Merging Zones Technique Research Articles

Spectrophotometric determination of Salicylamide one of the novel COVID -19 protocols via new design Flow Injection with Merging-Zone Technique

Recently, attention has turned to drugs like salicylamide for treating COVID-19. Several studies have reported simple, fast, and sensitive methods for measuring salicylamide levels. However, potential limitations remain regarding interference from other drugs and accuracy of results. To tackle this issue, researchers combined the standard addition technique with flow injection analysis. As part of this investigation, the reaction involving Fe (III), salicylamide, and 1,10-phenanthroline at a temperature of 55°C was examined using a spectrophotometer set at a wavelength of 528 nm. Thus, the new design was able to show an excellent linearity over the concentration range of (2-30 μg/mL) and (25-300 μg/mL), with correlation coefficients ( ) of 0.9669 and 0.9781, respectively. In addition, physical and chemical variables were optimized to obtain the best results. There was a significant positive correlation between the new design and NIR micro-spectrometers device (handheld) outcomes.

Hybrid Microfluidic-Flow Injection System for Determining Copper(II) in Aqueous Solution by Homemade Microfluidic-Chip

Background: A new technique was designed for determining copper in an aqueous solution. Copper was determined by a hybrid system microfluidic coupled with flow injection. The homemade microfluidic chip (MFC) is used for injecting copper and 2,9-Dimethyl-1,10-phenanthroline (2,9DMP) reagent as a merging zone technique, whereas uric acid is used as a reducing agent and carrier. Methods: A microfluidic chip was made by a Computer Numerical Control (CNC) laser machine using the AutoCAD application for the study of copper by the hybrid system. The chip contains two microchannels with a volume of 60 μL for copper(II) and 2,9DMP reagent. As a carrier solution and reducing agent, 40 mg/L of uric acid was pumped at a flow rate of 5.2 mL/min. Conditions of the coupled technique and analyses were measured at 454 nm. Results: This system's approach has a linear range, a detection limit (S/N=3), and a quantitation limit (S/N=10) at 0.1-25 mg/L (r2 0.9979), 0.03 and 0.09 mg/L, respectively. Also, repeatability of analyses (n=7) with an average RSD of 0.97 % for concentrations of 5, 10, and 20 mg/L. The dispersion coefficients were 1.977, 1.789, and 1.555 for the three concentrations 5,10, and 20 mg/L, respectively. The recovery of copper in the aqueous solution was estimated to be 103.5%. Dead volume and throughput were zero and 62 per hour, respectively. Sandell’s sensitivity and molar absorptivity were 2.467×10-3 µg/cm2 and 1.947×105 L/mol cm, respectively. Conclusion: The analysis in the novel hybrid microfluidic-flow injection system is efficient, simple, and fast, and it can be used to determine the concentration of copper in an aqueous solution. The homemade microfluidic chip is a low-cost component that uses only an small volume of copper and reagent during analysis.

Indirect Way for the Assay of Captopril Drug in Dosage FormsUsing1,10-Phenanthroline as a Selective Spectrophotometric Agent for Fe(II) Via Homemade CFIA /Merging Zones Technique

Indirect Way for the Assay of Captopril Drug in Dosage FormsUsing1,10-Phenanthroline as a Selective Spectrophotometric Agent for Fe(II) Via Homemade CFIA /Merging Zones Technique

Flow injection titration basing on the merging-zone technique

The proposed approach relies on titration of a sample that is gradually diluted in strictly controlled way in the flow injection system developed. On each step of sample dilution equal volumes of the sample and titrant solutions are simultaneously injected into two carrier streams and the zones are merged with each other. Then, they are mixed completely in the mixing chamber, merged with a stream of indicator and directed to a detector. It has been revealed that the method provides the results with accuracy better than ±3.3% (RE) and with mean repeatability lower than 1.0% (RSD). When the analyte concentration in a sample is too low to be determined directly, the procedure of titration with standard addition is exploited. The proposed approach has been successfully applied to the determination of total acidity in vinegars and magnesium and calcium in pharmaceutical products. The results obtained were comparable with those provided by the reference methods. The proposed procedure is characterized by low consumption of sample (usually less than 2 mL), titrant (about 3 mL) and indicator (about 0.6 mL). Average time of a single analysis is similar to time of traditional batch analysis.

