Flow Injection Experiments Research Articles

Combining high-speed countercurrent chromatography three-phase solvent system with electrospray ionization-mass spectrometry and nuclear magnetic resonance to profile the unconventional food plant Syzygium malaccense

Syzygium malaccense (L.) Merr. & L.M. Perry is a native tree to Malaysia, but also occurs in other tropical regions of the world, including Brazil. The increasing interest in the consumption of its leaves motivated the investigation of compounds of the plant. Metabolite profiling of S. malaccense leaves was achieved by high-speed countercurrent chromatography (HSCCC) fractionation coupled off-line to electrospray mass-spectrometry (ESI-MS) detection and nuclear magnetic resonance (NMR) analysis. The ethanolic leaf extract was submitted to HSCCC using a three-phase solvent system (TPSS) composed by n-hexane – ethyl acetate – acetonitrile – H2O (2:1:1:1, v/v). The stepwise gradient elution was employed due to the extract's chemical complexity. HSCCC fractions were further analyzed by ESI-MS/MS using a flow injection experiment and by NMR acquiring 1H, HSQC and HMBC spectra. MS based dereplication was achieved by comparing acquired data to those available in public and commercial databases. Results were also correlated to previously isolated compounds described for the Syzygium genus. This process led to the annotation of 90 compounds. The NMR data provided structural confirmation and substitution patterns for some of them. Extract chemical composition is characterized by having flavonoids, benzoic acids, hydroxycinnamic acids, quinic acids, hydrolizable tannins, fatty acids, anacardic acids and others primary metabolites. Most of these compounds were described for the first time in the plant. This approach greatly facilitates phytochemical analysis and could be applied to improve metabolite discovery in other studies.

Flow Confinement Enhancement of Heterogeneous Immunoassays in Microfluidics

This paper aims to enhance the analyte transport toward the sensing area and to enhance biosensors performances. A microchannel-based flow confinement method for rapid delivery of small sample volumes to sensor surface is described. To confine the flow, a sample flow is joined with a perpendicular makeup flow and is confined into a thin layer above the reaction surface. The numerical simulation of the confinement effect on the binding reaction is performed using the finite-element method. The influence of several parameters on the binding reaction is provided, such as the average flow velocity at the inlet of the microchannel and the velocity of the confinement flow, the characteristics of the flow confinement. The numerical results reveal that the flow confinement enhances mass transport of analytes and increase its velocity. The obtained results could be exploited in flow injection experiments for low volume.

Amperometric detection in the presence of carbon nanotubes dispersed in background electrolyte: Evaluating its suitability for capillary electrokinetic chromatography separations of polyphenolic compounds.

This work reports on the positive effects observed upon both the separation and analytical signals in electrophoretic separations of selected phenolic compounds when using aqueous BGE containing carbon nanotubes (CNTs) in connection to electrochemical detection (ECD). The influence of the presence of surfactant-coated CNTs in the BGE upon the amperometric response of probe compounds was evaluated under hydrodynamic regime in capillary flow injection experiments as well as electrophoretic separations. Among the surfactants employed to disperse CNTs within BGE, SDS shows the best results in terms of dispersion stability and degree of dispersion of the CNTs. ECD allows working with BGEs containing CNTs concentrations of, at least, 24.0 mg/L without increasing of baseline noise, on the opposite to that reported when using UV-visible detection, and the presence of CNTs in the BGE improves the electrochemical response of some of the tested compounds. These benefits were reflected in higher sensibility in the electrochemical signal and additional improved resolution in the electrophoretic separation of (±)-catechin and sinapic acid when using these BGE containing CNTs.

Alleviation of electrochemical oxidation for peptides and proteins in electrospray ionization: obtaining more accurate mass spectra with induced high voltage.

Accurate mass spectrometry (MS) signal for peptide/protein analysis, which could be affected by various MS conditions, plays an essential role in identification and quantification of biological samples. Herein, we tried to alleviate the possible interferences from electrochemical oxidations during electrospray ionization (ESI). Three most common electrochemical oxidation reactions in ESI include oxidation of analyte, solvent, and electrode. With introduction of induced electrospray ionization (IESI) (a variant form of ESI), these interferences were significantly alleviated for peptides/proteins. That effect was also tested with flow injection experiments with different solution flow rates, electrolyte concentrations and solvent compositions, which was to simulate various chromatography conditions in conventional liquid chromatography (LC) separations. For all chromatography conditions tested, electrochemical oxidation was significantly alleviated for the absence of physical contact between spray solution and electrode.

