Bromophenol Blue Indicator Research Articles

Pengembangan Indikator Bromofenol Biru dan Metil Merah pada Label Pintar sebagai Sensor Kematangan Buah Tomat

The novel on-package color indicator label has been fabricated based on bromophenol blue and a mixture between bromophenol blue and methyl red, and tests have been conducted to assess the ripeness of tomatoes (Lycopersicum commune). Bromophenol blue (BPB) and a mixture between bromophenol blue and methyl red (MM) were immobilized onto the Whatman paper membrane via the adsorption method. The BPB and mixture between BPB and MM/ Whatman paper membrane as color indicator work based on pH decrease as the volatile organic compounds. They are produced gradually in the package headspace during the development of tomato fruit. Subsequently, the combination indicator between bromophenol blue and methyl red changes from purple to red foul conditions, while the bromophenol blue indicator changes from blue to yellow foul conditions that can be seen visually. The results showed the color indicator can be used to determine the maturity conditions of tomatoes (Lycopersicum commune) at room temperature and chiller temperature. Furthermore, there are also changes in several parameters (pH, texture, weight loss, sensory evaluation) that are commonly used for the ripeness characteristics of tomatoes (Lycopersicum commune). Therefore, this indicator can be used for visual monitoring of the maturing of the tomatoes in packaging.

Demonstration of Composition Changes in a Distillation Column by Use of Bromophenol Blue Indicator

In demonstrations of column distillation for the general public or in other demonstration settings, the audience often lacks the equipment or knowledge to access the distillation process. Distillation of solvents usually gives colorless solution. By adding bromophenol blue (BPB) to the distillation of water and ethanol, the authors have developed a setup sensitive to different ethanol concentrations, allowing direct visualization of the distillation process. The color in the distillation column changes from blue to yellow in the distillation column as ethanol concentration changes. Bromophenol blue indicator can also be used to quickly and semiquantitatively determine the ethanol concentration in binary ethanol–water mixtures in laboratory settings.

Quantitative Cathodic Preparation of Selected Aqueous Reagents Used in an Undergraduate Laboratory

A guide for instructors and laboratory assistants to prepare several aqueous reagents used in an undergraduate laboratory is presented. Dilute reagents consisting of OH–(aq), Fe2+(aq), and Sn2+(aq) were prepared by electrolytic reduction of the respective precursors at the cathode. Concurrently, water was electrolyzed at the anode. A known mass of anhydrous Na2CO3 (a primary standard) was added to the anode compartment. Electrolytically produced H+(aq) ions were titrated in situ against Na2CO3 using bromophenol blue indicator. The electrolysis was promptly stopped when the indicator changed color from blue to yellow. The amount of H+(aq) produced at the anode was determined from the mass of Na2CO3. Because the same current passed through the electrolysis cell, the stoichiometric relation between the cathode and anode reactions facilitated the determination of the reagent prepared at the cathode. The concentration of reagent prepared at the cathode was independently confirmed by the volumetric titration method. The electrolysis cell, powered by 18 V dc power supply, eliminated the requirement of a coulometer or a constant current power source. Setup of an electrolysis cell and experimental details for preparing reagents are presented.

Pectin methylesterase activity determined by different methods and thermal inactivation of exogenous pme in mango juice

Pectin methylesterase (PME) hydrolyzes methyl ester groups in pectin chains to form carboxylic groups, releasing methanol and H3O+. The aim of this study was to determine PME activity in samples of pectinases by UV-VIS spectroscopy, to measure the acid and methanol produced in the reaction of pectin with pectinase and to verify the thermal inactivation of exogenous PME in mango juice. The activity of PME in samples of pectinase was determined by potentiometry, UV-VIS spectroscopy, and by the action of alcohol oxidase. The reaction showed greater activity at pH 4.0 to 4.5 and at a temperature of 45° C. PME activity determined by UV-VIS spectroscopy with bromophenol blue indicator showed a good correlation with the activity determined by potentiometry and with alcohol oxidase. The results showed that bromophenol blue indicators can be used to determine PME activity in samples of pectinases where the optimum pH is located in the acidic range. The thermal inactivation of exogenous PME in mango juice occurred at 75° C for 20 min of exposure.

An intelligent optical fibre pH sensor based on sol-gel advanced material and artificial neural network

The application of artificial neural network (ANN) in signal processing of optical fibre pH sensor is presented. The pH sensor is developed based on the use of bromophenol blue indicator immobilized in a sol-gel thin film as a sensing material. A three layer feed-forward network was used and the network training was performed using the back-propagation algorithm. Spectra generated from the pH sensor at several selected wavelengths are used as the input for the ANN. The bromophenol blue indicator, which has a limited dynamic range of 3.00-5.50 pH units, was found to show higher pH dynamic range of 2.00-12.00 and low calibration error after training with ANN. The trained ANN was successfully employed to predict several spectra from unknown buffer solution with an average error of 0.06 pH units.

Applications of artificial neural network on signal processing of optical fibre pH sensor based on bromophenol blue doped with sol–gel film

In this paper, the applications of artificial neural network (ANN) in signal processing of optical fibre pH sensor is presented. The pH sensor is developed based on the use of bromophenol blue (BPB) indicator immobilized in a sol–gel thin film as a sensing material. A three layer feed-forward network was used and the network training was performed using the back-propagation (BP) algorithm. Spectra generated from the pH sensor at several selected wavelengths are used as the input data for the ANN. The bromophenol blue indicator, which has a limited dynamic range of 3.00–5.50 pH units, was found to show higher pH dynamic range of 2.00–12.00 and with low calibration error after training with ANN. The enhanced ANN could be used to predict the new measurement spectra from unknown buffer solution with an average error of 0.06 pH units. Changes of ionic strength showed minor effect on the dynamic range of the sensor. The sensor also demonstrated good analytical performance with repeatability and reproducibility characters of the sensor yield relative standard deviation (R.S.D.) of 3.6 and 5.4%, respectively. Meanwhile the R.S.D. value for this photostability test is 2.4% and it demonstrated no hysteresis when the sensor was cycled from pH 2.00–12.00–2.00 (acid–base–acid region) of different pH. Performance tests demonstrated a response time of 15–150 s, depending on the pH and quantity of the immobilized indicator.

