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- New method for determination of (E)resveratrol in wine based on microextraction using packed sorbent and ultra-performance liquid chromatographyPublication . Gonçalves, João; Câmara, José S.An ultra-fast and improved analytical methodology based on microextraction by packed sorbent (MEPS) combined with ultra-performance LC (UPLC) was developed and validated for determination of (E)-resveratrol in wines. Important factors affecting the performance of MEPS such as the type of sorbent material (C2, C8, C18, SIL, and M1), number of extraction cycles, and sample volume were studied. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (50–250mL) in one extraction cycle (extract–discard) and in a short time period (about 3 min for the entire sample preparation step). (E)-Resveratrol was eluted by 1 250mL of the mixture containing 95% methanol and 5% water, and the separation was carried out on a highstrength silica HSS T3 analytical column (100 mm 2.1 mm, 1.8mm particle size) using a binary mobile phase composed of aqueous 0.1% formic acid (eluent A) and methanol (eluent B) in the gradient elution mode (10 min of total analysis). The method was fully validated in terms of linearity, detection (LOD) and quantification (LOQ) limits, extraction yield, accuracy, and inter/intra-day precision, using a Madeira wine sample (ET) spiked with (E)-resveratrol at concentration levels ranging from 5 to 60mg/mL. Validation experiments revealed very good recovery rate of 9575.8% RSD, good linearity with r2 values 40.999 within the established concentration range, excellent repeatability (0.52%), and reproducibility (1.67%) values (expressed as RSD), thus demonstrating the robustness and accuracy of the MEPSC8/UPLC-photodiode array (PDA) method. The LOD of the method was 0.21mg/mL, whereas the LOQ was 0.68mg/mL. The validated methodology was applied to 30 commercial wines (24 red wines and six white wines) from different grape varieties, vintages, and regions. On the basis of the analytical validation, the MEPSC8/UPLC-PDA methodology shows to be an improved, sensitive, and ultra-fast approach for determination of (E)-resveratrol in wines with high resolving power within 6 min.
- Development of MEPS–UHPLC/PDA methodology for the quantification of clozapine, risperidone and their major active metabolites in human urinePublication . Gonçalves, João L.; Alves, Vera L.; Conceição, Carlota J.F.; Teixeira, Helena M.; Câmara, José S.A new, fast and reliable methodology using a digitally controlled microextraction by packed sorbent (MEPS), followed by ultrahigh pressure liquid chromatography (UHPLC) separation combined with a photodiode array (PDA) detection, has been developed and validated for the simultaneous determination of clozapine and risperidone, and their active metabolites, in urine samples. Important parameters affecting MEPS performance, including type of sorbent material (C2, C8, C18, SIL, M1, R-AX, R-CX, PGC, PEP, HLB-DVB and H-DVB), elution solvent system, number of extraction cycles, sample volume, elution volume, and sample pH, were evaluated. The optimal experimental conditions involved the loading of 500 μl of sample through a C18 sorbent in a five extraction cycles and in a short time period (5 min for the entire sample preparation step). The obtained extract was analyzed by UHPLC, using a binary mobile phase, composed of aqueous 0.1% formic acid and methanol in the gradient elution mode (10 min total analysis). Good results were obtained under the optimized conditions, in terms of linearity with correlation coefficients (r2) values higher than 0.9986. Low detection limits, ranging between 0.052 and 0.055 μg ml− 1 were achieved, whereas the lowest quantification limit was 0.1 μg ml− 1, corresponding to the lowest concentration of the standard curve. Satisfactory results were found with accuracy values ranging from 83% to 116%, and with precision results from 2.65% to 18%. Recoveries ranged between 76% and 96%, which was in agreement with results reported by other studies.
