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- A reagentless flow injection system for the quantification of ethanol in beverages based on the schlieren effect measurementPublication . Vidigal, Susana S.M.P.; Rangel, António O. S. S.A flow injection system comprising a gas-diffusion unit and schlieren effect detection was arranged in order to develop a simple methodology for the quantification of ethanol in different alcoholic beverages. It was possible to establish a linear range up to 25% (v/v), with a LOD and a LOQ of 0.6% and 2.0% (v/v), respectively; with good repeatability, RSD < 4.6%. Only 80 mu l. of sample was needed for quantification with a determination rate of one determination per minute. To evaluate the accuracy of the proposed method, a total of 43 alcoholic beverages, red and white table wine, port wine, beers, liquors, spirits and brandies were analysed. The results obtained by the developed method were in good agreement with the ones obtained by the reference method.
- Bioactive sugarcane lipids in a circular economy contextPublication . Teixeira, Francisca S.; Vidigal, Susana S.M.P.; Pimentel, Lígia L.; Costa, Paula T.; Pintado, Manuela E.; Rodríguez-Alcalá, Luís M.Most of the global sugar and ethanol supply trade comes from the harvesting of Saccharum officinarum (i.e., sugarcane). Its industrial processing results in numerous by-products and waste streams, such as tops, straw, filter cake, molasses and bagasse. The recovery of lipids (i.e., octacosanol, phytosterols, long-chain aldehydes and triterpenoids) from these residues is an excellent starting point for the development of new products for various application fields, such as health and well-being, representing an important feature of the circular economy. By selecting green scalable extraction procedures, industry can reduce its environmental impact. Refluxed ethanol extraction methods have been demonstrated to meet these characteristics. On the other hand, effective non-solvent methodologies such as molecular distillation and supercritical CO2 extraction can fractionate lipids based on high temperature and pressure application with similar yields. Sugarcane lipophilic extracts are usually analyzed through gas chromatography (GC) and liquid chromatography (LC) techniques. In many cases, the identification of such compounds involves the development of high-temperature GC–MS/FID techniques. On the other hand, for the identification and quantification of thermolabile lipids, LC–MS techniques are suitable for the separation and identification of major lipid classes. Generically, its composition includes terpenes, phytosterols, tocopherol, free fatty acids, fatty alcohols, wax esters, triglycerides, diglycerides and monoglycerides. These compounds are already known for their interesting application in various fields such as pharma and cosmetics due to their anti-hypercholesterolemic, anti-hyperglycemic, antioxidant and anti-inflammatory properties.
- Monitoring a Dynamic System with a Low Pressure Liquid Chromatography System: Application to a Vinification ProcessPublication . Vidigal, Susana; Rangel, António O. S. S.
- Miniaturization of enzymatic assay based on the LOV-sequential injection system: application to the determination of ethanol in alcoholic beveragesPublication . Vidigal, Susana S. M. P.; Tóth, Ildikó V.; Rangel, António O. S. S.
- Sequential injection-LOV format for peak height and kinetic measurement modes in the spectrophotometric enzymatic determination of ethanol: Application to different alcoholic beveragesPublication . Vidigal, Susana S. M. P.; Tóth, Ildikó V.; Rangel, António O. S. S.The objective of this work was to make a contribution to study the potential of the sequential injectionlab-on-valve (SI-LOV) format for the miniaturization of enzymatic assays, by using different measurement modes (peak height and initialrate-based measurement). A LOV system was developed for the enzymatic assay of ethanol in beverages, based on the conversion of ethanol to acetaldehyde by alcohol dehydrogenase, using spectrophotometric detection. The use of the kinetic-based approach permits the applicability of the enzymatic determination to samples with intrinsic absorption, with a higher determination throughput. A linear dynamic application range up to 0.040% (v/v)was achieved for both initial rate and for the peak height measurement, with good repeatability (R.S.D. < 5.0% and <1.0%, respectively). Enzyme, NAD+, buffer and sample consumption per assay were 0.12U, 0.066 mg, 150 and 15µL, respectively. The determination rate achieved was 37 and 27 determinations h−1 for the initial rate and for the peak height measurement, respectively. The results obtained for several alcoholic beverages, including a certified sample material, were not statistically different from those obtained by the reference procedures.
- Automated analytical microsystem for the spectrophotometric monitoring of titratable acidity in white, rosé and red winesPublication . Sández, Natàlia; Calvo-López, Antonio; Vidigal, Susana S. M. P.; Rangel, António O. S. S.; Alonso-Chamarro, JuliánThe design, construction and evaluation of a low-cost cyclic olefin copolymer (COC)-based continuous flow microanalyzer with optical detection to determine the titratable acidity content of wine is here presented. The analysis method is based on the monitoring of the blue coloration decrease of a buffered bromothymol blue (BTB) solution in the presence of the acidic compounds of wine. The microanalyzer monolithically integrates the required microfluidic motifs as well as an optical flow cell where the measurements are performed by using a miniaturized and versatile photometric detection system. Fluid management is totally automated by the use of computer-controlled microvalves, permitting the automatic calibration of the system as well as the automatic sampling, including in-line dilution and analysis. The reduced size of the whole system along with its high simplicity and automation make it suitable for its application to the on-line monitoring of titratable acidity during wine-making processes. With the optimal conditions, a linear range up to 0.50 g L−1 tartaric acid, a quantification limit (LOQ) of 0.01 g L−1 and a detection limit (LOD) of 0.004 g L−1 were obtained, covering the most common acidity content of musts and wines. A sampling rate up to 26 h−1 could be achieved, consuming less than 3 mL of inexpensive reagents per analysis and requiring no pretreatment of the sample. The microsystem has been successfully applied to the quantification of the titratable acidity content of several wine samples, being the results in excellent agreement with the ones obtained by the reference method.
