FIA System Research Articles

2D-ReS2 & diamond nanoparticles-based sensor for the simultaneous determination of sunset yellow and tartrazine in a multiple-pulse amperometry FIA system

We present a flow injection system with a multiple pulse amperometric detection (FIA-MPA)-based methodology for the simultaneous analysis of sunset yellow and tartrazine. As transducer, we have developed a novel electrochemical sensor based on the synergistic effect of ReS2 nanosheets and diamond nanoparticles (DNPs). Among several transition dichalcogenides for the sensor development, we have selected ReS2 nanosheets since it yields a better response towards both colourants. Scanning probe microscopy characterization shows that the surface sensor is composed by scattered and stacked ReS2 flakes and large aggregates of DNPs. With this system, the gap between the oxidation potential values of sunset yellow and tartrazine is wide enough to allow the simultaneous determination of both dyes. Under the optimum potential pulse conditions (0.8 and 1.2 V) during 250 ms, a flow rate of 3 mL/min and a volume injection of 250 μL, detection limits of 3.51 × 10−7 M and 2.39 × 10−7 M for sunset yellow and tartrazine, respectively, were obtained. This method exhibits good accuracy and precision with Er minor than 13% and RSD lower than 8% with a sampling frequency of 66 samples per hour. Pineapple jelly samples were analyzed by the standard addition method, obtaining 53.7 mg/kg and 29.0 mg/kg of sunset yellow and tartrazine, respectively. From the analysis of fortified samples, recoveries of 94% and 105% were obtained.

Photometric flow injection analysis of As(III) by using a homemade, LED-based flow-cell device and methyl orange reagent

Inorganic arsenic especially As(III) is considered a carcinogenic substance and its measurement is important in water samples. In this work, an inexpensive flow injection analysis system was designed for the photometric determination of As(III) at low concentrations. For this purpose, a light-emitting diode (LED) based photometer with a miniaturized detector, was fabricated and used as a determination apparatus and methyl orange was used as a detecting reagent. The fabricated photometer employed the LEDs, as a light source and the light detector. The λmax of emission for emitter and detector LEDs were 525 and 625 nm, respectively. Determination of As (III) was based on its inhibition effect on the redox reaction between methyl orange and X2 (Cl2 or Br2). The decolorization of the reaction products in the FIA system was monitored using the homemade flow cell detector. Analytical figures of merit including linear responses ranging from 0.03 to 3.0 mg/l of As(III) (r = 0.994), detection limits of 0.007 mg/l As(III), RSD% of 1.5% (n = 7), low reagent consumption per determination, and sampling throughput of 50 determinations per hour were achieved.

Determination of serum procalcitonin and total antioxidant capacity in patients of sepsis before and after treatment, in a tertiary care hospital

Introduction: Sepsis is a medical emergency, occurring due to the body's systemic immunological response to an infection. It is among the most common reasons for intensive care unit admissions worldwide and is one of the top 10 leading causes of death worldwide. Procalcitonin (PCT) is the marker of sepsis, and total antioxidant capacity (TAC) is a marker of oxidative stress and gives a mirror image about patient's antioxidant status. The purpose of the study was to estimate serum PCT and TAC levels in sepsis patients, before and after treatment, and to find the correlation between them. Materials and Methods: In this observational follow-up study, 60 sepsis patients were recruited using purposive sampling method, and samples were taken before and after treatment. Separated serum was used to measure PCT and TAC. PCT was measured by a rapid quantitative test using a sandwich immunodetection method based on fluorescence immunoassay technology, on a Finecare FIA system. Values over 0.5 ng/ml were considered significant. TAC was measured using the ferric-reducing antioxidant power method based on reduction of a colorless Fe3+-TPTZ on interaction with a potential antioxidant, into an intense blue Fe2+-TPTZ complex. Results: The mean PCT in subjects before treatment was as high as 40.62 ± 12.02 ng/ml, and the difference between before and after treatment values was highly significant (P = 0.000). For TAC also, before treatment value was higher (485.64 ± 106.53 μm/l) than the after treatment (277.79 ± 74.17 μm/l) value with a significantly high difference (P = 0.000). Furthermore, a strong positive correlation between PCT and TAC (r = 0.754, P = 0.000) was observed. Conclusion: It was concluded that in sepsis, there is a concomitant existence of inflammation and oxidative stress. Since TAC values correlate with values of PCT, TAC could be a reliable prognostic marker and may be helpful in evaluating interventions on follow-up of patients.

