A. Ruiz-Medina

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.

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.

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.

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.

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.

Analysis of Bisphenol A in milk by using a multicommuted fluorimetric sensor

Bisphenol A (BPA) is a polyphenol widely used in industry as an intermediate in the production of polycarbonate plastics and epoxy resins, which are applied to produce plastic food containers, inner surface coating of food and beverage cans. Hence, BPA can migrate from these containers and cans with epoxy coating into foods. It is dangerous taking into account that BPA is considered as a potential endocrine disruptor, which mimics the action of the hormone estrogen. The method here proposed for the determination of BPA involves the implementation of solid-phase spectroscopy (SPS) in an automatic flow system. With this purpose, the measurement of the native fluorescence of BPA, retained on C(18) silica gel together with the implementation of multicommutation have been employed for its determination in different types of milk. The analytical measurements were made at 271/305nm (λ(ex)/λ(em)) obtaining a detection limit (LOD) of 0.06ngmL(-1). The pre-cleaning procedure and the posterior extraction with C(18) applied to the samples allowed the removal of proteins and the extraction of BPA from the matrix, respectively. The method showed an RSD lower than 6.0% (n=10). BPA was determined in powdered milk, infant formula and pure liquid milk samples, being found in five samples at levels lower than the maximum residue limit (MRL) established by the European Union. In addition, a recovery study has been carried out where values close to 100% were observed in all cases, so demonstrating that the proposed analytical method fulfills the requirements for its application in quality control analyses.

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.

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).

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.