Blanca Gallo

A review of solid phase extraction : basic principles and new developments

SummaryA review with 178 references on the basic principles and recent developments in the solid phase extraction is presented. New solid phases, chromatographic modes, experimental configurations and off-line and on-line automated devices are discussed.

A general analytical strategy for the characterization of phenolic compounds in fruit juices by high-performance liquid chromatography with diode array detection coupled to electrospray ionization and triple quadrupole mass spectrometry

In the present study, a methodology based on liquid chromatography with diode array detection (HPLC/DAD) coupled to an electrospray ionization (ESI) interface and a triple quadrupole mass spectrometer for the simultaneous identification of phenolic compounds in fruit juices has been developed. 72 available phenolic compound standards from diverse families present in fruits have been studied in order to analyze their fragmentation pattern. As a result, a general strategy for the characterization of unknown phenolic compounds in fruit juices was designed: (i) taking into account its UV-visible spectrum and elution order, assign the unknown polyphenol to a polyphenol class, (ii) identify the quasi-molecular ion using positive and negative MS spectra, being supported by adducts generated with solvent or sodium and molecular complexes, (iii) determinate the pattern of glycosylation in positive mode using ESI(+)-CID MS/MS product ion scan experiments, selecting the quasi-molecular ion as precursor ion, and finally, (iv) study the identity of the aglycone through ESI(+)-CID MS/MS product ion spectra from the protonated aglycone, [Y(0)](+). This strategy was successfully employed for the characterization of known and unknown phenolic compounds in juices from 17 different fruits.

Pressurized liquid extraction for the determination of polyphenols in apple

Pressurized liquid extraction (PLE) has been optimized for the determination of polyphenols in Golden Delicious apple peel and pulp. The effects of experimental variables, such as solvent composition, temperature, static extraction time and pressure, on PLE efficiency have been studied. Once the optimum conditions were established the recovery and the precision of the method for each analyte was tested by means of repeated analysis.

Solid-phase clean-up in the liquid chromatographic determination of polycyclic aromatic hydrocarbons in edible oils.

A solid-phase extraction (SPE) method for sample clean-up, followed by reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection is reported for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils. The effects of experimental variables, such as washing and elution solvents, sample solvent and drying time have been studied using C18 cartridges. Recoveries and selectivity using other sorbent materials (C8, C2, CH, PH and NH2) were also examined, with C18 being the best one. The recoveries ranged between 50 and 103% depending on the molecular mass of the PAH. The limits of quantitation were lower than 1 ng/g for most PAHs and good precision was achieved. The method was validated using certified reference materials.

New features on the fragmentation and differentiation of C-glycosidic flavone isomers by positive electrospray ionization and triple quadrupole mass spectrometry.

Six flavone mono-C-glucosides, four standards (beta-D-glucopyranosyl-(1 --> C-6)- and -(1 --> C-8)- apigenin and luteolin) and two others from lemon juice (beta-D-glucopyranosyl-(1 --> C-6)- and -(1 --> C-8)-diosmetin) have been studied in order to analyze their fragmentation patterns. Initial separation was carried out using high-performance liquid chromatography with diode-array detection (HPLC/DAD) coupled to an electrospray ionization (ESI) interface and a triple quadrupole mass spectrometer. Several systematic differences between collision-induced dissociation tandem mass (CID-MS/MS) spectra of C-6- and C-8-isomers have been found and some general guidelines and two new diagnostic product ions have been proposed for the differentiation of C-6- and C-8-flavonoid glycosides. These results have been successfully applied to the characterization of two flavone C-glycosides found in lemon juice, and mass spectra of a flavone di-C-glycoside detected in lemon juice have been studied and interpreted.

A validated solid-liquid extraction method for the HPLC determination of polyphenols in apple tissues Comparison with pressurised liquid extraction

A solid-liquid extraction procedure followed by reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with a photodiode array detector (DAD) for the determination of polyphenols in freeze-dried apple peel and pulp is reported. The extraction step consists in sonicating 0.5g of freeze-dried apple tissue with 30mL of methanol-water-acetic acid (30:69:1, v/v/v) containing 2g of ascorbic acid/L, for 10min in an ultrasonic bath. The whole method was validated, concluding that it is a robust method that presents high extraction efficiencies (peel: >91%, pulp: >95%) and appropriate precisions (within day: R.S.D. (n = 5) <5%, and between days: R.S.D. (n = 5) <7%) at the different concentration levels of polyphenols that can be found in apple samples. The method was compared with one previously published, consisting in a pressurized liquid extraction (PLE) followed by RP-HPLC-DAD determination. The advantages and disadvantages of both methods are discussed.

