Phenolic profile and antioxidant activity of Euonymus japonicus Thunb.

The aim of this study was to characterise the phenolic profile and evaluate the antioxidant activity of aqueous and methanol leaf extracts from Euonymus japonicus Thunb., a species of flowering plant in the Celastraceae family. Liquid chromatography (HPLC) with diode array and electrospray-tandem mass spectrometry (DAD-ESI-MSn) detection was used to characterise and quantify phenolic compounds. Thirty-two compounds were detected; among them, flavonoids (mainly quercetin and kaempferol glycosides) were the most abundant compounds in both extracts. The results obtained for DPPH and ABTS assays in the extracts were in agreement with the highest content of phenolics in the methanol extract.

Comparative study of the phytochemical and mineral composition of fresh and cooked broccolini.

Broccolini is originated from crossing the regular broccoli with Chinese kale. Consequently, it has similar properties to these vegetables, but other very particular characteristics. Its consumption has increased in the last few years and, consequently, there have been some studies related to its quality parameters and the influence of different cooking methods. Nevertheless, changes on its phenolic composition and mineral content originated by its cooking have not been investigated in-depth so far. Here we report the phytochemical profile of broccolini before and after boiling, steaming, and griddling cooking treatments. The mineral content and phytochemicals were assessed by inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography-mass spectrometry (HPLC-MS), respectively. The main phenolics (mainly hydroxycinnamic acid derivatives from caffeic, coumaric, ferulic and sinapic acids) were quantified. Three oxylipins, three flavonoid glycosides and the glucosinolate glucobrassicin were also identified. ABTS and DPPH assays were also used as screening methods to assess the antioxidant potential of broccolini. A significant loss of the phenolic compounds and a reduction of the antioxidant activity were observed after the three cooking methods. Clear disadvantages were detected when broccolini was boiled, namely high losses of phenolic acids and derivatives (70%). Steaming and griddling also led to a significant loss of phenolics (50%) from fresh broccolini. The mineral content of this vegetable after domestic cooking procedures is also reported for the first time, calculating the contribution of broccolini consumption to official daily recommendations.

Phenolic profile and antioxidant activity of Jasonia glutinosa herbal tea. Influence of simulated gastrointestinal in vitro digestion.

In order to value J. glutinosa DC (rock tea), we characterised its phenolic profile and antioxidant activity. The study was performed in aqueous extracts before and after a simulated in vitro digestion to obtain data regarding phenolics bioavailability. Methanolic extracts were also analysed for comparison purposes. Phytochemical profiles were determined by high-performance liquid chromatography with mass spectrometric detection, whereas total phenolic content (TPC) and antioxidant assays were performed by conventional spectrophotometric methods. The most abundant compounds were dicaffeoylquinic acids, representing more than 90% of phenolics in tea infusions. Statistically significant differences were observed for all parameters except for TPC in methanol and aqueous extracts. Both phenolics amount and antioxidant activities were lower after the in vitro digestion of the infusions. However, although phenolics were lost during the simulated digestion, rock tea is still a good source of bioactive compounds with potential applications in the pharmaceutical or nutraceutical industries.

A novel multi-commutated method for the determination of hydroxytyrosol in enriched foods using mercaptopropionic acid-capped CdTe quantum dots.

Hydroxytyrosol (HXT) has been reported to have beneficial effects for human health, such as antioxidant and antimicrobial properties and an important contribution to the prevention of cardiovascular disease. Hence, exhaustive research is currently being performed to prepare functional foods, such as tomato juice or milk, with HXT. This paper presents a multi-commutated flow method based on the quenching effect that HXT has on the fluorescence of water-soluble mercaptopropionic acid-capped CdTe quantum dots. Under optimal conditions a linear working range was obtained for concentrations between 10 and 250 ng µl⁻¹. In order to demonstrate the suitability of the proposed method for the determination of HXT, HXT-enriched samples were prepared. Using a QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure for extraction, HXT was determined in the prepared functional foods (milk, infant formula, tomato juice and tomato soup). Recoveries of 100% ± 8%, relative standard deviations (RSDs) lower than 5% and high sample throughput of 70 samples per h show the potential of the system for the analysis of HXT in food samples.

