Eulogio J. Llorent-Martínez

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.

Lanthanide-Sensitized Luminescence as a Promising Tool in Clinical Analysis

Abstract The recent applications and novelties of lanthanide-sensitized luminescence (LSL) as a detection technique in clinical analysis are here reviewed. In LSL, lanthanide ions form complexes with organic compounds; in these complexes, the energy absorbed by the organic chromophore (usually the analyte) at its characteristic excitation wavelength is transferred to a triplet state of the molecule and then transferred to a resonance level of the lanthanide ion, which finally emits luminescence at its particular emission wavelength. The characteristics of this process will be reviewed and particular attention will be paid to the development of automatic methods of analysis, fluorescence probes, or flow-through optosensors, due to their potential applications in clinical analysis. A critical discussion of the advantages and handicaps of each analytical method is done and the trends of analytical chemistry in this research field are also presented.

Determination of vitamin C in foods: Current state of method validation

Vitamin C is one of the most important vitamins, so reliable information about its content in foodstuffs is a concern to both consumers and quality control agencies. However, the heterogeneity of food matrixes and the potential degradation of this vitamin during its analysis create enormous challenges. This review addresses the development and validation of high-performance liquid chromatography methods for vitamin C analysis in food commodities, during the period 2000-2014. The main characteristics of vitamin C are mentioned, along with the strategies adopted by most authors during sample preparation (freezing and acidification) to avoid vitamin oxidation. After that, the advantages and handicaps of different analytical methods are discussed. Finally, the main aspects concerning method validation for vitamin C analysis are critically discussed. Parameters such as selectivity, linearity, limit of quantification, and accuracy were studied by most authors. Recovery experiments during accuracy evaluation were in general satisfactory, with usual values between 81 and 109%. However, few methods considered vitamin C stability during the analytical process, and the study of the precision was not always clear or complete. Potential future improvements regarding proper method validation are indicated to conclude this review.

Multicommutation in Flow Systems: A Useful Tool for Pharmaceutical and Clinical Analysis

Multicommutation is a methodology of increasing use for the development of chemical analysis systems. Spe- cifically, it refers to continuous-flow configurations designed with computer-controlled commutators. The flow system, based on the implementation of solenoid valves in Flow Injection Analysis (FIA), is called Multicommutated Flow Sys- tem (MCFIA). These flow systems can be easily re-configured by just changing the procedure with the software, resulting in increased versatility, potential for automation and minimization of both reagent consumption and waste generation. The use of solenoid pumps for propelling the solutions has been recently introduced and is known as Multipumping Flow Sys- tems (MPFS). Finally, Multisyringe Flow Injection Analysis (MSFIA) has been developed implementing multicommuta- tion principles in a modified Sequential Injection Analysis (SIA) system. This review covers a brief description about the fundamentals of the above mentioned methodologies as well as their ap- plication to pharmaceutical and clinical analysis. Several examples are given and some particular aspects are highlighted, such as the differences between measuring the analytical signal in solution or on a solid support (flow-through optosen- sor), a detailed classification of the reported methods in terms of the flow technique employed, or the novelty of each pub- lished method.

Recent progress of flow-through optosensing in clinical and pharmaceutical analysis

The applications of flow-through optosensing in clinical and pharmaceutical analysis in the last decade are here reviewed. A classification of the flow methodologies employed (conventional flow injection analysis, multicommutated flow analysis and sequential injection analysis) is introduced and their principal characteristics explained. The fundamentals of flow-through optosensing together with the main detection techniques are described and, later, the main applications of these flow methods are highlighted, paying special attention to the recent incorporation of new detection techniques in optosensing and to the design of multiparameter sensors. Finally, the advantages and disadvantages of the different flow methodologies here described are critically discussed.

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.

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.

Lathyrus aureus and Lathyrus pratensis: characterization of phytochemical profiles by liquid chromatography-mass spectrometry, and evaluation of their enzyme inhibitory and antioxidant activities

Different wild plants commonly used in folk medicine, such as different species from the genus Lathyrus, may represent new sources of biologically active compounds. Hence, a study of the composition and (bio)chemical behaviour of extracts from these plants may provide valuable information. To evaluate the phytochemical profile, and the enzyme inhibition and antioxidant activities of the aerial parts of L. pratensis and L. aureus, extracts from both plants were analyzed by high-performance liquid chromatography with electrospray ionization mass spectrometric detection (HPLC-ESI-MSn). The in vitro antioxidant activity (phosphomolybdenum, β-carotene bleaching, DPPH, ABTS, FRAP, CUPRAC and metal chelating) and enzyme inhibitory activity (acetyl cholinesterase, butyrylcholinesterase, tyrosinase, α-amylase and α-glucosidase) were also investigated for these Lathyrus species. Flavonoids and saponins were the main groups of compounds detected in the extracts from both plants. Generally, the methanol and water extracts presented remarkable antioxidant and enzyme inhibitory effects; all the observed results are critically discussed. The content of organic compounds and the antioxidant and enzyme assays suggest that these plants may be further used in phytopharmaceutical or food industry applications.

Multi‐commutated Flow‐through Multi‐optosensing: A Tool for Environmental Analysis

Abstract Multi‐commutation, which refers to the use of solenoid valves to construct the flow network, has been widely used for providing automation in flow injection analysis. In this paper, the coupling of multi‐commutation and multi‐optosensing is developed for the analysis of two pesticides in environmental water samples, fuberidazole and o‐phenylphenol. In optosensing, the use of the solid support allows the discrimination between the analytes and other compounds that, if measuring in solution, would interfere in the analysis; in addition, the sensitivity needed when facing environmental samples is obtained. The two analytes are separated by using C18 silica gel as solid support, taking into account their different kinetics of sorption/desorption when interacting with the solid support microbeads; the separation is performed in the same flow‐cell where the sensing detection is carried out (by using an additional amount of solid support in the cell itself above the irradiated microzone), so both separation and determination are integrated in the cell. The native fluorescence of fuberidazole and o‐phenylphenol was simultaneously measured at 314/356 and 250/345 nm, respectively. The detection limits obtained were 0.18 and 6.1 ng mL−1 for fuberidazole and o‐phenylphenol respectively, with a sampling frequency of about 12 samples per hour. A recovery study was performed in waters obtained for wells and rivers, with satisfactory results. The authors were invited to contribute this paper to a special issue of the journal entitled “Spectroscopy and Automation”. This special issue was organized by Miguel de la Guardia, Professor of Analytical Chemistry at Valencia University, Spain.

Application of quantum dots in clinical and alimentary fields using multicommutated flow injection analysis.

In recent years, the number of scientific papers regarding the use of quantum dots (QDs) has increased almost exponentially, especially emphasizing their use for new applications and describing new approaches. One of the future trends in the development of new methods of analysis is the use of automated methodologies. Among them, Multicommutated Flow Injection Analysis has been here selected in order to show its potentiality in pharmaceutical and food analysis. Using water-soluble CdTe QDs modified by mercaptopropionic acid, a flow system was developed for the determination of ascorbic acid. The system was based on the quenching effect produced by ascorbic acid on the fluorescence of QDs. Under the optimized conditions, the relationship between the fluorescence intensity of the QDs and ascorbic acid concentration was linear in the range of 12-250 μg mL(-1), obtaining a sample throughput of 68 determinations per hour. The proposed method was applied to the determination of ascorbic acid in pharmaceutical formulations, goji capsules and fruit juices. The results obtained were in good agreement with those showed by a reference method, so indicating the utility of the proposed method in the clinical and alimentary fields.