Reaction Coil Length Research Articles

Flow injection analysis system with smart phone for the determination of total phenolic compounds in wastewater using Folin Ciocalteu reagent

Smart phones are playing a big role in daily life and are being employed as supporting hardware in a variety of chemical analysis applications. flow injection analysis method for the rapid, simple, and straightforward determination of total phenols using Folin-Cioclteu reagent .The sample or standard solutions were injection into a carrier stream to react with reagent and detected by spectrophotometer at 765 nm . The experimental conditions such as flow rate of reagent and carrier ,reagent volume ,length of reaction coil and concentration of reagent were optimized .A good linear calibration curve in the range of (250-2000 mg L-1 ) was obtained with regression equation ( y=0.0123 x + 0.1857) ,( R= 0.999 ), the limit of detection was in the amount of ( 0.0102 mg L-1) .The method was successfully applied for the determination of the total phenols in wastewater .

A Rapid and Sensitive Colorimetric Sequential Injection System for Cu(II) ion Determination Using New Azo Reagent

A sensitive and accurate Sequential Injection Analysis technique for determining Cupper (II) ion in different samples, using a new azo derivative reagent of 8-hydroxy quinoline (HQDABA). The reagent and Cu(II) complex diagnosis included Infrared spectroscopy, Ultraviolet-Visual radiation, Elemental Analysis (CHN), Energy dispersive X-ray spectroscopy (EDX), nuclear magnetic resonance spectroscopy 1HNMR and mass spectroscopy techniques. The method depends on the reaction of Cupper (II) with the (Azo derivative of 8-hydroxy Quinoline) reagent in a neutral medium to form a Brown complex which gave a maximum absorbance at 420 nm. The optimum conditions such as flow rate, Copper (II) volume, reagent volume; pH, reagent concentration, and reaction coil length are thoroughly examined. A Copper (II) curve is constructed, and the suggested method obeys Beer's law over ration range of 1-10 mg/ L. The limits of detection (LOD) and on (LOQ) are determined to be (0.361) mg/ L and(1.204) mg/ L, while Sandell's sensitivity and molar absorption coefficient are to be (0.120) µg/ cm2 and (527.05) L/ mol. cm respectively. The recommended method has given good accuracy with recovery rates ranging from (77.82% - 115% ).

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.

Ammonium determination by merging-zone flow injection analysis and a naphthalene-based fluorescent probe

This paper discusses the first-time study of a naphthalene-based fluorescent probe—naphthalene-2,3-dicarboxaldehyde (NDA), in combination with merging-zone flow injection analysis for the automated fluorescence determination of ammonium. The determination was contingent on detecting the fluorescent product of NDA-SO32--NH4+, which has maximum excitation and emission wavelengths of 508 nm and 564 nm, respectively. And the possible sensing mechanism of NDA-NH4+ was proposed. The effects of the reaction parameters, including reagent concentrations, reaction flow rate, coil length, reaction temperature, and pH were optimized. Under optimal conditions, this method afforded a sampling rate of 8 h−1, a limit of detection of 0.045 μmol L−1, and RSD of 3.68% (n = 14) with 1.50 μmol L−1 ammonium, and the calibration range was 0.045–6.00 μmol L−1. Examination of the organic nitrogen interference confirmed that the method attracts minimal interference from organic nitrogen, and the stability of the NDA reagent facilitates its field application. Other exhibited advantages include low reagent consumption and high automation; the method has been utilized in the successful determination of ammonium in freshwater and rainwater. The development of NDA applications for ammonium determination also provides more options for fluorometric determination of ammonium.

Semi – Automation Design Using Flow Injection Analysis System with Smart Phone for the Determination of Total Phenols in Wastewater

Smart phone used as supporting hardware in different applications in chemical analysis are becoming increasingly important in everyday life. Rapid, easy, and straightforward analytical system flow injection analysis system for the determination of the total phenols was conducted using 4-aminoantipyrine reagent. The detection method was based on the reaction total phenols with reagent in the basic media and subsequent formation of a yellow color product. The samples or standard solutions were injection into a carrier stream to react with 4-aminoantipyrine reagent and ammonium chloride with ammonium hydroxide to give yellow color product, which was detected by spectrophotometer at 510 nm. The experimental condition such as flow rate of reagent and carrier, reagent volume, length of reaction coil and concentration of reagent were optimized. A good linear calibration curve in the range of 250-2000 mg L-1 was obtained with regression equation (y=0.0108 x + 0.3453), (R= 0.9989). The limit of detection was in the amount of 0.0112 mg L-1. The method was successfully applied for the determination of the total phenols in wastewater.

