU Regulation 37/2010 with regard to the occurrence of veterinary drugs in food.

RESULTS

The analytes were isolated from the matrix by ultrasonication-assisted leaching in a micellar solution, and the supernatant was filtered and directly injected. The fluoroquinolones were resolved in < 19 min using a C18 column, with an isocratic mobile phase of 0.05 mol L^-1 sodium dodecyl sulfate - 8% 1-butanol - 0.5% triethylamine buffered at pH 3. The limits of quantification (0.01-0.05 mg kg^-1 ) were below the maximum residue limits (0.15-0.4 mg kg^-1 ). The method was validated by EU Commission Decision 2002/657/EC guidelines.

CONCLUSION

The method shows practical advantages such as simplicity, low cost, eco-friendliness, safety, and applicability for routine analysis, and is useful for surveillance programs. © 2018 Society of Chemical Industry.

Development and validation of a fully automated solid phase microextraction high throughput method for quantitative analysis of multiresidue veterinary drugs in chicken tissue

This paper presents the development and validation of a fully automated, high-throughput multiclass, multiresidue method for quantitative analysis of 77 veterinary drugs in chicken muscle via direct immersion solid phase microextraction (DI-SPME) and ultra-high pressure liquid chromatography-electrospray ionization - tandem mass spectrometry (UHPLC-ESI-MS/MS). The selected drugs represent more than 12 different classes of drugs characterized by varying physical and chemical properties. A Hydrophilic-lipophilic balance (HLB)/polyacrylonitrile (PAN) extraction phase, prepared using HLB particles synthesized in-house, yielded the best extraction/desorption performance among four different SPME extraction phases evaluated in the current work. The developed SPME method was optimized in terms of SPME coating and geometry, desorption solvent, extraction and rinsing conditions, and extraction and desorption times. Multivariate analysis was performed to determine the optimal desorption solvent for the proposed application. The developed method was validated according to the Food and Drug Administration (FDA) guidelines, taking into account Canadian maximum residue limits (MRLs) and US maximum tolerance levels for veterinary drugs in meat. Method accuracy ranged from 80 to 120% for at least 73 compounds, with relative standard deviation of 1-15%. Inter-day precision ranged from 4 to 15% for 70 compounds. Determination coefficients values were higher than 0.991 for all compounds under study with no significant lack of fit (p > 0.05) at the 5% level. In terms of limits of quantitation, the method was able to meet both Canadian and US regulatory levels for all compounds under study.

A review of the pharmaceutical exposome in aquatic fauna

Pharmaceuticals have been considered 'contaminants of emerging concern' for more than 20 years. In that time, many laboratory studies have sought to identify hazard and assess risk in the aquatic environment, whilst field studies have searched for targeted candidates and occurrence trends using advanced analytical techniques. However, a lack of a systematic approach to the detection and quantification of pharmaceuticals has provided a fragmented literature of serendipitous approaches. Evaluation of the extent of the risk for the plethora of human and veterinary pharmaceuticals available requires the reliable measurement of trace levels of contaminants across different environmental compartments (water, sediment, biota - of which biota has been largely neglected). The focus on pharmaceutical concentrations in surface waters and other exposure media have therefore limited both the characterisation of the exposome in aquatic wildlife and the understanding of cause and effect relationships. Here, we compile the current analytical approaches and available occurrence and accumulation data in biota to review the current state of research in the field. Our analysis provides evidence in support of the 'Matthew Effect' and raises critical questions about the use of targeted analyte lists for biomonitoring. We provide six recommendations to stimulate and improve future research avenues.

Freeze-thaw approach: A practical sample preparation strategy for residue analysis of multi-class veterinary drugs in chicken muscle

Seven drugs from different classes, namely, fluoroquinolones (enrofloxacin, ciprofloxacin, sarafloxacin), sulfonamides (sulfadimidine, sulfamonomethoxine), and macrolides (tilmicosin, tylosin), were used as test compounds in chickens by oral administration, a simple extraction step after cryogenic freezing might allow the effective extraction of multi-class veterinary drug residues from minced chicken muscles by mix vortexing. On basis of the optimized freeze-thaw approach, a convenient, selective, and reproducible liquid chromatography with tandem mass spectrometry method was developed. At three spiking levels in blank chicken and medicated chicken muscles, average recoveries of the analytes were in the range of 71-106 and 63-119%, respectively. All the relative standard deviations were <20%. The limits of quantification of analytes were 0.2-5.0 ng/g. Regardless of the chicken levels, there were no significant differences (P > 0.05) in the average contents of almost any of the analytes in medicated chickens between this method and specific methods in the literature for the determination of specific analytes. Finally, the developed method was successfully extended to the monitoring of residues of 55 common veterinary drugs in food animal muscles.