Polyethylenimine carbon nanotube fiber electrodes for enhanced detection of neurotransmitters.

Carbon nanotube (CNT)-based microelectrodes have been investigated as alternatives to carbon-fiber microelectrodes for the detection of neurotransmitters because they are sensitive, exhibit fast electron transfer kinetics, and are more resistant to surface fouling. Wet spinning CNTs into fibers using a coagulating polymer produces a thin, uniform fiber that can be fabricated into an electrode. CNT fibers formed in poly(vinyl alcohol) (PVA) have been used as microelectrodes to detect dopamine, serotonin, and hydrogen peroxide. In this study, we characterize microelectrodes with CNT fibers made in polyethylenimine (PEI), which have much higher conductivity than PVA-CNT fibers. PEI-CNT fibers have lower overpotentials and higher sensitivities than PVA-CNT fiber microelectrodes, with a limit of detection of 5 nM for dopamine. The currents for dopamine were adsorption controlled at PEI-CNT fiber microelectrodes, independent of scan repetition frequency, and stable for over 10 h. PEI-CNT fiber microelectrodes were resistant to surface fouling by serotonin and the metabolite interferant 5-hydroxyindoleacetic acid (5-HIAA). No change in sensitivity was observed for detection of serotonin after 30 flow injection experiments or after 2 h in 5-HIAA for PEI-CNT electrodes. The antifouling properties were maintained in brain slices when serotonin was exogenously applied multiple times or after bathing the slice in 5-HIAA. Thus, PEI-CNT fiber electrodes could be useful for the in vivo monitoring of neurochemicals.

Flow injection of liquid samples to a mass spectrometer with ionization under vacuum conditions: a combined ion source for single-photon and electron impact ionization

Electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo-ionization (APPI) are the most important techniques for the ionization of liquid samples. However, working under atmospheric pressure conditions, all these techniques involve some chemical rather than purely physical processes, and therefore, side reactions often yield to matrix-dependent ionization efficiencies. Here, a system is presented that combines both soft single-photon ionization (SPI) and hard 70 eV electron impact ionization (EI) of dissolved compounds under vacuum conditions. A quadrupole mass spectrometer was modified to enable direct EI, a technique developed by Cappiello et al. to obtain library-searchable EI mass spectra as well as soft SPI mass spectra of sample solutions. An electron beam-pumped rare gas excimer lamp working at 126 nm was used as well as a focusable vacuum UV light source for single-photon ionization. Both techniques, EI and SPI, were applied successfully for flow injection experiments providing library-matchable EI fragment mass spectra and soft SPI mass spectra, showing dominant signals for the molecular ion. Four model compounds were analyzed: hexadecane, propofol, chlorpropham, and eugenol, with detection limits in the picomolar range. This novel combination of EI and SPI promises great analytical benefits, thanks to the possibility of combining database alignment for EI data and molecular mass information provided by SPI. Possible applications for the presented ionization technology system are a matrix-effect-free detection and a rapid screening of different complex mixtures without time-consuming sample preparation or separation techniques (e.g., for analysis of reaction solutions in combinatorial chemistry) or a switchable hard (EI) and soft (SPI) MS method as detection step for liquid chromatography.

Effect of Polar Protic and Polar Aprotic Solvents on Negative-Ion Electrospray Ionization and Chromatographic Separation of Small Acidic Molecules

A comprehensive study investigated the effect of polar protic (methanol and water) and polar aprotic (acetonitrile and acetone) solvents on the chromatographic separation and negative-ion electrospray (ESI) response of 49 diverse small, acidic molecules. Flow injection experiments on a triple quadrupole were used to measure the response in neat solvents after optimization of source conditions and implementation of a rigorous quality control program (the later ensured that changes in analyte response were due to the analyte/solvent measured and not changes in instrument performance over time). In all solvents, compounds with electron-withdrawing groups and extended conjugation ionized best due to resonance and inductive effects. Ionization was greatest in methanol or water for all compounds that elicited a response, thus revealing that enhanced sensitivity and lower limits of detection are achieved with polar protic solvents. Response in acetone was equal to or slightly lower than response in acetonitrile in flow injection experiments; however, the water/acetonitrile and water/acetone mobile phases produced the better chromatographic separation. Water/methanol produced slightly less satisfactory separation but the greatest overall response. This increase in response was attributed to the protic nature of methanol and the elution of compounds in a higher organic mobile phase composition (retention times were ∼30% later in methanol). This work is intended to facilitate rational liquid chromatography/mass spectrometry method development for small molecule applications, including metabolomics.

