Automated Flow Injection Analysis Research Articles

Automated identification of unknown doping agents in confiscation samples by flow-injection mass spectrometry and mass spectral library searches.

Rapid and accurate identification of unknown compounds within suspicious samples confiscated for sports doping control and law enforcement drug testing is critical, but such analyses are often conducted manually and can be time-consuming. Here, we report a methodology for automated identification of unknown substances in confiscation samples by rapid automatic flow-injection analysis on a liquid chromatography coupled to high-resolution mass spectrometry system and identifying unknown compounds with Compound Discoverer software. The developed methodology was validated by comparing the automated identification results with those obtained from manual syringe-infusion experiments and manual tandem mass spectral library searches. The automated methodology resulted in far higher throughput and remarkably shorter turnaround time for analysis when compared with manual procedures and, in most cases, yielded more compounds. As this is the first such report to the authors' knowledge, this methodology may potentially transform analysis of confiscated samples in sports doping control and law enforcement drug testing.

A simple and fast flow injection amperometry for the determination of methimazole in pharmaceutical preparations using an unmodified boron-doped diamond electrode.

In this work, an automated flow injection analysis (FIA) connected to a boron-doped diamond electrode (BDDE) was originally developed for the analysis of methimazole in pharmaceutical preparations. At a modification-free BDDE, methimazole was easilly oxidized. For the analysis of the mechanisms occurring at the electrode surface, cyclic voltammetry was employed to evaluate the impact of fundamental experimental parameters, such as pH and scan rate, on the BDDE response. For the quantitative detection, the FIA amperometric approach was constructed and used as a fast and sensitive method. The suggested approach provided a broad linear range of 0.5-50 μmol/L and a low detection limit of 10 nmol/L (signal-to-noise ratio = 3). Furthermore, the BDDE was successfully utilized to quantify methimazole in genuine samples from a variety of medicines, and its performance remained steady after more than 50 tests. The findings of amperometric measurements exhibit excellent repeatability, with relative standard deviations of less than 3.9 and 4.7 % for intra-day and inter-day, respectively. The findings indicated that, compared with traditional approaches, the suggested method has the following advantages: quick analysis time, simplicity, highly sensitive output, and no need for complicated operational processes.

Bulid-up a flow injection analysis unit for ammonium determination in the Shatt Al-Arab water

A Semi- automated flow injection analysis (FIA) unit was build-up for determination of ammonium ion in water samples from the Shatt Al-Arab River during the period from October 2009 to September 2010. The ammonium concentrations in water have been measured, at each of the eight stations (Qurnah (Tigres), Qurnah (Euphrates), Saad Bridge, Garmat Ali, Ashar, Abu Al-Khaseeb, Al-Seeba and Fao), monthly. The results indicated that (NH4+) concentrations increasing during May, June and July, 2010 especially in stations 5 and 6 were 0.95, 1.35 µg/ml , 1.30, 1.25 µg/ml and 1.45, 1.40 µg/ml, respectively. The FIA unit was applied successfully for the determination of ammonium in Shatt Al-Arab water sample and provide simple, fast, and reproducible methods for ammonium determination in water.

Improving the measurement of total dissolved sulfide in natural waters: A new on-site flow injection analysis method

Total dissolved sulfide (TDS) plays multiple important roles in the aquatic environments. However, the determination of trace levels of TDS in natural waters is challenging because TDS is vulnerable to oxidation and volatilization. In this study, a fully automated flow injection analysis spectrophotometric system, incorporating a hollow fiber membrane contactor (HFMC) and a long path length liquid waveguide capillary cell, was fabricated to facilitate the on-site measurement of trace TDS in natural waters. The HFMC was used for matrix separation and analyte preconcentration. The measurement was based on the reaction of sulfide and N,N-dimethyl-p-phenylenediamine in the presence of FeCl3 under acidic conditions to yield methylene blue (MB). The proposed method was highly sensitive, with detection and quantification limits of 0.57 and 1.90 nmol L−1, respectively. The linear working range was from 1.90 to 150 nmol L−1, with a correlation coefficient of 0.9995. The repeatability, expressed as the relative standard deviation, was less than 0.86% (n = 15) and the recoveries varied from 76.2 ± 0.1% to 103.9 ± 0.6% (n = 3) for spiked samples. This method was applied to conduct a field analysis of TDS in a reservoir, giving results aligned with those obtained using a standard MB method. This work demonstrates that the new method for determining TDS was effective for both laboratory analysis and on-site measurement.