Isolation and determination of ivermectin in post-mortem and in vivo tissues of dung beetles using a continuous solid phase extraction method followed by LC-ESI+-MS/MS

A new analytical method based on solvent extraction, followed by continuous solid-phase extraction (SPE) clean-up using a polymeric sorbent, was demonstrated to be applicable for the detection of ivermectin in complex biological matrices of dung beetles (hemolymph, excreta or dry tissues) using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI⁺–MS/MS). Using a signal-to-noise ratio of 3:1, the limit of detection (LOD) in the insect matrices at trace levels was 0.01 ng g^–1 and the limit of quantification (LOQ) was 0.1 ng g^–1. The proposed method was successfully used to quantitatively determine the levels of ivermectin in the analysis of small samples in in vivo and post mortem samples, demonstrating the usefulness for quantitative analyses that are focused on future pharmacokinetic and bioavailability studies in insects and the establishment of a new protocol to study the impact of ivermectin on non-target arthropods such as dung beetles and other insects that are related with the “dung community”. Because satisfactory precision and accuracy values were obtained in both in vivo matrices, we suggest that the method can be consistently used for quantitative determinations that are focused on future pharmacokinetic and bioavailability studies in insects. Furthermore, this new analytical method was successfully applied to biological samples of dead dung beetles from the field suggesting that the method can be used to establish a new routine analysis of ivermectin residues in insect carcasses that is applied to complement typical mortality tests.

Veterinary pharmaceuticals in aqueous systems and associated effects: an update

Environmental studies have shown that pharmaceuticals can contaminate aqueous matrices, such as groundwater, surface water, sediment as well as aquatic flora and fauna. Effluents from sewage and wastewater treatment plants, pharmaceutical industries and hospitals have been implicated in such contamination. Recent studies have however revealed significant concentrations of pharmaceuticals in wastewater from animal facilities in proximal aquatic habitats. Furthermore, epidemiological studies have shown a consistent positive correlation between exposure to some drugs of veterinary importance and increased adverse effects in aquatic biota largely due to induction of endocrine disruption, antibiotic resistance, neurotoxicity, genotoxicity and oxidative stress. The aquatic habitats and associated biota are important in the maintenance of global ecosystem and food chain. For this reason, anything that compromises the integrity and functions of the aquatic environment may lead to major upset in the world's ecosystems. Therefore, knowledge about this route of exposure cannot be neglected and monitoring of their occurrence in the environment is required. This review focuses on scientific evidence that link the presence of pharmaceuticals in aqueous matrices to animal production facilities and presents means to reduce the occurrence of veterinary pharmaceutical residues in the aquatic habitats.

A global inter-laboratory study to assess acquisition modes for multi-compound confirmatory analysis of veterinary drugs using liquid chromatography coupled to triple quadrupole, time of flight and orbitrap mass spectrometry

