DETERMINAÇÃO COLORIMÉTRICA DE METABISSULFITO

Metabisulfite anion is widely used as an antioxidant agent and preservative of anumber of industrialized products. The interaction of this agent with pararosaniline dye can reduce the absorption band of the pigment within the visible area. From the best experimental conditions such as Britton-Robinson buffer solution, pH 5.0, and dye in a solution of 1.0x10-4 mol L-1, it was possible to obtain a relation between concentration of metabisulfite and absorbance in a range from 1,3x10-6 mol L-1 to 3.0x10-5 mol L-1. The detection limit was calculated in 5.0x10-7 mol L-1. The methodology was applied on real samples.

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Selective Voltammetric Detection of Dopamine in the Presence of Ascorbic Acid at Poly(p-methoxyphenol)-Modified Electrode

Sensor Letters ◽

10.1166/sl.2020.4206 ◽

2020 ◽

Vol 18 (3) ◽

pp. 222-226

Author(s):

Gamze Erdoğdu

Keyword(s):

Ascorbic Acid ◽

Detection Limit ◽

Modified Electrode ◽

Oxidative Polymerization ◽

Phosphate Buffer Solution ◽

Relative Sensitivity ◽

High Concentration ◽

Buffer Solution ◽

Solution Ph ◽

Voltammetric Detection

A gold electrode was modified with electropolymerized films of p-methoxyphenol by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was then used to determine dopamine (DA) in the presence of a high concentration of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity DA/AA were affected by the potential window used for the polymerization. For polymerization between 0 and 1.0 V, the peak potentials recorded in a phosphate buffer solution (pH = 7.2) were 516 and 312 mV versus Ag/AgCl for DA and AA, respectively. In addition to the effects of pH and the type of electrolyte on the linearity range and detection limit are investigated. The detection limit for 3s-test is 0.1 nM. The high selectivity and sensitivity for DA was found to be due to charge discrimination/analyte accumulation.

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Electrochemical characterization of luminol and its determination in real samples

Analytical Methods ◽

10.1039/c4ay01281j ◽

2014 ◽

Vol 6 (19) ◽

pp. 7809-7813 ◽

Cited By ~ 10

Author(s):

Gulcemal Yildiz ◽

Ugur Tasdoven ◽

Necati Menek

Keyword(s):

Cyclic Voltammetry ◽

Glassy Carbon ◽

Electrochemical Behavior ◽

Differential Pulse ◽

Carbon Electrode ◽

Buffer Solution ◽

Solution Ph ◽

Real Samples ◽

Pulse Voltammetry

The electrochemical behavior of luminol, an important molecule in forensic science, was studied in Britton–Robinson buffer solution (pH 2–pH 13) at a glassy carbon electrode using cyclic voltammetry and differential pulse voltammetry techniques.

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Effect of ohmic heating processing conditions on color stability of fungal pigments

Food Science and Technology International ◽

10.1177/1082013216689514 ◽

2017 ◽

Vol 23 (4) ◽

pp. 338-348 ◽

Cited By ~ 5

Author(s):

Diederich Aguilar-Machado ◽

Lourdes Morales-Oyervides ◽

Juan C Contreras-Esquivel ◽

Cristóbal Aguilar ◽

Alejandro Méndez-Zavala ◽

...

Keyword(s):

Ohmic Heating ◽

Degradation Mechanism ◽

Color Stability ◽

Model System ◽

Processing Conditions ◽

Buffer Solution ◽

Solution Ph ◽

Experimental Conditions ◽

Good Thermal Stability ◽

Heating Treatment

The aim of this work was to analyze the effect of ohmic heating processing conditions on the color stability of a red pigment extract produced by Penicillium purpurogenum GH2 suspended in a buffer solution (pH 6) and in a beverage model system (pH 4). Color stability of pigmented extract was evaluated in the range of 60–90 ℃. The degradation pattern of pigments was well described by the first-order (fractional conversion) and Bigelow model. Degradation rate constants ranged between 0.009 and 0.088 min−1 in systems evaluated. Significant differences in the rate constant values of the ohmic heating-treated samples in comparison with conventional thermal treatment suggested a possible effect of the oscillating electric field generated during ohmic heating. The thermodynamic analysis also indicated differences in the color degradation mechanism during ohmic heating specifically when the pigment was suspended in the beverage model system. In general, red pigments produced by P. purpurogenum GH2 presented good thermal stability under the range of the evaluated experimental conditions, showing potential future applications in pasteurized food matrices using ohmic heating treatment.

