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Highlights • Ultrasonic-assisted extraction of catalase and lipase from bovine and poultry livers. • Successful coupling of a lab-made ultrasonic reactor to a flow-batch analyzer. • Lab-made ultrasonic reactor with efficiency 40 times higher than that of mechanical stirring. • Accurate catalase and lipase determinations with relative errors lower than 2.1%., An ultrasonic reactor (UR) was developed and coupled to a digital movie-based flow-batch analyzer (DM-FBA) for the ultrasonic-assisted extraction (UAE) and fast determination of catalase and lipase activities in bovine and poultry livers. The lab-made UR mainly consisted of a borosilicate glass container and a piezoelectric disc. The DM-FBA mainly consisted of a webcam, an ultrasonic actuator controller, a peristaltic pump, six solenoid valves, a valve driver, a mixing chamber, a magnetic stirrer, an Arduino Mega 2560, and a personal computer. This setup, named UR-DM-FBA, was controlled by custom software. Ultrasound (US) frequency, US power, sonication time, and concentration of extraction agent were optimized using the Taguchi method. Experiments at silent conditions (mechanical stirring at 1500 rpm) were carried out to evaluate extraction efficiency. Optimized parameters for the UAE of catalase were US frequency of 30 kHz, 2.0 mL of Triton X-100, sonication time of 270 s, and US power of 10.8 W. For the UAE of lipase, the optimized parameters were US frequency of 20 kHz, 0.30 mL of triethanolamine, sonication time of 270 s, and US power of 18 W. Catalase and lipase activities obtained with the UR were, on average, 1.9 × 103% and 2.0 × 103% higher than those obtained at silent conditions, respectively, which indicates that that the lab-made UR was capable of extracting these enzymes more efficiently. Determinations using the UR-DM-FBA were highly accurate (relative error ranging from −1.98% to 1.96% for bovine catalase, −0.65% to 0.76% for bovine lipase, −2.03 to 2.08% for poultry catalase, and −0.55% to 0.64% for poultry lipase) and precise (overall coefficient of variation 69 h−1) and low sample/reagent consumption (

A green, rapid and sensitive automated analytical method with imaging detection for the determination of sulfite in vinegars using the pararosaniline (PRA)–formaldehyde–sulfite reaction is demonstrated. This work proposes the use of a flow-batch analyzer (FBA) in association with digital images (DIs) obtained from a webcam to perform fast and accurate quantification of sulfite in vinegar samples with low waste generation and high sensitivity. The FBA designed for the monitoring of the PRA–formaldehyde–sulfite reaction under non-equilibrium conditions consisted of a mixing chamber (MC) with a lateral glass window and an ultra-bright LED mounted on top of the MC. Rigorous luminosity and time control were required to acquire accurate and precise data from digital images taken during the reaction. An algorithm based on RGB norm vectors (∥νRGB∥) with gamma correction was developed for absorbance calculations. The proposed method was applied to sulfite quantification in five different vinegar samples (apple cider, distilled, lemon, and white and red wine), with iodometric titration as a comparative method. The estimated LOD was 0.04 mg L−1, with a linear range of from 0.13 to 32.7 mg L−1, recoveries were in the range 94–107%, and the sample throughput was 43 h−1 at a reaction time of 30 s. Both the proposed and reference methods were statistically compared using a paired t-test at a confidence level of 95% and the maximum standard deviation was 1.6 and 1.7 mg L−1, respectively. All of the results reported here confirm the proposed method's potential to be a very rapid, low-cost and trustworthy tool, applicable for the quality control of sulfite in a wide variety of vinegar. The low levels of reagent consumption and waste generation in the proposed method qualify the analytical procedure as environmentally friendly and in alignment with green chemistry guidelines.

This study addresses the challenge of performing fast and accurate titrations with end points that are difficult to identify. In this sense, the combination of digital movies (DMs) with a flow-batch analyzer (FBA) has shown to be a promising analytical tool. In a digital movie-based automatic titrator (DMB-AT), a DM is recorded by a webcam as the titrant is added in the mixing chamber (MC). The DM is then decompiled into frames that are ordered sequentially. In the first frame, the region of interest (ROI) of 257 × 255 pixels is defined. The red (R) component is used to calculate the Pearson's correlation coefficient (r) between the first frame and each subsequent one. The titration curve is obtained in real time by plotting r values and the opening time of the titrant valve. The experimental titration curve is fitted in a sigmoidal regression, and the new titration curve is used to estimate the end point by means of the second derivative method. A software program written in Adobe AIR for a desktop platform programmed in ActionScript 3.0 controlled the opening time of the solenoid valves, gathered the analytical signal and carried out the analytical procedure in real time. The feasibility of the method was confirmed by determining the total hardness and the total alkalinity in mineral waters. The results were compared with classical batch titration and did not exhibit statistically significant differences when the paired t-test at the 95% confidence level was applied. The proposed method is able to process approximately 67 and 86 samples h− 1 for total hardness and total alkalinity, respectively. Its precision was confirmed by overall relative standard deviation (RSD) values of less than 1.0% in both applications.