First Results of Magnetized Plasma Flow Injection on the TPE-RX Reversed-Field Pinch

Magnetic helicity and plasma flow injection experiments using a magnetized coaxial plasma gun on a reversed-field pinch were performed for the first time. In the initial experiments, increases in the electron density and toroidal flux were observed. The dependence of flux change on the polarity of the injected helicity indicates the possibility of the magnetic helicity injection and the poloidal current drive.

Efficient analyte oxidation in an electrospray ion source using a porous flow-through electrode emitter

This article describes the components, operation, and use of a porous flow-through electrode emitter in an electrospray ion source. This emitter electrode geometry provided enhanced mass transport to the electrode surface to exploit the inherent electrochemistry of the electrospray process for efficient analyte oxidation at flow rates up to 800 microL/min. An upstream current loop in the electrospray source circuit, formed by a grounded contact to solution upstream of the emitter electrode, was utilized to increase the magnitude of the total current at the emitter electrode to overcome current limits to efficient oxidation. The resistance in this upstream current loop was altered to control the current and "dial-in" the extent of analyte oxidation, and thus, the abundance and nature of the oxidized analyte ions observed in the mass spectrum. The oxidation of reserpine to form a variety of products by multiple electron transfer reactions and oxidation of the ferroceneboronate derivative of pinacol to form the ES active radical cation were used to study and to illustrate the performance of this new emitter electrode design. Flow injection, continuous infusion, and on-line HPLC experiments were performed.

Simultaneous electrochemical detection of uric acid and ascorbic acid at a poly( N, N-dimethylaniline) film-coated GC electrode

A polymer film of N, N-dimethylaniline (PDMA) having a positive charge on the quarternary ammonium group in its backbone was electrochemically deposited on a glassy carbon (GC) electrode surface. The resulting film-coated GC electrode was used to detect uric acid (UA) electrochemically in the presence of ascorbic acid (AA). Both UA and AA are anionic in a solution of pH 7 and thus were attracted to the film, which lowered their oxidation potentials and increased their oxidation currents. In cyclic voltammetric measurements, the negative shift of the oxidation potential of UA (by 0.28 V) compared with that at the bare electrode was larger than that of AA (by 0.2 V). Also the increase in the oxidation current of UA at the PDMA film-coated electrode was larger than that of AA. In square wave voltammetric measurements, the PDMA film-coated electrode could separate the oxidation peak potentials of UA and AA present in the same solution by about 200 mV though the bare electrode gave a single broad response. A successful elimination of the fouling effect by the oxidized product of AA on the response of UA has been achieved at the PDMA film-coated electrode. The detection limit of UA in the presence of 160-fold excess of AA was found as 1.25 μM and the current response for UA increased linearly with increase of its concentration from 1.25 to 68.75 μM in the presence of AA with a correlation coefficient of 0.999 and a sensitivity of 0.0276 μA μM −1. In flow injection analysis, a good linear relationship between the oxidation current and the concentration from 2 to 21 μM of UA was found. The sensitivity of the PDMA film-coated electrode towards UA was calculated as 0.0285 μA μM −1 with a correlation coefficient of 0.997. The stable and reproducible response for both AA and UA at the PDMA film-coated electrode was verified by flow injection experiments. As the response of UA was reproducible in the presence of AA, it was expected that the oxidized product of AA would not affect the electrode response of UA. Moreover, the physiologically common interferents (i.e., glucose, purine, urea and citrate) negligibly affected the response of UA. The PDMA film-coated electrode exhibited a stable and sensitive response to UA in the presence of interferents.