Development of shipboard automatic flow injection analysis-Surface-enhanced Raman spectroscopy instrument toward onsite detection of trace polycyclic aromatic hydrocarbons in water environment.

The qualitative and quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) has been important for the environmental control of persistent organic pollutants for decades. Considering the potential risk of deterioration, degradation, and external pollution during transportation, the development of rapid and onsite detection of trace PAHs is in demand. Here, taking the advantage of high sensitivity of surface-enhanced Raman spectroscopy (SERS), we developed a shipboard instrument by combining a portable Raman instrument and a flow injection device, integrating the sample pretreatment and target detection step by step. The feasibility of the instrument was demonstrated by detecting trace benzo[a]pyrene from different water environments with the lowest detection concentration less than 1 µg/l. The reliable stability and repeatability indicate that in the case of emergency response, the developed flow injection analysis-SERS instrument is very promising for the quantitative and qualitative analysis of diverse organic pollutants other than PAHs in water environments.

Decoupling of nutrient cycles in a Eucalyptus woodland under elevated CO2

Abstract Elevated atmospheric [CO2] (eCO2) is currently altering nutrient cycling and availability in ecosystems worldwide. If the availabilities and turnover rates of macro‐ and micronutrients are differentially affected, then nutrient cycles may become out of sync (i.e., decoupled). We evaluated the impacts of 3 years of eCO2 (550 µmol CO2/mol) on the availability, stability and coupling of eleven essential macro and micronutrients in a mature, P‐limited Eucalyptus woodland from Eastern Australia (EucFACE). Despite increases in N and P availability in the first 18 months of study, nutrient availabilities and their stoichiometric ratios were unaffected by eCO2 across the study period (26–57 months of experimental duration). In contrast, the stability of nutrient availability increased under eCO2, which was concomitant with a reduction in the degree of biogeochemical coupling. Synthesis. We demonstrate that macro‐ and micro‐nutrient cycles can quickly become out of sync (i.e., decoupled) under eCO2 in a low‐nutrient Australian eucalypt woodland, despite the lack of consistent effects on nutrient availability; such decoupling of nutrient cycles may have unpredicted consequences in terms of ecosystem functioning under the widely assumed positive relationship between biogeochemical coupling and ecosystem functioning.

Automated Determination of Chromium (VI) in Tannery Effluent Using Flow Injection Analysis with an Optical Flow Cell and Detector

Determination of hexavalent chromium (Cr (VI)) in tannery effluent is an important analytical objective for environmental monitoring and assessment. Here, a simple, accurate, and sensitive automated flow injection analysis (FIA) method is proposed in this paper. The procedure is based on a highly selective reaction between Ponceau S and Cr (VI) under acidic condition. The absorbance of the complex compounds was measured using an optical detector at 505 nm. The chemical factors and FIA variables that affect the system were fully discussed and optimized via univariate experimental design. Under the optimal conditions, a linear dynamic range of 0.1–3.0 mg/L with a satisfactory determination coefficient (R 2) of 0.9996 was obtained. The detection limit and relative standard deviation were 0.08 mg/L and 2.27%, respectively. Finally, the method was successfully applied to determine Cr (VI) in field samples of tannery effluent and the results have no significant difference comparing with one official method, indicating this FIA method could be practically promising for determination of Cr (VI) in tannery effluent.

