Flow Injection Analysis System Research Articles

Reusable graphite-based electrochemical sensors for L-dopa and dopamine detection.

Afully reusable electrochemical device is proposed for the first timemade from laser cutting and a homemade conductive ink composed of carbon and nail polish. As a sensor substrate, we applied polymethyl methacrylate, which allows the surface to be renewed by simply removing and reapplying a new layer of ink. In addition to the ease of renewing the sensor's conductive surface, the design of the device has allowed for the integration of different forms of analysis. The determination of L-Dopa was performed using DPV, which presented a linear response range between 5.0 and 1000.0μmol L-1, and a LOD of 0.11μmol L-1. For dopamine, a flow injection analysis system was employed, and using the amperometric technique measurements were performed with a linear ranging from 2.0 to 100.0μmol L-1anda LOD of 0.26μmol L-1. To demonstrate its applicability, the device was used in the quantification of analytes in pharmaceutical drug and synthetic urine samples.

Spectrophotometric determination of amoxicillin in pharmaceutical formulations using normal and reverse flow injection analysis systems: A comparison study

The combination of flow injection technique and spectrophotometric detection can be employed for the rapid and low-cost methods for antibiotic assay. In this work, two flow injection analysis (FIA) systems, normal and reverse (nFIA and rFIA), combined with UV-Vis spectrophotometric technique were used for amoxicillin determination in its pure and pharmaceutical preparations. A colorimetric coupling reaction between amoxicillin and diazotized p-toluidine produced a bright yellow azo dye and quantified at a maximum wavelength of 426 nm. For nFIA and rFIA procedures, the amoxicillin calibration graphs had an RSD of less than 2% and were linear in the ranges of 5-200 and 1-140 µg/mL, respectively. The limits of detection and quantification were 1.41 and 4.71 µg/mL of amoxicillin for nFIA and 0.39 and 1.31 µg/mL for rFIA, respectively. The physical and chemical factors that could influence color sensitivity were investigated. Various commercial formulations containing different amounts of amoxicillin were successfully tested using the developed approaches, which demonstrated to be easy, rapid, reproducible, and interference-free.
 KEY WORDS: Amoxicillin, Normal FIA, Reverse FIA, p-Toluidine, Diazotization reaction
 Bull. Chem. Soc. Ethiop. 2024, 38(3), 577-590. 
 DOI: https://dx.doi.org/10.4314/bcse.v38i3.3

Determination, Manufacturing and application of a nanoparticle lead ion-selective electrode as a sensor in flow injection systems

This study involves the construction of ion-selective electrodes for the determination of lead (II) ions and their utilization as sensors in a flow-injection analysis (FIA) system. The electrode was constructed using a simple environmentally friendly method from a green tea extract, and a Lead acetate solution of the cited ions as a cylindrical disc. A vertical, side-to-side cylinder, the whole is created in its centre and another lateral hole is created for the electrical attachment of the electrode, so the prepared electrode is suitable for use with the FIA system. The electrode was studied surface properties and characteristics of this electrode were analysed using X-ray diffraction and Fourier-transform infrared spectroscopy (FTR). via selection of the optimum conditions (i.e. linear calibration range, lowest Nernstian response, lowest detection limit, degree of dilution, and precision and accuracy of their analytical uses). Electrode which gave the best Nernstian response1.00×10<sup>-1</sup> to 1.00×10<sup>-10</sup> M, a correlation coefficient of 0.9980, with lower Nernstian response of 1×10<sup>-10</sup> M and detection limit of 1×10<sup>-11</sup> M. The sampling rate was 120 samples per hour the calculated time of the contact of the sample with the electrode surface is 6 seconds and the degree of dilution is 2.37625.

