Determination Of Total Acids Research Articles

Non-destructive detection of total acid of red globe grapes based on map fusion technique

Total acid is an important indicator of the internal quality of red globe grapes. This paper proposed a non-destructive method for the determination of total acid of red globe grapes based on hyperspectral fusion technique. A non-linear LSSVM prediction model based on spectral information, image information and the fusion of the two was built respectively for total acid. The results showed that the MSC-CARS-SPA-LSSVM model of samples about total acid built by fusing the spectra after feature wavelength extraction using the MSC-CARS-SPA algorithm and the image information after dimensionality reduction by the PCA algorithm using the graph fusion technique worked best. The correlation coefficients of the prediction sets of the optimal LSSVM model was 0.9907, which improved the accuracy over the unilateral models based on spectral or image information. A new method for nondestructive detection of total acid of red globe grapes by map fusion technique was discovered.

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.

Fast monitoring the dynamic change of total acids during apple vinegar fermentation process using a colorimetric IDA sensor array

In this work, a colorimetric sensor array (CSA) for quantitative determination of total acids in apple vinegar during fermentation was constructed. The sensor array was properly designed based on indicators displacement assay (IDA) using three metal ions (Cu2+, Zn2+ and Ni2+) as receptors to organic acids. The time stability results showed that the prepared CSA had good operational stability. Three quantitative models, including one linear (partial least square, PLS) and two nonlinear (support vector regression, SVR and back propagation artificial neural network, BP-ANN) models were used to estimate the content of total acids in fermentation broth of apple vinegar through image analysis. The correlation coefficient (RP), root mean square error of prediction (RMSEP) and residual predictive deviation (RPD) of the better SVR model were 0.8708, 0.0545 and 10.91, respectively. The results implied that the CSA had an excellent potential for quantitative monitoring of total acids in apple vinegar during fermentation.

Разработка комплекса моющих средств для мембранных установок в молочной промышленности

Aim. Development of a complex of detergents (acidic, alkaline, enzymatic, chlorine-containing, surfactant-containing additives) for membrane units used in the dairy industry. Materials and Methods. Methods for controlling the concentration of active substances in concentrates of agents are given on the example of KATELON 202 - determination of total acidity by the method of acid-base potentiometric titration (in terms of HNO3) and KATELON 114 – determination of the mass fraction of active chlorine by redox titration. Results. A complex of detergents for membrane plants (ultrafiltration (UV, UF), microfiltration (MF, MF), nanofiltration (NF, NF), reverse osmosis (RO, RO)), used in the dairy industry and including alkaline non-foaming, medium-, low-foam products KATELON 109, KATELON 110, KATELON 115; alkaline chlorine-containing non-foamy agent KATELON 114; acid non-foamy KATELON 202, KATELON 207, KATELON 208; high-foam neutral additives KATELON 308 and KATELON 309 – enhancers of the washing effect for KATELON 109, KATELON 110, KATELON 115; preservative non-foaming additive KATELON 310 for protection from microbiological contamination; enzyme medium supplement KATELON 601. The composition of all products, their brief characteristics and physicochemical indicators, as well as an approximate program of washing with a complex of developed preparations are given. The dependences of pH and electrical conductivity were obtained for KATELON 109, KATELON 110, KATELON 115, KATELON 202, KATELON 207, KATELON 208. Conclusion. The complex of detergents is successfully used at Kopylsky Butter Cheese Plant, Lyubansky Cheese Making Plant, Minsk Dairy Plant No. 1, Verkhnedvinsky Butter and Cheese Plant, Molodechno Dairy Plant, Volozhin production site of Minsk Dairy Plant No. 1, Tolochin Branch of Lepel Dairy Canning Plant.

Economic aspects of waste recovery in the wine industry. A multidisciplinary approach

The complex composition of grapes as well as the quite large variations of each component affect the processing thereof differently and at the same time influence the yield in must, its quality and the wine product; they also influence production losses, along with the quality and quantity of by-products. Vinification wastes cause ecological problems because the neutralization and use of fermentative wastes mixed with different compounds present a danger to the environment and to the health of the population. The ecological measures of protection of the environmental factors are very important, especially the economic efficiency obtained through the recovery of the by-products. This paper focuses on the possibilities of using the by-products obtained from the wine making process, based on the fact that this drink is the most widely known in the world, with the highest percentage in terms of beverage production and implicitly with the largest quantity of by-products obtained. The valorization of these by-products leads to obtaining very valuable products both from a nutritional and industrial point of view. Experimentally, the aim was to determine the physical and chemical characteristics of different types of grape pomace and must sampled from a winery in Romania. Thus, the determination of total acidity, conductivity, pH, total content of phenolic compounds, total nitrogen and total content of pectic substances was aimed. The experimental values obtained have shown that grape pomace is a valuable by-product of the wine industry and its valorization demonstrates an important economic efficiency.