- A sensitive microextraction by packed sorbent-based methodology combined with ultra-high pressure liquid chromatography as a powerful technique for analysis of biologically active flavonols in winesPublication . Silva, Catarina L.; Gonçalves, João L.; Câmara, José S.A new approach based on microextraction by packed sorbent (MEPS) and reversed-phase high-throughput ultra high pressure liquid chromatography (UHPLC) method that uses a gradient elution and diode array detection to quantitate three biologically active flavonols in wines, myricetin, quercetin, and kaempferol, is described. In addition to performing routine experiments to establish the validity of the assay to internationally accepted criteria (selectivity, linearity, sensitivity, precision, accuracy), experiments are included to assess the effect of the important experimental parameters such as the type of sorbent material (C2, C8, C18, SIL, and C8/SCX), number of extraction cycles (extract-discard), elution volume, sample volume, and ethanol content, on the MEPS performance. The optimal conditions of MEPS extraction were obtained using C8 sorbent and small sample volumes (250 μL) in five extraction cycle and in a short time period (about 5 min for the entire sample preparation step). Under optimized conditions, excellent linearity View the MathML source(Rvalues2>0.9963), limits of detection of 0.006 μg mL−1 (quercetin) to 0.013 μg mL−1 (myricetin) and precision within 0.5–3.1% were observed for the target flavonols. The average recoveries of myricetin, quercetin and kaempferol for real samples were 83.0–97.7% with relative standard deviation (RSD, %) lower than 1.6%. The results obtained showed that the most abundant flavonol in the analyzed samples was myricetin (5.8 ± 3.7 μg mL−1). Quercetin (0.97 ± 0.41 μg mL−1) and kaempferol (0.66 ± 0.24 μg mL−1) were found in a lower concentration. The optimized MEPSC8 method was compared with a reverse-phase solid-phase extraction (SPE) procedure using as sorbent a macroporous copolymer made from a balanced ratio of two monomers, the lipophilic divinylbenzene and the hydrophilic N-vinylpyrrolidone (Oasis HLB) were used as reference. MEPSC8 approach offers an attractive alternative for analysis of flavonols in wines, providing a number of advantages including highest extraction efficiency (from 85.9 ± 0.9% to 92.1 ± 0.5%) in the shortest extraction time with low solvent consumption, fast sample throughput, more environmentally friendly and easy to perform.
- Effectiveness of high-throughput miniaturized sorbent- and solid phase microextraction techniques combined with gas chromatography–mass spectrometry analysis for a rapid screening of volatile and semi-volatile composition of wines: a comparative studyPublication . Mendes, Berta Rodrigues; Gonçalves, João; Câmara, José S.In this study the feasibility of different extraction procedures was evaluated in order to test their potential for the extraction of the volatile (VOCs) and semi-volatile constituents (SVOCs) from wines. In this sense, and before they could be analysed by gas chromatography–quadrupole first stage masss spectrometry (GC–qMS), three different high-throughput miniaturized (ad)sorptive extraction techniques, based on solid phase extraction (SPE), microextraction by packed sorbents (MEPS) and solid phase microextraction (SPME), were studied for the first time together, for the extraction step. To achieve the most complete volatile and semi-volatile signature, distinct SPE (LiChrolut EN, Poropak Q, Styrene-Divinylbenzene and Amberlite XAD-2) and MEPS (C2, C8, C18, Silica and M1 (mixed C8-SCX)) sorbent materials, and different SPME fibre coatings (PA, PDMS, PEG, DVB/CAR/PDMS, PDMS/DVB, and CAR/PDMS), were tested and compared. All the extraction techniques were followed by GC–qMS analysis, which allowed the identification of up to 103 VOCs and SVOCs, distributed by distinct chemical families: higher alcohols, esters, fatty acids, carbonyl compounds and furan compounds. Mass spectra, standard compounds and retention index were used for identification purposes. SPE technique, using LiChrolut EN as sorbent (SPELiChrolut EN), was the most efficient method allowing for the identification of 78 VOCs and SVOCs, 63 and 19 more than MEPS and SPME techniques, respectively. In MEPS technique the best results in terms of number of extractable/identified compounds and total peak areas of volatile and semi-volatile fraction, were obtained by using C8 resin whereas DVB/CAR/PDMS was revealed the most efficient SPME coating to extract VOCs and SVOCs from Bual wine. Diethyl malate (18.8 ± 3.2%) was the main component found in wine SPELiChrolut EN extracts followed by ethyl succinate (13.5 ± 5.3%), 3-methyl-1-butanol (13.2 ± 1.7%), and 2-phenylethanol (11.2 ± 9.9%), while in SPMEDVB/CAR/PDMS technique 3-methyl-1-butanol (43.3 ± 0.6%) followed by diethyl succinate (18.9 ± 1.6%), and 2-furfural (10.4 ± 0.4%), are the major compounds. The major VOCs and SVOCs isolated by MEPSC8 were 3-methyl-1-butanol (26.8 ± 0.6%, from wine total volatile fraction), diethyl succinate (24.9 ± 0.8%), and diethyl malate (16.3 ± 0.9%). Regardless of the extraction technique, the highest extraction efficiency corresponds to esters and higher alcohols and the lowest to fatty acids. Despite some drawbacks associated with the SPE procedure such as the use of organic solvents, the time-consuming and tedious sampling procedure, it was observed that SPELiChrolut EN, revealed to be the most effective technique allowing the extraction of a higher number of compounds (78) rather than the other extraction techniques studied.