Determination, Manufacturing and application of a nanoparticle lead ion-selective electrode as a sensor in flow injection systems

This study involves the construction of ion-selective electrodes for the determination of lead (II) ions and their utilization as sensors in a flow-injection analysis (FIA) system. The electrode was constructed using a simple environmentally friendly method from a green tea extract, and a Lead acetate solution of the cited ions as a cylindrical disc. A vertical, side-to-side cylinder, the whole is created in its centre and another lateral hole is created for the electrical attachment of the electrode, so the prepared electrode is suitable for use with the FIA system. The electrode was studied surface properties and characteristics of this electrode were analysed using X-ray diffraction and Fourier-transform infrared spectroscopy (FTR). via selection of the optimum conditions (i.e. linear calibration range, lowest Nernstian response, lowest detection limit, degree of dilution, and precision and accuracy of their analytical uses). Electrode which gave the best Nernstian response1.00×10-1 to 1.00×10-10 M, a correlation coefficient of 0.9980, with lower Nernstian response of 1×10-10 M and detection limit of 1×10-11 M. The sampling rate was 120 samples per hour the calculated time of the contact of the sample with the electrode surface is 6 seconds and the degree of dilution is 2.37625.

Automated method for the solid phase extraction of tetracyclines in wastewater followed by fluorimetric determination

This work presents a multisyringe flow injection analysis (MSFIA) system for the automatic extraction and determination of tetracyclines in wastewater samples. The sample was adjusted with Na2EDTA buffer before solid-phase extraction with an Oasis HLB column used for the analyte preconcentration. The europium (Eu3+)-based and citrate-mediated method (using Tris-HCl buffer) was selected for the fluorimetric analysis (λexc/em = 400/612 nm). For fluorescence detection, a low-cost system consisting of an USB 2000 CCD detector and a 3D-printed support that holds a LED light source was used. Under optimized conditions, the proposed method provided low limits of detection (9.4 μg L−1) and quantification (31 μg L−1), and good values for intra-day (<4 %) and inter-day precisions (<6 %). Recoveries of spiked TCs in wastewater samples ranged from 87 to 106 %. The results of this work were in good agreement with the measurements obtained by liquid chromatography coupled to a fluorescence detector.

Development of a Simple and Compact Flow-injection Analysis System Using an LED-based Absorbance Detector and Micro-ring Pumps

Development of a Simple and Compact Flow-injection Analysis System Using an LED-based Absorbance Detector and Micro-ring Pumps

Development and Optimization of an Amperometric Bi-enzyme Biosensor for Aspartame Determination

An amperometric bi-enzyme biosensor based on α-chymotrypsin (CHY) and alcohol oxidase (AOX) was developed for detection of aspartame in a flow injection analysis (FIA) system. The CHY and AOX were separately immobilized on bead supports using an adsorption technique. The cleavage of aspartame was catalyzed by CHY to produce methanol that was converted by AOX to formaldehyde and hydrogen peroxide. The formed hydrogen peroxide was detected amperometrically at a platinum electrode. The biosensor performance was optimized with respect to enzyme immobilization and operating conditions. The most suitable conditions for enzyme immobilization were 250 U/mL CHY and 100 U/mL AOX with 60 min immobilization time. The optimal conditions for operating the developed aspartame biosensor were a flow rate of 0.5 mL/min and pH 8.0 at an applied potential of +0.70 V versus Ag/AgCl. Under the optimal conditions, the developed biosensor showed a linear response over the aspartame concentration range 0.15–1.0 mM (coefficient of determination (R2) = 0.9941) with a sensitivity of 5.52 μA/mM·cm2 and a detection limit of 0.10 mM. The developed biosensor was successfully applied in the determination of aspartame in commercial samples.

Normal and Reverse Flow Injection Analysis Methods for Estimation of Mesalazine in Pharmaceutical Dosage Forms

Determining the actual amounts of active ingredients in various pharmaceutical commercial forms is still receiving a lot of attention. Two flow injection analysis (FIA) methods were suggested for determination of mesalazine (MES) in pharmaceutical forms. Normal and reverse FIA systems (nFIA and rFIA) combined with UV-Vis spectrophotometric technique were used for the analysis. The methods involved using two mods of FIA systems for measuring a colored product result from coupling of MES with 2,2'-dihydroxybiphenyl after oxidized with sodium periodate in alkaline medium. The absorbance of the red colored dye was measured at maximum wavelength of 500 nm. The calibration graphs for MES were linear in the ranges 2.5-200 and 0.5-60 µg/mL with RSD of best than 3% for both methods respectively. Also the limits of detection were 1.2 and 0.2 µg/mL and limits of quantitation were 3.6 and 0.7 µg/mL of MSL for nFIA and rFIA systems respectively. All physical and chemical conditions of flow systems such as flow rate, reaction coil length and reagent concentrations were carefully studied. The proposed methods were applied for determining MES in four commercial tablets without any interferences.

