scholarly journals Revisiting the fundamentals of p-nitrophenol analysis for its application in the quantification of lipases activity. A graphical update.

Uniciencia ◽  
2020 ◽  
Vol 34 (2) ◽  
pp. 31-43
Author(s):  
Randall Syedd-León ◽  
Manuel Sandoval-Barrantes ◽  
Humberto Trimiño-Vásquez ◽  
Luis Roberto Villegas-Peñaranda ◽  
Gerardo Rodríguez-Rodríguez
Keyword(s):  
Lipase Activity ◽  
Ph Value ◽  
Protonated Form ◽  
Spectrophotometric Analysis ◽  
Spectrophotometric Methods ◽  
Ph Values ◽  
Reaction Media ◽  
Activity Quantification

p-Nitrophenol (pNP) is a widely used compound for analytical determinations of several esterases (EC. 3.1.1.X), including lipases (E.C. 3.1.1.3). Most enzymatic measurements employ pNP derivatives such as esters, which are broken down by enzymatic hydrolysis, releasing pNP that is quantified by its absorbance at 410 nm. Although this type of methods was developed a few decades ago, the spectrophotometric analysis of pNP requires analytical measurements of pH and temperature to achieve reliable determinations. The aim of this paper is to offer a graphical update of how pH and temperature affect the p-nitrophenol absorbance at different wavelengths in lipase emulsified media, due to its relevance for the quantitative determination of lipase activity using spectrophotometric methods. To highlight the importance of each variable involved in this analysis, we dissolved pNP in emulsified media (for lipase activity quantification) at several pH values from 4.00 to 11.00, and measured its absorbance in a range of 270 nm – 500 nm and at several temperatures from 25°C to 50°C. The absorption patterns of pNP under the established conditions were graphed in 3D plots. The constructed 3D plots showed that, regardless of the temperature, below pH 6.00, pNP predominantly absorbs at 317 nm, due to the greater abundance of its protonated form, which is completely predominant at pH 3.50 and below. On the other hand, at pH 10.0 and above, the major absorption occurs at about 401 nm, confirming that the equilibrium is completely shifted to the pNP anionic form. These results also indicate that close to neutral pH value pNP, it displays a temperature dependence effect, increasing absorbance to 410 nm at higher temperatures. Due to many analytical determinations of enzymatic activities, the release of pNP is carried around pH 7.00. It is necessary to consider the determinant role of both pH and temperature over these measurements, how these variables must be strictly controlled, and how the calibration curves and blanks should take the reaction media pH and temperature into account.

scholarly journals Significance of pH-value for meat quality of broilers: Influence of breed lines

2013 ◽  
Vol 67 (1-2) ◽  
pp. 67-73 ◽  
Author(s):  
M. Ristic ◽  
K. Damme
Keyword(s):  
Meat Quality ◽  
Ph Value ◽  
Storage Period ◽  
Breeding Line ◽  
Breast Meat ◽  
Ph Values ◽  
And Gender

For determination of poultry quality shortly after slaughtering, physical criteria (pH-value, conductivity, colour, juice retention) are of importance. However, they are affected by breeding, transport, cooling and the storage period. PH-values of breast meat (genetically structured material) were recorded shortly after slaughtering (15 min p.m.) and differences between breeding line and gender were found (n=5109). The pH1-values ranged from 5.50 to 6.79. Male broilers showed significantly lower pH1-values than female ones (6.02:6.10). There were also significant differences concerning breeding line and gender. Meat quality (PSE, DFD) of broilers can be recorded quickly and accurately determining the pH1-value of breast meat. Threshold ranges to be considered are ? 5.8 (PSE), 5.9-6.2 (standard meat properties) and ? 6.3 (DFD). This classification is not to be compared to the deviation of pork.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

2019 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte i.e. proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included in the model. It can be regarded as a kind of "minimal'' model in the sense that contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase, and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 to low pH-values (Pincus regime), is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

