Manuel Miró

Analysis of phenolic constituents of biological interest in red wines by high-performance liquid chromatography.

We describe a reversed-phase HPLC method that uses gradient elution and diode array detection to determine four biologically active phenolic constituents of red wines: gallic acid, trans-resveratrol, quercetin and rutin. The method permits direct injection without sample pre-treatment. ODS Hypersil served as the stationary phase; the gradient was formed by acetic acid, methanol, and water. Each analysis required an equilibration period of 10 min and a run time of 50 min for completion. Previously, total phenols were analysed according to the Folin-Ciocalteu method, using gallic acid as the standard, and the results are given as gallic acid equivalent.

Multisyringe flow injection analysis: characterization and applications

In this paper, the new multisyringe flow injection analysis (MSFIA) technique is reviewed and contrasted with previous flow techniques. Also covered are its fundamental background and instrument evolution, together with its proposed injection modalities and various analytical applications.

Determination of plutonium isotopes in waters and environmental solids: A review.

A number of analytical methods have been developed in the past few years for environmental monitoring of plutonium (Pu) isotopes around nuclear facilities within protocols for emergency preparedness as well as for risk assessment of contaminated areas resulting from nuclear weapon tests, nuclear accidents, and the discharge of nuclear waste. This article summarizes and critically compares recently reported methods for determination of Pu isotopes in waters and environmental solid substrates, in which sample pre-treatment is imperative for separation of the target species from matrix ingredients and/or potentially interfering nuclides prior to detection by radiometric or mass spectrometric techniques. Also discussed, via representative examples, is the automation of the entire analytical protocol by on-line extraction chromatography and ion exchange chromatography using flow injection (FI) or sequential injection (SI) approaches.

High-Resolution Colorimetric Assay for Rapid Visual Readout of Phosphatase Activity Based on Gold/Silver Core/Shell Nanorod

Nanostructure-based visual assay has been developed for determination of enzymatic activity, but most involve in poor visible color resolution and are not suitable for routine utilization. Herein, we designed a high-resolution colorimetric protocol based on gold/silver core/shell nanorod for visual readout of alkaline phosphatase (ALP) activity by using bare-eyes. The method relied on enzymatic reaction-assisted silver deposition on gold nanorod to generate significant color change, which was strongly dependent on ALP activity. Upon target ALP introduction into the substrate, the ascorbic acid 2-phosphate was hydrolyzed to form ascorbic acid, and then, the generated ascorbic acid reduced silver ion to metal silver and coated on the gold nanorod, thereby resulting in the blue shift of longitudinal localized surface plasmon resonance peak of gold nanorod accompanying a perceptible color change from red to orange to yellow to green to cyan to blue and to violet. Under optimal conditions, the designed method exhibited the wide linear range 5-100 mU mL(-1) ALP with a detection limit of 3.3 mU mL(-1). Moreover, it could be used for the semiquantitative detection of ALP from 20 to 500 mU mL(-1) by using the bare-eyes. The coefficients of variation for intra- and interassay were below 3.5% and 6.2%, respectively. Finally, this method was validated for the analysis of real-life serum samples, giving results matched well with those from the 4-nitrophenyl phosphate disodium salt hexahydrate (pNPP)-based standard method. In addition, the system could even be utilized in the enzyme-linked immunosorbent assay (ELISA) to detect IgG at picomol concentration. With the merits of simplification, low cost, user-friendliness, and sensitive readout, the gold nanorod-based colorimetric assay has the potential to be utilized by the public and opens a new horizon for bioassays.

Sequential injection–bead injection–lab-on-valve schemes for on-line solid phase extraction and preconcentration of ultra-trace levels of heavy metals with determination by electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry

This communication presents an overview of the state-of-the-art of the exploitation of sequential injection (SI)–bead injection (BI)–lab-on-valve (LOV) schemes for automatic on-line sample pre-treatments interfaced with ETAAS and ICPMS detection as conducted in the authors’ group. The discussions are focused on the applications of SI–BI–LOV protocols for on-line microcolumn based solid phase extraction of ultra-trace levels of heavy metals, employing the so-called renewable surface separation and preconcentration manipulatory scheme. Two types of sorbents have been employed as packing material, that is, the hydrophilic SP Sephadex C-25 cation exchange and iminodiacetate based Muromac A-1 chelating resins, and the hydrophobic poly(tetrafluoroethylene) (PTFE) and poly(styrene-divinylbenzene) copolymer alkylated with octadecyl groups (C18-PS/DVB). Using ETAAS as detection device, the easy-to-handle hydrophilic renewable reactors hold the features of improved R.S.D.s and LODs as compared to those operated in the conventional, permanent mode, in addition to the elimination of flow resistance. The hydrophobic columns fall into two categories, that is, the renewable one packed with C18-PS/DVB beads entails analogous R.S.D.s and LODs with respect to the conventional approach, while those with PTFE beads result in slightly inferior R.S.D.s and LODs by similar comparison, yet offering a wider dynamic range than when using an external permanent column. Moreover, the hydrophilic materials result in much higher enrichment of the analyte than the hydrophobic ones, although PTFE is the packing material that exhibits the best retention efficiency.

