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.

Graphene quantum dots-silver nanoparticles as a novel sensitive and selective luminescence probe for the detection of glyphosate in food samples.

Glyphosate (Gly) is the most widely used herbicide at the moment. It presents a broad spectrum of action, hence its use for many different crops. Regulatory agencies have constantly mentioned the low hazard potential of Gly to mammals. However, the International Agency for Research on Cancer concluded in 2015 that glyphosate is "probably carcinogenic to humans". For this reason, it is important to develop reliable analytical methods to quantify Gly in food samples. Here, we propose an analytical method that makes use of graphene quantum dots (GQDs) and cysteine-capped silver nanoparticles (AgNPs) for the screening of glyphosate, using QuEChERS as sample treatment. Gly quenched the luminescence of GQDs-AgNPs system, achieving an excellent sensitivity (detection limit of 9 ng mL-1) and selectivity. The method developed was applied to different types of pulses (peas and lupins), obtaining recoveries close to 100% and relative standard deviations lower than 4% in all cases. Its simplicity and rapidity make this method an interesting alternative to other existing methodologies for the analysis of this pesticide in food samples.

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.

Novel sequential separation and determination of a quaternary mixture of fungicides by using an automatic fluorimetric optosensor.

A versatile flow-through multi-optosensor is proposed for the separation and spectrofluorimetric determination of mixtures of four widely used pesticides: carbendazim, thiabendazole, carbaryl and o-phenylphenol at µg g-1 levels in fruits. The flow system is based on the online pre-concentration and separation of the pesticides on a solid sensing microzone, followed by the sequential measurement of their native fluorescence. The separation of the pesticides takes place on a solid support located in the same flow cell, on which analytes are temporarily immobilized and separated from the matrix due to their different retention/desorption kinetics when they interact with the C18 silica gel microbeads. Suitable analytical parameters were obtained for the selected analytes, with method detection and quantification limits ranging between 0.1-0.5 and 0.2-1.6 µg g-1, respectively. These values comply with the maximum residue limits (MRLs) established by the Codex Alimentarius for these commodities; in addition, carbendazim, thiabendazole and ortho-phenylphenol comply with the MRLs of The European Union. The developed method was applied to the analysis of citrus fruits by performing recovery studies. Recoveries between 85% and 115% were obtained in all cases, and the results were confirmed by a liquid chromatography-mass spectrometry reference method.

Exploiting the fluorescence resonance energy transfer (FRET) between CdTe quantum dots and Au nanoparticles for the determination of bioactive thiols.

This work focused the implementation of FRET processes between CdTe quantum dots (QDs), acting as donors, and gold nanoparticles (AuNPs), behaving as acceptors, for the determination of several bioactive thiols such as captopril, glutathione, l-cysteine, thiomalic acid and coenzyme M. The surface chemistry of the QDs and AuNPs was adjusted with adequate capping ligands, i.e. mercaptopropionic acid and cysteamine, respectively, to guarantee the establishment of strong electrostatic interaction between them and promoting the formation of stable FRET assemblies. Under these circumstances the fluorescence emission of the QDs was completely suppressed by the AuNPs. The assayed target analytes were capable of disrupting the donor-acceptor assemblies yielding a concentration-related reversion of the FRET process and restoring QDs fluorescence emission. Distinct mechanisms, involving enhancing of the QDs quantum yield (QY), AuNPs agglomeration, nanoparticles detachment, etc., could be proposed to explain the referred FRET reversion. The developed approach assured good analytical working ranges and demonstrate adequate sensitivity for the assayed compounds, anticipating great prospective for implementing rapid, simple and reliable sensing methodologies for the monitoring of pharmaceutical, food and environmental species. However, selectivity could be a hindrance in the detection of these bioactive thiols in more complex matrices such as environmental and food samples. This problem could be circumvented through the employment of multivariate chemometric methods for the analysis and processing of whole fluorometric response. Moreover, the proposed methodology shows a great analytical versatility since it is possible to easily adapt the surface chemistry, of both QDs and AuNPs, to the chemical nature of the target analyte.

Phytochemical profile and antioxidant activity of caper berries (Capparis spinosa L.): Evaluation of the influence of the fermentation process.

In this work, we report the phytochemical profile and antioxidant activity of caper berries (Capparis spinosa L.) before and after a fermentation process. The phytochemical profiles were evaluated by high-performance liquid chromatography with UV and electrospray ionization mass spectrometry detection (HPLC-DAD-ESI-MSn). Twenty-one compounds were characterized, and seven of them quantified. The main component of non-fermented berries was glucocapparin, which was degraded upon the fermentation process. Most of the compounds were quercetin and kaempferol glycosides, epicatechin, and proanthocyanidins. The main differences observed upon the fermentation process were a decrease in epicatechin concentration, the hydrolysis of quercetin glycosides, and the degradation of glucosinolates. Total phenolic and flavonoid contents, as well as the antioxidant activities by the in vitro antioxidant assays DPPH and ABTS+, were determined, observing that the values were slightly higher after the fermentation process.