Depth-Profiles of Corrosion Properties of Carbonitrided AISI 405 Steel

2012 ◽  
Vol 57 (2) ◽  
pp. 637-642 ◽  
Author(s):  
K. Jagielska-Wiaderek
Keyword(s):  
Stainless Steel ◽  
Cross Section ◽  
Acid Corrosion ◽  
Spectrophotometric Analysis ◽  
Corrosion Properties ◽  
Depth Profiles ◽  
Ph Values ◽  
Type Stainless Steel ◽  
Electrochemical Polarisation

Depth-Profiles of Corrosion Properties of Carbonitrided AISI 405 SteelElectrochemical polarisation characteristics of AISI 405 type stainless steel, carbonitrided in fluid flow, are presented. The evaluation of the corrosion resistance of carbonitrided stainless steel was carried out by using the so called progressive thinning method, consisting in determination of polarisation characteristics on increasingly-deeper situated regions of the top layer. This method made it possible to determine changes in particular corrosion parameters read out from potentiokinetic polarisation curves, thus enabling the depth profiles of these parameters. The resistance of the AISI 405 steel against acid corrosion was determined in acidified 0.5M sulphate solutions having three different pH values, namely 1, 2 and 4. The thickness of the carbonitrided layer has been evaluated on the basis of the spectrophotometric analysis of carbon content and microhardness on the cross section of the surfacial layer.

The Role of Acetate in Denitrification and Biological Phosphate Removal in Modified Bardenpho Systems

1989 ◽  
Vol 21 (4-5) ◽  
pp. 375-385 ◽  
Author(s):  
C. T. Winter
Keyword(s):  
Sodium Acetate ◽  
Ph Value ◽  
Phosphate Removal ◽  
Organic Substances ◽  
Phosphate Release ◽  
Ph Values ◽  
Experimental Systems ◽  
Removal Capacity ◽  
Equivalent Sequence

The importance of easily biodegradable organic substances such as acetate and propionate in biological phosphate removal has been recognised by many researchers. Laboratory-scale studies on the performance of three-stage modified Bardenpho nutrient removal systems, fed with settled sewage supplemented with 0, 50, 100 and 200 mg/l sodium acetate respectively are described. Particular attention is given to the effects of these additions on biological phosphate release and uptake and also to the fate of parameters such as pH, calcium, potassium, ammonia and nitrate. Additional phosphate of 10 mg/l (as P) was initially introduced into the feed in order to burden the experimental systems beyond their normal phosphate removal capacity. This was increased to 20 mg/l and eventually to 40 mg/l of phosphate (as P). Increasing concentrations of sodium acetate resulted in distinct increases in pH values, increase in phosphate release in the anaerobic zones and significantly improved overall phosphate removal in the experimental units. The correlation of phosphate removal on acetate concentration was found to be 0.9886. In some instances the unit receiving 200 mg/l acetate removed up to an average of 30 mg/l of phosphate (as P), constituting an improvement of up to 200% compared with the unit receiving no acetate. The alternating release and uptake of phosphate was accompanied by an equivalent sequence for potassium and magnesium. The high pH value plus the disappearance of phosphate, ammonia and magnesium places doubt on a purely biological phosphate removal but could point at the crystallization of ammonium magnesium phosphate.

scholarly journals Role of Charge Regulation and Fluctuations in the Conformational and Mechanical Properties of Weak Flexible Polyelectrolytes

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1962 ◽  
Author(s):  
Pablo M. Blanco ◽  
Sergio Madurga ◽  
Claudio F. Narambuena ◽  
Francesc Mas ◽  
Josep L. Garcés
Keyword(s):  
Mechanical Properties ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Persistence Length ◽  
Excluded Volume ◽  
Average Charge ◽  
Zero Force ◽  
Charge Regulation ◽  
Ph Values