Flow injection analysis coupled with photoelectrochemical immunoassay for simultaneous detection of anti-SARS-CoV-2-spike and anti-SARS-CoV-2-nucleocapsid antibodies in serum samples

A thin-layer flow cell of low internal volume (12 μL) is incorporated in a flow injection analysis (FIA) system for simultaneous and real-time photoelectrochemical (PEC) immunoassay of anti-SARS-CoV-2 spike 1 (S1) and anti-SARS-CoV-2 nucleocapsid (N) antibodies. Covalent linkage of S1 and N proteins to two separate polyethylene glycol (PEG)-covered gold nanoparticles (AuNPs)/TiO2 nanotube array (NTA) electrodes affords 10 consecutive analyses with surface regenerations in between. An indium tin oxide (ITO) allows visible light to impinge onto the two electrodes. The detection limits for anti-S1 and anti-N antibodies were estimated to be 177 and 97 ng mL−1, respectively. Such values compare well with those achieved with other reported methods and satisfy the requirement for screening convalescent patients with low antibody levels. Additionally, our method exhibits excellent intra-batch (RSD = 1.3%), inter-batch (RSD = 3.4%), intra-day (RSD = 1.0%), and inter-day (RSD = 1.6%) reproducibility. The obviation of an enzyme label and continuous analysis markedly decreased the assay cost and duration, rendering this method cost-effective. The excellent anti-fouling property of PEG enables accuracy validation by comparing our PEC immunoassays of patient sera to those of ELISA. In addition, the simultaneous detection of two antibodies holds great potential in disease diagnosis and immunity studies.

Amperometric flow injection analysis of hydroquinone in dermatological creams using a porous diamond-like carbon electrode

A porous diamond-like carbon film deposited on vertically aligned multi-walled carbon nanotubes (DLC:VAMWCNT) was evaluated as an electrode material in flow injection analysis (FIA) with amperometric detection. The redox behavior of hydroquinone (H2Q) was carried out as proof of concept. From cyclic voltammetry tests, H2Q gave a heterogeneous electron transfer rate constant (k0) of 4.9 × 10−3 cm s−1, which is comparable or better than those obtained with conventional electrodes. For the H2Q determination with the FIA-amperometry system, optimizations were performed regarding the supporting electrolyte, applied potential and FIA parameters (flow rate and sample injection volume). Under optimal conditions, the amperometric response of the DLC:VAMWCNT electrode was linear in the H2Q concentration range from 1.0 × 10−6 to 1.0 × 10−4 mol L−1, with a limit of detection (LOD) of 7.7 × 10−7 mol L−1. Interestingly, the DLC:VAMWCNT electrode displayed a very stable response under hydrodynamic conditions, with no memory effect while retaining accuracy towards the analysis of commercial H2Q-based dermatological creams. From these findings, DLC:VAMWCNT appears to be an outstanding candidate for flow injection analysis systems coupled to electrochemical detection.

Microfluidic flow injection analysis system for the electrochemical detection of dopamine using diazonium-grafted copper nanoparticles on multi-walled carbon nanotube-modified surfaces