Evaluation of antioxidant potential, enzyme inhibition activity and phenolic profile of Lathyrus cicera and Lathyrus digitatus: Potential sources of bioactive compounds for the food industry.

The genus Lathyrus has great importance in terms of food and agricultural areas. In this study, the in vitro antioxidant activity (phosphomolybdenum, DPPH, ABTS, FRAP, CUPRAC and metal chelating) and enzyme inhibitory activity evaluation (acetylcholinesterase, butyrylcholinesterase, α-amylase and α-glucosidase) of L. cicera and L. digitatus were investigated, as well as their phytochemical profiles. The screening of the main phytochemical compounds in aerial parts of L. cicera and L. digitatus was carried out by high-performance liquid chromatography with electrospray ionization mass spectrometric detection (HPLC-ESI-MSn), observing that flavonoids represent the highest percentage of identified compounds, with abundance of tri- and tetra-glycosilated flavonoids, including acylated ones, especially in L. cicera. Generally, L. digitatus exhibited stronger antioxidant and enzyme inhibitory activities in correlation with its higher level of phenolics. The high number of phenolic compounds and the results of the antioxidant and enzyme assays suggest that these plants may be further used as sources of bioactive compounds, and for the preparation of new nutraceuticals.

Development of an semi-automatic and sensitive photochemically induced fluorescence sensor for the determination of thiamethoxam in vegetables.

The determination of thiamethoxam (TMX), a widely known neonicotinoid pesticide, by a multicommutated optosensing device implemented with photochemically induced fluorescence (PIF) has been developed. The combination of both methodologies allows, on one hand a quick on-line photodegradation of TMX and, on the other hand, the preconcentration, quantification and desorption of the fluorescent photoproduct generated once retained on C18 silica gel filling the flow-cell which was monitored at 353 and 407nm for excitation and emission wavelengths, respectively. The proposed analytical method presents a detection limit of 3.6ngmL(-1) by using Multicommutated Flow Injection Analysis (MCFIA) as flow methodology. Recovery experiments have been carried out in different kinds of vegetables at levels same or below the legislated maximum residue limit, demonstrating that this method combines advantages such as simplicity, high sensibility and high selectivity, in addition to fulfill the requirements for its applications in quality control. The obtained results in the analysis of real samples were in good agreement with those provided by a reference liquid chromatography (HPLC) method.

Multi-commutated fluorometric optosensor for the determination of citrinin in rice and red yeast rice supplements.

Citrinin is a toxic secondary metabolite first isolated from Penicillium citrinum, although is also produced by other species of Penicillium and Aspergillus. It has highly toxic, mutagenic, teratogenic and carcinogenic properties and is often found in crops, vegetables and fruit. To our knowledge there is no specific legislation on maximum levels permitted for citrinin, so no official analytical method is currently available for its determination. Our laboratory developed a fluorometric flow-through optosensor using Sephadex SPC-25 as solid support. Multi-commutated flow injection analysis was used for the construction of the manifold and for handling solutions. In this way, we minimised waste generation and human intervention, which are critical aspects when dealing with highly toxic compounds such as citrinin. The optimum excitation/emission wavelengths were set at 330/494 nm; the calibration curve was linear in the concentration range 35-900 ng ml⁻¹. A detection limit of 10.5 ng ml⁻¹ and relative standard deviations (RSDs) lower than 3% were obtained. The developed optosensor was applied to the determination of citrinin in rice and dietary supplements containing red yeast rice.

Separation of a binary mixture of pesticides in fruits using a flow-through optosensor.

A flow-through optosensor is here proposed for the determination of mixtures of two widely used pesticides, carbendazim and o-phenylphenol, in fruits. The pesticides are separated on-line using an additional amount of solid support, C18 silica gel, in the flow-through cell. The resolution is performed due to the different retention/desorption kinetics of the analytes when interacting with the C18 microbeads. Therefore, both separation and determination are integrated in the same cell, considerably simplifying the system. In addition, the use of Sequential Injection Analysis provides a high degree of automation and minimum wastes generation. After the analytes are separated, their native fluorescence is measured, obtaining linearity in the 2.0-30 and 1.1-20 mg kg(-1) ranges for carbendazim and o-phenylphenol. The detection limits are 0.60 and 0.33 mg kg(-1) for carbendazim and o-phenylphenol respectively. The proposed method fulfills the maximum residue limits (MRLs) established in Europe and USA for these pesticides in cherries, pineapple, and mango: 5-10 mg kg(-1). In order to demonstrate the suitability of the method, several samples have been analyzed and the obtained results compared with a chromatographic method.

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.

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.

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.

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.

Implementation of terbium-sensitized luminescence in sequential-injection analysis for automatic analysis of orbifloxacin.