Assay of Famotidine in Pure Solutions and Pharmaceutical Preparatives using the Coated- graphite Electrode as a Detector in the FlA System

A simple electrochemical method was developed to estimate famotidine (FMT) in pure solutions and pharmaceutical preparatives by a flow-injection analysis system (FlA). This method includes preparation of a coated graphite electrode using FMT with the Phosphotungstic acid precipitant (PTA), di-butyl phthalate (DBP) and poly vinyl chloride (PVC). The electrode characteristics were examined by studying the optimum conditions, the carrier current, the injected model size, flow rate, the reaction coil length, pH, the range of concentrations, the minimum Nernst response, the response time, the detection limits, and the study also included identifying the electrode selectivity of the toward other interfering ions. The electrode showed that the best Nernst slope for the calibration curve was at 33.82 mv/decade within linear range of (1.0 × 10-6- 1.0 × 10-1M), correlation coefficient (R2) 0.9999, response time 10 seconds, the estimating speed is 90 sample/hour, while the rate of dilution degree (D) is 2.6452. The obtained results confirmed that it is of high accuracy and precision (Err 0.119%), (Rec 100.11%), (RSD 0.1233%). The proposed method was successfully applied to assay of FMT in commercial tablet forms.

A novel flow injection amperometric sensor based on carbon black and graphene oxide modified screen-printed carbon electrode for highly sensitive determination of uric acid

A simple, rapid, and cost-effective flow injection amperometric (FI-Amp) sensor for sensitive determination of uric acid (UA) was developed based on a new combination of carbon black (CB) and graphene oxide (GO) modified screen-printed carbon electrode (SPCE). The CB-GO nanocomposites were simply synthesized and modified on the working electrode surface to increase electrode conductivity and enhance the sensitivity of UA determination via the electrocatalytic activity toward UA oxidation. The morphologies and electrochemical properties of the synthesized nanomaterials were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The modified electrode was incorporated with FI-Amp to improve UA detection's sensitivity, stability, and automation. Some parameters affecting sensitivity were optimized, including pH of the electrolyte solution, applied potential, amount of CB-GO suspension, flow rate, injection volume, and reaction coil length. Using an applied potential of +0.35 V (vs Ag/AgCl), the anodic current was linearly proportional to UA concentration over the range of 0.05–2000 μM with a detection limit of 0.01 μM (3 S/N). Besides, the developed method provides a sample throughput of 25 injections h−1, excellent sensitivity (0.0191 μA/μM), selectivity, repeatability (RSD 3.1%, n = 7), and stability (RSD 1.08%, n = 50). The proposed system can tolerate potential interferences commonly found in human urine. Furthermore, a good correlation coefficient between the results obtained from the FI-Amp sensor and a hospital laboratory implies that the proposed system is accurate and can be utilized for UA detection in urine samples.

Spectrophotometric flow injection method for the determination of Bendiocarb insecticide in water samples using chromogenic reagent 2,4-dinitrophenylhydrazine

Objective: Bendiocarb (BEN) is an acutely toxic carbamate insecticide which is used in public places and agriculture. The present study describes a new, sensitive, and accurate flow injection analysis method for the determination of BEN in its pesticide formulations and water samples.Methods: The developed method is based on an alkaline hydrolysis of BEN in NaOH, and the resultant product was coupled with 2,4-dinitrophenylhdrazin in the presence of sodium periodate to form red-colored product which measured at 515 nm.Results: Under the optimum conditions established (sample volume 150 μL, flow rate 2 mL/min, with 75 cm reaction coil length) for spectrophotometric determination of Bendiocarb. Beer’s law is obeyed in the range of 1–150 μg/mL with a detection limit of 0.738 μg/mL, with average recovery of 100.737 and relative standard deviation % of 1.331%.Conclusion: The established method was successfully applied for the determination of BEN in pesticide formulation and real spiked water sample.