According to EU legislation a confirmatory method used for residue analysis should be able to confirm the identity of a compound beyond reasonable doubt. To provide an adequate instrumental set-up, Commission Decision 2002/657/EC introduced the concept of "identification points". A second aspect to assure unequivocal confirmation, is the establishment of ion ratio and retention time criteria. Currently, the gold standard for confirmatory analysis of most veterinary drug residues is liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS) in selected reaction monitoring (SRM) acquisition mode, isolating one precursor ion and monitoring two a priori selected product ions, yielding 4 identification points. We comprehensively evaluated the use of different low and high resolution LC-MS(/MS) techniques and acquisition modes with respect to the selectivity of 100 veterinary drugs in liver, muscle and urine extracts aiming to critically review the currently established identification points system. A comparison among MS/MS in SRM mode with high resolution mass spectrometry (HRMS) in full scan, all ion fragmentation and targeted MS/MS was made based on a unique inter-laboratory study, which comprises 21 laboratories from four different continents and equipment from all major vendors. In total 186 samples were analysed yielding results for 9282 analyte/matrix combinations. It was observed that the false positive rate approximately doubles if no ion ratio criterion is applied indicating that this criterion is important to prevent false positive results. Full scan HRMS analysis, only monitoring the molecular ion and allowing a ±5 ppm mass tolerance is, in general, less selective than low resolution MS/MS using SRM, and thus full scan alone is considered not sufficient for confirmatory analysis. Furthermore, even though the number of data on all ion fragmentation and targeted MS/MS at high resolution was limited, based on the data obtained, it was observed that the acquisition mode as well as the mass resolution needed, very much depend on the matrix and the compound itself. For complex matrix extracts and non-selective compounds (worst-case situation), only targeted MS/MS, monitoring the precursor ion and a single product ion in HR-MS using a maximum of ±5 ppm mass deviation, leads to comparable selectivity and false positive and negative rate as SRM monitoring two product ions in LR-MS. We conclude that the currently applied identification point system as established in commission decision 2002/657/EC should be revised with respect to the allocation of identification points.

Development and validation of rapid multiresidue and multi-class analysis for antibiotics and anthelmintics in feed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

A new multi-residue method for the analysis of veterinary drugs, namely amoxicillin, chlortetracycline, colistins A and B, doxycycline, fenbendazole, flubendazole, ivermectin, lincomycin, oxytetracycline, sulfadiazine, tiamulin, tilmicosin and trimethoprim, was developed and validated for feed. After acidic extraction, the samples were centrifuged, purified by SPE and analysed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. Quantitative validation was done in accordance with the guidelines laid down in European Commission Decision 2002/657/CE. Matrix-matched calibration with internal standards was used to reduce matrix effects. The target level was set at the authorised carryover level (1%) and validation levels were set at 0.5%, 1% and 1.5%. Method performances were evaluated by the following parameters: linearity (0.986 < R(2) < 0.999), precision (repeatability < 12.4% and reproducibility < 14.0%), accuracy (89% < recovery < 107%), sensitivity, decision limit (CCα), detection capability (CCβ), selectivity and expanded measurement uncertainty (k = 2).This method has been used successfully for three years for routine monitoring of antibiotic residues in feeds during which period 20% of samples were found to exceed the 1% authorised carryover limit and were deemed non-compliant.

Metabolic profile modifications in milk after enrofloxacin administration studied by liquid chromatography coupled with high resolution mass spectrometry

High resolution accurate mass spectrometry (HRMS) operating in full scan MS mode was used in the search and identification of metabolites in raw milk from cows medicated with enrofloxacin. Data consisting of m/z features were taken throughout the entire chromatogram of milk samples from medicated animals and were compared with blank samples. Twenty six different compounds were identified. Some of them were attributed to structures related to enrofloxacin while others were dipeptides or tripeptides. Additionally, enrofloxacin was administered in a controlled treatment for three days. Milk was collected daily from the first day of treatment and until four days after in the search for the identified compounds. The obtained data were chemometrically treated by Principal Component Analysis. Samples were classified by this method into three different groups corresponding to days 1-2, day 3 and days 4-7 considering the different concentration profile evolution of metabolites during the days studied. Tentative metabolic pathways were designed to rationalize the presence of the newly identified compounds.

Polymeric ionic liquid modified graphene oxide-grafted silica for solid-phase extraction to analyze the excretion-dynamics of flavonoids in urine by Box-Behnken statistical design

