Flow Injection Manifold Research Articles

Reverse Flow Injection Spectrophotometric Determination of Total Acidity in Beverages Using Butterfly Pea Flower Extract.

Monitoring total acidity during beverage production is crucial for quality control (QC). The standard acid-base titration, though widely used, is slow and generates hazardous waste through the use of acid-base indicators. To develop an analysis method for beverage samples to determine total acidity using a natural reagent from butterfly pea flower as the colorimetric reagent. The determination of total acidity in beverages was based on the reaction of citric acid with anthocyanin extracted from butterfly pea flowers. The decreased absorbance of anthocyanin was measured at 620 nm. A two-line reverse flow injection manifold was used to perform online dilution of samples. Under optimal conditions, the calibration curve equation 1/A = 0.03782C + 0.00241 (A = absorbance and C = concentration) was linear over a range of 0.050-0.25% (w/v) citric acid. The LOD and LOQ were 0.0123 and 0.0409% (w/v), respectively. The system achieved a throughput of 120 samples per hour with comparable accuracy and precision to the standard titrimetric method. The injection of butterfly pea flower extract into beverage samples with online dilution in a reverse flow injection system (FIS) was reported for the first time for the determination of total acidity. Use of a green reagent in the method reflects its alignment with the principles of green analytical chemistry, providing a rapid and straightforward solution.

New magnetic chelating sorbent for chromium speciation by magnetic solid phase extraction on-line with inductively coupled plasma optical emission spectrometry

A novel sorbent material employing magnetic nanoparticles (MNPs) coupled to graphene oxide (GO) functionalized with 4-aminobenzenesulfonic acid (M@GO-ABS) has been synthesized and applied to develop an inexpensive and automatic method for Cr(III) and Cr(VI) speciation in environmental samples; the developed method combines inductively coupled plasma optical emission spectrometry (ICP-OES) with on-line magnetic solid phase extraction (MSPE). Two magnetic-knotted reactors containing M@GO-ABS were installed in the eight-port injection valve of a flow injection (FI) manifold. Two different eluents were used, one for Cr(VI) (the most toxic chromium species) and one for total Cr concentration. Cr(III) concentration was calculated by the difference between Cr(VI) concentration and total Cr concentration. The optimized method presented detection limits (LOD, peak height) of 0.1 μg L−1 for chromium (VI) and 0.08 μg L−1 for total chromium, and enrichment factors of 15 and 23, respectively. Certified reference materials (TMDA 54.5 fortified lake water and SPS-SW2 surface water) and spiked aqueous samples were used to validate the developed method. The developed method was fruitfully applied to chromium speciation in environmental water samples such as seawater, well water and tap water collected in Málaga (Spain). The obtained values were in good agreement with the certified values, and the recoveries were found in the range of 91–108% for the spiked samples.

Spectrophotometric Determination of Vitamin B1 in Dosage forms Using Drugs Compounds as Reagents by Normal and Reverse Flow Injection Methods

Background: Thiamine hydrochloride (THY), also known as vitamin B1, is a water soluble vitamin usually found in food, and considered as a dietary supplement and treatment in case of vitamin deficiency for example in malabsorption and chronic diarrhea. Objective: Rapid, green, and sensitive methods for the assay of vitamin B1 (thiamine hydrochloride, THY) in pharmaceutical forms, using normal and reverse flow injection manifolds and sulfonamide drugs as green and safe reagents were reported. Sulfamethoxazole and sulfadimidine drugs were used rather than toxic and expensive reagents. Methods: nFIA and rFIA manifolds were used for automated the reaction of THY with diazotized sulfamethoxazole (DSMZ) and diazotized sulfadimidine (DSDM) in an alkaline medium, respectively. The absorbance of the resultant red-orange azo dyes was monitored spectrophotometrically at λmax494 and 496nm for both methods, respectively. Results: The linearity of the suggested methods was in the ranges 2–80 µg/mL (LOD 0.69 µg/mL, % RSD 0.32, n=6) for nFIA method and 0.5-70 µg/mL (LOD 0.29 µg/mL, %RSD 0.85, n=6) for rFIA. Sampling frequency was 84 and 51 injections per hour for nFIA and rFIA methods respectively. Chemical and physical variables for both methods were studied carefully. Conclusion: Both flow injection modes were effectively applied in assay of THY in its pharmaceutical forms. The results were compared with those of standard pharmacopeia method and the statistical analysis indicated insignificant differences in accuracy and precision between the methods.