Ultrasound- and microwave-assisted extractions followed by hydride generation inductively coupled plasma optical emission spectrometry for lead determination in geological samples

Followed the current idea of simplified sample pretratmet before analysis we evaluated the procedure for the determination of Pb in calcium-rich materials such as dolomites after ultrasound- or microwave- assisted extraction with diluted acids using hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP-OES). Corresponding Pb hydride was generated in the reaction of an acidified sample solution with NaBH4 after pre-oxidation of Pb(II) to Pb(IV) by K3[Fe(CN)6]. Several chemical (acidic media: HCl, HNO3 or CH3COOH, concentration of the reductant as well as type and concentration of oxidazing agents) and physical (reagents flow rates, reaction coil length) parameters affecting the efficiency of plumbane formation were optimized in order to improve the detectability of Pb using HG-ICP-OES. Limitation of the method derived from the matrix effects was pointed out. Employing Pb separation by HG technique allows the significant reduction of interferences caused by sample matrix constituents (mainly Ca and Mg), nevertheless they could not be overcame at all, hence calibration based on the standard addition method was recommended for Pb quantification in dolomites. Under the selected conditions, i.e. 0.3molL−1 HCl, HNO3 or CH3COOH, 1.5% NaBH4 and 3.0% K3[Fe(CN)6] the limits of detection (LODs) between 2.3–5.6μgL−1 (3.4–6.8μgL−1 considering matrix effects) and the precision below 5% were achieved. The accuracy of the procedure was verified by analysis of certified reference materials (NCS DC70308 (Carbonate Rock) and NIST 14000 (Bone Ash)) and recovery test with satisfactory results of Pb recoveries ranging between 94–108% (CRMs analysis) and 92–114% (standard addition method). The applicability of the proposed method was demonstrated by the determination of Pb in dolomites used by different fertiliser factories.

Simultaneous determination of iron (II) and ascorbic acid in pharmaceuticas based on flow sandwich technique.

The simple and easy performed flow system based on sandwich technique has been developed for the simultaneous separate determination of iron (II) and ascorbic acid in pharmaceuticals. The implementation of sandwich technique assumed the injection of sample solution between two selective reagents and allowed the carrying out in reaction coil two chemical reactions simultaneously: iron (II) with 1,10-phenanthroline and ascorbic acid with sodium 2,6-dichlorophenolindophenol. For achieving of excellent repeatability and considerable reagent saving the various parameters such as flow rate, sample and reagent volumes, reaction coil length were also optimized. The limits of detection (LODs) obtained by using the developed flow sandwich-type approach were 0.2 mg L(-1) for iron (II) and 0.7 mg L(-1) for ascorbic acid. The suggested approach was validated according to the following parameters: linearity and sensitivity, precision, recoveries and accuracy. The sampling frequency was 41 h(-1).

Online spectrophotometric determination of Fe(II) and Fe(III) by flow injection combined with low pressure ion chromatography

A simple and new low pressure ion chromatography combined with flow injection spectrophotometric procedure for determining Fe(II) and Fe(III) was established. It is based on the selective adsorption of low pressure ion chromatography column to Fe(II) and Fe(III), the online reduction reaction of Fe(III) and the reaction of Fe(II) in sodium acetate with phenanthroline, resulting in an intense orange complex with a suitable absorption at 515nm. Various chemical (such as the concentration of colour reagent, eluant and reductive agent) and instrumental parameters (reaction coil length, reductive coil length and wavelength) were studied and were optimized. Under the optimum conditions calibration graph of Fe(II)/Fe(III) was linear in the Fe(II)/Fe(III) range of 0.040–1.0mg/L. The detection limit of Fe(III) and Fe(II) was respectively 3.09 and 1.55μg/L, the relative standard deviation (n=10) of Fe(II) and Fe(III) 1.89% and 1.90% for 0.5mg/L of Fe(II) and Fe(III) respectively. About 2.5 samples in 1h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of water samples.