An air-driving FI device with merging zones technique for the determination of formaldehyde in beers

An air-driving flow injection device with merging zones technique is proposed for the rapid determination of formaldehyde in pale beers based on its catalytic action on the redox reaction between Victoria Blue B and potassium bromate in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of Victoria Blue B at the maximum absorption wavelength of 618 nm. Only 160 μL reagents and 40 μL sample solutions are needed. Formaldehyde in the range 8–700 ng mL −1 can be determined at a rate of about 50 samples h −1, the RSD for the determination of 20 ng m L −1 formaldehyde is 2.1%. Due to appropriate consideration of the beer matrix, formaldehyde in beers can be determined directly and satisfactory results were obtained.

Determination of Iron in Tap and Waste Water Using Liquid?Liquid Extraction in a Flow-Injection System

A flow-injection procedure for the determination of iron(III) in water is described. The procedure is based on the formation of an ion pair between the tetraphenylarsonium (Ph4As+) (TPA) or tetrabutylammonium (But4N+) (TBA) cations and the tetrathiocyanatoferrate(III) complex (TTF). This ion pair is extracted with chloroform, and the absorbance of the organic phase is measured at 503 nm (for Ph4As+) or 475 nm (for But4N+). Iron concentrations higher than 0.9×10−6 mol L−1 (50 µg L−1) can be detected in the first case, with a relative standard deviation of 1.9% (n=12), a linear application range’of between 1.34 and 54.0×10−6 mol L−1 (75–3015 µg L−1), and a sampling frequency of 30 h−1. For the ion pair with But4N+, the detection limit is 0.52×10−6 mol L−1 (29 µg L−1), with a relative standard deviation of 1.6% and a linear application range between 0.73 and 54.0×10−6 mol L−1. Under the proposed working conditions, only Pd(IV), Cu(II) and Bi(III) interfere. With the application of the merging zones technique, considerable amounts of organic reagent can be saved. The TBA method was applied to the analysis of iron(III) in tap and industrial waste waters.

Determination of Ethanol in Wines by Flow Injection Spectrophotometry Using Gas-Diffusion and an Immobilized Enzyme Reactor

A flow injection analysis (FIA) system for the spectrophotometric determination of ethanol in wines using an immobilized alcohol dehydrogenase reactor was developed. A gas diffusion unit was used to achieve a large dilution and to separate ethanol from the matrix. This way, the contact of the sample with the reactor was avoided and possible interferences in the spectrophotometric measurements were significantly reduced. The alcohol dehydrogenase enzyme was immobilized on alkylaminated controlled pore glass, and the consumption of the NAD cofactor was minimized (0.6 µmol per assay) by using the merging zone technique. The detection limit was 0.4% (v/v). Good precision was achieved, with relative standard deviations less than 2.2% (n = 9). For 20 samples of different types of table and Port wines, the results showed good agreement with the OIV usual procedure, the relative deviation being less than 4.4%. Thirty determinations per hour can be carried out within the ethanol concentration range of 5% to 25% (v/v), without any sample pretreatment.

DETERMINATION OF TOTAL SULPHUR DIOXIDE IN BEER BY FLOW INJECTION SPECTROPHOTOMETRY USING GAS-DIFFUSION AND THE MERGING ZONES TECHNIQUE

A flow injection system for the determination of total sulphur dioxide in beer is described. The methodology involves the same colorimetric reaction of the reference method between SO2, prosaniline and formaldehyde. The sample is introduced into the manifold without previous pretreatment, the hydrolysis process, isolation of the SO2 from the matrix and the colorimetric reaction, being carried out inside the flow tubes. To isolate the SO2, a gas-diffusion unit was included in the system and to minimise p-rosaniline consumption, a merging zones technique was used. The results obtained were in good agreement with a reference method (relative deviations lower than 5%), the precision being better than 2.5% (relative standard deviation). A sampling-rate of 30 samples per hour was obtained and the consumption of p-rosaniline was reduced 10 fold when compared to the reference method.

Merging Zones Standard Addition Technique for Determination of Copper in Beer by Flow Injection Atomic Absorption Spectrophotometry

A flow injection system for determination of copper in beer by atomic absorption spectrophotometry by the standard additions method is described. The manifold, based on the merging zone technique, prevents the burner head from clogging, as observed with the conventional reference method. With 5 standard additions, results are comparable with those of the reference method. Relative deviations were less than 5.8%, precision was better than 6.4%, and sampling rate was about 30 samples/ h. A less precise, less accurate, but faster procedure (75 samples/h) is possible with only 2 standard additions. The detection limit was 5 micrograms/L.

