Multicommuted Flow Analysis Research Articles

Integrated instrumental setup comprising an automatic solution handling module and homemade luminometer with two photodetectors for the determination of antioxidants in wines.

This study describes the development of an integrated instrumental setup, comprising a multi-commuted flow analysis module for solution handling and a homemade luminometer assembled with two photodetectors for luminescence detection. This setup controlled by an Arduino Due board was used to develop an analytical procedure for determining antioxidants in red and white wines, using chemiluminescence detection. The analytical procedure is based on the reaction of hypochlorite with antioxidants present in wine, followed of oxidizing reaction with luminol in an alkaline medium (pH > 9). After determining the optimal operational parameters, the following analytical parameters were obtained: linear responses for gallic acid concentrations ranging from 0.75 to 4.0 g L-1 (r2 = 0.999) for red wine and from 75 to 500 mg L-1 (r2 = 0.994) for white wine, a coefficient of variation of 2.71% (n = 9) for a wine sample with an antioxidant concentration of 1.57 g L-1 in gallic acid equivalent, recoveries ranging from 85 to 114%, an analytical throughput of 100 determinations per hour, consumption of 0.35 μg of hypochlorite and 53 mg of luminol per determination, and limits of detection of 0.25 g L-1 and 29 mg L-1 for red and white wine, respectively.

Multicommutation flow analysis system for non-enzymatic lactate determination based on light-driven photometric assay

A fully-mechanized bioanalytical system for the photometric light-driven lactate determination is presented. The system is based on highly integrated four diode flow-through cell in which two UV-LEDs are used for the photochemical reduction of Fe(III) in the presence of lactate whereas LED-photodiode system allows the photometric detection of Fe(II)-Ferrozine complex to be registered. The developed multicommutation flow analysis system consisting of bifunctional optoelectronic device (photodegradation of Fe(III)-lactate complex and detection), solenoid micropumps and microvalves, is fully controlled and powered by the Arduino-compatible electronics. In consequence, independent and precise control of crucial parameters of the assay, including irradiation time and current supplying UV-LEDs is possible. Under optimized condition the system is useful for the lactate determination in the sub-milimolar range of concentration (6.0–300.0 μmol/L) with satisfactory sensitivity (597.1 AU·L/μmol) and detection limit (3.4 μmol/L), significant reduction of sample and reagents consumption (1.25 μL or 0.5 μL for 40- and 100-fold dilution of human serum samples, respectively) and high sample flow throughput (24 detections per hour). As the system offers the monitoring of detection process, the kinetic discrimination of effects from potential interferents is possible, improving the assay selectivity. The practical utility of the designed system was confirmed by its used for analysis of human serum standards. The recovery values were in the range of 92.1–104.2%. As the limit of quantitation offered by the system is significantly lower than physiological lactate levels, the serum samples have to be diluted what results in further decrease of both sample volume required for analysis and nonselective effects from matrix.

A new flow cell design for chemiluminescence detection using an improved signal transduction network. Determination of hydrogen peroxide in pharmaceuticals

In this study, it proposed for the first time, a setup consisting of a flow cell shaped like a hollow coin for chemiluminescence detection and a luminometer consisting of two photodiodes assembled with a new configuration. The feasibility of the proposed luminometer for signal transduction was ascertained using a light-emitting diode (LED) to simulate chemiluminescence emissions. The feasibility for analytical purposes was evaluated using the oxidizing reaction of luminol with hydrogen peroxide catalyzed by hexacyanoferrate(III) inion in alkaline medium. The system that handles sample and reagent solutions is based on the multicommuted flow analysis (MCFA) approach. It uses solenoid mini-pumps and peristaltic mini-pumps controlled by an Arduino Due board for fluid propulsion. After optimizing the operational conditions, peroxide samples (pharmaceutical formulation) were analyzed. The accuracy was assessed by comparing the results with those obtained using a reference method. The results of a paired t-test at the 95% confidence level demonstrate no significant difference between the results. Other favorable characteristics of our method include: a linear response between 1 and 100 μmol L−1 hydrogen peroxide (r2 = 0.999); limit of detection and limit of quantification of 0.13 and 0.43 µmol L−1 H2O2, respectively; luminol and hexacyanoferrate(III) inion consumption of 60 µg (0.3 µmol L−1) and 1.9 mg (6 µmol L−1) per determination, respectively; a sampling rate of 230 determinations per hour; waste generation of 0.63 mL per determination; and a coefficient variation of 1.5% (n = 11) for a 0.17 mg L−1 (5 µmol L−1) hydrogen peroxide solution.