New Turbidimetric Method for Determination of Cefotaxime Sodium in Pharmaceutical Drugs Using Continuous Flow Injection Manifold Design with CFTS- Vanadium Oxide Sulfate System

The determination of Cefotaxime sodium pure from and pharmaceuticals (tablets) by continuous flow injection scatter light has been created using a new, simple, rapid, and sensitive approach. Using a handmade ISNAG-FIuorimeter, the technique was predicated on the interaction of Cefotaxime sodium with vanadium oxide sulfate to produce a precipitate. The optimal value had a linear dynamic range of 0.01-20 mmoI/L for the instrument response to Cefotaxime sodium concentration, while the L.O.D was 0.334 g /sample from the stepwise dilution for the lowest concentration in the calibration graph's scatter plot range. For the scatter plot range and the linear dynamic range, the correlation coefficient (r) was 0.9769 and 0.9978, respectively, while percentage linearity (R2% percent) was 95.43 percent and 99.56 percent, respectively. With a concentration of 2.5 mmol/L, the RSD percent for repeatability (n=8) was lower than 0.23% percent for the determination of cefotaxime sodium. The proposed method was effectively used to determine the concentration of cefotaxime sodium in pharmaceutical tablets. The newly developed technique was compared with the conventional methods of analysis, i.e., Turbidemtric method and UV-spectrophotometer method, utilizing the usual addition method and paired t-test. The computed t-value at 95 percent confidence interval from the established approach revealed that there was no significant difference between the quoted figures of any individual firm.

New turbidimetric method for determination of ciprofloxacin hydrochloride in pharmaceutical drugs using continuous flow injection manifold design with CIP.HCL-sodium nitro prusside system

A new, simple, fast and sensitive method was developed for the determination of Ciprofloxacin. HCI pure from and drugs (tablets) by continuous flow injection scatter light. The method was based on the reaction of the Ciprofloxacin. HCI with sodium nitro prussside to form a precipitate, using homemade ISNAG-FIuorimeter. Optimum parameters have been studied to increase the sensitivity for the developed method. The scatter plot range and the linear dynamic range for the instrument response versus Ciprofloxacin. HCI concentration was 0.03-15 mmoIl L while the L.O.D was 65.3660 µg/sample from the step wise dilution for the minimum concentration of lowest concentration in the scatter plot range of the calibration graph. The correlation coefficient (r) was 0.9150 and 0.9972 while percentage linearity (R2%) was 83.73% and 99.44 for the scatter plot range and the linear dynamic range, respectively. RSD % for the repeatability (n=8) was lower than 0.2% for the determination of ciprofloxacin. HCI, with concentration of 4,13 mmol/L. The developed method was applied successfully for the determination of ciprofloxacin.HCI in pharmaceutical tablets. A comparison was made between the newly-developed method with the classical method, i.e. Turbidemtric method, of analysis using the standard addition method via the use of paired t-test. It showed that there was no significant difference between the quoted values of each individual company with calculated t-value at 95% confidence interval from developed method.

Multi-Element Analysis Based on an Automated On-Line Microcolumn Separation/Preconcentration System Using a Novel Sol-Gel Thiocyanatopropyl-Functionalized Silica Sorbent Prior to ICP-AES for Environmental Water Samples.