Silica-Based Solid Acid Catalyst with Different Concentration of H2SO4 and Calcination Temperature: Preparation and Characterization

Silica-based solid acid catalysts have been successfully prepared and characterized. This research aimed to study the effect of sulfuric acid and calcination temperature on the properties of silica-based solid acid catalyst chemically and physically. The catalyst was synthesized with tetraethyl ortho silicate (TEOS) as precursor of SiO2 through the sol gel method using sulfuric acid (H2SO4) with various concentrations (1 M, 2 M, and 3 M). Next, the gel formed was calcined with various temperatures (500, 600, 700, 800, and 900 °C). The synthesized sample was then tested for total acidity determination and was characterized using various instrumentations: FTIR, XRD, Gas Sorption Analyzer (GSA), and SEM. The total acidity increased with the increasing acid concentration and calcination temperature up to 700 °C. The N2 adsorption-desorption data showed a relatively large surface area 410,97 m2/g which can provide space for catalytic reaction for fatty acids. The catalytic study was carried out for esterification reaction using reflux system to reduce free fatty acids (FFA) content up to 49% and be possibly to be selected as pretreatment step for low grade feedstock biodiesel conversion.

Rapid and simultaneous determination of acidity and salt content of pickled vegetable brine by using thermal infrared enthalpimetry

A rapid and high throughput method was developed for determination of the total acidity and salt content of brine from pickled vegetables (containing cauliflower, cucumber, carrot and onion) using thermal infrared enthalpimetry (TIE). An infrared camera was combined with disposables microplates to perform enthalpimetric analysis using a multichannel pipette for reagent addition. Microplates were charged with a stoichiometric excess of reagents (NaOH and AgNO3) with the subsequent addition of the sample. The temperature rise of reactions was measured instantaneously and the total acidity and salt content of brine were obtained simultaneously by comparison with calibration curves. For total acidity determination, calibration curves were established with both lactic and acetic acids with no difference between them. An interference study was performed and interferences of brine composition were not observed. The results obtained by TIE analysis were in agreement with the results of recommended methods in official compendia (between 94% and 103%). Using TIE, 3min were enough to perform 12 measurements of both total acidity and salt content, reaching 240 measurements per hour. For the same number of measurements by conventional method (titration) one or two days were required, which shows the feasibility of the proposed method for rapid analysis.

KAJIAN KARAKTERISTIK OBJEKTIF DAN SUBJEKTIF TUAK AREN (Arenga pinnata) BERDASARKAN LAMA WAKTU PENYIMPANAN

Palm tuak is one of the traditional drink that is usually consumed by majority people in Bali. Tuak palm is produced from fermented palm juice. The fermentation process makes sucrose contained in palm juice will turn into alcohol and continues to acetic acid. The aim of this research is to know the characteristic objective and subjective palm tuak (Arenga pinnata) based on the storage time. The method in this research was quasi experiment design. The samples of palm tuak were stored at room temperature (24-30°C) on the first day to fifth day. This research was conducted by measuring characteristics objective and subjective at palm tuak, determination of ethanol's concentration by gas chromatography (GC), determination of the pH by pH stick, determination of total acid by titration method, and organoleptic test by acceptance test method. The results showed that the ethanol content obtained during time storage of first to fifth day are 8,1512%, 8,234%, 9,117%, 10,6214%, dan 11,615% respectively. The pH was determined is 4. While total acid obtained during time storage of first to fifth day are 0,321%, 0,421%, 0,433%, 0,472%, dan 0,480%. The result of organoleptic test palm tuak showed that palm tuak that were stored on the first day are the most preferred among the others in terms of taste, color, and aroma.

New approach to H-point standard addition method for detection and elimination of unspecific interferences in samples with unknown matrix

A novel method for correction of unknown unspecific (additive) interferences was developed in sequential injection analysis (SIA) using a Lab on Valve module (LOV) with spectrophotometric detection. The method implements a novel idea to calibrate by the standard addition method in several different chemical conditions created in such a way to measure different signal for an analyte and unchanged signal for interferents causing additive effect. This approach, being an enhancement of the H-point standard addition method (HPSAM), enables to quantify unbiased concentration of an analyte in the presence of unknown interferences. The method was tested on the example of the determination of ascorbic acid in soft drinks and juices basing on reduction of Fe(III) to Fe(II) and reaction of the latter with o-phenanthroline to the ferroin complex absorbing at 512.0nm. The analytical utility of the method has been verified and confirmed by the spectrophotometric determination of total acidity in rose and red wines in the presence of bromothymol blue absorbing at 616.0nm. Calibration solutions were prepared automatically in the designed flow system. Ascorbic acid was determined with LOD of 1.4mgL−1 and LOQ of 4.2mgL−1 within linear working range up to 80mgL−1, while in case of the determination of total acidity the values of 4.2, 11.8 and 100, respectively, were obtained. A sample was consumed in volumes of 400 and 1000µL in both cases. The analyses are simple, “green”, and non-expensive. The developed method is readily applicable to analysis of real samples of complex unknown matrices and adaptable to different analytical methods.