シリカの連続自動モニタリングFIA システムの開発と プラントの水質管理への応用

シリカの連続自動モニタリングFIA システムの開発と プラントの水質管理への応用

Association of High Sensitivity C-Reactive Protein with In-Hospital Mortality in Patients with Acute St-Segment Elevation Myocardial Infarction

Background and Aims: Among the various biomarkers, high sensitivity C-Reactive Protein (hs-CRP) has been widely studied and is easy to use in the prognostication of patients with acute ST elevation myocardial infarction (STEMI). This study aimed to associate serum level of hs-CRP with in-hospital mortality in patients presented with acute STEMI.
 Methods: This was a hospital-based prospective observational study conducted in Shahid Gangalal National Heart Centre among patients presented to the emergency department with chest pain of less than 24 hours duration, who were diagnosed subsequently to have STEMI. Patients who had known chronic inflammatory diseases, septic foci and chest pain of over 24 hours were excluded from the study. Blood sample for Hs-CRP was sent from the emergency department and was measured with Finecare TM FIA system; Model number: FS-112. The study was conducted from April 2019 to March 2020. Patient outcomes were stratified as per the four groups of serum level of hs-CRP and among them the relationship between mortality and hs-CRP level was tested with chi-square test. The p-value across the groups was again tested for inter-group significance using the Bonferroni adjusted significance level.
 Results: 140 patients (112 males and 28 females) with mean age of 58.1±14.86 years were enrolled in the study. There was no increased in-hospital mortality in acute STEMI patients who had serum level of hs-CRP below 3 mg/l. In-hospital mortality showed an increasing trend above this level but it reached statistical significance beyond 10 mg/l only. Thirty five percent of our patients of acute STEMI were found to have serum level of hs-CRP above this threshold. The total in-hospital mortality was 13 (9.28%).
 Conclusion: The increased serum level of hs-CRP was associated with increased in-hospital mortality in patients with acute STEMI.

Development of an interference-minimized amperometric-FIA glucose biosensor at a pyrocatechol violet/glucose dehydrogenase-modified graphite pencil electrode

A modified disposable electrode formed by immobilization of glucose dehydrogenase (DHG) onto pyrocatechol violet (Pcv)-modified graphite pencil electrode (GPE) was proposed for the flow injection (FI) amperometric glucose biosensor. Cyclic voltammetric experiments show that Pcv illustrates a good electrocatalytic effect towards the oxidation of enzymatically produced NADH. Although electrocatalytic oxidation of enzymatically generated NADH at the DHG/Poly-Pcv/GPE was successfully performed at + 250 mV in FIA system, some molecules such as ascorbic acid (AA), dopamine (DA) and uric acid (UA) give a significant positive interference due to their oxidation at this working potential. To overcome these interferences, an injector filled with a pre-oxidant, sodium bismuthate (NaBiO3), was used in the FI amperometric glucose biosensor at the DHG/Poly-Pcv/GPE. Results showed that the interferences of these molecules were significantly minimized, because they were oxidized by NaBiO3 in the injector before reaching the electrode surface in the flow cell. The constructed biosensor showed that a linear calibration curve was obtained in the range between 5.0 µM and 500 µM glucose with a detection limit of 1.2 µM. This proposed glucose biosensor including elimination of interferences of some oxidizable species was successfully applied to the real and artificial samples.