A sol-gel thiocyanatopropyl-functionalized silica sorbent was synthesized and employed for an automated on-line microcolumn preconcentration platform as a front-end to inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the simultaneous determination of Cd(II), Pb(II), Cu(II), Cr(III), Co(II), Ni(II), Zn(II), Mn(II), Hg(II), and V(II). The developed system is based on an easy-to-repack microcolumn construction integrated into a flow injection manifold coupled directly to ICP-AES’s nebulizer. After on-line extraction/preconcentration of the target analyte onto the surface of the sorbent, successive elution with 1.0 mol L−1 HNO3 was performed. All main chemical and hydrodynamic factors affecting the effectiveness of the system were thoroughly investigated and optimized. Under optimized experimental conditions, for 60 s preconcentration time, the enhancement factor achieved for the target analytes was between 31 to 53. The limits of detection varied in the range of 0.05 to 0.24 μg L−1, while the limits of quantification ranged from 0.17 to 0.79 μg L−1. The precision of the method was expressed in terms of relative standard deviation (RSD%) and was less than 7.9%. Furthermore, good method accuracy was observed by analyzing three certified reference materials. The proposed method was also successfully employed for the analysis of environmental water samples.

Charge Transfer Spectrophotometric Determination of Metronidazole in Pharmaceutical Formulations by Normal and Reverse Flow Injection Analysis Coupled with Solid-Phase Reactor Containing Immobilized FePO4

Two rapid, simpleand sensitive flow injection methods were developed for the estimation of metronidazole (MRZ) in pharmaceutical formulations. The proposed methods were based on charge transfer reaction between metol (N-methyl-p-aminophenol sulfate) as a π-acceptorand reduced MRZ as an n-donor to produce a blue colored chargetransfer complex. Method A depends on the reaction of reduced MRZ with metol (MT) in the presence of NaIO4 using two lines manifold to form blue colored product exhibiting absorption maxima at 700 nm.While method B depends on charge transfer reaction of reduced MRZ with MT in presence of a solid phase reactorcontainingfixedFePO4 on cellulose acetateusing reverse flow injection manifold to form a blue colored productwhich was measured spectrophotometrically at690 nm.Various experimental parameters for both methods were studied. Beer's law was obeyed in the ranges of2.5-200 and 2.5-150 μg mL-1,with r2 of 0.9995 and 0.9972;whilethe detection limit values were2.53 and 2.12μg mL-1 for methods A and B, respectively. Both of the suggested methods were successfully applied for the estimation of MRZ in commercial formulations. The results of the developed methods were compared with those obtained by the British pharmacopeia method, showinghigh accuracy and precision.

New Turbidimetric Method for Determination of Ketotifen Fumarate in Pharmaceutical Drugs by using line-continuous flow injection manifold design of KTF-Ammonium molybdate (Am) system

New Turbidimetric Method for Determination of Ketotifen Fumarate in Pharmaceutical Drugs by using line-continuous flow injection manifold design of KTF-Ammonium molybdate (Am) system

An asymmetric flow injection determination of hydroquinone and catechol: An analytic hierarchy and artificial neural network approach

A new reaction rate system was introduced for differential kinetic simultaneous determination of hydroquinone (HQ) and Catechol (CC). The method is based on the different kinetic behavior of HQ and CC in their reaction with iron (III) in the presence of 1, 10-phenanthroline (Phen) as a chromogenic reagent. An asymmetric double line flow injection manifold coupled with a spectrophotometric detector was designed and optimized using TOPSIS (Technique of ranking Preferences by Similarity to the Ideal Solution) methods based upon AHP (Analytic Hierarchy Process). Under optimal conditions, Bayesian Regularized Artificial Neural Network (BR-ANN) trained by back-propagation of errors was utilized as a non-linear model calibration of flow injection manifold. Detection limits of 0.05 and 0.07 mg L−1 were obtained for HQ and CC, respectively. The linear dynamic range was 0.5–3.0 mg L−1 for both analytes. The suggested method was applied for simultaneous determination of HQ and CC in real samples.