Ultra-simple adaptor to convert batch cells with mercury drop electrodes in voltammetric detectors for flow analysis

A simple, robust and fast-responding flow adaptor for mercury drop electrodes (MDEs) is described. An L-shaped PTFE tube with an internal diameter of 0.5 mm is fixed with a silicone ring on the glass capillary of a MDE, in such a way as to direct the outcoming flow onto the mercury drop, from a distance of about 0.5 mm. Any commercial or laboratory-made batch cell, provided with an MDE, serves for the purpose. The level of supporting electrolyte in the cell is maintained constant through a siphon or a lateral draining orifice. The adaptor is compatible with all the different brands and operating modes of the MDEs (free dropping, controlled drop time, renewable static drop, hanging drop or sessile drop). Flow injection experiments were conducted with the following amperometric detection modes: sampled-DC, reverse pulse amperometry (RPA), and anodic stripping voltammetry (ASV). The FIA-RPA peaks presented a R.S.D.<0.8% for 1.0×10 −5 mol l −1 lead(II) (N=30, V sample=100 μl). The response time (0–63% of the signal maximum) to a concentration step is 1.2 s for 500 μl injections of 0.1 mmol l −1 ascorbic acid in acetate buffer at a flow rate of 1 ml min −1, which corresponds to a response volume of 20 μl. As an example of practical application, copper(II) was determined in fertilizers by RPA using the standard addition method, at an analytical frequency of 90 injections per h.

Electrochemical determination of captopril at boron-doped diamond thin film electrode applied to a flow injection system

A boron-doped diamond thin film (BDD) electrode was first used to study the electroanalysis of captopril in phosphate buffer (pH=9) by several techniques such as cyclic voltammetry, hydrodynamic voltammetry and flow injection with amperometric detection. Cyclic voltammetry was used to study the reaction as a function of concentration of analyte. The results were compared with a glassy carbon (GC) electrode at the same condition. Captopril undergoes irreversible reaction at both electrodes. However, the BDD electrode provided highly reproducible, well-resolved cyclic voltammogram and higher signal-to-background (S/B) ratio comparing with GC electrode. Linear range from 50 μM to 3 mM and detection limit of 25 μM (S/B≈3) were obtained from the BDD electrode using cyclic voltammetry. The potential sweep rate dependence of captopril oxidation (peak currents for 1 mM captopril linearly proportional to v 1/2, within the range of 0.01 to 0.3 V s −1) indicates that the oxidation current is diffusion controlled with negligible adsorption on the BDD surface. The flow injection experiments of the BDD electrode at the concentration from 0.5 to 100 μM provided a linear dynamic range and very low detection limit of 10 nM were obtained (S/N≈3). In addition, the determination of captopril in the commercial available tablets by flow injection system with amperometric detection at diamond electrodes has also been investigated. The results show very good precision (1.21–2.15%).

Flow injection analysis in a microfluidic format.

A microfluidic flow injection analysis system has been designed and evaluated. The system incorporates within a single two-layer poly(dimethylsiloxane) monolith multiple pneumatically driven peristaltic pumps, an injection loop, a mixing column, and a transparent window for fluorescence detection. Central to this device is an injection system that mimics the operation of a standard six-port, two-way valve used in conventional liquid chromatography and flow injection experiments. Analyte and carrier solutions continuously flow through this injection system allowing for measurements and sample changes to be performed rapidly and simultaneously. Injection volumes of 1.25 nL generated peak area reproducibility of better than 3% relative standard deviation. The flow injection device was evaluated with fluorescent dyes and demonstrated a detection limit of 400 zmol for fluorescein. A rudimentary sample selection system allowed calibration curves to be rapidly produced, often in less than 10 min. The hydrolysis of fluorescein diphosphate by alkaline phosphatase demonstrates that chemical assays can be carried out with this device in a manner characterized by short analysis times and low sample consumption.

Continuous monitoring of amino acids and related compounds with poly(3-methylthiophene)-coated cylindrical carbon fiber microelectrodes