Flow Injection System with Potentiometric Detection for the Determination of Urea Content in Milks

Two variant manifolds of a flow injection analysis (FIA) system are described for the determination of urea content in milks. This determination consists of the enzymatic reaction of urea with urease in which ammonium ion is formed. Ammonium is converted to ammonia by adding a NaOH solution and then led to a gas diffusion unit in which it diffuses to an acceptor channel (Tris/HCl, pH 7.5). Here, it is reconverted to ammonium ion and determined by a tubular configuration electrode sensitive to this ion. One of the FIA manifolds is based on the merging zones technique, whereas the other uses an immobilized enzyme. The results obtained were compared with those given by the Boehringer UV test and by the Official Method of Analysis of the Association of Official Analytical Chemists (AOAC) which can be applied to animal feed and adapted to the matrix studied. The relative deviation was less than 5%, and the precision of the developed methodologies considering RDS (%) was always less than 2%. Keywords: Ion-selective electrodes; milk; urea; immobilized enzyme; merging zones

Simultaneous determination of iron(II) and iron(III) by flow injection analysis A mathematical simulation of the detector response

A mathematical model for the description of the detector signal obtained in flow injection asynchronous merging zone technique (FIA-AMZ) is proposed. FIA-AMZ is based on the separate injection of a sample and an appropriate reagent in such a way that both injected solutions are covered only partly. The resulted detector signal consists of two consecutive peaks whose heights are proportional to the concentration of the detectable component present in the sample and another component which becomes detectable after the reagent has been added. The detector signals (the concentration profiles of the analytes) are described by a modified Gauss curve, which proved to be better than a combination of Gauss-Lorentz curves. The conversion of undetectable to detectable form of the analyte is described by a sigmoidal function the slope of which corresponds to the frontal dispersion of the added reagent and to the reaction kinetics. The model is tested on the system for the simultaneous spectrophotometric determination Fe 2+ and Fe 3+. It is shown that fitting of the experimental curves with a model function enables the optimisation of the experimental conditions at applied FIA manifold, and consequently the simultaneous determination of concentrations of Fe 2+ and Fe 3+ ions in a single measurement.

Enzymic flow injection determination of free L-carnitine in infant formulae.

Infant formula samples were analysed to determine their free L-carnitine content by using flow injection (FI) with an incorporated immobilised carnitine acetyltransferase bioreactor. The methodology was based on the spectrophotometric determination through its reaction with carnitine acetyltransferase coupled with acetyl coenzyme A (acetyl-CoA) and dithiobenzoate. The merging zones technique was used to minimise acetyl CoA consumption. Linearity was observed over the concentration range 10-80 mg l-1 with L-carnitine as standard (r = 0.9998) and the rate of analysis was 50 h-1 infant formula samples. The enzymic FI method afforded a low RSD (2.2%). Comparisons were made with other methods of known accuracy. The enzymic reactors were stable for 3 months when used daily at the optimum pH.

Flow injection on-line acid digestion and pre-reduction of arsenic for hydride generation atomic absorption spectrometry—a feasibility study

A flow injection (FI) manifold is described which makes possible on-line microwave-assisted acid digestion, followed by pre-reduction of As(V) to As(III) and its determination by hydride generation atomic absorption spectrometry. The merging zone technique is used in order to reduce acid consumption for digestion. The efficiency of acid digestion is increased by pressure which is built up in-line by a flow restrictor. Flows for sample pretreatment and hydride generation can be optimized independently. L-cysteine was found superior to potassium iodide as the pre-reductant because much lower reagent and acid concentrations are required, much harsher conditions can be tolerated for acid digestion, and the integrated absorbance signals for arsenic in blood and standards are essentially identical, making possible the use of the standard calibration procedure. The sampling frequency is 7–10/hr, depending on the conditions chosen, and the limit of detection, i.e. the concentration giving a signal equal to three times the standard deviation of the signal of the blank solution, is 0.25 μg/l for a 500 μl sample volume. The recovery of 10 μg/l As(V) added to a blood sample was 94 ± 2 and 98 ± 2% ( n = 3) in absorbance and integrated absorbance, respectively.