In this study, a micro-flow-batch analyzer (μFBA) using an in-line cadmium reduction microcolumn for the photometric determination of nitrate and nitrite in dairy samples is described. The method is based on the Griess-Llosvay reaction and measuring of the absorbance at 540 nm using a green LED integrated into the μFBA built in the urethane-acrylate resin. Initially, the nitrite content of the dairy sample is analyzed in the mixing chamber, while the nitrate is reduced to nitrite in cadmium sponge microcolumn coupled to the microsystem. Nitrate content was calculated from the difference between nitrate plus nitrite (expressed as nitrite) and nitrite content. The analytical curve for nitrate and nitrite was linear in the work range of 10.0–100.0 μg L−1 with a correlation coefficient of 0.992 and 0.998, respectively. The limit of detection and relative standard deviation were estimated at 0.39 μg L−1 and

This study proposes a digital image-based flow-batch analyzer (DIB-FBA) for aluminum (III) and chromium (VI) determinations in natural water. A webcam with a CCD sensor and RGB data are used. The method for determining aluminum is based on an Al(III) ion, quercetin, and cetyltrimethylammonium bromide (CTAB) reaction which yields a yellow colored complex in an acetate buffer medium (pH 5.5). The determination of chromium is based on a Cr(VI) ion with 1,5-diphenylcarbazide (DPC) reaction whose product is a violet colored complex. Digital images present the color of the emergent (complementary) radiation to that absorbed by the complexes formed in each analysis. RGB data were employed to build the analytical curves. All standard solutions were prepared in-line, and all analytical processes were completed by simply changing the operational parameters in the DIB-FBA control software. The working ranges were from 10 to 600 μg L − 1 for Al(III) with r = 0.9994 (n = 5), and 10 to 300 μg L − 1 for Cr(VI) with r = 0.999 (n = 5), the limits of detection were 3.97 and 2.65 μg L − 1 respectively for Al(III) and Cr(VI). The relative standard deviation (RSD %) and sampling rate were estimated at 1.5% and 137 h − 1 and at 1.7% and 134 h − 1 for Al(III) and Cr(VI), respectively. Comparing with the reference method, no statistically significant differences were observed when applying the paired t -test at a 95% confidence level.

In this study a flow-batch analyzer (FBA) was utilized and its feasibility was demonstrated for the determination of Fe(III) in edible and lubricating oils without external pretreatment. The FBA method uses the reaction of this ion with thiocyanate in organic medium. The formed red complex was monitored by employing a light emitting diode (LED, λmax = 520 nm) and a phototransistor linked to the mixing chamber by optical fibers. All standard solutions were prepared in-line and all analytical processes were carried out by simply changing the operational parameters in FBA control software. Comparing with the reference method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. The relative standard deviation, analytical frequency and limit of detection were estimated for both viscous matrices (edible and lubricating oils) at

This paper introduces for the first time the combination of digital images taken with a webcam and a micro-flow-batch analyzer as a novel strategy for implementing quantitative chemical analysis. The digital image-based micro-flow-batch analyzer (DIB-μFBA) was formed using urethane-acrylate resin, glass slides and ultraviolet lithography. The glass slides were used as sealant layers on both sides of the substrate urethane-acrylate and provide the necessary transparency to the microsystem to conduct studies using digital images. DIB-μFBA uses digital images obtained from a webcam with CCD sensor, based on the RGB (red–green–blue) color model. The analyzer was used for determining the tannins in green tea employing the well-known ferrous tartrate method. All standard solutions were prepared in-line, and all analytical processes were completed by simply changing the operational parameters in DIB-μFBA control software. The paired t test, at a 95% confidence level, showed no statistically significant differences between results obtained by DIB-μFBA and the spectrophotometric reference method. The proposed microsystem presented satisfactory physical and chemical properties while keeping the flexibility, versatility, robustness and multi-task characteristics of conventional flow-batch analysis. Therefore, it was possible to build a low-cost device with high sample throughput (about 190 h− 1) and reduced reagent consumption (about 300 times less than the reference method), contributing to the basic principles of green chemistry and the advancement of micro-analytical procedures.