Automated analytical procedure using multicommuted flow analysis and organic solvent extraction controlled by an Arduino Due board for photometric determination of zinc in water

In this study, an automated analytical procedure that utilizes solvent extraction for the photometric determination of zinc in water is described. The procedure involved the reaction of diphenylthiocarbazone (dithizone) with Zn(II) in the alkaline medium and extraction with chloroform. The instrumental setup, combined with flow-batch and multicommuted flow analyses approaches, was designed to facilitate microextraction without using a dispersant organic solvent. Fluid propulsion occurred through two mini peristaltic pumps and a homemade syringe pump. Photometric detection was performed using a homemade LED-based photometer equipped with a flow cell (50 mm in length). The control of the instrumental setup, analytical procedure, and data acquisition algorithm was achieved using an Arduino Due board along with a software developed for this study. After determining the optimal values of the control variables using Zn(II) standard solutions, the effectiveness of the proposed method was evaluated. For this purpose, a set of water samples was analyzed. For assessing accuracy, the samples were also analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). By comparing the paired t-test results of the two analyses, it was observed that at 95% confidence level, there is no significant difference. Other advantageous results of the proposed method were as follows: the linear response range was 10–100 µgL−1 (r2 = 0.9934), the limit of detection was 8.3 µgL−1, the coefficient of variation was 3.3% (n = 9), the consumption of chloroform and dithizone was 200 µL and 4 µg, respectively, per determination, and the sampling rate was 19 determinations per hour.

Automatic multicommuted flow-batch setup for photometric determination of mercury in drinking water at ppb level

Herein, a multicommuted flow-batch setup and a photometric procedure for the determination of mercury at the ppb level in aqueous samples are described. The setup was designed to implement a versatile solvent extraction and pre-concentration strategy by combining flow-batch and multicommuted flow analysis approaches. The photometric method was based on Hg(II) reaction with dithizone in a chloroform medium, which was also used as the extracting organic solvent. The flow analysis system was composed of a homemade syringe pump module, a set of solenoid valves, two Aquarius mini-pumps, and a flow-batch chamber. The homemade photometer was comprised of a light emitting diode (LED), photodiode, and homemade flow cell (50 mm length). The flow system and photometer were controlled using an Arduino Due board, running custom-written software. After optimizing the operational conditions, the effectiveness of the developed system was evaluated for the determination of the mercury concentration in drinking water. For accuracy assessment, samples were analyzed using a spiking methodology and an independent method, yielding a recovery ranging from 92% to 108%. Other important characteristics of the proposed method were found as follows: linear response range, 0.5–10.0 μg L−1 (r = 0.9984); limit of detection 0.38 μg L−1 Hg(II); consumption of dithizone and chloroform, 1.85 μg L−1 and 0.8 mL per analysis, respectively; coefficient of variation, 2% (n = 10); sampling throughput, 20 determinations per h.

Automatic Procedure to Determine Acidity in Fuel Ethanol by Photometric Titration Using Binary Search and Multicommuted Flow Analysis

An automatic photometric titration procedure was developed to determine the acidity of fuel ethanol. The procedure was implemented by using a binary search algorithm and a multicommuted flow analysis approach. Solution-handling setup included a homemade syringe pump and a set of solenoid valves, which were assembled to treat the solution-handling as a time function controlled by a microcomputer. Photometer detection was performed using a compact homemade light emitting diode (LED)-based photometer. Aiming to evaluate the accuracy, samples were analyzed by employing the methodologies recommended by the Brazilian Association of Technical Standards (ABNT) and the American Society for Testing and Materials (ASTM). Accuracy was assessed by applying the Student’s t-test for paired samples at the 95% confidence level (n = 4), which shown that there is no significant difference between results. Other useful features included relative standard deviation of < 1% and waste generation volume ten times lower than those produced by ABNT and ASTM methods.