In this proof-of-concept study, a microfluidic flow injection analysis (FIA) system was developed using multi-walled carbon nanotube-modified screen-printed carbon electrodes (CNTSPEs) that were modified with copper nanoparticles (CuNPs) following the electrodeposition of the diazonium salt of 4-aminothiophenol to form 4-thiophenol-conjugated CuNPs (CuNPs-CNTSPE). Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) were used to characterize the size of CuNPs, morphology and elemental analysis of CuNPs-CNTSPE, respectively. Using electrochemical impedance spectroscopy (EIS), the charge-transfer resistance (Rct) of CuNPs-CNTSPE was found to be 20-fold lower than that of CNTSPE. The CuNPs-CNTSPE displayed an oxidation peak for dopamine at −0.08 V which is ∼80 mV lower than the one detected using CNTSPE. The modified electrode was used in microfluidic flow injection analysis and offline systems for sensitive detection of dopamine (DA). The pH, flow rate, loop volume, concentration, and type of surfactant were all optimized for on-chip detection. Under the optimal conditions, using phosphate electrolyte solution (pH 6) containing 0.05% (w/v) Tween 20® as the carrier at a flow rate of 0.6 mL min−1 and a loop volume of 50 μL, the calibration curve was linear from 1.5 to 500 nM with a limit of detection of 0.33 nM. This technique was used for the successful detection of DA in real samples with recovery ranging from 96.5% to 103.8%. The microfluidic FIA system described here has the potential to be used as an electrochemical point-of-care device for rapid DA detection with high sensitivity and reproducibility.

High-Throughput Analysis of Bacterial Toxic Lipopolysaccharide in Water by Dual-Wavelength Monitoring Using a Ratiometric Fluorescent Chemosensor.

Lipopolysaccharide (LPS) is a bacterial toxin that causes fever in humans. Our small-molecule chemosensor named Zn-dpa-C2OPy shows rapid ratiometric fluorescence response to LPS in water with a detection limit of 11 pM, which is lower than that of our previously reported sensor. Spectroscopic measurements (fluorescence, absorbance, 1H NMR, and fluorescence lifetime), dynamic light scattering measurements, and transmission electron microscopy observations revealed that the fluorescence response was induced by the changes in the aggregation state via multi-point recognition of LPS through hydrophobic and electrostatic interactions, in addition to the coordination between the zinc(II)-dipicolylamine moiety of the chemosensor and the phosphate group of LPS. The proposed Zn-dpa-C2OPy chemosensor was applied to an original flow injection analysis (FIA) system with a self-developed dual-wavelength fluorophotometer, and a high throughput of 36 samples per hour was achieved. These results demonstrate the feasibility of this unique methodology combining a ratiometric fluorescent chemosensor and FIA for continuous online monitoring of LPS in water.

Application of Highly Sensitive Immunosensor Based on Optical Waveguide Light-Mode Spectroscopy (OWLS) Technique for the Detection of the Herbicide Active Ingredient Glyphosate.

The herbicide active ingredient glyphosate is the most widely applied herbicidal substance worldwide. Currently it is the market-leading pesticide, and its use is projected to further grow 4.5-fold between 2022 and 2029. Today, glyphosate use exceeds one megaton per year worldwide, which represents a serious environmental burden. A factor in the overall boost in the global use of glyphosate has been the spread of glyphosate-tolerant genetically modified (GM) crops that allow post-emergence applications of the herbicide on these transgenic crops. In turn, cultivation of glyphosate-tolerant GM crops represented 56% of the glyphosate use in 2019. Due to its extremely high application rate, xenobiotic behaviour and a water solubility (11.6 mg/mL at 25 °C) unusually high among pesticide active ingredients, glyphosate has become a ubiquitous water pollutant and a primary drinking water contaminant worldwide, presenting a threat to water quality. The goal of our research was to develop a rapid and sensitive method for detecting this herbicide active ingredient. For this purpose, we applied the novel analytical biosensor technique optical waveguide light-mode spectroscopy (OWLS) to the label-free detection of glyphosate in a competitive immunoassay format using glyphosate-specific polyclonal antibodies. After immobilising the antigen conjugate in the form of a glyphosate conjugated to human serum albumin for indirect measurement, the sensor chip was used in a flow-injection analyser system. For the measurements, an antibody stock solution was diluted to 2.5 µg/mL. During the measurement, standard solutions were mixed with the appropriate concentration of antibodies and incubated for 1 min before injection. The linear detection range and the EC50 value of the competitive detection method were between 0.01 and 100 ng/mL and 0.60 ng/mL, respectively. After investigating the indirect method, we tested the cross-reactivity of the antibody with glyphosate and structurally related compounds.

Simultaneous Determination of Uric Acid and Caffeine by Flow Injection Using Multiple-Pulse Amperometry.