Study of the quenching effect of quinolones over CdTe-quantum dots using sequential injection analysis and multicommutation.

The field of light-emitting nanoparticles has experienced an enormous development over the past two decades. The fluorescence of these nanometer-size crystalline particles, called quantum dots (QDs), can be both quenched and enhanced by different compounds. Since a high percentage of articles related to QDs are focused on theoretical studies, the development of analytical methods with real applications is an important step in order to progressively demonstrate the versatility of these particles. Moreover, taking into account that most of the QDs-based analytical methods are non-automated, the development of automated flow methodologies is still a field that presents an important analytical potential. With this purpose, two automatic methodologies, multicommutated flow injection analysis and sequential injection analysis, have been here applied to the analysis of quinolones in pharmaceutical formulations, making use of the quenching effect caused by the analytes over mercaptopropionic acid-capped CdTe QDs fluorescence. Both methodologies were compared in terms of versatility, sample throughput, sensitivity, etc., and applied to the determination of five quinolones in pharmaceutical preparations available in the Spanish Pharmacopoeia. The detection limits ranged between 26 and 50µmolL(-1), and Relative Standard Deviations lower than 3% were observed in all cases.

Fluorimetric determination of thiabendazole residues in mushrooms using sequential injection analysis.

Thiabendazole is a benzimidazole fungicide of general use that is specifically used to control mushroom diseases, mainly cobweb diseases, which is caused by members of the genus Cladobotryum. Although this compound is legislated and its maximum residue limit established at 60mgkg(-1) by Codex Alimentarius, there is almost a complete absence of analytical methods available for its determination in mushrooms. Here, we propose an automated method, using Sequential Injection Analysis with fluorescence detection (λ(exc)/λ(em)=305/345nm) for the determination of thiabendazole in mushrooms. We have developed a flow-through optosensor using C(18) silica gel as solid support placed in the flow-cell where the determination is performed. This method presents a detection limit of 0.5mgkg(-1), and recovery experiments have been carried out in different kinds of mushrooms at levels below the legislated maximum residue limit, demonstrating that the proposed analytical method fulfils the requirements for its applications in quality control of mushrooms.

Investigation by ICP-MS of trace element levels in vegetable edible oils produced in Spain.

The content of trace elements (Ag, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Ti, Tl and V) in edible oils (virgin olive, olive, pomace-olive, sunflower, soybean and corn) from Spain was determined, using inductively-coupled plasma-mass spectrometry (ICP-MS) after microwave digestion, employing only nitric acid in this step. The method has been validated by using both an oil reference material and recovery experiments over different oil samples, obtaining satisfactory results in all cases. Inter-day repeatabilities lower than 10% were observed for all of the analysed elements in the different kinds of oil samples. Studying the content of trace elements, in order to detect tendencies in the samples of the same type of oil, principal components analysis was used. Promising groupings were observed using a model with two principal components and retaining 75.3% of the variance.

Trends in flow-based analytical methods applied to pesticide detection: a review.

Recent applications of flow-based analytical methods for pesticide determinations are reviewed. This review is focused on the description of electrochemical and optical flow sensors, describing the most relevant applications in this field. The different approaches employed up to date in electrochemical biosensors, together with the possible modifications in the flow methodology and the development of multiparameter flow-through optosensors have also been extensively described. Advantages, handicaps and current trends of each detection technique are critically discussed. The article ends up with a comparison between flow-based analytical methods and chromatography when applied to pesticide determination.

Development of a rapid and automatic optosensor for the determination of cromolyn in biological samples.

Disodium cromoglycate (SCG) is an anti-allergic drug, which is applied locally or inhaled. After administration, a very small portion of the drug is absorbed, being the most eliminated part unchanged in the urine and bile; therefore, its determination in urine is indicative of the dose absorbed. Here, the first spectroscopic method for the determination of SCG, making use of a sequential injection optosensor with terbium-sensitized luminescence detection, is described. The cationic resin Chelex-100 was used as solid support in the detection area. The measurements were made at 336/545 nm (lambda(ex)/lambda(em)) and the system was calibrated for two sample volumes, 150 and 800 microl, depending on the samples analyzed. A detection limit of 15 ng ml(-1) and a RSD lower than 2% (n=10) were observed using the highest sample volume. The proposed method does not use any organic solvent or surfactant, so being environmental friendly. The analyte was satisfactorily determined in pharmaceuticals and human urine, the latter being spiked at the concentrations found after the administration of the drug.