(Invited) New Flexible Electrodes for Electrochemical Analysis: A Step Forward Towards Wearable Sensors

Electrochemical sensors present many advantages to develop wearable sensors and to be applied for real samples as at the point-of-care using. They are easy to use, low cost and above all, they allow easy integration with the electronics and different parts of the system. However, there are several problems still to be solved in order to carry out the complete integration of these systems. Currently flexible electronics is already a reality, so, the manufacture of the sensor itself on a flexible substrate without losing any of its relevant functionalities takes on paramount importance. In this sense, printing technologies offer a suitable solution for the development of flexible electrodes as well as electronics to use them. Therefore, these technologies open the door to the development of a whole new range of flexible devices for many applications in biosensing, Point-of-Care (PoC) analysis and wearable systems. In this work, the fabrication process of carbon-based electrochemical sensors on flexible plastic substrates has been optimized. Thus, different flexible substrates; including several materials, thickness and color; have been evaluated for printing the new sensors. These sensors have been printed using different carbon and silver ink formulations with several mesh screens (stainless steel, polyester…). The selection of the ink formulations and mesh affects to the final surface morphology as well as the shelf-life and performance of electrodes. In the same way, a critical step in the fabrication of flexible sensors has been the selection of the drying conditions. This step enables the curing of the inks by removing the organic solvents, but without affecting to the flexible substrates. In most of the cases, the plastic substrates show a low glass transition temperature. Therefore, the drying time and temperature as well as the methodologies (box oven, conveyor dryer…) have been essential for avoiding some physical change in the substrate and electrode surface. As a flexible substrate is used, the final electrode structures should also show stretchable features. A microscopy and electrochemical characterization has been carried out with the new flexible carbon-based electrodes. The final sensor consists of a multilayer structure integrating the working (WE), reference (RE) and counter (CE) electrode as well as a dielectric layer on the same bendable substrate ( Figure 1A ). Thus, the surface morphology of the electrodes was observed by using scanning (SEM) and transmission (TEM) electron microscopy in order to check the effect of the substrate, printing conditions and ink compositions. The performance of new electrodes has been also evaluated by using different electrochemical techniques such cyclic voltammetry (CV), amperometry and electrochemical impedance spectroscopy (EIS), in static, and specially, dynamic conditions. The new flexible sensors were integrated into a basic flow analysis system by using a modular platform ( Figure 1D ). This platform enables the interfacing between the sensor and the other components of the FIA system; peristaltic pump, injection valve and electrochemical station ( Figure 1 B and C ). A portable All-in-One electrochemical station with built-in EIS analyzer ( Figure 1 E ) was used for performing the electrochemical measurements. The performance of the new flexible electrochemical sensors has been evaluated with different benchmark redox compounds in the FIA system. This work has been supported by EU (MANUNET) and IDEPA (IDE/2017/000124) Figure 1

Selective Determination of Verapamil in Pharmaceutics and Urine Using a Boron‐doped Diamond Electrode Coupled to Flow Injection Analysis with Multiple‐pulse Amperometric Detection

AbstractThis work presents a simple and low‐cost method for fast and selective determination of Verapamil (VP) in tablets and human urine samples using a boron‐doped diamond working electrode (BDD) coupled to a flow injection analysis system with multiple pulse amperometric detection (FIA‐MPA). The electrochemical behaviour of VP in 0.1 mol L−1 sulfuric acid showed three merged oxidation peaks at around +1.4 V and upon reverse scan, one reduction peak at 0.0 V (vs. Ag/AgCl). The MPA detection was performed applying a sequence of three potential pulses on BDD electrode: (1) at +1.6 V for VP oxidation, (2) at +0.2 V for reduction of the oxidized product and (3) at +0.1 V for cleaning of the working electrode surface. The FIA system was optimized with injection volume of 150 μL and flow rate of 3.5 mL min−1. The method showed a linear range from 0.8 to 40.0 μmol L−1 (R>0.99) with a low limit of detection of 0.16 μmol L−1, good repeatability (RSD<2.2 %; n=10) and sample throughput (45 h−1). Selective determination of VP in urine was performed at+0.2 V due to absence of interference from ascorbic and uric acids in this potential. The addition‐recovery tests in both samples were close to 100 % and the results were similar to an official method.