A novel multicommuted flow analysis strategy for the spectrophotometric determination of cadmium in water at μg L−1 levels without using a preconcentration step

An automated flow analysis approach for the photometric determination of cadmium in water with improved sensitivity is described.

Fully automated photometric titration procedure employing a multicommuted flow analysis setup for acidity determination in fruit juice, vinegar, and wine

This work deals with a fully automated multicommuted flow analysis setup employing a homemade syringe pump for fluid propulsion and solenoid valves for solution handling, assembled to carry out photometric titrations using a homemade LED-based photometer. The data acquisition and control software was designed to perform titrations following the binary search concept, in which the course of titration is decided based on previous measurements. The operation conditions were optimized and the setup efficiency was then evaluated by analyzing samples of fruit juice, vinegar, and wine. Furthermore, in order to assess the accuracy, the samples were also analyzed using an independent method. Upon applying the paired t-test to the results, no significant differences at the 95% confidence level were observed. Other useful features are also reported, such as intraday precision of 1.2%, relative standard deviation of 0.9% for an acetic acid solution with a concentration of 0.106molL−1, and a titration range of 0.036 to 0.176molL−1.

A Sensitive Photometric Procedure for Cobalt Determination in Water Employing a Compact Multicommuted Flow Analysis System.

In this work, a multicommuted flow analysis procedure is proposed for the spectrophotometric determination of cobalt in fresh water, employing an instrument setup of downsized dimension and improved cost-effectiveness. The method is based on the catalytic effect of Co(II) on the Tiron oxidation by hydrogen peroxide in alkaline medium, forming a complex that absorbs radiation at 425 nm. The photometric detection was accomplished using a homemade light-emitting-diode (LED)-based photometer designed to use a flow cell with an optical path-length of 100 mm to improve sensitivity. After selecting adequate values for the flow system variables, adherence to the Beer-Lambert-Bouguer law was observed for standard solution concentrations in the range of 0.13-1.5 µg L-1 Co(II). Other useful features including a relative standard deviation of 2.0% (n = 11) for a sample with 0.49 µg L-1 Co(II), a detection limit of 0.06 µg L-1 Co(II) (n = 20), an analytical frequency of 42 sample determinations per hour, and waste generation of 1.5 mL per determination were achieved.

An Automated Multicommuted Flow Analysis Procedure for Photometric Determination of Reducing Sugars in Wine Employing a Directly Heated Flow‑Batch Device

This work presents an automated analytical procedure for the photometric determination of reducing sugars in wines. The procedure is based on the reaction of reducing sugars with potassium hexacyanoferrate(III) in an alkaline medium, and was implemented employing a multicommuted flow analysis (MCFA) approach. Sample heating to promote the reaction was accomplished using a flow-batch device, which was heated to 50 °C without the use of a fluid for heat exchange. The ability of the MCFA approach to handle small solution volumes was exploited in order to develop an analytical procedure that meets green analytical chemistry guidelines. After optimizing the operational variables, the analytical procedure afforded a linear response ranging from 0.75 to 6.00% (m/v) fructose (R(2) = 0.999), a limit of detection of 0.14% fructose (n = 11), a 3.5% relative standard deviation, reagent consumption and waste generation of 112 mg and 2.2 mL per determination, respectively, and an analytical throughput of 75 determinations per hour.

A Highly Sensitive Multicommuted Flow Analysis Procedure for Photometric Determination of Molybdenum in Plant Materials without a Solvent Extraction Step.

A highly sensitive analytical procedure for photometric determination of molybdenum in plant materials was developed and validated. This procedure is based on the reaction of Mo(V) with thiocyanate ions (SCN−) in acidic medium to form a compound that can be monitored at 474 nm and was implemented employing a multicommuted flow analysis setup. Photometric detection was performed using an LED-based photometer coupled to a flow cell with a long optical path length (200 mm) to achieve high sensitivity, allowing Mo(V) determination at a level of μg L−1 without the use of an organic solvent extraction step. After optimization of operational conditions, samples of digested plant materials were analyzed employing the proposed procedure. The accuracy was assessed by comparing the obtained results with those of a reference method, with an agreement observed at 95% confidence level. In addition, a detection limit of 9.1 μg L−1, a linear response (r = 0.9969) over the concentration range of 50–500 μg L−1, generation of only 3.75 mL of waste per determination, and a sampling rate of 51 determinations per hour were achieved.