Development of an automated chemiluminescence flow-through sensor for the determination of 5-aminosalicylic acid in pharmaceuticals: a comparative study between sequential and multicommutated flow techniques.

This work is aimed at demonstrating the potential of the implementation of automatic flow systems in optosensors using chemiluminescence detection. With this purpose, two automatic methodologies, multicommutation and sequential injection analysis (SIA), have been applied to the analysis of 5-aminosalicylic acid (ASA). The analyte is determined for the first time making use of its chemiluminescence reaction with permanganate anion, previously immobilized on an appropriate solid support in the detection area. First, the study of the most appropriate commercial flow-through cell and the optimum conditions for the reaction were performed. Second, the main differences in terms of flow variables and analytical parameters for multicommutation and SIA approaches were stated. Both methodologies were applied to the determination of the analyte in pharmaceuticals obtaining satisfactory results. Finally, the advantages and disadvantages of both proposed methods and the recoveries obtained from pharmaceuticals were statistically compared.

Development of a photochemically induced fluorescence-based optosensor for the determination of imidacloprid in peppers and environmental waters.

A novel flow-through solid phase spectroscopic assembly implemented with photochemically induced fluorescence (PIF) has been developed for the rapid, sensitive and selective determination of imidacloprid. The pesticide is derivatized on-line by irradiation with ultraviolet light providing an intensively fluorescent compound. The determination is carried out by measuring the fluorescence intensity of the photoproduct once retained on C(18) silica gel filling the flow-cell. The method proposed has been applied to the determination of imidacloprid in natural waters and peppers. The quantification limit (QL) (0.015mgkg(-1)) in peppers was lower than the maximum residue limit (MRL) established by Spanish Legislation (0.5mgkg(-1)). The method also seems to be suitable for environmental water analysis providing satisfactory recoveries (94.0-108.6%). The results obtained in the analysis of real samples are in good agreement with those provided by a reference liquid chromatography (HPLC) method.

A flow injection sensor for simultaneous determination of sulfamethoxazole and trimethoprim by using Sephadex SP C-25 for continuous on-line separation and solid phase UV transduction.

A flow-through sensor based on integration of spectrophotometric detection and the different kinetics of retention/elution of analytes on a solid support is proposed for the simultaneous determination of sulfamethoxazole (SMZ) and trimethoprim (TMP). The solid support (Sephadex SP C-25) fills both, a microcolumn placed on-line and the sensing microzone. The intrinsic absorbance of both compounds is monitored directly on the solid phase at 269 nm and so, no derivatization step is required. Using two alternate solutions, 10(-4) M hydrochloric acid and 0.20 M NaAc/HAc (pH 5.0) buffer, the sensor responds linearly in the measuring range of 50-250 and 10-70 microg ml(-1) with detection limits of 9.5 and 0.6 microg ml(-1) (500 microl of sample volume) for SMZ and TMP, respectively. The main advantages of the sensor are simplicity, rapidity and low reagents consumption. Its application to SMZ and TMP determination in synthetic samples and pharmaceutical preparations is demonstrated. The results obtained by the proposed method were compared with those obtained by a standard HPLC method.

The potential of flow-through optosensors in pharmaceutical analysis.

The fundamental principles of flow-through optosensors, together with the most significant procedures and alternatives developed in the applications of flow-through optosensors to pharmaceutical analysis are reviewed. The most frequently used solid sensing zones, flow-through cells, manifolds, regeneration step and types of detection are considered. Single parameter, biparameter, and multiparameter sensors developed are reviewed and their most relevant features presented. Finally, a critical comparison with other analytical methodologies/techniques is performed and the potential of flow-through optosensors in pharmaceutical analysis and their future trends discussed.

A flow-through optosensing device with fluorimetric transduction for rapid and sensitive determination of dipyridamole in pharmaceuticals and human plasma.