Orbifloxacin (ORBI) is a third-generation fluoroquinolone developed exclusively for use in veterinary medicine, mainly in companion animals. This antimicrobial agent has bactericidal activity against numerous gram-negative and gram-positive bacteria. A few chromatographic methods for its analysis have been described in the scientific literature. Here, coupling of sequential-injection analysis and solid-phase spectroscopy is described in order to develop, for the first time, a terbium-sensitized luminescent optosensor for analysis of ORBI. The cationic resin Sephadex-CM C-25 was used as solid support and measurements were made at 275/545 nm. The system had a linear dynamic range of 10-150 ng mL(-1), with a detection limit of 3.3 ng mL(-1) and an R.S.D. below 3% (n = 10). The analyte was satisfactorily determined in veterinary drugs and dog and horse urine.

Fast determination of salicylic acid in pharmaceuticals by using a terbium-sensitized luminescent SIA optosensor.

In this article, we report the coupling of sequential injection analysis (SIA) and solid phase lanthanide-sensitized luminescence as a detection technique; in this technique, the energy absorbed by the analyte (retained on a solid support) is transferred to the lanthanide ion, which finally emits the luminescence signal. By using this automatic system, the determination of salicylic acid (SA) is easily, rapidly, and selectively achieved. Microspheres of commercial solid support, Sephadex-QAE A-25, are used to fill the flow-through cell and retain analyte and terbium ions; after the signal from SA-terbium complex is obtained, the solid support is easily regenerated by using an ethylenediaminetetraacetic acid disodium salt 2-hydrate (EDTA) solution. Over 200 determinations can be carried out without replacing the resin microbeads. The proposed method shows a 0.045 microg mL(-1) detection limit, with an R.S.D. lower than 3% and a sampling frequency up to 30 samples per hour. The system has been applied to the determination of SA in pharmaceuticals obtained from the Spanish Pharmacopoeia, with satisfactory results; an additional recovery study has been carried out with recoveries close to 100%.

Fluorimetric SIA optosensing in pharmaceutical analysis: determination of paracetamol.

The coupling of sequential injection analysis (SIA) and fluorimetric solid phase transduction is here applied to the determination of paracetamol in pharmaceuticals. The reaction product between the analyte and sodium nitrite in acidic medium is inserted, after alkalinization, in the system. This product is transitorily retained on the active solid sensing phase (the anionic solid support QAE A-25) developing its native fluorescence signal, which is measured at 325/430 nm for the excitation and emission wavelengths respectively. The described system is linear within the range 6.6-80 microg ml(-1), with a 2 microg ml(-1) detection limit and a 2.5% R.S.D (n=10). The proposed fluorimetric SIA optosensor has been applied to the determination of paracetamol in several pharmaceutical preparations, obtaining satisfactory results.

Development of a multicommuted flow-through optosensor for the determination of a ternary pharmaceutical mixture.

The combination of multicommutation and flow-through multioptosensing is presented in this work as a powerful strategy for the routine analysis of active principles in pharmaceuticals. By coupling methodologies, the selectivity and sensitivity of optosensors is maintained, while the use of the multicommutation approach provides additional advantages, such as low reagent consumption, low waste generation and reduced human supervision. The potential of this integration is enhanced when implemented with multiwavelength detection mode. An UV sensor is here developed for the simultaneous determination of three widely used active principles: salicylamide, caffeine and propyphenazone. The measuring wavelengths were 276 nm for caffeine and propyphenazone, and 302 nm for salicylamide. The five three-way solenoid valves used in the system are controlled by Java-written home-made software. The sensor is based on the on-line selective retention of two of the three analytes on a precolumn placed just before the sensing zone and filled with the same solid support than the flow-through cell (C(18) silica gel). This approach allows the sequential arrival of the analytes to the sensing zone, so allowing their determination with only one sample injection. So, the use of C(18) placed, in both the precolumn and the flow-cell combines the advantages of the increase of sensitivity and selectivity in the detection solid zone with the additional increase of the selectivity in the precolumn. The sensor was applied to the determination of the analytes in several pharmaceutical preparation of the Spanish Pharmacopoeia, obtaining satisfactory results.

Chemiluminescence optosensing implemented with multicommutation: determination of salicylic acid.

In this paper we have coupled, for the first time, chemiluminescent detection with multicommuted optosensing principles. This approach has been implemented with the use of a commercial flow cell of 1mm optical path length filled with an appropriate anionic exchanger gel as chemiluminescence sensing phase. The cell was placed in front of the window of the photosensor module of a home-made luminometer developed in our laboratory and a flat mirror was stuck on the back of the cell. The suitability of using chemiluminescence as detection technique in multicommuted flow-through optosensors has been demonstrated: the determination of salicylic acid by simple oxidation with permanganate on the sensing solid phase was chosen as model reaction. The proposed system allows the determination of salicylic acid in pharmaceuticals, with a sample frequency as high as even 60 samples h(-1) and showing a detection limit of 0.30 microg mL(-1), the linear response range is 1-30 microg mL(-1) and the R.S.D. is 3.1%. Satisfactory results have been obtained when applying the sensor to pharmaceuticals. The accuracy of the proposed methodology has been tested by using a reference method.