Application of Allura Red in the construction of a novel amperometric flow sensor for the automatic determination of hydroquinone and catechol using a two-line flow injection manifold with a single-sensor/double-pulse amperometric detection

A novel amperometric flow sensor was constructed by the successive voltammetric cycling of a glassy carbon electrode (GCE) in a basic solution of Allura Red. The performance of the constructed treated GCE sensor was characterized in the new flow injection amperometric manifold with a single-sensor/double-pulse amperometric simultaneous detection of hydroquinone (HQ) and catechol (CC). A programmed sequence of two potential steps with magnitudes of +0.18 (at the time of the first sample injection) and +0.26 V (at the time of the second injection) was applied. By designing a proper time delay between a sequence of two sample injections and potential steps, two separate flow injection amperometric peaks were recorded. The first peak corresponds to HQ and the second peak is related to the oxidation of both HQ and CC. The currents obtained from the subtraction of two recorded peaks is utilized to obtain the amount of CC. Under the optimized chemical and instrumental parameters, the relation between the concentration and response of the sensor has a good linearity in the ranges of 0.2–600.0 and 0.2–300.0 µmol l−1 for HQ and CC, respectively. The detection limit obtained for both was 0.15 µmol l−1 (signal-to-noise ratio = 3). The proposed flow sensor was employed for the determination of HQ and CC in the real samples with satisfying precision and accuracy.

On-Line Photoinduced Fluorescence for Carbamazepine Determination after Multivariate Optimization

This work presents a simple and sensitive flow injection fluorimetric method for the determination of carbamazepine (CBZ) in pharmaceutical samples. It is based on the fluorescence signal measurement of the product generated by photoinduced (λex = 251 nm; λem = 434 nm) using a flow injection manifold containing an online homemade photoreactor. In order to optimize the experimental setup, the variable conditions were studied using a multivariate optimization method, thus finding the set of optimum parameters according to the evaluated responses (sensitivity and sampling frequency) and minimizing the number of experiments performed. Under optimal experimental conditions, linear relationship with good correlation coefficient (0.9956) was found between the fluorescence intensity and CBZ concentration in the range of 0.13 - 40 μg·mL-1. The limit of detection was 0.04 μg·mL-1. The precision of the method was satisfactory; the values of relative standard deviations were better than 4.36%. The proposed method was validated and successfully applied to the determination of CBZ in pharmaceuticals with good accuracy; being the recovery values from 89.45% - 112.20%.

Determination of Nifedipine in Pharmaceutical forms using Selective Flow-Injection Spectrophotometric Technique combined with Immobilized Manganese dioxide as a Solid Phase Reactor

A sensitive new economic method was presented to determine nifedipine (NIF) in pharmaceutical forms using oxidative coupling reaction between reduced NIF and pyrocatechol oxidized by MnO2 packed in solid phase reactor fastened in reversed flow injection manifold with one channel solution stream. The optimization conditions for solid phase reactor, flow injection system and pyrocatechol concentration were studied and established. The results revealed that the range (5–160)μg.mL−1obey beer's low with high sensitivity and good linearity (r =0.9990) and the limit of detection and quantitation 2.243μg.mL−1 and 7.478μg.mL−1 respectively. The method offered good accuracy and precision; moreover the sample frequency was 45 injections per hour and found that the solid phase reactor lifetime 40 replicated injection with RSD%=2.93 as acceptable value. Application carried out by the use of NIF tablets in different concentrations, high recovery and repeatability was recorded. The proposed method was compared with standard method by calculated student-t and F-test which confirmed that no significant differences between the two methods, so it could be used in routine pharmaceutical analysis.

Sensitive assay of pharmaceutical amines in environmental samples and formulations by oxygenated graphene quantum dots