Improved activity of α-chymotrypsin in mixed micelles of cetyltrimethylammonium bromide (CTAB) and ionic liquids: A kinetic study resorting to sequential injection analysis

In the present work an automatic methodology, based on sequential injection analysis, (SIA) for the kinetic evaluation of α-chymotrypsin (α-CT) activity in cetyltrimethylammonium bromide (CTAB)/ionic liquid (IL) mixed micelles, was developed. The α-CT-catalysed hydrolysis of N-succinyl-l-phenylalanine-p-nitroanilide (SPpNA) was monitored by following the change in absorbance at 410nm brought about by the formation of p-nitroaniline (pNA). The influence of parameters such as reagents concentration, flow rate, as well as reaction coil length, on the sensitivity and performance of the SIA system were studied and the optimum reaction conditions were subsequently selected. The effect of CTAB/IL micelles on the catalytic constant Kcat and apparent Michaelis–Menten constant (KM) for SPpNA hydrolysis was then studied. The kinetic assays evidence that CTAB/ILs mixed micellar systems can induce α-CT superactivity. In order to perform a critical evaluation of the obtained results, CMC and average micellar size of CTAB/hmim[Cl], CTAB/bmim[Cl], CTAB/bmpyr[Cl] and CTAB/bmpy[Cl] mixed micelles were evaluated by fluorescence and dynamic light scattering, respectively. The SIA methodology showed to be an interesting tool for evaluation of α-CT activity in mixed micelles as it proved to be robust and exhibited good repeatability in all the assay conditions leading also to a reduction of the consumption of solvents as well as of effluent production.

Improved on-line high performance liquid chromatography method for detection of antioxidants in Eucommia ulmoides Oliver flower

Eucommia ulmoides Oliver is a traditional Chinese medicine and material for functional food with a strong antioxidant activity. To investigate antioxidants in E. ulmoides Oliver flower, an improved on-line high performance liquid chromatography method with the radical cation 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS(+)) as a stable model free radical for the detection of radical scavenging ability was developed. The radical concentration, flow rate, and length of reaction coil were optimized with rutin as a model antioxidant. Under the optimized instrumental set-up, a radical solution of 0.32 mM ABTS(+) is delivered by a pump equipped with a superloop at 0.5 mL/min through a reaction coil of 10 m × 0.25 mm. This method showed a high sensitivity since the system noise was reduced by the superloop. The minimum detecting concentration of the method was in the range of 0.03-0.10 μM for the negative peaks of rutin, quercetin, ascorbic acid, and α-tocopherol. Importantly, the method could be not only used for detection of antioxidants in plant extracts but also combined with mass spectrometry to obtain the structural messages of peaks in high performance liquid chromatography profiles. After analysis by the method, nineteen antioxidants were found in E. ulmoides Oliver flower extract, and the main active compound was identified as chlorogenic acid.

NEW DESIGN OF FLOW INJECTION ANALYSIS UNIT USING ( CE4++ I-+ H3O+) SYSTEM FOR THE DETERMINATION OF CERIUM(IV) BY MERGING ZONE TECHNIQUE .

The aim of this work was to design a new flow injection analysis unit for the determination of cerium(IV) by the reaction of potassium iodide with Ce4+ in an acidic medium to released I2 which have yellow color and give a λmax in 351 nm. The method involves the design of a new valve from cheap material and select the best design for unit .The optimum condition such as acid concentration , flow rate, potassium iodide concentration, acid volume, sample volume, reaction coil length, and interference effects were studied. Beer's law is obeyed over concentration rang (1- 40 mg/l), correlation coefficient(R2) was 0.998.

DPPH Assay Adapted to the FIA System for the Determination of the Antioxidant Capacity of Wines: Optimization of the Conditions Using the Response Surface Methodology

The objective of the present work was to adapt the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay to a system of flow injection analysis (FIA) of merging zones to determine the antioxidant capacity of wine samples. The conditions of the FIA system proposed here were optimized with the response surface methodology using central composite rotatable design. The optimization parameters studied here were the carrier flow rate, the length of the sampling and reagent loops, and the length of the reaction coil. The experimental data were fitted to a polynomial model, and the optimal conditions were: flow rate of 1.12 mL min−1, loop length of 18.5 cm, and reaction coil length of 234.60 cm. The limits of detection and quantification were 2.65 and 8.82 μM of Trolox, respectively. The method proposed had an analytical frequency of 41 analyses per hour and a reagent consumption economy of 57.3 % for DPPH in relation to the conventional method. The results of the antioxidant activities of the wine samples obtained with the proposed method were correlated and compared to those of the conventional method.