A clean photometric method for the determination of losartan potassium in pharmaceuticals exploiting light scattering effect and employing a multicommuted flow analysis approach

This paper describes an environmentally friendly procedure for the determination of losartan potassium (Los-K) in pharmaceuticals. The photometric method was based on the light scattering effect due to particles suspension, which were formed by the reaction of Los-K with Cu (II) ions. The method was automated employing a multicommuted flow analysis approach, implemented using solenoid mini-pumps for fluid propelling and a homemade LED based photometer. Under the optimized experimental conditions, the procedure showed a linear relationship in the concentration range of 23.2–417.6mgL–1 (r=0.9997, n=6), a relative standard deviation of 1.61% (n=10), a limit of detection (3.3*σ) estimated to be 12.1mgL–1, and a sampling rate of 140 determinations per hour. Each determination consumed 12µg of copper (II) acetate and generated 0.54mL of waste.

Development of a photometric procedure for tin determination in canned foods employing a multicommuted flow analysis approach

This work describes an automated analytical procedure for the photometric determination of tin in canned foods, employing a multicommuted flow analysis process. The flow system manifold comprises a set of three-way solenoid valves to handle solutions and a multisyringe module for fluid propelling.

A Novel Multicommuted Flow Method with Nanocolloidal Manganese(IV)-Based Chemiluminescence Detection for the Determination of the Total Polyphenol Index

An automatic flow procedure based on a multicommuted flow analysis (MCFA) for the determination of the total polyphenolic content in food samples employing chemiluminescence (CL) as a detection technique is described. The concept of applying three-way solenoid valves in flow injection analysis was chosen in order to develop an environmentally friendly system which enables minimal consumption of reagents and waste generation. The method was based on the enhancing effect of polyphenolic antioxidants on CL of Mn(IV)–formaldehyde–hexametaphosphate system. The calibration graph obtained for standard solutions of gallic acid was linear in the range 5–150 μg L−1 with a detection limit of 1.5 μg L−1. The relative standard deviation for 20 measurements was between 1.1 and 2.4 %. The sampling rate was 60 determinations per hour. The proposed method was found to be selective to polyphenol detection and was successfully applied to the determination of the total polyphenol index in 27 diverse plant-derived food samples (wine, tea, coffee, fruit and vegetable juices, herbs, spices and extracts of olive oil). A significant correlation between the total phenolic contentment determined by the MCFA-CL method and the total reducing capacity determined by Folin–Ciocalteu method and total antioxidant activity estimated by the DPPH method was observed.

Development of a new procedure for the determination of captopril in pharmaceutical formulations employing chemiluminescence and a multicommuted flow analysis approach.

This paper describes a new technique for the determination of captopril in pharmaceutical formulations, implemented by employing multicommuted flow analysis. The analytical procedure was based on the reaction between hypochlorite and captopril. The remaining hypochlorite oxidized luminol that generated electromagnetic radiation detected using a homemade luminometer. To the best of our knowledge, this is the first time that this reaction has been exploited for the determination of captopril in pharmaceutical products, offering a clean analytical procedure with minimal reagent usage. The effectiveness of the proposed procedure was confirmed by analyzing a set of pharmaceutical formulations. Application of the paired t-test showed that there was no significant difference between the data sets at a 95% confidence level. The useful features of the new analytical procedure included a linear response for captopril concentrations in the range 20.0-150.0 µmol/L (r = 0.997), a limit of detection (3σ) of 2.0 µmol/L, a sample throughput of 164 determinations per hour, reagent consumption of 9 µg luminol and 42 µg hypochlorite per determination and generation of 0.63 mL of waste. A relative standard deviation of 1% (n = 6) for a standard solution containing 80 µmol/L captopril was also obtained.