The present study reports the development and application of a flow injection analysis (FIA) system for the simultaneous determination of uric acid (UA) and caffeine (CAF) using cathodically pretreated boron-doped diamond electrode (CPT-BDD) and multiple-pulse amperometry (MPA). The electrochemical profiles of UA and CAF were analyzed via cyclic voltammetry in the potential range of 0.20-1.7 V using 0.10 mol L-1 H2SO4 solution as supporting electrolyte. Under optimized conditions, two oxidation peaks at potentials of 0.80 V (UA) and 1.4 V (CAF) were observed; the application of these potentials using multiple-pulse amperometry yielded concentration linear ranges of 5.0 × 10-8-2.2 × 10-5 mol L-1 (UA) and 5.0 × 10-8-1.9 × 10-5 mol L-1 (CAF) and limits of detection of 1.1 × 10-8 and 1.3 × 10-8 mol L-1 for UA and CAF, respectively. The proposed method exhibited good repeatability and stability, and no interference was detected in the electrochemical signals of UA and CAF in the presence of glucose, NaCl, KH2PO4, CaCl2, urea, Pb, Ni, and Cd. The application of the FIA-MPA method for the analysis of environmental samples resulted in recovery rates ranging between 98 and 104%. The results obtained showed that the BDD sensor exhibited a good analytical performance when applied for CAF and UA determination, especially when compared to other sensors reported in the literature.

Amperometric bienzymatic biosensor in flow injection analysis system for determination of aspartame in foods.

An amperometric bienzymatic biosensor was developed for the determination of aspartame in a flow injection analysis (FIA) system, consisting of two enzyme reactor columns packed with immobilized α-chymotrypsin (CHY) and alcohol oxidase (AOX) beads and a hydrogen peroxide electrode, connected in series. The CHY and AOX were separately immobilized on glutaraldehyde (GA)-activated beads through covalent bonding. The biosensor fabrication and operational conditions were optimized. The optimal fabrication conditions were: 2% GA with 120min activation time; and 250 U/mL CHY and 100 U/mL AOX, with 180min enzyme immobilization time. The optimal operational conditions were a flow rate of 0.5mL/min and pH 8.0 at room temperature. The developed biosensor showed linearity over the aspartame concentration range 0.01-1.2mM, with a detection limit of 0.005mM. The developed biosensor was satisfactorily applied for detecting aspartame in beverage samples without any excessive pretreatments.

The determination of zinc using flow injection and continuous flow analysis combined with a polymer inclusion film-coated column: Application to the determination of zinc in alloys and commercial lithium chloride

A column coated with a polymer inclusion film (PIF) containing Aliquat 336 as carrier cast on glass beads packed in a glass tube is described for the separation, preconcentration, and determination of zinc(II) in flow injection analysis (FIA) and continuous flow analysis (CFA) systems. In the FIA method, 200 μL of a sample solution containing 2 mol/L lithium chloride is injected into a 2 mol/L lithium chloride stream. This converts zinc(II) ion into its anionic chlorocomplexes which are then extracted into the Aliquat 336-based PIF by anion exchange. The extracted zinc(II) is then back-extracted into a stream of 1 mol/L sodium nitrate solution and determined spectrophotometrically using 4-(2-pyridylazo)resorcinol as the color reagent. The limit of detection (LOD, S/N = 2) was determined as 0.017 mg/L. The usability of the PIF-based FIA method was demonstrated by the determination of zinc in alloys. The PIF-coated column was also employed successfully in the CFA determination of zinc(II) as an impurity in commercial lithium chloride samples. For this, 2 mol/L commercial lithium chloride solution was passed through the column for a predetermined time period followed by stripping in a stream of 1 mol/L sodium nitrate solution.