Automated determination of nitrate plus nitrite in aqueous samples with flow injection analysis using vanadium (III) chloride as reductant

Determination of nitrate in aqueous samples is an important analytical objective for environmental monitoring and assessment. Here we report the first automatic flow injection analysis (FIA) of nitrate (plus nitrite) using VCl3 as reductant instead of the well-known but toxic cadmium column for reducing nitrate to nitrite. The reduced nitrate plus the nitrite originally present in the sample react with the Griess reagent (sulfanilamide and N-1-naphthylethylenediamine dihydrochloride) under acidic condition. The resulting pink azo dye can be detected at 540nm. The Griess reagent and VCl3 are used as a single mixed reagent solution to simplify the system. The various parameters of the FIA procedure including reagent composition, temperature, volume of the injection loop, and flow rate were carefully investigated and optimized via univariate experimental design. Under the optimized conditions, the linear range and detection limit of this method are 0–100µM (R2=0.9995) and 0.1µM, respectively. The targeted analytical range can be easily extended to higher concentrations by selecting alternative detection wavelengths or increasing flow rate. The FIA system provides a sample throughput of 20h−1, which is much higher than that of previously reported manual methods based on the same chemistry. National reference solutions and different kinds of aqueous samples were analyzed with our method as well as the cadmium column reduction method. The results from our method agree well with both the certified value and the results from the cadmium column reduction method (no significant difference with P=0.95). The spiked recovery varies from 89% to 108% for samples with different matrices, showing insignificant matrix interference in this method.

A chemometric study: Automated flow injection analysis method for the quantitative determination of humic acid in Ilgın lignite

A rapid, sensitive and provident flow injection analysis (FIA) method was developed within the framework of a chemometric approach for the quantification of humic acid (HA) in the lignite obtained from Ilgın, Konya, Turkey. The proposed method allows automatic determination of 60 samples per hour over a wide calibration range (0–2000mgL−1, R2: 0.9988) and needs only 10μL of sample at a flow rate of mobile phase (X1), 2mLmin−1; pH of mobile phase (X2), 8, and system temperature (X3), 20°C. The limits of detection (LOD) and quantification (LOQ) were calculated as 9.18mgL−1 and 30.60mgL−1, respectively, and the relative standard deviation (RSD) for 500mgL−1 HA was calculated as 3.44 (n: 9). It was revealed that the standard deviation (SD) values of the proposed FIA method are lower than those of the spectrophotometric method.

Automatic flow injection analysis (FIA) determination of total reducing capacity in serum and urine samples.

Automation of total antioxidant capacity assessment can substantially increase the determination throughput, allowing large scale studies and screening experiments. Total reducing capacity evaluation can be implemented under different chemistries, including the CUPRAC-Cupric Ion Reducing Antioxidant Capacity -assay. This assay is based on reduction of Cu(II)-neocuproine complex to highly colored Cu(I)-neocuproine complex by reducing (antioxidant) components of biological samples. In this chapter, we propose an automatic flow injection method for evaluation of total reducing capacity in serum and urine samples, attaining end-point data within 4 min using a kinetic matching strategy.

Paramagnetic particles coupled with an automated flow injection analysis as a tool for influenza viral protein detection

Currently, the influenza virus infects millions of individuals every year. Since the influenza virus represents one of the greatest threats, it is necessary to develop a diagnostic technique that can quickly, inexpensively, and accurately detect the virus to effectively treat and control seasonal and pandemic strains. This study presents an alternative to current detection methods. The flow-injection analysis-based biosensor, which can rapidly and economically analyze a wide panel of influenza virus strains by using paramagnetic particles modified with glycan, can selectively bind to specific viral A/H5N1/Vietnam/1203/2004 protein-labeled quantum dots. Optimized detection of cadmium sulfide quantum dots (CdS QDs)-protein complexes connected to paramagnetic microbeads was performed using differential pulse voltammetry on the surface of a hanging mercury drop electrode (HMDE) and/or glassy carbon electrode (GCE). Detection limit (3 S/N) estimations based on cadmium(II) ions quantification were 0.1 μg/mL or 10 μg/mL viral protein at HMDE or GCE, respectively. Viral protein detection was directly determined using differential pulse voltammetry Brdicka reaction. The limit detection (3 S/N) of viral protein was estimated as 0.1 μg/mL. Streptavidin-modified paramagnetic particles were mixed with biotinylated selective glycan to modify their surfaces. Under optimized conditions (250 μg/mL of glycan, 30-min long interaction with viral protein, 25°C and 400 rpm), the viral protein labeled with quantum dots was selectively isolated and its cadmium(II) content was determined. Cadmium was present in detectable amounts of 10 ng per mg of protein. Using this method, submicrogram concentrations of viral proteins can be identified.