Photolysis of diaryliodonium salts (UV/Vis, EPR and GC/MS investigations)

The photodecomposition of commercial lipophilic diaryliodonium hexafluoroantimonate SarCat ® SR-1012 was investigated in acetonitrile (ACN) and ACN/H 2O mixed solvents by means of UV/Vis spectroscopy, an EPR in situ spin trapping technique and GC/MS analysis. The application of the spin traps nitrosodurene (ND) and 5,5-dimethyl-1-pyrroline N-oxide gave evidence for the production of radical intermediates corresponding to the breaking of the carbon–iodine bond, in addition to carbon–oxygen bonds in SR-1012 aryl substitution. The photolytic products analyzed in aprotic acetonitrile were iodobenzene, acetanilide, biphenyl and C 12H 25CH(OH)CH 3, while in ACN/H 2O (1:1, vol.) solution iodobenzene, biphenyl, C 12H 25CH(OH)CH 2OC 6H 4OH and hydroxylated biphenyls were identified. The influence of oxygen on the product distribution in both solvent systems was inconsequential. The proton concentrations photogenerated in the irradiated SR-1012 ACN/H 2O solutions were quantified spectrophotometrically using bromophenol blue indicator.

Determination of sulfuric acid in metallurgical process streams by discontinuous flow analysis

Discontinuous flow analysis was applied to the determination of sulfuric acid in metallurgical process samples by photometric titration using a bromophenol blue indicator. Over-estimation of the level of acid due to the precipitation of metal hydroxides and oxides was prevented by titrating with sodium acetate. At a throughput of 110 samples h −1, the method exhibited excellent repeatability and reproducibility, with relative standard deviations of less than 1% throughout. Determinations on samples taken from copper, manganese and zinc refining operations compared well with results obtained using the existing industry procedure of manual titration with hydroxide to a pH 3.9 endpoint. Of twelve metals investigated, only arsenic(V) and iron(III) interfered to a significant extent. High levels of cadmium, chromium(III), copper(II) and lead(II) resulted in small positive errors, whereas calcium, cobalt(II), magnesium, manganese(II), nickel(II) and zinc did not interfere.

The effect of high pressure on the ion pair equilibrium constant of alkali metal fluorides: A spectrophotometric study

Bromophenol blue indicator was used in UV-visible spectrophotometric measurements to study ion association constants of alkali metal fluorides. The equilibrium constants for the ion pair formation of the alkali metal fluorides were determined as a function of ionic strength at one atmosphere pressure and 25°C. The effect of pressure on these association constants was measured at a constant total ionic strength of 1.0 mol-kg−1 over a pressure range of 1 to 2000 atmospheres at 25°C. The pressure dependences of the stoichiometric association constants of the alkali metal fluorides are given by: lnK LiF * =0.77–2.47×10−4P−2.12×10−8P2; lnK NaF * =0.53–1.08×10−4P−1.66×10−8P2; lnK KF * =0.24–4.41×10−5P−7.15×10−8P2; lnK RbF * =−0.17–8.65×10−5P−4.51×10−8P2; and lnK CsF * = −0.37–1.14×10−4P−6.82×10−8P2, where P is the pressure in atmospheres. The stoichiometric molar volume and compressibility changes for ion pair formation of the alkali metal fluorides were evaluated from the pressure dependence of K MF * data. The thermodynamic association constants were also calculated making use of activity coefficient data from the Pitzer equations. The partial molal volume and compressibility changes for ion pair formation of each alkali metal fluoride are reported.

Direct Titrimetric Determination of Aromatic Quaternary Ammonium Salts and Long Chain Aliphatic Sulfates and Sulfonates

Aromatic quaternary ammonium salts and long chain aliphatic sulfates and sulfonates can be assayed by a rapid, single phase aqueous titration. Sodium tetraphenylboron serves as a direct standard in the assay of the quaternaries and benzalkonium chloride as the tirrant for anionic detergents. Bromophenol blue indicator gives a purple to blue color change when the anionic substances are titrated in strongly alkaline solution. The results of this method show excellent agreement with the standard chloroform extraction titration.

Direct Acidimetric Analysis of Papaverine in Concentrated Lithium Chloride Solution

Hydrochloric acid was used as the titrant for papaverine base in two different media: (a) 18.5% ethanol and 81.5% 8 M lithium chloride solution, and (b) 10% tetrahydrofuran, 5% ethanol, and 85% 8 M lithium chloride solution. Per cents were calculated on a weight to weight basis. All of the titrations were carried out potentiometrically and the end points were determined by the first derivative method. It was found that bromophenol blue indicator could also be used to determine end points in medium a. The mean per cent recovery for the titrations in medium a, with the end points determined by the first derivative method, was 98.85 with a standard deviation of 0.69. In the same medium, using bromophenol blue for end point determination, the recovery was 99.48 with a standard deviation of 0.96. In medium b, the recovery was 100.02 with a standard deviation of 1.27.