Simultaneous Determination of Magnesium (Mg2+) and Ammonium (NH4+) by Flow Injection Analysis

An automatic method for the simultaneous determination of magnesium and ammoniun by flow injection analysis is described. This analysis used two detectors, potentiometry and spectrophotometry, for the determination of magnesium and ammonium simultaneously. Potentiometric detectors are used to detect ammonium ions, whereas spectrophotometer detectors are used to detect the presence of magnesium ions. The performance of the FIA system includes linear range linearity, limit of detection, sensitivity, reproducibility and recovery test. Spectrophotometry FIA showed good performance with several criteria of linearity with regression value of 0.9918, the detection limit of 0.06 ppm, a sensitivity of 0.0115, repeatability of less than 2% and the percent recovery of 91,6%. While potentiometric FIA showed th performance with several criteria of linearity with regression value of 0.9896, the detection limit of 0.17 ppm, a sensitivity of 40.747 mV per decade of concentration, repeatability of less than 2% and the percent recovery of 89,7%.
 Keywords: Flow Injection Analysis, spectrophotometry, potensiometry, simultaneous

Enzyme-free amperometric method for rapid determination of histamine by using surface oxide regeneration behavior of copper electrode

Abstract This work demonstrated a novel amperometric method to measure the concentration of histamine directly without using any enzymatic reaction or a complicated derivation scheme. Based on the strong chelating property between histamine and cupric (II) ions, cupric oxide would be dissolved by the histamine and a cupric-histamine complex would be formed on the electrode surface, subsequently, an oxidative current resulted from the regeneration of the surface cupric oxide was used to reflect the concentration of the histamine in the sample. Under the optimal conditions with operating potential at 200 mV in a 100 mM phosphate buffer, pH 10.0, containing 50 mM acetate, a suitable dynamic range of histamine from 1 to 750 μM with a sensitivity of 15 nA/μM (R = 0.999) and a detection limit of 0.33 μM was achieved on a typical FIA system. Subsequently, the performance of this scheme was integrated with high-performance liquid chromatography as an electrochemical detector. In optimal conditions, the linear range is estimated from 10 to 2500 μM (0.5–125 nmol per injection), which is an adequate range for the determination of the freshness quality of a seafood. Finally, the feasibility of this scheme in real sample application was demonstrated by evaluating the histamine level in a fresh saury fish and a defrost one, respectively.

Thin Layer Disposable Flow Cells As (Spectro)Electrochemical Detectors in FIA Systems

In this work different flow-cell electrochemical platforms where channel slide is directly mounted over the screen-printed electrodes are proposed. Flow-cells for screen-printed electrodes are usually wall-jet type but due to the transparent cover that defines the channel (height 400μm, and 100μL of volume), a thin layer is formed over the electrochemical cell. The cover’s transparency allows the detection of air bubbles inside the cell. The injection is done through an “in-line luer injection port” where sample volume can be easily controlled by operator through a Hamilton syringe. Different configurations of the electrodes in the electrochemical platform can be used, rectangular or circle electrodes, only a working electrode or dual sensors as well as different materials such gold, platinum or carbon, etc. These electrochemical flow cells combining with the adequate holder and fittings allow us to have an user friendly FIA system with a great possibility of applications based on electrochemical or spectroelectrochemical detection, depending on the set-up used to carry out the measurement. Here in several samples of the use of these thin layer electrochemical flow-cells as transducers of enzymatic sensors or as detectors are presented showing a good performance, simple operability and effectiveness of working in FIA systems. The work was carried out in the framework of the European project “BIOENERGY”. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 607793”.

Development of a Small Distillation Device Including FIA System and its Application for Environmental Analysis

Development of a Small Distillation Device Including FIA System and its Application for Environmental Analysis

Electrochemical Biosensor Powered by Pre‐concentration: Improved Sensitivity and Selectivity towards Lactate

AbstractWe report on the flow‐injection (FIA) electrochemical system coupling with ion‐exchange pre‐concentration column. The response of the FIA system is provided by the advanced lactate biosensor based on Prussian Blue as an electrocatalyst. The FIA system powered by pre‐concentration is characterized by improved selectivity avoiding influence of non‐anionic interfering compounds. The attractive performance characteristics of the system with pre‐concentration which are advantageous over conventional FIA combined with a similar biosensor are: (i) the 50 times improved sensitivity (7.0 A cm−2 M−1) and (ii) the calibration range shifted by almost two orders of magnitude towards lower analyte concentrations. The developed FIA system was tested for lactate detection in exhaled breath condensate samples collected from pulmonary patients and sportsmen.