Developing a validated liquid chromatography–mass spectrometric method for the simultaneous analysis of five bioactive quassinoid markers for the standardization of manufactured batches of Eurycoma longifolia Jack extract as antimalarial medicaments

An extensive comparative study on the electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) mass spectrometry using automated flow injection analysis (FIA), was performed on eurycomanone ( 1), 13 α(21)-epoxyeurycomanone ( 2), eurycomanol ( 3), eurycomanol-2- O- β- d-glucopyranoside ( 4), and 13,21-dihydroeurycomanone ( 5), the bioactive markers isolated from Eurycoma longifolia. The effects of eluent mixture (methanol or acetonitrile in water) and acidic modifiers (acetic acid, formic acid and trifluoroacetic acid) on the ionization efficiency of the markers were also investigated. The ESI in the positive ion mode with methanol containing 0.1% (v/v) acetic acid was selected for the subsequent optimization of nebulizer pressure, dry gas flow, dry gas temperature and capillary voltage to improve the sensitivity of the total ion chromatogram (TIC). Fragmentation of the analytes was further investigated by varying the capillary exit offset voltage and fragmentation amplitude in positive mode of ESI. The detection limits (LODs) were determined in isolation mode (selected ion monitoring, SIM). Their limits of detection (LODs) ranged between 0.03 and 0.1 μg mL −1 while the intra-day and inter-day precisions were less than 5.72% and 4.82%, respectively. The method was next applied for the simultaneous analysis of the markers to standardize various batches of manufactured extracts of E. longifolia for potential use as antimalarial products. Multiple Reaction Monitoring (MRM) mode was used for the quantification of analytes which gave protonated molecular ion, [M+H] +. For those without pseudo-molecular ions, SIM mode was used to quantify the analytes. The batches contained 5.65–9.95% of eurycomanone ( 1), 5.21–19.75% of eurycomanol ( 3) and 7.59–19.95% of eurycomanol-2- O- β- d-glucopyranoside ( 4) as major quassinoids whereas, 13 α(21)-epoxyeurycomanone ( 2), and 13,21-dihydroeurycomanone ( 5) were much lower in concentrations of 0.78–3.90% and 0.47–1.76%, respectively.

Development of a Fully Automated Flow Injection Analyzer Implementing Bioluminescent Biosensors for Water Toxicity Assessment

This paper describes the development of an automated Flow Injection analyzer for water toxicity assessment. The analyzer is validated by assessing the toxicity of heavy metal (Pb2+, Hg2+ and Cu2+) solutions. One hundred μL of a Vibrio fischeri suspension are injected in a carrier solution containing different heavy metal concentrations. Biosensor cells are mixed with the toxic carrier solution in the mixing coil on the way to the detector. Response registered is % inhibition of biosensor bioluminescence due to heavy metal toxicity in comparison to that resulting by injecting the Vibrio fischeri suspension in deionised water. Carrier solutions of mercury showed higher toxicity than the other heavy metals, whereas all metals show concentration related levels of toxicity. The biosensor’s response to carrier solutions of different pHs was tested. Vibrio fischeri’s bioluminescence is promoted in the pH 5–10 range. Experiments indicate that the whole cell biosensor, as applied in the automated fluidic system, responds to various toxic solutions.