Oxygenated graphene quantum dots (GQDs) were prepared and used as a new colorimetric reagent for analysis of pharmaceutical amines. Citric acid was thermalized to prepare GQDs with functional groups along their edges. The prepared GQDs were used as a coupling reagent in an azo dye formation for dapsone (DAP) and metoclopramide (MET) determination. The characterization was done by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy, Energy dispersive X-ray spectroscopy, EDX-mapping, dynamic light scattering, photoluminescence spectroscopy, Raman and FT-IR spectroscopy. DAP and MET were diazotized by nitrite to their related diazonium cations in acidic condition through a flow injection manifold. Then they were coupled to GQDs to produce the yellow colored products. Detection of the products was performed by spectrophotometry at 423 nm. Various chemical and instrumental parameters were optimized by a univariate procedure and a central composite design (CCD) chemometrics approach. The analytical method showed the linear calibrations for DAP and MET in the ranges of 0.03–20 and 0.1–40 µg mL−1, respectively. The limit of detection for both DAP and MET was of 0.01 µg mL−1, respectively. The inter-day experiments showed a satisfactory robustness of the method for determination of DAP and MET. The sample throughput found in this method was about 60 h−1. Lake, river and well water samples as well as soil samples along with some pharmaceutical formulations were analyzed.

Rapid colorimetric flow injection sensing of hypochlorite by functionalized graphene quantum dots

Graphene quantum dots (GQDs) with oxygen-containing functional groups along their edges have been prepared by controlled thermalization of citric acid to develop a new spectrophotometric reagent for hypochlorite determination. 2, 4-Dinitrophenylhydrazine (DNPH) was reacted with hypochlorite to form 2, 4-dinitrophenyl diazonium cation (DNPDC) in acidic condition through a flow injection manifold and then coupled to GQDs to produce a colored product. Characterization of the appropriate materials were performed by applying different imaging and spectroscopic techniques. The results obtained from the CCD optimization approach revealed that all of the chemical reagents had a significant role individually while their interactions were not of any importance. Under optimum condition, Beer’s law was obeyed for hypochlorite determination at 423 nm in the range of 0.2–12.3 μg mL−1. The obtained detection limit of hypochlorite was 0.1 μg mL−1. Also, the intra-day experiments (n = 10 at 0.7 and 11.0 μg mL−1 of hypochlorite) showed recoveries of 100.2 and 99.8%, respectively and that of inter-day (n = 5 at 0.7 and 11.0 μg mL−1 of hypochlorite) presented, respectively, 99.3 and 99.5% recoveries. The sample throughput was about 100 h−1. Tap and pool water samples as well as bleach solutions were analyzed by this and other appropriate reference analytical methods. No statistical differences were observed between the results of the presented method and the results obtained by the reference methods. Beside the studies, a model structure of a typical functionalized GQD was optimized using density functional theory. The natural charges on the carbons along the edge of GQD were calculated, and the results indicated that the ortho positions with respect to the phenolic OH moieties are the most preferable sites for the electrophilic substitution reactions.

Redesigning flow injection after 40 years of development: Flow programming

Automation of reagent based assays, by means of Flow Injection (FI), is based on sample processing, in which a sample flows continuously towards and through a detector for quantification of the target analyte. The Achilles heel of this methodology, the legacy of Auto Analyzer®, is continuous reagent consumption, and continuous generation of chemical waste. However, flow programming, assisted by recent advances in precise pumping, combined with the lab-on-valve technique, allows the FI manifold to be designed around a single confluence point through which sample and reagents are sequentially directed by means of a series of flow reversals. This approach results in sample/reagent mixing analogous to the traditional FI, reduces sample and reagent consumption, and uses the stop flow technique for enhancement of the yield of chemical reactions. The feasibility of programmable Flow Injection (pFI) is documented by example of commonly used spectrophotometric assays of, phosphate, nitrate, nitrite and glucose. Experimental details and additional information are available in online tutorial http://www.flowinjectiontutorial.com/

Fast Automated Determination of Total Tocopherol Content in Virgin Olive Oil Using a Single Multicommuted Luminescent Flow Method

Tocopherols are natural fluorophores of great importance for the characterization and authentication of virgin olive oil. Herein, a single automatic multicommuted flow method has been developed for the determination of total tocopherol content as well as the semi-quantitative estimation of α-tocopherol in extra virgin olive oil (EVOO) samples. Only appropriate dilution of samples with 2-propanol was necessary for their direct analysis by a multicommuted flow injection (MCFIA) manifold based on three solenoid valves with fluorescence detection. The peak height at λ em = 330 nm (emission) with λ exc at 296 nm was used as analytical signal. Linear response was observed within the range from 50 to 350 mg of tocopherols (expressed as α-tocopherol kg−1 olive oil), suitable to cover the usual range for tocopherols in (extra) virgin olive oil ((E)VOO)). The results were consistent with those obtained by reversed-phase HPLC reference method, whereas the analysis time was significantly reduced. The sample frequency of the proposed automatic method was close to 40 samples h−1, in contrast to typically 15–30 min required by HPLC. The method is fast, straightforward, cost-effective, and easy to implement in routine laboratories for screening purposes.