A Compact Microcontrolled Microfluidic System for Photometric Determination of Phosphate in Natural Water Samples

A compact environmentally friendly microcontrolled microfluidic device ideal for in situ phosphate determination was developed based on a microsystem based on low-temperature co-fired ceramics (LTCC) coupled to a light-emitting diode (LED)–photometer with a multicommutation flow analysis (MCFA) approach. The experimental parameters of the MCFA analyzer were optimized by chemometric studies. Under the best experimental conditions, limits of detection and quantification of 0.02 mg P L–1 and 0.07 mg P L–1, respectively, and a sampling frequency of 67 h–1 were estimated. Moreover, a low sample consumption of only 60 μL per determination was the other advantage that fully meets the requirements of sustainable research and green chemistry purposes.

Multi-commutation flow system with on-line solid phase extraction exploiting the ion-imprinted polymer and FAAS detection for chromium speciation analysis in sewage samples

A multi-commutation flow analysis system using on-line solid phase extraction and flame atomic absorption spectrometric detection (MCFA-FAAS) was developed for the study of chromium speciation in sewage samples.

Development of a multicommuted flow analysis procedure for simultaneous determination of sulfate and chloride in petroleum coke employing a homemade syringe pump and a LED-based photometer

Diagram of the flow system and its working pattern.

Development of a portable setup and a multicommuted flow analysis procedure for the photometric determination of Fe(III) and Fe(II) in fresh water

In this work, a portable instrument setup comprising a LED based photometer, a multicommuted flow analysis module, and a procedure for the determination of Fe(III) and Fe(II) in fresh water are described. The photometric procedure was based on the reaction of Fe(III) with SCN−. An oxidizing step using a K2S2O8 solution was included to allow iron (II) determination. The compound was monitored using a blue LED (λ=474nm) as a radiation source. The robustness of the equipment setup and analytical procedure for work in adverse operational conditions was ascertained by carrying out the assays without controlling the temperature of the laboratory, which varied daily from 22°C to 35°C. Baseline drift and noise increases were not observed. Furthermore, reagent solutions presented a 10 days lifetime. Accuracy assessed by employing FAAS and o-phenantroline photometric procedure as reference methods indicated that there was no significant difference at a 95% confidence level. Useful features included linear responses ranging from 0.1 up to 2.0mgL−1 Fe(II) (r=0.997) and Fe(III) (r=0.999), respectively; detection limits of 0.08mgL−1 Fe (II) and 0.06mgL−1 Fe (III), respectively; a coefficient of variation of 1.7% (n=7) for both analytes; reagent consumption of 4.8mg KSCN and 0.8mgK2S2O8 per determination; a sampling throughput of 64 determination per hour; and a waste generation of 1.42mL per determination. The weight of the equipment, including solenoid micro-pumps, photometer, electric batteries and the metallic box used for its accommodation was approximately 3kg. The electric battery used to feed the setup worked 55h without reloading, while the reagent solutions had a lifetime of 10 days.

A spectrophotometric procedure for malic acid determination in wines employing a multicommutation approach.

This work describes an automated procedure to determine L-malic acid (MA) in wine samples using a multicommuted flow analysis. The MA quantification was based on an enzymatic reaction between MA and L-malate dehydrogenase (L-MDH) in the presence of nicotinamide adenine dinucleotide (NAD(+)), producing nicotinamide adenine dinucleotide dehydrogenase (NADH), which was monitored at 340 nm. The L-MDH was immobilized on a surface of modified silica with amino groups in the presence of glutaraldehyde. For studying optimization, the system was maintained with 200 μL (288 U) of the L-MDH in 0.5 g of modified silica. Under the optimum experimental conditions, a linear response ranging from 0.1 to 1.5 g L(-1) MA (R = 0.997 and n = 7), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.02 and 0.06 g L(-1), respectively, a standard deviation relative of 1.8% (n = 7) for a sample of 0.5 g L(-1) MA, a sampling rate of 67 samples per hour were achieved. Analyzing ten wines samples and applying the t-test to the results found and those obtained using reference procedures (HPLC) provided no significant differences at the 95% confidence level.