Analysis of total dissolved mercury in waters after on-line preconcentration on an active gold column

A reagent-free fully automated flow injection analysis (FIA) system coupled to atomic fluorescence spectrometry (AFS) for mercury (Hg) quantification is reported, using active nano-structured gold collectors for direct preconcentration of dissolved mercury species from natural waters. Recently we had shown the potential of such an approach for Hg analysis in seawater. This paper now describes the optimisation and validation of the proposed method including the investigation of possible limitations arising with matrix constituents, such as dissolved organic carbon (DOC). A broad variety of water matrices (seawater, river water, moorland water, effluent from wastewater treatment plant) were investigated in order to check the feasibility of the proposed method for total dissolved Hg determination in natural waters. All FIA parameters were optimised by checking Hg recovery in real water samples. Figures of merit of the proposed method - working range, carry over effects, detection limit, reproducibility, etc. - were determined. The method provides a high sensitivity (detection limit: 0.2pgHg) and very good reproducibility (RSD 1.1%, [Hg]=5ngL(-1), n=10). It offers several advantages because no reagents are needed for species conversion, preconcentration, or desorption and therefore the risk of contamination and blank values are lowered, reagent and time consumption are minimized. The system was successfully validated by measurement of a series of recoveries in real waters (all >96%) and in the certified standard reference material BCR 579 (mercury in coastal sea water, recovery 100.5%). Furthermore, the proposed method was applied to 15 real water samples for Hg ultra trace analysis.

Determination of free and total sulfites in wine using an automatic flow injection analysis system with voltammetric detection

An automated flow injection analysis (FIA) system, based on an initial analyte separation by gas-diffusion and subsequent determination by square-wave voltammetry (SWV) in a flow cell, was developed for the determination of total and free sulfur dioxide (SO2) in wine. The proposed method was compared with two iodometric methodologies (the Ripper method and a simplified method commonly used by the wine industry). The developed method displayed good repeatability (RSD lower than 6%) and linearity (between 10 and 250 mg l−1) as well as a suitable LOD (3 mg l−1) and LOQ (9 mg l−1). A major advantage of this system is that SO2 is directly detected by flow SWV.

An Open-Ended Experiment: Development from Batch to Automated Flow Injection Analysis for Phenolics Determination

This student-design project, consisting of three types of experiments, involves the development of a continuous colorimetric method for analyzing phenol. With the goal of enhancing student motivation, this open-ended experiment is presented as a fictitious industrial problem concerned with off-flavors from phenol in fermented beverages. Experience has shown that students are more motivated when working in an interactive and realistic way. The goal is the development of a continuous-analysis spectrophotometric method. Accomplishing this goal requires more than simply carrying out procedural instructions. Instead, thought and experimentation by the students are necessary to improve and automate the analysis method. The students start with an established batch analysis method for phenol. Using suitable components, the process is made continuous (continuous flow analysis) and finally a flow injection method (flow injection analysis) is designed. Because of the modular concept of the unit, dispersion experiments, colorimetric procedures, and other exercises can be carried out alternatively. The system used can be easily and rapidly modified to apply different methods. As in a real-life situation, the experimental results should not be considered only in terms of their analytical aspects, but also as a means of gathering chemical information in a simple, rapid, and economical manner.

Automated system for spectrophotometric detection of liquid phase hydrogen peroxide for concentrations up to 5% w/w

An automated flow injection analysis system for H(2)O(2) detection in the liquid phase, based on the photometric determination of the complex between hydrogen peroxide and a titanium (IV) reagent is presented. The system was tested for monitoring the H(2)O(2) concentration in a lab-scale experimental setup for H(2)O(2) direct synthesis. In its final configuration, the developed system allows a reliable and reproducible determination of H(2)O(2) for a broad concentration interval between 1.02x10(-3) mol l(-1) and 1.16 mol l(-1).