Slurry Sampling—An Analytical Strategy for the Determination of Metals and Metalloids by Spectroanalytical Techniques

Abstract This article critically overviews the state-of-the-art of slurry sampling as an approach for the minimization of sample preparation prior to the determination of metals and metalloids in complex matrices by spectroanalytical techniques. Relevant factors involved in the optimization of slurry-based analytical procedures and the dependence of the quality of the results on the calibration method selected are discussed in detail. The advantages and limitations compared to solid sampling for the analysis of solid matrices are highlighted and discussed. Analytical applications of slurry sampling reported in the literature emphasizing publications between 2004 and 2009 are comprehensively compiled covering detection by flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ET-AAS), cold vapor atomic absorption spectrometry (CV-AAS), hydride generation atomic absorption spectrometry (HG-AAS), hydride generation atomic fluorescence spectrometry (HG-AFS), inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS).

Recent Developments in Flow Injection/Sequential Injection Liquid-Liquid Extraction for Atomic Spectrometric Determination of Metals and Metalloids

Abstract This review aims to provide a critical overview of automated flow injection and sequential injection liquid-liquid extraction for preconcentration and/or separation of ultra-trace metal and metalloid species hyphenated with atomic spectrometric detection systems, including some new trends and applications in the subbranches of cloud point extraction (CPE), wetting film extraction (WFE), supported liquid membrane extraction (SLME), extraction chromatography (EChr), and liquid-phase microextraction (LPME) techniques. The analytical performance of flow-injection/sequential injection liquid-liquid extraction methods is markedly affected by the components of the flow network such as segmentor, extraction coil, and phase separator. Thus, an overall presentation of system components along with some novel strategies for interface with atomic spectrometers is discussed and exemplified with selected applications.

Pre-concentration procedure for determination of copper and zinc in food samples by sequential multi-element flame atomic absorption spectrometry.

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).

Exploiting the bead-injection approach in the integrated sequential injection lab-on-valve format using hydrophobic packing materials for on-line matrix removal and preconcentration of trace levels of cadmium in environmental and biological samples via formation of non-charged chelates prior to ETAAS detection

The potentials of the bead injection scheme integrated into the sequential injection (SI) lab-on-valve (LOV) format, using reversed-phase materials for on-line matrix removal and analyte preconcentration, and interfaced with detection by electrothermal atomic absorption spectrometry (ETAAS), are exploited for the ultratrace determination of cadmium. The proposed approach relies upon the renewable surface concept and involves the incorporation of hydrophobic beads into channels of the LOV microconduit, thus serving as transient microcolumn packed reactors. After on-line analyte derivatization with diethyldithiophosphate (DDPA) in 1.3% (v/v) nitric acid medium, the resulting non-charged chelate is adsorbed onto the surface of the column material. The analyte loaded beads are afterwards eluted with 30 µl of ethanol which, via air segmentation, is subsequently introduced into the graphite tube for quantification. The used beads are then backflushed and delivered to waste. The ETAAS measurement is synchronized with the separation/preconcentration steps of the ensuing sample. Two reversed-phase sorbents, that is, poly(styrene-divinylbenzene) copolymer alkylated with octadecyl groups (C18-PS/DVB) and poly(tetrafluoroethylene) (PTFE), were selected in view of their different morphology and physical properties. Although C18-PS/DVB beads fulfil the basic requirements to be handled readily in a renewable fashion in the LOV microconduits, i.e., bead size homogeneity and perfect spherical shape, yielding improved reproducibility as compared to the PTFE beads (3.4% versus 4.3%), the latter material results in better retention efficiency (74% versus 28%), enrichment factor (17.2 versus 7.4), linear dynamic range (0.05–1 µg l−1 Cd versus 0.2–1.5 µg l−1 Cd), and detection limit (5 ng l−1versus 135 ng l−1) for a sample loading volume of 1.25 ml. The designed procedure, which handles 12 samples h−1, was validated by determination of the cadmium content in environmental CRM and NIST standard reference materials and by cadmium spike recoveries of a human urine sample. Statistical comparisons between the proposed procedure and certified values revealed no significant differences at the 95% confidence level.

Magnetic bead-based fluorescence immunoassay for aflatoxin B1 in food using biofunctionalized rhodamine B-doped silica nanoparticles.

A simple and sensitive fluorescence immunoassay for the detection of aflatoxin B(1) (AFB(1), as a model compound) in food was developed using AFB(1)-bovine serum albumin conjugate (AFB(1)-BSA)-functionalized magnetic beads as immunosensing probes. The recognition elements were prepared by doping of rhodamine B (RB) fluorophore into silica nanoparticles followed by immobilization of monoclonal anti-AFB(1) antibodies on the silica shell. Based on a competitive-type immunoassay format, the assay was performed both in low-binding polypropylene 96-well microtiter plates (MTPs) and in an automated sequential injection (SI) format. Similar detection limit (LOD) of 0.2 ng mL(-1)vs. 0.1 ng mL(-1) but narrower dynamic working linear range of 0.5-7 ng mL(-1)vs. 0.5-30 ng mL(-1) was obtained toward AFB(1) standards with the flow setup compared to the MTP format. Intra-batch assay precision was substantially improved (≤5.3% vs.≤8.7%) by resorting to the SI manifold. The proposed method features unbiased identification of negative (blank) and positive samples. No significant differences at the 95% confidence level were encountered in the analysis of naturally contaminated peanut samples between the proposed immunoassay and liquid chromatography for determination of AFB(1).