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Study on the fluorescence properties of the interaction between felodipine and bovine serum protein

E3S Web of Conferences ◽

10.1051/e3sconf/202130001023 ◽

2021 ◽

Vol 300 ◽

pp. 01023

Author(s):

Shuxian Li ◽

Jialuo Bu ◽

Wenbin Liu ◽

Cuijuan Liu ◽

Yuguang Lv

Keyword(s):

Fluorescence Quenching ◽

Serum Protein ◽

Bovine Serum ◽

Control Variable ◽

Complex Compounds ◽

Uv Spectrophotometry ◽

Buffer Solution ◽

Solution Ph ◽

Experimental Conditions ◽

Bovine Serum Protein

The interaction between felodipine and bovine serum protein was studied, the optimal experimental conditions were selected, and the fluorescence quenching mechanism was discussed. The interaction between filodipine and bovine serum protein was determined by UV spectrophotometry, and the optimal experimental conditions were selected by control variable method. The mechanism of fluorescence quenching in the system was explored by fluorescence spectrophotometry. The fluorescence intensity of the system between felodipine and bovine serum protein was the most obvious under the experimental conditions of buffer solution pH 7.4, felodipine concentration 8.0*10-4mol/L, reaction time 30min and 25°C. Static fluorescence quenching caused by the formation of complex compounds.

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Detection of Hepatitis a Virus in Drinking Water by Enzyme -Immunoassay Using Ultracentrifugation for Virus Concentration

Water Science & Technology ◽

10.2166/wst.1985.0093 ◽

1985 ◽

Vol 17 (10) ◽

pp. 39-41 ◽

Cited By ~ 1

Author(s):

A. Schnattinger

Keyword(s):

Membrane Filtration ◽

Hepatitis A ◽

Hepatitis A Virus ◽

Solid Phase ◽

Phosphate Buffer Solution ◽

Enzyme Linked Immunosorbent Assay ◽

Virus Concentration ◽

Buffer Solution ◽

Solution Ph ◽

Two Stage

Ten litres of tapwater were seeded with 200 µl (8×108 HAV particles) of a commercial (Organon Teknika) suspension of hepatitis A virus. Following WALTER and RÜDIGER (1981), the contaminated tapwater was treated with a two-stage technique for concentration of viruses from solutions with low virus titers. The two-stage technique consists of aluminium hydroxideflocculation (200 mg/l Al2(SO4)3. 18 H2O, pH 5,4-5,6) as first stage, the second stage of a lysis of aluminium hydroxidegel with citric acid/sodium citrate-buffer (pH 4,7; 1 ml/l sample), separation of viruses from the lysate by ultracentrifugation and suspension in 1 ml phosphate buffer solution (pH 7,2). A commercial solid phase enzyme-linked immunosorbent assay (ELISA) was used for the detection of HAV. HAV was detecterl in the 10.000:1 concentrates, but not in the seeded 101 samples. Approximately 4×108 of the inoculated 8×108 HAV particles were found in the 1 ml concentrates. The efficiency of detection is about 50%, the virus concentration 5000-fold. Although the percentage loss of HAV in comparison with concentration by means of membrane filtration is similar, the ultracentrifugation method yields a larger sample/concentrate ratio, so that smaller amounts of HAV can be detected more efficiently because of the smaller end-volume.