A solid-phase extraction method for the efficient analysis of the excretion-dynamics of flavonoids in urine was established and described. In this work, in situ surface radical chain-transfer polymerization and in situ anion exchange were utilized to tune the extraction performance of poly(1-vinyl-3-hexylimidazolium bromide)-graphene oxide-grafted silica (poly(VHIm(+)Br(-))@GO@Sil). Graphene oxide (GO) was first coated onto the silica using a layer-by-layer fabrication method, and then the anion of poly(VHIm(+)Br(-))@GO@Sil was changed into hexafluorophosphate (PF6(-)) by in situ anion exchange. The interaction energies between two PILs and four flavonoids were calculated with the Gaussian09 suite of programs. A Box-Behnken design was used for the optimization of four greatly influential parameters after single-factor experiments to obtain more accurate and precise results. Coupled to high performance liquid chromatography, the poly(VHIm(+)PF6(-))@GO@Sil method showed acceptable extraction recoveries for the four flavonoids, with limits of detection in the range of 0.1-0.5μgL(-1), and wide linear ranges with correlation coefficients (R) ranging from 0.9935 to 0.9987. Under the optimum conditions, the proposed method was applied to analyze the urines collected from a healthy volunteer. The excretion amount-time profiles revealed that 4-15h was the main excretion time for the detected flavonoids. The results indicated that the newly developed method offered the advantages of being feasible, green and cost-effective, and could be successfully applied to the extraction and enrichment of flavonoids in human body systems allowing the study of the metabolic kinetics.

Glyoxal-Urea-Formaldehyde Molecularly Imprinted Resin as Pipette Tip Solid-Phase Extraction Adsorbent for Selective Screening of Organochlorine Pesticides in Spinach

A new kind of glyoxal-urea-formaldehyde molecularly imprinted resin (GUF-MIR) was synthesized by a glyoxal-urea-formaldehyde (GUF) gel imprinting method with 4,4'-dichlorobenzhydrol as a dummy template. The obtained GUF-MIR was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) and applied as a selective adsorbent of miniaturized pipet tip solid-phase extraction (PT-SPE) for the separation and extraction of three organochlorine pesticides (dicofol (DCF), dichlorodiphenyl dichloroethane (DDD), and tetradifon) in spinach samples. The proposed pretreatment procedures of spinach samples involved only 5.0 mg of GUF-MIR, 0.7 mL of MeOH-H2O (1:1, v/v) (washing solvent), and 0.6 mL of cyclohexane-ethyl acetate (9:1, v/v) (elution solvent). In comparison with other adsorbents (such as silica gel, C18, NH2-silica gel, and neutral alumina (Al2O3-N)), GUF-MIR showed higher adsorption and purification capacity for DCF, DDD, and tetradifon in aqueous solution. The average recoveries at three spiked levels ranged from 89.1% to 101.9% with relative standard deviations (RSDs) ≤ 7.1% (n = 3). The presented GUF-MIR-PT-SPE method combines the advantages of molecularly imprinted polymers (MIPs), GUF, and PT-SPE and can be used in polar solutions with high affinity and selectivity to the analytes in complex samples.

The assessment of selectivity in different Quadrupole-Orbitrap mass spectrometry acquisition modes

Selectivity of the confirmation of identity in liquid chromatography (tandem) mass spectrometry using Q-Orbitrap instrumentation was assessed using different acquisition modes based on a representative experimental data set constructed from 108 samples, including six different matrix extracts and containing over 100 analytes each. Single stage full scan, all ion fragmentation, and product ion scanning were applied. By generating reconstructed ion chromatograms using unit mass window in targeted MS(2), selected reaction monitoring (SRM), regularly applied using triple-quadrupole instruments, was mimicked. This facilitated the comparison of single stage full scan, all ion fragmentation, (mimicked) SRM, and product ion scanning applying a mass window down to 1 ppm. Single factor Analysis of Variance was carried out on the variance (s(2)) of the mass error to determine which factors and interactions are significant parameters with respect to selectivity. We conclude that selectivity is related to the target compound (mainly the mass defect), the matrix, sample clean-up, concentration, and mass resolution. Selectivity of the different instrumental configurations was quantified by counting the number of interfering peaks observed in the chromatograms. We conclude that precursor ion selection significantly contributes to selectivity: monitoring of a single product ion at high mass accuracy with a 1 Da precursor ion window proved to be equally selective or better to monitoring two transition products in mimicked SRM. In contrast, monitoring a single fragment in all ion fragmentation mode results in significantly lower selectivity versus mimicked SRM. After a thorough inter-laboratory evaluation study, the results of this study can be used for a critical reassessment of the current identification points system and contribute to the next generation of evidence-based and robust performance criteria in residue analysis and sports doping.