The use of cylindrical carbon fiber microelectrodes (CFMEs) modified with poly(3-methylthiophene) (P3MT) films as amperometric microsensors for continuous monitoring of some amino acids such as tyrosine (Tyr), tryptophan (Trp), L-dopa, and related compounds such as tyramine and ascorbic acid, as well as small peptides such as Trp–Ala and Tyr–Gly, is discussed. Important practical advantages with respect to conventional glassy carbon (GC) electrodes, and also with respect to P3MT-coated GC electrodes of conventional size are demonstrated. The electrocatalytic ability of the modified surface allows the possibility of applying moderate potentials for the amperometric detection of the above mentioned compounds. Flow-injection experiments carried out using a phosphate buffer solution of pH 7.0 as the carrier, and an applied potential of +0.8 V showed that no cleaning or regeneration pretreatment was needed when working with the same polymer modified electrode during the whole working day. The effect of the presence of acetonitrile or methanol in the flowing solution was evaluated. A flow-injection method with amperometric detection was developed for the determination of L-dopa in pharmaceutical preparations. Finally, the modified microelectrodes have also shown suitable for amperometric detection in liquid chromatography (LC). A mobile phase composed of 5 : 95 (v/v) methanol : phosphate buffer solution of pH 7.0 allowed a good separation of mixtures of ascorbic acid, L-dopa, Tyr, tyramine and Trp, with detection limits of around 160 pmol. Furthermore, the possibility of detection of Tyr- and Trp-containing oligopeptides was also demonstrated.

HPLC Analysis of Carbohydrates with Electrochemical Detection at a Poly-1-naphthylamine/Copper Modified Electrode

Carbohydrates are detected by constant potential amperometric detection at a modified electrode consisting of poly-1-naphthylamine coated glassy carbon with copper ions incorporated into the polymeric matrix. The polymer is electrodeposited onto the glassy carbon surface by cyclic voltammetric experiments, and copper ions incorporated by immersion of the modified electrode in a 0.10 M cupric ions solution. The amount of copper incorporated into the polymeric matrix is regulated by controlling the immersion time. Cyclic voltammetric experiments showed that glucose was oxidized at the modified electrode surface. The catalytic current for glucose oxidation was dependent on the amount of copper incorporated. Flow injection experiments allowed the determination of the working electrode potential at which maximum signal-to-noise ratios were obtained. The electrode was successfully used in the high performance liquid chromatographic analysis of various carbohydrates.

Nickel content dependence of electrochemical behavior of carbohydrates on a titanium–nickel alloy electrode and its application to a liquid chromatography detector

A highly sensitive amperometric detector for the liquid chromatographic analysis of carbohydrates has been developed based on the optimization of the Ni content in a Ni–Ti alloy electrode. An optimum nickel content of 30 at. % was obtained from a signal-to-noise analysis in a flow injection experiment on glucose in 0.1 M NaOH. An optimum working potential of 0.5 V vs. Ag/AgCl was obtained from a hydrodynamic voltammogram. The glucose detection limit in the flow injection analysis was 11 fmol. The electrode was applied to an LC detector with a microbore column and the detection limit was 50 fmol.

Amperometric detection with microelectrodes in flow injection analysis: theoretical aspects and application in the determination of nitrite in saliva

The construction of a wall-jet cell with amperometric detection using a set of disc electrodes whose radii ranged from 5 to 750 μm has been proposed. The influence of some experimental parameters like flow rate and electrode radius on hydrodynamic voltammograms recorded for a 0.5 mmol dm −3 potassium ferrocyanide solution also containing 0.1 mol dm −3 KCl has been discussed. Some considerations regarding the current signals obtained from flow injection experiments using both a 5- and a 750-μm radius platinum electrode were carried out in order to achieve the lowest limit of detection, a value of 0.03 μmol dm −3 ferrocyanide being calculated by using the 5-μm radius microelectrode as amperometric detector. The wall-jet cell has been used in the determination of nitrite in saliva by quantifying the triiodide formed in the reaction of the analyte with excess iodide in acidic medium. A 12.5-μm platinum disc microelectrode maintained at +0.2 V vs. Ag/AgCl was used as amperometric detector. Peaks obtained in fiagrams after injection of diluted saliva to the carrier stream containing 0.1 mol dm −3 sulphuric acid and 20 mmol dm −3 potassium iodide were compared to an analytical curve obtained in the same conditions ( r 2=0.997) for a nitrite concentration in the range 1–10 μmol dm −3. The concentration of nitrite in the saliva sample after the appropriate correction for dilution was found to be 2.3 ppm (0.05 mmol dm −3), in a good agreement with results obtained by using a standard spectrophotometric procedure (2.5 ppm). The limit of detection of the method was calculated as 0.2 μmol dm −3, and the reproducibility was checked by measuring the peak current for 19 injections of 10 μM nitrite, the standard deviation being 3.7%.