A near real-time system for continuously monitoring airborne subtilisin-type enzymes in the industrial atmosphere

We describe the development and validation of a portable system comprising an air sampler coupled to an automated flow injection analysis device. The system is able to monitor airborne concentrations of subtilisin-type enzymes in the workplace atmosphere on a continuous basis. Sampling is in two stages: using a sampling head that is designed to mimic human respiration at approx. 1 m s(-1) at a sampling rate of 600 l min(-1). In the second stage, the captured particles are deposited by impaction from the air stream onto the inner surface of a cyclone that is continuously washed with a jet of buffer solution. Deposited particles are then washed into a reservoir from which samples are taken every 5-6 min and injected automatically into a continuous flow injection analysis system. Proteolytic enzyme in the sample passes through a bioreactor maintained at about 40 degrees C. This contains a cellulose solid phase matrix on which is covalently immobilised Texas Red-labelled gelatin as substrate. The passing enzyme partially digests the substrate releasing fluorophore that is detected down stream in a flow cell coupled to a fluorimeter. The system is calibrated using enzyme standards and the intensity of the resulting peaks from the ex-air samples is converted to airborne concentrations using a mathematical model programmed into a PC. The system has a limit of detection of 4.8 ng m(-3) and a dynamic range of 5-60 ng m(-3). The within assay precision (RSD) is 6.3-9.6% over this range. The within batch precision is 20.3% at 20 ng m(-3) and the corresponding between batch value is 19.5%. The system has been run for periods up to 8 h in the laboratory and for up to 4 h at a factory site and the values obtained compared with time-averaged values obtained from a conventional Galley sampler and in-house analysis when reasonable agreement of the results was observed. The stability of the system over 21 days of continuous use with standards injected periodically was studied. Linearity was observed for all the standard plots throughout. At the end of 21 days, after a total exposure equivalent to 2395 ng ml(-1) of Savinase, the signal due to the 5.0 ng ml(-1) standard was still easily detectable.

On-line preconcentration cold vapour atomic absorption spectrometry for the determination of trace mercury in edible seaweeds

Possibilities for the use of an inexpensive sulfydryl cotton fiber (SCF) adsorbent to separate and preconcentrate traces of mercury from acid digests from edible seaweed have been evaluated. Commercial empty cartridges were filled with around 0.75 g of laboratory-made adsorbent and they were incorporated in the 5-way valve of an automatic flow injection analysis system. Traces of mercury in acid digests were pumped through the cartridges for 45 s (flow rate of 8.8 ml min−1) and then eluted from cartridges with 0.5 M hydrochloric acid and 1.0 M sodium chloride solution for 45 s at a flow rate of 5.8 ml min−1. At the same time that mercury is eluted from the cartridges, the eluate is mixed with a 0.05% (m/v) sodium tetrahydroborate solution and the mercury cold vapour is swept through the atomization cell with an argon flow of 50 ml min−1. The overall procedure (mercury separation/preconcentration and mercury cold vapour generation/atomization) is completed after around 90 s. The developed method implies an enrichment factor of 10.2 with a limit of detection of 5.23 ng g−1. Repeatability of the overall procedure and accuracy were successfully assessed.

Development of enzyme flow calorimeter system for monitoring of microbial glycerol conversion

Glycerokinase from Cellulomonas sp. was used to develop biosensor based on flow calorimetry for quantitative analysis of glycerol during bioconversion process. An automatic flow injection analysis device with the glycerol biosensor was built and tested during growth on glycerol of 1,3-propanediol-producing bacteria. The biosensor exhibited an extreme storage and operational stability enabling us to use it for more than 2 years without significant loss of sensitivity. No interference with 1,3-propanediol and fermentation medium was observed. The linear range of glycerol concentration up to 70 mM was extended by developed automatic dilution technique with the aim of automatic online monitoring of microbial process. The analytical system was able to monitor the bioconversion process in a fully automatic way during the whole run with sampling frequency of one sample per 10 min.