Development and Validation of Spectrophotometric Methods for the Quantitative Determination of Doxycycline Hyclate in Pure Form and Pharmaceutical Formulations Using Flow‐Injection and Batch procedures: A Comparative Study

AbstractDoxycycline hyclate is an antibiotic drug with a broad‐spectrum activity against a variety of gram‐positive and gram‐negative bacteria and is frequently used as a pharmacological agent and as an effector molecule in an inducible gene expression system. A sensitive, reliable and fast spectrophotometric method for the determination of doxycycline hyclate in pure and pharmaceutical formulations has been developed using flow injection analysis (FIA) and batch procedures. The proposed method is based on the reaction between the chromogenic reagent (V4+) and doxycycline hyclate in a neutral medium, resulting in the formation of a yellow compound that shows maximum absorbance at 396 nm. In a batch procedure, the proposed method was validated over the concentration range of 1.0–80 μg mL−1 with a sampling frequency of 30/h, and commercial pharmaceutical samples were successfully determined. The proposed method was successfully adapted with an FIA system where the peak heights are proportionally connected to doxycycline hyclate over the concentration range of 25–400 μg mL−1 with a sampling frequency of 50/h. The limits of detection (LOD) and quantification (LOQ) were 0.9 and 10.44 μg mL−1 and 3.01 and 34.81 μg mL−1 for batch and FIA respectively. The samples were submitted to an HPLC analysis, and the outcomes demonstrated excellent agreement with the suggested procedures. The adopted FIA procedure allows fast monitoring of doxycycline hyclate in pharmaceutical formulations and it can be used for quality control purposes during the production processes of doxycycline hyclate.

Rapid fluorometric determination of ammonium in exhaled breath condensate based on digital image of a windowless falling drop cell via a low-cost digital microscope

Measurement of ammonia in exhaled breath is of interest in medical and health sciences. The fluorometric determination of NH3 in exhaled breath condensate (EBC) was developed based on a digital image of a windowless falling drop (WFD) cell at the end of tube via a sensitive and selective reaction of NH3-OPA-sulfite in flow injection analysis system (FIA). A low-cost USB microscope as a facile instrumentation without expensive optical parts, an amplifier circuit, and a data acquisition unit, was used as a fluorescence light detector for the WFD cell via instant reporting temporal profile of digital value. A linear calibration graph of NH4+ in the range of 0.5–10 µmol L−1 can be obtained with a limit of detection of 0.5 µmol L−1 NH4+, and repeatability of 5.5% RSD (n = 11). The fluorescence (FL) signal obtained from the low-cost USB microscope was not different from that using the photodiode detector via a cross-shape flow cell. The proposed device was successfully applied for NH4+ determination in EBC and air absorbing solution samples with the recovery of 98–110%. The approach for instant reporting of a temporal profile of digital image value from a camera shows a potential to be applied for rapid chemical analysis in other microfluidics systems.

Estimating the concentration of total phenols in wastewater using ultrasonic flow injection analysis system

Flow injection analysis is can analyze multiple samples, high accuracy, a very fast response time , modern technical devices that are small. This research intended to study the efficiency of ultrasound waves were determined total phenols in wastewater using Folin-Ciocalteu reagent in basic media .The sample or standard phenol solution were injected into a carrier stream to react with Folin-Ciocalteu reagent then expose it to ultrasound waves (46 kHz) which was detected by spectrophotometer at 765 nm. The calibration curve for this method was in the range of (250-2000 ppm ) .The average correlation coefficient was equal to(0.999) . Results of the experiments showed that the ultrasonic method significantly increase peak height after using ultrasound waves . The method was successfully applied for the determination of the total phenols in wastewater

High-throughput determination of lipopolysaccharide by flow injection analysis using dipicolylamine-type fluorescent probe

Endotoxin (lipopolysaccharide: LPS), a bacterial toxin, is currently quantified by batch analysis using a reagent made from Limulus amebocyte lysate (LAL). Although the LAL method is sensitive, a long measurement time and gelation have hindered its application to online water quality monitoring. In this paper, we report a novel high-throughput analytical technique that combines flow injection analysis (FIA) and a dipicolylamine-type fluorescent probe, which was previously reported to exhibit strong fluorescence emission in response to LPS. A comparison of normal and reverse FIA systems revealed that the normal FIA offers more rapid detection with throughput of 30 samples per hour, which is the highest among known LAL methods and alternative LPS detection methods that have been recently reported. On the other hand, the reverse FIA requires much less reagent (480 μL per sample). Continuous online monitoring of water quality and analysis of real samples spiked with LPS were realized by this technique.