Since its inception, flow-based analysis has dramatically transformed the way that sample analysis is handled. What used to be manual, slow and prone to error has become automated, rapid and precise. Though many improvements and modifications have already been explored, a most promising development has been the flow-batch analyzer. Through use of an instantaneous stop-mixing chamber and computer-controlled, flow-based sampling, it achieves extraordinarily high sampling rates. We review its historical evolution, components, features and operation, and analytical applications.

The increasing development of miniaturized flow systems and the continuous monitoring of chemical processes require dramatically simplified and cheap flow schemes and instrumentation with large potential for miniaturization and consequent portability. For these purposes, the development of systems based on flow and batch technologies may be a good alternative. Flow-batch analyzers (FBA) have been successfully applied to implement analytical procedures, such as: titrations, sample pre-treatment, analyte addition and screening analysis. In spite of its favourable characteristics, the previously proposed FBA uses peristaltic pumps to propel the fluids and this kind of propulsion presents high cost and large dimension, making unfeasible its miniaturization and portability. To overcome these drawbacks, a low cost, robust, compact and non-propelled by peristaltic pump FBA is proposed. It makes use of a lab-made piston coupled to a mixing chamber and a step motor controlled by a microcomputer. The piston-propelled FBA (PFBA) was applied for automatic preparation of calibration solutions for manganese determination in mineral waters by electrothermal atomic-absorption spectrometry (ET AAS). Comparing the results obtained with two sets of calibration curves (five by manual and five by PFBA preparations), no significant statistical differences at a 95% confidence level were observed by applying the paired t-test. The standard deviation of manual and PFBA procedures were always smaller than 0.2 and 0.1mugL(-1), respectively. By using PFBA it was possible to prepare about 80 calibration solutions per hour.

In this work, a micro-flow-batch analyzer (µFBA) using webcam for spectrophotometric determination of ortho-phosphate and aluminium(III) in tap water is proposed. PO43- and Al3+ determinations were performed by employing molybdenum blue and quecertin methods, respectively. In order to build linear analytical curves, a mathematical model was used on the basis of the RGB (red, green and blue) values. Working ranges were from 25 to 500 µg L-1 for both analytes with estimated limits of detection, relative standard deviation (RSD, n = 5) and sampling rate of 0.82 µg L-1, < 0.8% and 160 h-1 for PO43-, and 0.93 µg L-1, < 1.1% and 160 h-1 for Al(III). Comparing with the reference methods, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. Recovery study shows results between 98.1 and 102.8%. The proposed µFBA presented satisfactory portability, robustness, flexibility, low-cost device and reduced chemicals consumption.

In this study, a micro-flow-batch analyzer (μFBA) with solenoid micro-pumps for the photometric determination of iodate in table salt is described. The method is based on the reaction of iodate with iodide to form molecular iodine followed by the reaction with N,N-diethyl-p-phenylenediamine (DPD). The analytical signal was measured at 520 nm using a green LED integrated into the μFBA built in the urethane-acrylate resin. The analytical curve for iodate was linear in the range of 0.01-10.0 mg L(-1) with a correlation coefficient of 0.997. The limit of detection and relative standard deviation were estimated at 0.004 mg L(-1) and

A method for the determination of phosphorus in mineralized biodiesel using a micro-flow-batch analyzer (μFBA) with solenoid micro-pumps was proposed. The samples were mineralized using an ashing procedure at 550 °C followed by dissolution of the residue. The determination of phosphorus was performed by employing the well-known molybdenum blue method. The measures of the absorbance were performed at 850 nm using an InfraRed LED integrated into the μFBA. Comparing with the reference method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. Recovery study shows results between 97.9% and 105.8%. The proposed microsystem using solenoid micro-pumps presented satisfactory robustness and high sampling rate (190 h −1 ), with satisfactory reproducibility (relative standard deviation n =3), low reagents consumption (32 μL per analysis) and cost to build the device. Moreover, μFBA presents limit of detection (0.014 mg Kg −1 ), precision and accuracy compatible with the biodiesel regulations that establish a maximum concentration of 10 mg Kg −1 (Brazil, USA, EU), suggesting that it is a good alternative for the determination of phosphorus in biodiesel.