An automated electro‐osmotic sample introduction/separation interface for automated electro‐osmotic flow flow‐injection mass spectrometry, infusion mass spectrometry and capillary electrochromatography mass spectrometry

A novel automated electro-osmotic flow (EOF) sample introduction and separation interface has been designed, developed and successfully coupled to an electrospray mass spectrometer. The system consists of a small-footprint automated capillary electrochromatography (CEC) injection and separation interface that has an integrated autosampler and connects to the outside world via a proprietary controller for automated CEC/MS, EOF infusion and flow-injection analysis (EOFFIA). The system utilizes a previously described CEC/MS/MS micro-electrospray interface that allows optimization of the spray conditions. Short CEC columns or open capillaries are immobilized in a hollow stainless steel needle that is located in a pincher bar through which injection and running high voltage is applied. The needle assembly is easily removed for ease of column installation and changeover. At the heart of the automated system is a microprocessor-based controller which allows both manual and automated control via a 12-way key pad. The controller provides automatic indexing of a 10 position sample carousel, control of kV supply so that injection and running voltages can be set independently for full flexibility and mass spectometer synchronizing signals. The design, although currently on a Finnigan TSQ 7000, has been made flexible in both mechanical and electronic design to be easiliy adaptable to other mass spectrometers. Examples of all functions of the system are presented here including rapid flow injection and controllable infusion experiments. Simple mixtures could be separated by CEC/MS with great efficiency and sensitivity in a short time. An example of multiple automated analytical runs performed continuously over a period of 10 hours are described. We believe this is the first report of a custom built CEC system with an integrated CEC/MS/MS interface that obviates the need for an expensive and unsuitable converted commercial CE system for sample introduction whilst allowing for a useful degree of automation. This system addresses many of the robustness and reduction-to-practice problems of CEC/MS and will catalyse the development of CEC/MS and allow the systematic optimization and evaluation of the technique. © 1998 John Wiley & Sons, Ltd.

An automated electro-osmotic sample introduction/separation interface for automated electro-osmotic flow flow-injection mass spectrometry, infusion mass spectrometry and capillary electrochromatography mass spectrometry

A novel automated electro-osmotic flow (EOF) sample introduction and separation interface has been designed, developed and successfully coupled to an electrospray mass spectrometer. The system consists of a small-footprint automated capillary electrochromatography (CEC) injection and separation interface that has an integrated autosampler and connects to the outside world via a proprietary controller for automated CEC/MS, EOF infusion and flow-injection analysis (EOFFIA). The system utilizes a previously described CEC/MS/MS micro-electrospray interface that allows optimization of the spray conditions. Short CEC columns or open capillaries are immobilized in a hollow stainless steel needle that is located in a pincher bar through which injection and running high voltage is applied. The needle assembly is easily removed for ease of column installation and changeover. At the heart of the automated system is a microprocessor-based controller which allows both manual and automated control via a 12-way key pad. The controller provides automatic indexing of a 10 position sample carousel, control of kV supply so that injection and running voltages can be set independently for full flexibility and mass spectometer synchronizing signals. The design, although currently on a Finnigan TSQ 7000, has been made flexible in both mechanical and electronic design to be easiliy adaptable to other mass spectrometers. Examples of all functions of the system are presented here including rapid flow injection and controllable infusion experiments. Simple mixtures could be separated by CEC/MS with great efficiency and sensitivity in a short time. An example of multiple automated analytical runs performed continuously over a period of 10 hours are described. We believe this is the first report of a custom built CEC system with an integrated CEC/MS/MS interface that obviates the need for an expensive and unsuitable converted commercial CE system for sample introduction whilst allowing for a useful degree of automation. This system addresses many of the robustness and reduction-to-practice problems of CEC/MS and will catalyse the development of CEC/MS and allow the systematic optimization and evaluation of the technique. © 1998 John Wiley & Sons, Ltd.

Electrooxidation of thiocyanate on the copper-modified gold electrode and its amperometric determination by ion chromatography.

Cyclic voltammetry was used to investigate the electrochemical behavior of an Au/Cu electrode towards the electrooxidation of thiocyanate ion in alkaline medium. The effects of pH, copper loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate have been investigated. Flow injection experiments and ion-chromatography (IC) were performed to characterise the electrode as an amperometric sensor for the thiocyanate determination. The effects of carbonate concentration and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 microM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 microM (29 ppb) in a 50 microlitres injection. An example of analytical application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.