Determination of total acid content in biomass hydrolysates by solvent-assisted and reaction based headspace gas chromatography

This work reports on a novel method for the determination of total acid (TA) in biomass hydrolysates by a solvent-assisted and reaction-based headspace gas chromatography (HS-GC). The neutralization reaction between the acids in hydrolysates and bicarbonate in an ethanol (50%) aqueous solution was performed in a closed headspace sample vial, from which the carbon dioxide generated from the reaction was detected by HS-GC. It was found that the addition of ethanol can effectively eliminate the precipitation of some organic acids in the biomass hydrolysates. The results showed that the reaction and headspace equilibration can be achieved within 45min at 70°C; the method has a good precision (RSD<3.27%) and accuracy (recovery of 97.4–105%); the limit of quantification is 1.36μmol. The present method is quite suitable to batch analysis of TA content in hydrolysate for the biorefinery related research.

An automatic system for acidity determination based on sequential injection titration and the monosegmented flow approach

An automatic sequential injection system, combining monosegmented flow analysis, sequential injection analysis and sequential injection titration is proposed for acidity determination. The system enables controllable sample dilution and generation of standards of required concentration in a monosegmented sequential injection manner, sequential injection titration of the prepared solutions, data collecting, and handling. It has been tested on spectrophotometric determination of acetic, citric and phosphoric acids with sodium hydroxide used as a titrant and phenolphthalein or thymolphthalein (in the case of phosphoric acid determination) as indicators. Accuracy better than |4.4|% (RE) and repeatability better than 2.9% (RSD) have been obtained. It has been applied to the determination of total acidity in vinegars and various soft drinks. The system provides low sample (less than 0.3mL) consumption. On average, analysis of a sample takes several minutes.

Conductimetría y titulaciones, ¿cuándo, por qué y para qué?

The conductimetric and potentiometric measurements detect the changes experimented by the system following the course of neutralization reactions in colored electrolytic dissolutions allowing accurate detection of equivalence point. Moreover, wines are susceptible to adulteration of different types, from dissolution with water to more complex as the addition of mineral acids. The conductimetric and potentiometric titrations are very useful in investigating the addition of mineral acid to wines. This experimental work allowed comparing the applicability and utility of the conductimetric and potentiometric measurements. Furthermore, some red wine samples were analyzed obtaining, on one hand, the graphical representation of the variation of the conductivity of the dissolution according to the volume of the titrant dissolution; on the other hand, the graphical representation of the variation of the pH according to the volume of the titrant dissolution using the analytical method of the first derivative. The obtained results in the visual assessments, conductimetric and potentiometric showed the following averages of 5,35±0,06 g/L (c.v.=1,12%); 5,16±0,03 g/L (c.v.= 0,05%); and 7,99±0,06 g/L (c.v.= 0,75%) of total acidity expressed as tartaric acid, respectively. The conductimetric monitoring system showed a higher sensitivity in the determination of total acidity in diluted and colored samples.

Sequential injection titration method using second-order signals: Determination of acidity in plant oils and biodiesel samples

A new concept of flow titration is proposed and demonstrated for the determination of total acidity in plant oils and biodiesel. We use sequential injection analysis (SIA) with a diode array spectrophotometric detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS). This system is based on the evolution of the basic specie of an acid-base indicator, alizarine, when it comes into contact with a sample that contains free fatty acids. The gradual pH change in the reactor coil due to diffusion and reaction phenomenona allows the sequential appearance of both species of the indicator in the detector coil, recording a data matrix for each sample. The SIA-MCR-ALS method helps to reduce the amounts of sample, the reagents and the time consumed. Each determination consumes 0.413ml of sample, 0.250ml of indicator and 3ml of carrier (ethanol) and generates 3.333ml of waste. The frequency of the analysis is high (12 samples h(-1) including all steps, i.e., cleaning, preparing and analysing). The utilized reagents are of common use in the laboratory and it is not necessary to use the reagents of perfect known concentration. The method was applied to determine acidity in plant oil and biodiesel samples. Results obtained by the proposed method compare well with those obtained by the official European Community method that is time consuming and uses large amounts of organic solvents.