A flow-through optosensor with fluorimetric transduction has been prepared for the sensitive and selective determination of dipyridamole in aqueous solutions and biological fluids. The method is based on a monochannel flow-injection analysis system using Sephadex QAE A-25 resin, placed into a Hellma 176-QS fluorimetric flow-through cell, as an active sorbing substrate. The native fluorescence of dipyridamole fixed on the solid sorbent is continuously monitored at wavelengths of 305 and 490 nm for excitation and emission, respectively. After obtaining the maximum fluorescence intensity, the eluent solution (KH(2)PO(4)/NaOH buffer solution, c(T)=0.05 mol l(-1), pH 6.0) is allowed to reach the flow cell, the analyte is removed, and the resin support is regenerated. When an NaOH (10(-4) mol l(-1))/NaCl (0.1 mol l(-1)) solution is used as carrier solution, at a flow-rate of 1.56 ml min(-1), the sensor responds linearly in the measuring range of 10-500 microg l(-1) with a detection limit of 0.94 microg l(-1) and a throughput of 22 samples per hour (300 microl of sample volume). The relative standard deviation for ten independent determinations (200 microg l(-1)) is less than 0.82%. The method was satisfactorily applied to the determination of dipyridamole in pharmaceutical preparations and human plasma.

Simultaneous determination of thiamine and pyridoxine in pharmaceuticals by using a single flow-through biparameter sensor.

For the first time, an UV-photometric flow-through sensing device has been developed for the simultaneous determination of two cationic species (thiamine and pyridoxine). The sensor is based on the retention of the analytes on a cationic ion-exchanger gel placed in the detection zone itself into a quartz flow-cell. A double discrimination is used for detecting the analytes: (a) a double and simultaneous working wavelength, performed by the use of a diode array detector; and (b) a temporary sequentiation in the arrival of the analytes to the sensing zone by on line separation using a cationic ion-exchanger (the same used in the sensing zone) placed into a minicolumn just before the flow cell. Pyridoxine is determined the first (by measuring its intrinsic absorbance at 293 nm) because it passes through the minicolumn while thiamine is strongly retained on it. Then, thiamine is conveniently eluted from the precolumn and its intrinsic UV absorbance measured at 255 nm. In both cases, transitory signals were obtained because both the carrier (in the case of the pyridoxine) and the eluting (in the case of thiamine) solutions used also eluted the respective analyte from the sensing zone. Using 1000 microl of sample, the analytical signal showed a very good linearity in the range 2-30 microg ml(-1) for both analytes with detection limits of 0.10 and 0.084 microg ml(-1) for thiamine and pyridoxine, respectively. The optosensor was satisfactorily applied to the determination of these two analytes in pharmaceuticals.

Flow-through UV spectrophotometric sensor for determination of (acetyl)salicylic acid in pharmaceutical preparations.

The solid phase spectrophotometry technique, in which the absorbance of the species of interest sorbed on a solid support is measured directly, was applied to the determination of salicylic acid using flow injection-analysis. Salicylic acid was determined by monitoring of its intrinsic absorbance at 297 nm sorbed on Sephadex QAE A-25 resin placed in an appropriate flow-through cell. The method proposed improves the selectivity compared with the corresponding solution-phase method and the sensitivity is increased by a factor of 30 or more. The flow-through sensor proposed allows working with several calibration lines simply by varying the sample volume injected. Thus, linear dynamic ranges from 1 to 20 and from 2 to 40 microg ml(-1) can be obtained by using 1000 and 300 microl, respectively, with detection limits being 0.064 and 0.135 microg ml(-1). Relative Standard Deviations (RSDs) of 0.52 and 0.38%, and sampling frequencies of 18 and 25 h(-1), respectively, were also achieved. The sensor also allows the indirect determination of acetylsalicylic acid previous hydrolysis on-line to salicylic acid. For acetylsalicylic acid, a linear dynamic range from 5 to 120 microg ml(-1) and 25 h(-1) of sampling frequency (300 microl of sample volume) were obtained. The proposed flow-through sensor has been successfully applied to the determination of both analytes in pharmaceutical preparations.