- Development of sequential injection enzymatic and bead injection assays in lab on valve formatPublication . Vidigal, Susana Maria Socorro de Matos Peixoto; Rangel, António O. S. S.; Tóth, Ildikó V.The development of bioengineering and biotechnology has promoted the interest for faster and more reliable methods for monitoring biochemical processes. Flowbased systems stand out as the most effective in the automation and miniaturization of these methods. A significantly reduction on the analysis time and dispensing skilled labour is achieved, thus becoming an important tool for implementation and enforcement of these assays. The main objective was the development of new methodologies for the miniaturization of biochemical analysis system using a sequential injection lab-onvalve (SI-LOV) system. In this context, analytical methodologies were developed based on enzymatic assays for the detection of enzyme substrates, for measurements of enzyme activity, or for enzymatic inhibition studies. Under this program, some enzymatic methodologies were developed: determination of ethanol in alcoholic beverages; determination of hydrogen peroxide in cleaning solutions for contact lenses, with and without dilution in line; and determination of the activity of peroxidase in vegetable extracts. The developed method for the enzymatic assay of ethanol in beverages (Chap.3) was based on the conversion of ethanol to acetaldehyde by alcohol dehydrogenase (ADH), using spectrophotometric detection. The quantification of hydrogen peroxide (H2O2) (Chap.4) and peroxidase activity (Chap.5) was based on the reaction of oxidation of 2,2’-Azino-bis(3-Ethilbenzothiazoline 6-sulfonic acid) (ABTS) with hydrogen peroxide in the presence of peroxidase (HRP). Another major goal was to explore the potential of the SI-LOV systems to execute solid phase spectrophotometry, demonstrating its suitability for handling complex samples. This process, in the form of bead injection, was implemented inside the flow system. For this purpose, we used the resin "NitriloaceticAcid (NTA) Superflow", capable of retaining metal ions, which can be derivatized and measured by spectrophotometry (solid-phase spectrophotometry). These methods were used for the quantification of iron and protein content in wine samples. The developed method for the quantification of iron in wine samples (Chap. 6) was based on the reaction of Fe3+ with SCN-, where the Fe3+ ions were retained at the surface of the NTA beads. The total iron content was achieved by performing the inline oxidation of the Fe2+ to Fe3+. The methodology for total protein content in white wine samples (Chap.7) was based on the Lowry method. The NTA beads were initially charged with Cu2+ to complex with the proteins present in the sample. The quantification was achieved by the colour reaction of the proteins with the Folin Ciocalteau reagent. As for detection system, UV/Vis spectrophotometry was used in all of the developed methodologies.
- Sequential injection lab-on-valve system for the for the determination of the activity of peroxidase in vegetablesPublication . Vidigal, Susana S. M. P.; Toth, Ildiko V.; Rangel, António O. S. S.Horseradish peroxidase (HRP) has been broadly used and investigated for many analytical purposes; it is an enzyme that catalyzes the reduction of hydrogen peroxide in the presence of a reducing compound. The objective of this work was to develop a methodology for the spectrophotometric determination of the activity of peroxidase in vegetable extracts using a flow method with a sequential injection lab-on-valve format. The developed system is based on the reaction between hydrogen peroxide (H2O2) and 2,2-azinobis(3-ethylbenzothiazoline-6)sulfonic acid (ABTS) catalyzed by the enzyme (HRP). The method presented a sample consumption of 15 μL per assay and a consumption of ABTS and H2O2 of 24 μg and 12 μg per assay, respectively. It was also possible to monitor online the thermal inactivation of peroxidase at different temperature ranges.
- Low pressure chromatographic flow system for wine fermentation monitoringPublication . Vidigal, Susana S. M. P.; Rangel, António O. S. S.
- Sequential injection system for the enzymatic determination of ethanol in alcoholic beverages with in-line dilutionPublication . Pais, Teresa F. M.; Vidigal, Susana S. M. P.; Tóth, Ildikó V.; Rangel, António O. S. S.A sequential injection system for the enzymatic determination of ethanol in wines with spectrophotometric detection was developed. The determination was based on the enzymatic reaction involving ethanol and NAD(+) in the presence of alcohol dehydrogenase. A gas-diffusion unit was introduced in the system to perform an in-line dilution. It was possible to operate the system with a reagent consumption of 1.3 mg of NAD(+), 0.45 U of ADH, and 32 mu L of sample, per assay with a determination rate of 21 h(-1). The results obtained from the analysis of wine samples were statistically equivalent to those obtained by the reference method, with good repeatability; the relative standard deviation (n = 10) was <1% with a LOQ of 0.3% (v/v). (C) 2012 Elsevier Ltd. All rights reserved.