Ion Imprinted Polymer for Preconcentration and Determination of Ultra-Trace Cadmium, Employing Flow Injection Analysis with Thermo Spray Flame Furnace Atomic Absorption Spectrometry.

This work proposes a preconcentration method using an ion imprinted polymer (IIP) for determination of cadmium, in several samples, employing a mini-column filled with the polymer coupled into a flow injection analysis system with detection by thermospray flame furnace atomic absorption spectrometry (FIA-TS-FF-AAS). The polymer was synthesized via bulk using methacrylic acid and vinylimidazole as a functional monomer. For the FIA system initial assessment, the variables: pH, eluent concentration and buffer concentration were studied, employing a 23 full factorial design. To obtain the optimum values for each significant variable, a Doehlert matrix was employed. After the optimization conditions as: pH 5.8, eluent (HNO3) concentration of 0.48 mol L-1 and buffer concentration of 0.01 mol L-1, were adopted. The proposed method showed a linear response in the range of 0.081-10.0 μg L-1, limits detection and quantification of 0.024 and 0.081 μg L-1, respectively; preconcentration factor of 165, consumptive index of 0.06 mL, concentration efficiency 132 min-1, and frequency of readings equal to 26 readings h-1 The accuracy was checked by analysis of certified reference materials for trace metals and recovery tests. The obtained results were in agreement with 95% confidence level (t-test). The method was adequate to apply in samples of: jewelry (earrings) (2.38 ± 0.28 μg kg-1), black tea (1.09 ± 0.15 μg kg-1), green tea (3.85 ± 0.13 μg kg-1), cigarette tobacco (38.27 ± 0.22 μg kg-1), and hair (0.35 ± 0.02 μg kg-1).

Automatic bionalyzer using an integrated amperometric biosensor for the determination of L-malic acid in wines

A new automatic bioanalyzer for L-malic acid using an integrated amperometric biosensor as detector is reported for the first time in this work. The biosensor is constructed by gold film sputtering deposition on a stainless steel disk electrode and co-immobilization of the enzymes malate dehydrogenase (MDH) and diaphorase (DP) together with the redox mediator tetrathiafulvalene (TTF) by means of dialysis membrane. The analytical performance of the biosensor was evaluated when it was used as amperometric detector in three different analytical methodologies: stirred solutions, semiautomatic FIA system and automatic bioanalyzer. The bienzyme biosensor exhibited great analytical performance in terms of sensitivity, selectivity and reproducibility of the measurements and its usefulness was demonstrated by analyzing wine reference materials with certified content of L-malic acid. The attractive analytical and operational characteristics demonstrated by the automatic bioanalyzer make it a promising simple, rapid and field-based tool for routine wine and fruit control.

Employment of electrostatic interactions for amperometric detection of carbon nanoparticles in a FIA system.

The development of methods for nanoparticle detection is highly desirable due to their increasing presence in the environment. Recently, we have shown that the electrochemical detection in flow is one of the possible solutions. Here we demonstrate a dramatic improvement of analytical parameters of such detection. The significant enhancement of an amperometric signal resulting from the electrocatalytic oxidation of ascorbic acid (AA) in a negatively charged phenylsulphonated carbon nanoparticle suspension in the millifluidic flow injection analysis system as compared to earlier results (D. Ogończyk, et al., Electrochem. Commun., 2014, 43, 40) is presented. This effect results from the tailoring of electrostatic interactions, e.g. optimization of the supporting electrolyte and AA concentration and/or immobilization of positively charged functionalities at the electrode surface. The sensitivity is improved by almost three orders of magnitude and the limit of detection of carbon nanoparticles is decreased by two orders of magnitude down to 0.001 mg mL(-1).