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Development and Validation of Stability Indicating HPLC Method for the Determination of Impurities in the Sterile Mixture of Cefoperazone and Sulbactam

Current Pharmaceutical Analysis ◽

10.2174/1573412914666180914163419 ◽

2019 ◽

Vol 15 (7) ◽

pp. 762-775

Author(s):

Ramu Ivaturi ◽

Thuttagunta Manikya Sastry ◽

Satyaveni Sunkara

Keyword(s):

Quantitative Estimation ◽

Ammonium Hydroxide ◽

Hplc Method ◽

Forced Degradation ◽

Buffer Solution ◽

Solution Ph ◽

Pharmaceutical Dosage Forms ◽

Stability Indicating ◽

Validation Parameters ◽

Abdominal Infections

Background: Cefoperazone Sulbactam injection is a cephalosporin antibiotic with a β- lactamase inhibitor used in the treatment for intra abdominal infections, Urinary track infections, surgical infections, etc. The combination is not official in any of the pharmacopeia for their content and impurities determination. Introduction: The present study involves the development of a simple, rapid, accurate, sensitive and stability indicating RP-HPLC method for the quantitative estimation of Cefoperazone Sulbactam mixture and its impurities in bulk and pharmaceutical dosage forms. Methods: 0.005 M Tetrabutyl ammonium hydroxide buffer solution pH adjusted to 6.80 and Acetonitrile combination has been used in a gradient programme with a flow rate of 1.0 ml/min. The retention time of Cefoperazone and Sulbactam were observed at around 8.5 and 19.5 minutes respectively. The UV detection was carried out at a wavelength of 230 nm. The chromatographic separation was achieved using Waters xbridge C18-150*4.6 mm, 3.5 µm HPLC column. The method has been validated according to the current International Council for Harmonization (ICH) guidelines for the method validation parameters such as Specificity, linearity, range, accuracy, precision, robustness and sensitivity. Results: The validation results indicate that the method is specific, as the known impurities and other impurities formed during the forced degradation studies were not co-eluting with the main components. Moreover, all these impurities were found to be spectrally pure, proving the stability indicating power of the method. The linearity and range of the method is in the range of 0.01-150%, highly accurate (100.2%), precise (<1%) and robust. Conclusion: The proposed method was accurate and specific for the quantitative analysis of Cefoperazone and Sulbactam and their related impurities in the sterile mixture. Hence the proposed method can be used for the quantification of impurities in routine as well as stability analysis in the development as well as quality control laboratories.

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Non-enzymatic determination of purine nucleotides using a carbon dot modified glassy carbon electrode

Analytical Methods ◽

10.1039/c9ay00718k ◽

2019 ◽

Vol 11 (30) ◽

pp. 3866-3873 ◽

Cited By ~ 1

Author(s):

R. Karthikeyan ◽

D. James Nelson ◽

S. Abraham John

Keyword(s):

Glassy Carbon ◽

Low Cost ◽

Phosphate Buffer Solution ◽

Purine Nucleotides ◽

Buffer Solution ◽

Solution Ph ◽

Carbon Dot ◽

Enzymatic Determination ◽

Sensitive Determination

Selective and sensitive determination of one of the purine nucleotides, inosine (INO) using a low cost carbon dot (CD) modified glassy carbon (GC) electrode in 0.2 M phosphate buffer solution (pH 7.2) was demonstrated in this paper.

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Electro-Polymerized Titan Yellow Modified Carbon Paste Electrode for the Analysis of Curcumin

Surfaces ◽

10.3390/surfaces4030017 ◽

2021 ◽

Vol 4 (3) ◽

pp. 191-204

Author(s):

Edwin S. D’Souza ◽

Jamballi G. Manjunatha ◽

Chenthattil Raril ◽

Girish Tigari ◽

Huligerepura J. Arpitha ◽

...

Keyword(s):

Carbon Paste Electrode ◽

Limit Of Detection ◽

Phosphate Buffer Solution ◽

Modified Carbon Paste Electrode ◽

Carbon Paste ◽

Buffer Solution ◽

Solution Ph ◽

Real Sample Analysis ◽

Titan Yellow ◽

Paste Electrode

A modest, efficient, and sensitive chemically modified electrode was fabricated for sensing curcumin (CRC) through an electrochemically polymerized titan yellow (TY) modified carbon paste electrode (PTYMCPE) in phosphate buffer solution (pH 7.0). Cyclic voltammetry (CV) linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) approaches were used for CRC detection. PTYMCPE interaction with CRC suggests that the electrode exhibits admirable electrochemical response as compared to bare carbon paste electrode (BCPE). Under the optimized circumstances, a linear response of the electrode was observed for CRC in the concentration range 2 × 10−6 M to 10 × 10−6 M with a limit of detection (LOD) of 10.94 × 10−7 M. Moreover, the effort explains that the PTYMCPE electrode has a hopeful approach for the electrochemical resolution of biologically significant compounds. Additionally, the proposed electrode has demonstrated many advantages such as easy preparation, elevated sensitivity, stability, and enhanced catalytic activity, and can be successfully applied in real sample analysis.