Feasibility study of FT-MIR spectroscopy and PLS-R for the fast determination of anthocyanins in wine.

The feasibility of using Fourier Transform Mid-Infrared Spectroscopy (FT-MIR) combined with Partial Least Squares Regression (PLS-R) for the determination of 12 anthocyanins (3-O-glucosides of delphinidin, cyanidin, petunidin, peonidin and malvidin, as well as acetic acid esters and p-coumaric acid esters of petunidin, peonidin and malvidin and caffeic acid ester of malvidin) and three sums (sum of non-acylated anthocyanins, sum of acetylated anthocyanins and sum of coumaroylated anthocyanins), in red wines has been tested. Reference values of anthocyanin concentrations by reverse-phase High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) were used to calibrate the models. A Principal Component Analysis (PCA) was applied to these reference values and a differentiation of wine samples by wine type (young wines of 2005, young wines of 2004 and crianza and reserva wines) has been possible. A calibration model using PLS-R was built with 153 samples of Rioja wines and the prediction of the anthocyanin concentrations using this model was evaluated by internal and external validation sample sets. Most of the anthocyanins and their sums have been predicted with a Standard Error of Prediction (SEP) of 15-30% for young wines recently bottled. However, for young wines after one year of being bottled, and for crianza and reserva wines, these errors were unacceptable. The obtained results suggest that the model built for FT-IR instrument calibration is a useful tool for a quick determination of the anthocyanin content of young wines of the current vintage, but a careful robust external validated calibration of the technique is necessary in order to maintain the prediction errors within controlled limits.

Solid-phase extraction with liquid chromatography and ultraviolet detection for the assay of antidepressant drugs in human plasma.

A solid-phase extraction (SPE) method for sample clean-up followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure for the assay of five antidepressant drugs (trazodone, doxepin, desipramine, maprotiline and imipramine) is reported. The drugs were recovered from plasma buffered at a suitable pH using C18 Bond-Elut cartridges and mixtures of methanol-aqueous buffer as washing and elution solvents. The recoveries of the drugs using other sorbent materials (C8, C2, cyclohexyl, cyanopropyl and phenyl Bond Elut and copolymer HLB waters cartridges) were also examined. The selectivity of SPE was examined by using spiked plasma samples and the CH cartridge gave rise to the cleanest extracts. Cyclohexyl cartridges were conditioned successively with 2 ml of methanol and 1 ml of acetic acid-sodium acetate buffer (0.1 M, pH 4.0). Plasma sample was buffered at pH 4.0 and then applied to the sorbent. The washing step was performed subsequently with 1.5 ml of acetate buffer (0.1 M, pH 4.0), 100 microl of acetonitrile and 1 ml of methanol-acetate buffer (30:70, v/v). Finally, the analytes were eluted with 0.5 ml of methanol-acetate buffer (70:30, v/v). The extract was evaporated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with ultraviolet detection at 215 nm. The recoveries of trazodone, doxepin, desipramine, maprotiline and imipramine from spiked plasma samples using the CH cartridge were 58 2, 84 3, 83 3, 83 3 and 82 2%, respectively. The within-day and between-day repeatabilities were lower than 6% and 9%, respectively. The linearity of calibrations for the five antidepressants was between 0.005 and 2 microg/ml. The limits of detection were 1 ng/ml for trazodone, doxepin and desipramine and 2 ng/ml for maprotiline and imipramine.

Biopharmacological data and high-performance liquid chromatographic analysis of 1,4-benzodiazepines in biological fluids: A review

A review with 123 references on the analysis of 1,4-benzodiazepines in biological samples using HPLC is presented. Some important physico-chemical and biopharmacological data for the development of analytical methods are collected. Different methods of sample pretreatment, chromatographic conditions and detection systems are discussed.

Study of semi-automated solid-phase extraction for the determination of acaricide residues in honey by liquid chromatography

A solid-phase extraction (SPE) method followed by a reversed-phase high-performance liquid chromatography (HPLC) procedure is reported for the assay of a wide polarity range acaricide residues in honey. After selection of suitable chromatographic and detection conditions, most steps of the SPE procedure that may affect to the recovery were investigated. Honey sample was buffered at pH 6 and then applied to the preconditioned C18 sorbent. A washing step was performed with 1 ml of a mixture of tetrahydrofuran (THF)-phosphate buffer (10:90, v/v) and finally, the analytes were eluted with 1 ml of THF. The extract was evaporated to dryness, reconstituted in mobile phase and chromatographed on a reversed-phase C18 column with diode array detection. The recoveries of the more polar acaricides were higher than 80% and 60-70% for the more apolar ones. Limits of detection obtained ranged from 1 to 200 ng/g.