Simultaneous determination of multicomponents by flow injection analysis: Determination of copper and zinc in serum by using zincon as colouring reagent

A flow injection system is described for the simultaneous determination of copper and zinc with a single detector. Two sample plugs are injected into the same carrier stream sequentially. One is for zinc determination and the other is for the sum of copper and zinc. For zinc determination, copper masking reagent is simultaneously injected into a parallel carrier stream and merged with the sample plug by using the merging zone technique. Zincon is used as the colour reagent for the spectrophotometric determination of copper and zinc. The results for the analysis of serum by the proposed method correspond well with those obtained by an AAS method. The rate of analysis is about 45 samples/hr.

Determination of proteolytic enzymes by flow-injection analysis

Quantitation of proteolytic enzymes using N-succinyl- l-Ala- l-Pro- l-Phe- p-nitroanilide has been adapted to flow-injection analysis. This procedure has been developed using two different proteases: subtilisin and chymotrypsin. For both enzymes the influence of substrate concentration on spectrophotometric response has been studied. The assay is based on the merging zones technique combined with a washing step. Results are obtained in less than 15 s and samples may be run at a rate of 90/h with good reproducibility. A linear relation between peak heights and enzyme concentrations was observed for 0–0.15 Anson unit/liter of subtilisin and for 0–30 mg/liter of a commercial preparation of chymotrypsin. The method requires only small sample volumes, and the consumption of the chromogenic substrate is reduced to a minimum by using intermittent pumping.

Direct determination of calcium, magnesium, sodium and potassium in water by flow injection flame atomic spectroscopy, using a dilution chamber

A simple procedure to carry out the direct analysis of calcium, magnesium, sodium and potassium in water by flow injection analysis (FIA) using flame atomic absorption spectroscopy (AAS) or flame photometry (FP) has been developed, using a well stirred dilution chamber to extend the calibration range, and both a double injector and the merging zone technique to add a lanthanum solution to samples and standards. The results obtained in the analysis of real samples agree with those found by a batch flame atomic procedure. The use of the dilution chamber makes it possible to carry out the calibration using the dilution profile of a single concentrate standard for each element, and an empirical dilution equation, which could be employed for all the elements is determined in each work session.

Spectrophotometric Flow Injection Analysis of Silicates for Manganese

A flow injection Spectrophotometric method has been developed for the determination of manganese in silicate rocks with formaldoxime as a chromogenic reagent. A rock solution is prepared by fusion with a mixture of lithium carbonate and boric acid and subsequent dissolution of the cake in 1M hydrochloric acid. An aliquot of the sample solution is treated with hydrofluoric and perchloric acids and passed through a cellulose phosphate column to remove polyvalent cations like iron(III) and aluminum(III). A definite portion of the filtrate is injected into the flow system where the manganese-formaldoxime complex allows to be formed and monitored at 452nm. Nickel is masked with 2-aminoethanethiol by a merging zone technique. The flow injection analysis system permits throughput of 45 samples per hour. The relative standard deviations (n=10) for 0.5 and 2.0ppm manganese solutions are 0.80 and 0.33%, respectively. The procedure has been applied to a variety of standard silicate rocks of the U.S.Geological Survey and of the Geological Survey of Japan, yielding the results which are in satisfactory agreement with the recommended or reported values.

Determination of Glucose by Flow Injection Analysis with Merging Zone Technique

Determination of Glucose by Flow Injection Analysis with Merging Zone Technique

A model immunoassay using automated flow injection analysis

A model immunoassay between concanavalin A (antibody) and yeast mannan (antigen) was investigated using a microcomputer-controlled flow injection analysis (FIA) manifold with turbidimetric detection at 400 nm. The automated injection procedure gave good precision for a turbidimetric method and the stop-flow merging zones technique gave an acceptable sample throughput (50 samples per hour) with minimum consumption of sample (30 µl). The system described could therefore be used routinely for immunoprecipitin analysis in clinical laboratories, e.g., lgG in human serum, and also to study kinetic aspects of such reactions.

Controlled dispersion analysis: flow-injection analysis without injection.

Flow-injection analysis is a precise, elegant, and economical technique, but its most troublesome feature is the mode of injection of the sample slug. We describe an alternative approach in which the sample is aspirated by the sample probe. In the simplest version the probe normally rests in reagent; when sampling is to take place, the pump is stopped and the probe is transferred to the sample container. The pump makes a predetermined angular movement, the probe is returned to reagent, and the pump is restarted. In more advanced versions the same approach is combined with the merging zone technique. The system is economical, precise, and capable of full automation in a multichannel discretionary analyzer.