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Phosphorus removal from aqueous solution using a novel granular material developed from building waste

Water Science & Technology ◽

10.2166/wst.2017.019 ◽

2017 ◽

Vol 75 (6) ◽

pp. 1500-1511 ◽

Cited By ~ 3

Author(s):

Shengjiong Yang ◽

Pengkang Jin ◽

Xiaochang C. Wang ◽

Qionghua Zhang ◽

Xiaotian Chen

Keyword(s):

Granular Material ◽

Chemical Precipitation ◽

Phosphate Removal ◽

Precipitation Process ◽

Order Kinetic ◽

Solution Ph ◽

Experimental Conditions ◽

Removal Capacity ◽

Order Kinetic Model ◽

Pseudo Second Order

In this study, a granular material (GM) developed from building waste was used for phosphate removal from phosphorus-containing wastewater. Batch experiments were executed to investigate the phosphate removal capacity of this material. The mechanism of removal proved to be a chemical precipitation process. The characteristics of the material and resulting precipitates, the kinetics of the precipitation and Ca2+ liberation processes, and the effects of dosage and pH were investigated. The phosphate precipitation and Ca2+ liberation processes were both well described by a pseudo-second-order kinetic model. A maximum precipitation capacity of 0.51 ± 0.06 mg g−1 and a liberation capacity of 6.79 ± 0.77 mg g−1 were measured under the experimental conditions. The processes reached equilibrium in 60 min. The initial solution pH strongly affected phosphate removal under extreme conditions (pH <4 and pH >10). The precipitates comprised hydroxyapatite and brushite. This novel GM can be considered a promising material for phosphate removal from wastewater.

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Antigen retrieval technique utilizing citrate buffer or urea solution for immunohistochemical demonstration of androgen receptor in formalin-fixed paraffin sections.

Journal of Histochemistry & Cytochemistry ◽

10.1177/41.11.7691930 ◽

1993 ◽

Vol 41 (11) ◽

pp. 1599-1604 ◽

Cited By ~ 197

Author(s):

S R Shi ◽

B Chaiwun ◽

L Young ◽

R J Cote ◽

C R Taylor

Keyword(s):

Androgen Receptor ◽

Enzymatic Digestion ◽

Antigen Retrieval ◽

Urea Solution ◽

Paraffin Sections ◽

Buffer Solution ◽

Solution Ph ◽

Citrate Buffer ◽

Formalin Fixed Paraffin ◽

Formalin Fixed

We developed a staining protocol for demonstration of androgen receptor (AR) in formalin-fixed, paraffin-embedded tissue sections. The method is based on the antigen retrieval microwave (MW) heating technique. Results are compared with different types of enzyme digestion pre-treatments. The strongest immunostaining signal and clearest background were obtained by MW heating of dewaxed paraffin sections in 5% urea or citrate buffer solution (pH 6); pure distilled water gave less consistent results. Enzymatic digestion with pepsin (0.05% in 2 N HCl) for 30 min at room temperature, or trypsin followed by pronase, or pronase digestion alone, also produced enhanced staining of AR in some cases, but there was more nonspecific background, and specific reactivity was less intense. The antigen retrieval MW method can be used to demonstrate AR epitope in prostate tissue after fixation in formalin for as long as 7 days. AR immunolocalization was also compared in frozen and paraffin sections processed from the same specimen of prostate carcinoma tissue and was found to be qualitatively and quantitatively similar. This study also provided new information concerning the basic principles of the antigen retrieval MW method that may be helpful in further development of this technique.

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