Fast determination of paracetamol by using a very simple photometric flow-through sensing device.

A simple flow-through UV optosensing device was developed for the determination of paracetamol based on its transient retention and concentration on a suitable active solid support (Sephadex QAE A-25 anion-exchange resin) packed in the flow cell and the continuous monitoring of its native absorbance on the solid phase at 264 nm. The sample was injected into a 0.08-M NaCl carrier stream at pH 11.0 by using a simple monochannel FIA manifold. After developing the analytical signal, paracetamol was desorbed from the solid support by the carrier solution itself. A very good linear response was found in the concentration range 0.5-8.0 microg ml(-1) with a RSD (%) of 1.24, a detection limit of 0.022 microg ml(-1) and a sampling rate of 40 h(-1). A strong increase in sensitivity as well as a very much higher selectivity were achieved as compared with the conventional flow injection method as a consequence of the separation of the analyte from the sample plug and its retention on the active solid support placed in the detection area. Applicability of the proposed sensor to direct determination of paracetamol in pharmaceuticals (to solve the sample being the only treatment) was successfully demonstrated.

Simultaneous determination of paracetamol, caffeine and acetylsalicylic acid by means of a FI ultraviolet pls multioptosensing device.

A simple and rapid analytical procedure is proposed for the simultaneous determination of caffeine (CF), acetylsalicylic acid (ASA) and paracetamol (PCT) in pharmaceutical preparations by partial least-squares (PLS) treatment of a flow-through multisensor based on the integration of the retention and UV detection of the analytes on a solid support. Diode-array spectrophotometry has been used to obtain spectra (240-350 nm) of the analytes retained on C18 bonded phase beads packed in a flow cell. By using a 0.5% pH 1 HClO4 solution as the carrier, the multisensor responds linearly in the measuring range without requiring additional reagents or derivatization processes and the active microzone is regenerated by using methanol as eluting agent. Spectra of the corresponding analytes were used to provide multivariate data for the multivariate procedure. The statistical parameters obtained by the application of PLS methods at different reaction times were analysed, from which the optimum reaction time for the simultaneous determination of the analytes was selected. In the analysis of real and synthetic samples, precise and accurate values were obtained.

A rapid and selective solid-phase UV spectrophotometric method for determination of ascorbic acid in pharmaceutical preparations and urine.

Ascorbic acid was determined by a solid-phase UV spectrophotometry technique through the sorption of this on a dextran-type anion-exchange resin, Sephadex QAE A-25 and posterior direct measurement of its absorbance on the resin at 267 and 400 nm, packed in a 1-mm cell. The calibration graph was linear over the range 0.3-5.0 microg ml(-1). The sensitivity obtained is more than 50 times higher than that of the corresponding solution method. The detection limit was 0.05 microg ml(-1) and the relative standard deviation 0.74% (n = 10). This method is very rapid and highly selective for determining ascorbic acid in the presence of other species absorbing in the ultraviolet region and which are normally encountered with it. The one-step method proposed was successfully applied in the determination of ascorbic acid in pharmaceutical preparations and urine and the results were of comparable accuracy as indicated by a statistical analysis of the data, using both t- and F-tests.

Integrated flow injection-solid phase spectrophotometric determination of minoxidil.

A flow-through solid phase spectrophotometric (SPS) sensing device is proposed for the determination of minoxidil. The analyte is concentrated on Sephadex SP-C25 ion-exchanger packed in a flow cell and it is monitored by UV-Vis spectrophotometry at 282 nm, without derivatization reaction. When a HCl (10(-2) mol l(-1))/NaCl (5x10 (-2) mol l (-1)) solution is used as carrier/desorbing solution, the sensor responds linearly in the measuring range of 0.2-7, 0.1-4 and 0.05-2 mug ml(-1) with detection limits of 60, 33 and 6 ng ml(-1) for 600, 1000 and 2000 mul of sample, respectively. The relative standard deviations (%) for these volumes are 0.38, 1.06 and 2.63, respectively. The method was satisfactorily applied to the determination of minoxidil in pharmaceutical preparations and the results were compared with those obtained by high performance liquid chromatography (HPLC).