- Current trends on microextraction by packed sorbent – fundamentals, application fields, innovative improvements and future applicationsPublication . Pereira, Jorge A. M.; Gonçalves, João; Porto-Figueira, Priscilla; Figueira, José A.; Alves, Vera; Perestrelo, Rosa; Medina, Sonia; Câmara, José S.MEPS, the acronym of microextraction by packed sorbent, is a simple, fast and user- and environmen tally-friendly miniaturization of the popular solid-phase extraction technique (SPE). In fact, it has been widely shown that MEPS can easily replace SPE for most, if not all, previous applications. It can attain this with obvious gains in sample and solvent usage, which is greatly reduced without compromising the extraction efficiency. Furthermore, MEPS can be operated with semiautomatic electronic syringes, making it very reliable and versatile, particularly to handle very low and very high sample volumes. This review will focus on the strengths and weaknesses of this technique and the different MEPS architectures commer cially available in the context of the MEPS applications reported in the last five years. Additionally, innova tive improvements will be highlighted, particularly those related with new applications and recent MEPS configurations and sorbents, such as the controlled directional flow or the innovative µSPEed variant.
- An attractive, sensitive and high-throughput strategy based on microextraction by packed sorbent followed by UHPLC-PDA analysis for quantification of hydroxybenzoic and hydroxycinnamic acids in winesPublication . Gonçalves, João; Silva, Catarina L.; Castilho, Paula C.; Câmara, José S.An attractive, fast, low-consumption and very promising high-throughput strategy based on microextraction by packed sorbent (MEPS), and reversed phase ultra-high pressure liquid chromatography (UHPLC), was developed and validated for the determination and quantification of hydroxybenzoic (gallic acid, protocatechuic acid, gentisic acid, vanillic acid, syringic acid), and hydroxycinnamic acids (p-coumaric acid, m-coumaric acid, o-coumaric acid, ferrulic acid and cinnamic acid) in wines. Important factors affecting the performance of MEPS such as the type of sorbent material (C2, C8, C18, SIL and C8/SCX), number of extraction cycles (extract–discard), sample volume and elution volume were tested and optimized. The optimal MEPS extraction conditions were obtained using C8 phase as sorbent and 50 μL of the sample in five extraction cycles. The analytes were separated on a new Trifunctional High Strength Silica analytical column (HSS T3; 100% silica particle), specially designed for polar compounds, using a binary mobile phase composed of aqueous 0.1% formic acid (eluent A) and methanol (eluent B) in the gradient elution mode (10 min of total analysis). This new stationary phase, proved to be an excellent alternative to conventional C18 columns for the determination of benzoic and cinnamic acids derivatives in wines. The analytical method was fully validated in terms of linearity, limits of detection (LOD), limits of quantification (LOQ), extraction yield, accuracy and inter/intra-day precision, using a synthetic wine spiked with hydroxybenzoic and hydroxycinnamic acids, and demonstrated good linearity with r2‐values > 0.998 within the established concentration range (0.2–40 μg mL− 1). Under the optimized conditions, LOD of 0.01–0.2 μg mL− 1, LOQ of 0.03–0.7 μg mL− 1, and precision, expressed as the relative standard deviation (RSD %), within 0.3–6% were observed. The proposed method was also applied to the analysis of hydroxybenzoic and hydroxycinnamic acids in red and white wines and recoveries of 80–100% and 77–99%, respectively, were obtained. The new approach offers an attractive alternative for analysis of phenolic acids from wine samples, providing a number of advantages including decreased sample preparation, faster sample throughput and easy to perform as compared to traditional methodologies. Moreover it could potentially be extended to other extraction media.