Double injection/single detection asymmetric flow injection manifold for spectrophotometric determination of ascorbic acid and uric acid: Selection the optimal conditions by MCDM approach based on different criteria weighting methods

A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe3+ in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe2+/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50–5.00 and 0.50–4.00mgL−1 for AA and UA, respectively. The 3σ detection limits were 0.07mgL−1 for AA and 0.12mgL−1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.

A novel method for total protein analysis of protein mixtures using enzyme hydrolysis and derivatisation with o-phthaldialdehyde – Application to dairy products

A novel approach to analysis of proteins in dairy products was demonstrated using enzyme hydrolysis followed by derivatisation with o-phthaldialdehyde (OPA) and fluorescence detection. Unlike the response of other dye-binding methods, enzyme hydrolysis significantly eliminated dependence of the fluorescence intensity upon protein primary sequence and, compared with chemical hydrolysis, was achieved under relatively mild conditions. Enzyme hydrolysis and OPA-derivatisation steps were successfully automated using a flow-injection manifold, with a method coefficient of repeatability <6%. The enzyme-OPA (eOPA) method was applied to analysis of total (TP) and serum-soluble proteins (SSP, proteins soluble at pH 4.6) in reference standards spanning two decades of protein concentration. Method accuracy was very good for analysis of TP and acceptable for analysis of SSP. Discrepancies between the eOPA and standard methods for SSP were explained by sample preparation and not analytical factors. The eOPA method may be suitable for automation into a portable or miniaturised device.

Development of a Photoinduced Chemiluminescent Method for the Determination of the Herbicide Quinmerac in Water.

A new, simple, and sensitive method, based on photoinduced chemiluminescence, was developed for the determination of quinmerac. The photoproduct, obtained after ultraviolet irradiation in basic medium, was mixed with sodium sulfite (sensitizer), and Ce(IV) (oxidant) in acid medium. A wide linear dynamic range (2-600 ng mL(-1)) and a limit of detection of 0.6 ng mL(-1) were obtained without any pretreatment (0.08 ng mL(-1) after solid-phase extraction). The determination was performed using a flow-injection manifold, which allowed a high throughput (144 h(-1)). The interday reproducibility was 5.6% (n = 5), and the intraday repeatability was 3.9 and 2.9% for 20 and 200 ng mL(-1) of quinmerac, respectively (n = 21). Finally, the method was applied to surface water and groundwater, with recoveries ranging from 78.1 to 94.5%.

Judgment of pure fermented soy sauce by fluorescence resonance energy transfer of OPA-tryptophan adduct

Tryptophan was detected with a flow-injection manifold after reacting with mM order of fluorogenic o-phthalaldehyde (OPA)/thiol reagent (pH 10.0) in the carrier stream (0.63mL/min). Based on the intra-molecular fluorescence resonance energy transfer of OPA-tryptophan adduct, the difference in fluorescence intensity obtained at 280 and 300nm excitation was used to detect tryptophan content with satisfactory precision (CV<6.5% for concentration higher than 0.5μM), linearity (0.1–10μM, R2=0.9893) and sensitivity (≈10nM). Since tryptophan will decompose during manufacturing non-fermented soy sauce by acid-hydrolysis procedure, the method was used to discriminate pure fermented soy sauces, adulterated soy sauces and chemical soy sauces in less than 5min. The ratio of tryptophan to total amino acid content served as the index for the judgment, and the results were validated by capillary electrophoresis.