An amperometric FIA system with carrier recycling: an environmentally friendly approach for atenolol determination in pharmaceutical formulations

Carrier solution recirculation in an amperometric FIA system allows ATN quantification with very low reagent consumption and waste generation.

A Prussian blue-carbon paste electrode for selective cathodic amperometric determination of nitrite using a flow-injection analysis system with carrier recycling

A selective, simple, and low cost method for nitrite determination was developed using an FIA system with a Prussian blue-carbon paste electrode (PB-CPE) as an amperometric detector. The electrochemical sensor was prepared by a fast, simple, and inexpensive procedure, and the long-term stability of the electrode was quite satisfactory as the performance was maintained over one year. PB acted as an effective redox mediator for nitrite electroreduction in acidic media, allowing nitrite detection at +0.2V vs. Ag/AgClsat, a potential at which most possible interfering species are not electroactive. Consequently, the proposed method was completely free from interference from nitrate, dissolved oxygen, ascorbic acid, and other species usually present in water and food samples. The electrochemical cell used in the FIA system was similar to a batch injection analysis cell, enabling recirculation of the carrier solution. This is an attractive feature because it allows the use of a high flow rate (6mLmin−1) leading to high sensitivity and analysis speed, while keeping reagent consumption low. Under the optimized conditions, the proposed method had a detection limit of 9μmolL−1 and was successfully employed for nitrite quantification in water and sausage samples. For all analyzed samples, recovery percentages close to 100% were obtained, which is indicative of the accuracy and reliability of the proposed method.

Reagent-free flow-injection amperometric sensor for quantification and speciation of iron for bio-hydrometallurgical applications

Iron ions are monitored in processes such as bio-leaching, bio-oxidation, ferric leaching, passivation control, and others. The role of iron in different hydrometallurgy processes is very important because it affects strongly several industrial ore production, as chalcopyrite cooper extraction. In this work we present an amperometric FIA system that allows rapid quantification and speciation of iron in bio-mining processes. Linearity range, passivation of the working electrode and interferences were studied. We found a useful lineal range from 10 to 1500mgL−1 for each of the ions, with a detection limit (Fe2+ and Fe3+) determined at 15±2mgL−1. High copper concentrations could interfere with the amperometric readings, though not in the copper/iron relationship encountered in this industry. Real samples, including an acid mine drainage sample, and the monitoring of the bio-oxidation kinetics of iron by Acidithiobacillus ferrooxidans were also quantified. In all cases, our results were compared with a standard colorimetric method that allows iron speciation (1,10-phenanthroline), showing good agreement between both methods. The electrochemical method presented here allows high sample throughput (ca. 45samplesh−1), fast analysis (ca. 1min), and reagent free quantification of total iron, ferric and ferrous ions.

Flow injection analysis of organic peroxide explosives using acid degradation and chemiluminescent detection of released hydrogen peroxide

The applicability of acid degradation of organic peroxides into hydrogen peroxide in a pneumatically driven flow injection system with chemiluminescence reaction with luminol and Cu2+ as a catalyst (FIA-CL) was investigated for the fast and sensitive detection of organic peroxide explosives (OPEs). The target OPEs included hexamethylene triperoxide diamine (HMTD), triacetone triperoxide (TATP) and methylethyl ketone peroxide (MEKP). Under optimised conditions maximum degradations of 70% and 54% for TATP and HMTD, respectively were achieved at 162µLmin−1, and 9% degradation for MEKP at 180µLmin−1. Flow rates were precisely controlled in this single source pneumatic pressure driven multi-channel FIA system by model experiments on mixing of easily detectable component solutions. The linear range for detection of TATP, HMTD and H2O2 was 1–200µM (r2=0.98–0.99) at both flow rates, while that for MEKP was 20–200µM (r2=0.97) at 180µLmin−1. The detection limits (LODs) obtained were 0.5µM for TATP, HMTD and H2O2 and 10µM for MEKP. The detection times varied from 1.5 to 3min in this FIA-CL system. Whilst the LOD for H2O2 was comparable with those reported by other investigators, the LODs and analysis times for TATP and HMTD were superior, and significantly, this is the first time the detection of MEKP has been reported by FIA-CL.