SIMPLE FLOW INJECTION SPECTROPHOTOMETRIC DETERMINATION OF ACETAMINOPHEN IN PHARMACEUTICAL FORMULATIONS USING 1,2-NAPHTHOQUINONE-4-SULPHONATE AS CHEMICAL DERIVATIZATION CHROMOGENIC REAGENT

A simple method for the determination of paracetamol (acetaminophen) with sodium 1,2-naphthoquinone-4-sulphonate (NQS) in alkaline medium using flow injection analysis (FIA) was developed and validated. The effect of variables such as flow rate, NQS concentration, reaction coil length, NaOH concentration, and detection wavelength were studied. Linear response was found over the concentration range 3–35 mg L−1 (r2 = 0.9995), the relative standard deviation from replicate injections (n = 9) of 20 mg L−1 of paracetamol was 0.89%. A sampling rate of 82 samples h−1 was obtained. The method was applied for the determination of paracetamol in pharmaceutical tablets, and results have been compared with those obtained by the official method.

Amperometric flow system for blood glucose determination using an immobilized enzyme magnetic reactor

An amperometric flow system for glucose determination in blood serum samples after enzymatic reaction with glucose oxidase immobilized on magnetite covered with silica gel modified propylamine is described. The solid was magnetically retained on a mini-column and placed into the flow injection system preceding the amperometric detector using a modified screen printed electrode with [Fe(tris(3,5-dimetyl-1-pyrazolyl)borate)2]+[FeCl4]−. The variables involved in the system such as flow rate, enzyme concentration, injection volume and reaction coil length were evaluated using a Taguchi parameter design. Under optimal conditions, the calibration curve of glucose sample was linear between 0.24 and 6.00mM, and with a limit of detection of 0.08mM. The repeatability for a 4.0mM glucose solution was 1.0%.The method was validated by comparing the obtained results to those provided by the enzymatic spectrophotometric method; no significant differences were observed.

Amperometric biosensor for oxalate determination in urine using sequential injection analysis.

An amperometric flow biosensor for oxalate determination in urine samples after enzymatic reaction with oxalate oxidase immobilized on a modified magnetic solid is described. The solid was magnetically retained on the electrode surface of an electrode modified with Fe (III)-tris-(2-thiopyridone) borate placed into a sequential injection system preceding the amperometric detector. The variables involved in the system such as flow rate, aspired volumes (modified magnetic suspension and sample) and reaction coil length were evaluated using a Taguchi parameter design. Under optimal conditions, the calibration curve of oxalate was linear between 3.0–50.0 mg·L−1, with a limit of detection of 1.0 mg·L−1. The repeatability for a 30.0 mg·L−1 oxalate solution was 0.7%. The method was validated by comparing the obtained results to those provided by the spectrophotometric method; no significant differences were observed.

Determination of cadmium in high salt content matrices by flow injection cold vapor atomic absorption spectrometry

Flow injection cold vapor atomic absorption spectrometry (FI-CVAAS) was used for determination of cadmium in high salt matrices such as dialysis concentrates and textile leach solutions. The parameters such as acidity, concentration of reducing agent, reaction coil length, and carrier gas flow rate were investigated to obtain the best sensitivity. No significant background signal was observed even at high salt concentrations. Under the optimized conditions the limit of detection value (3s_b m^{-1}, where s_b is the standard deviation of the blank signals and m is the slope of the calibration graph) was found to be 0.05 ng mL^{-1} for an injection volume of 250 \mu L and the precision in terms of relative standard deviation was 3.2% using 11 consecutive measurements of 0.5 ng mL^{-1} standard. The standard addition method was used for quantitation. The accuracy of the method was tested using ETAAS as a comparison method and a certified reference material (Waste Water EU-L-1). In both cases, the results were in good agreement at 95% confidence level. The concentrations of cadmium in textile product leach solutions were found to be below the limit value assigned by Oeko-Tex standards.

Rapid antioxidant capacity screening in herbal extracts using a simple flow injection-spectrophotometric system

A simple flow injection (FI)-spectrophotometric system for the screening of antioxidant capacity in herbal extracts was developed. The analysis was based on the color disappearance due to the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by antioxidant compounds. DPPH and ascorbic acid were used as reagent and antioxidant standard, respectively. Effects of the DPPH concentration, DPPH flow rate, and reaction coil length on sensitivity were studied. The optimized condition provided the linear range of 0.010–0.300mM ascorbic acid with less than 5%RSD(n=10). Detection limit and quantitation limit were 0.004 and 0.013mM, respectively. Comparison of antioxidant capacity in some herbal extracts determined by the FI system and a standard method was carried out and no significant difference was obtained.