SPECTROPHOTOMATRIC &amp; POTENTIOMETRIC STUDY OF AQUEOUS &amp; ETHANOLIC EXTRACTS OF HIBISCUS SABDARIFFA L. FLOWERS (KUJARAT TEA)

The spectrophotomatric spectra in UV, Visible and IR regions have revealed the presence of many functional groups in the aqueous and ethanolic extracts of Hibiscus sabdariffa L. flowers .Paper, thin-layer and column chromatographic techniques have shown the presence of three pigments in both extracts ; Gossypetin, Anthocynin, and Querectin .Five organic acids were also separated and identified in both extracts .All these compounds were identified by UV, Visible and IR spectrophotomatry of electromagnetic radiation .Flame atomic absorption and emission technique haveoffered high levels of determination of calcium, barium, potassium and magnesium, while sodium, lithium, iron, manganese, copper, zinc and nickel were found in traces .pH and potential titrations of the extracts with standardized NaOH have shown high inflections at equivalence points which were exploited in the determination of total acids in the extract which was more than 28% .The sudden colour change from violet, red or pinkish of the extract into green has led us to exploit the extracts as an acid-base indicator . The data and results obtained have clarified that the extracts of Hibiscus sabdariffa L. flowers are matching the action of other indicators used in acid-base titrations

Natural Sulphide Minerals as Sensors for Determination of Total Acidity of Humic and Fulvic Acids

Natural Sulphide Minerals as Sensors for Determination of Total Acidity of Humic and Fulvic Acids

Amperometric Determination of Total Acid of Beverages Based on the Reduction of Quinone

not Available.

Flow injection titration basing on the merging-zone technique

The proposed approach relies on titration of a sample that is gradually diluted in strictly controlled way in the flow injection system developed. On each step of sample dilution equal volumes of the sample and titrant solutions are simultaneously injected into two carrier streams and the zones are merged with each other. Then, they are mixed completely in the mixing chamber, merged with a stream of indicator and directed to a detector. It has been revealed that the method provides the results with accuracy better than ±3.3% (RE) and with mean repeatability lower than 1.0% (RSD). When the analyte concentration in a sample is too low to be determined directly, the procedure of titration with standard addition is exploited. The proposed approach has been successfully applied to the determination of total acidity in vinegars and magnesium and calcium in pharmaceutical products. The results obtained were comparable with those provided by the reference methods. The proposed procedure is characterized by low consumption of sample (usually less than 2 mL), titrant (about 3 mL) and indicator (about 0.6 mL). Average time of a single analysis is similar to time of traditional batch analysis.

Application of Flow Injection Gradient Titration Based on the Standard Addition and Dilution Procedure to the Determination of Total Acidity in Vinegars and Soft Drinks

The proposed approach relies on successive dilution of a solution containing a sample with standard addition and on titration of the solutions obtained until receiving a signal lower than the signal measured for the sample alone. Equations are derived for subsequent dilution factors for the automatic flow injection system applied. The overall calibration strategy including the possibility of prediction of the number of required standard solutions and of positioning the sample signal within the calibration range is presented. The method has been tested on the spectrophotometric determination of hydrochloric acid at two concentration levels (0.193 and 1.21 mol L(-1)) with sodium hydroxide as titrant. The results of accuracy better than |3.9|% (RE) and repeatability better than 1.3% (RSD) were obtained. The method has been applied to the determination of total acidity in vinegars and soft drinks. The average time necessary to analyze one sample is about 10 min.

Novel approaches to analysis by flow injection gradient titration

Two novel procedures for flow injection gradient titration with the use of a single stock standard solution are proposed. In the multi-point single-line (MP-SL) method the calibration graph is constructed on the basis of a set of standard solutions, which are generated in a standard reservoir and subsequently injected into the titrant. According to the single-point multi-line (SP-ML) procedure the standard solution and a sample are injected into the titrant stream from four loops of different capacities, hence four calibration graphs are able to be constructed and the analytical result is calculated on the basis of a generalized slope of these graphs. Both approaches have been tested on the example of spectrophotometric acid–base titration of hydrochloric and acetic acids with using bromothymol blue and phenolphthalein as indicators, respectively, and sodium hydroxide as a titrant. Under optimized experimental conditions the analytical results of precision less than 1.8 and 2.5% (RSD) and of accuracy less than 3.0 and 5.4% (relative error (RE)) were obtained for MP-SL and SP-ML procedures, respectively, in ranges of 0.0031–0.0631 mol L −1 for samples of hydrochloric acid and of 0.1680–1.7600 mol L −1 for samples of acetic acid. The feasibility of both methods was illustrated by applying them to the total acidity determination in vinegar samples with precision lower than 0.5 and 2.9% (RSD) for MP-SL and SP-ML procedures, respectively.

Conductometric determination of total acidity and chloride content in automotive fuel ethanol

The use of conductometric titration in the determination of corrosive agents in automotive fuel ethanol has been studied. The methodology proposed is simple, fast, and sensitive and affords a larger repeatability and sensitivity in the analysis of total acidity and chloride content than the reference methods specified in the directives of ANP (National Petroleum Agency).