This work addresses the role of charge regulation (CR) and the associated fluctuations in the conformational and mechanical properties of weak polyelectrolytes. Due to CR, changes in the pH-value modifies the average macromolecular charge and conformational equilibria. A second effect is that, for a given average charge per site, fluctuations can alter the intensity of the interactions by means of correlation between binding sites. We investigate both effects by means of Monte Carlo simulations at constant pH-value, so that the charge is a fluctuating quantity. Once the average charge per site is available, we turn off the fluctuations by assigning the same average charge to every site. A constant charge MC simulation is then performed. We make use of a model which accounts for the main fundamental aspects of a linear flexible polyelectrolyte that is, proton binding, angle internal rotation, bond stretching and bending. Steric excluded volume and differentiated treatment for short-range and long-range interactions are also included. This model can be regarded as a kind of “minimal” in the sense that it contains a minimum number of parameters but still preserving the atomistic detail. It is shown that, if fluctuations are activated, gauche state bond probabilities increase and the persistence length decreases, so that the polymer becomes more folded. Macromolecular stretching is also analyzed in presence of CR (the charge depends on the applied force) and without CR (the charge is fixed to the value at zero force). The analysis of the low force scaling behavior concludes that Pincus exponent becomes pH-dependent. Both, with and without CR, a transition from 1/2 at high pH-values (phantom chain) to 3/5 at low pH-values (Pincus regime) is observed. Finally, the intermediate force stretching regime is investigated. It is found that CR induces a moderate influence in the force-extension curves and persistence length (which in this force regime becomes force-dependent). It is thus concluded that the effect of CR on the stretching curves is mainly due to the changes in the average charge at zero force. It is also found that, for the cases studied, the effect of steric excluded volume is almost irrelevant compared to electrostatic interactions.

scholarly journals Characterizing the impact of MnO2 addition on the efficiency of Fe0/H2O systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Ph Value ◽  
Iron Corrosion ◽  
Dissolved Iron ◽  
Ph Values ◽  
Solid Iron ◽  
Initial Ph ◽  
Fixation Capacity ◽  
Co Precipitation ◽  
The Impact

AbstractThe role of manganese dioxide (MnO2) in the process of water treatment using metallic iron (Fe0/H2O) was investigated in quiescent batch experiments for t ≤ 60 d. MnO2 was used as an agent to control the availability of solid iron corrosion products (FeCPs) while methylene blue (MB) was an indicator of reactivity. The investigated systems were: (1) Fe0, (2) MnO2, (3) sand, (4) Fe0/sand, (5) Fe0/MnO2, and (6) Fe0/sand/MnO2. The experiments were performed in test tubes each containing 22.0 mL of MB (10 mg L−1) and the solid aggregates. The initial pH value was 8.2. Each system was characterized for the final concentration of H+, Fe, and MB. Results show no detectable level of dissolved iron after 47 days. Final pH values varied from 7.4 to 9.8. The MB discoloration efficiency varies from 40 to 80% as the MnO2 loading increases from 2.3 to 45 g L−1. MB discoloration is only quantitative when the operational fixation capacity of MnO2 for Fe2+ was exhausted. This corresponds to the event where adsorption and co-precipitation with FeCPs is intensive. Adsorption and co-precipitation are thus the fundamental mechanisms of decontamination in Fe0/H2O systems. Hybrid Fe0/MnO2 systems are potential candidates for the design of more sustainable Fe0 filters.

scholarly journals The role of pH values in porcine reproductive tracts of male and female individuals

2008 ◽  
Vol 24 (3-4) ◽  
pp. 101-108 ◽  
Author(s):  
T. Smiljakovic ◽  
S. Josipovic ◽  
O. Kosovac ◽  
N. Delic ◽  
S. Aleksic ◽  
...  
Keyword(s):  
Reproductive Tract ◽  
Ph Value ◽  
Rete Testis ◽  
Female Reproductive Tract ◽  
Ductus Deferens ◽  
Male And Female ◽  
Ph Values ◽  
Small Peak

For a long time, in practice, and science, has been known that pH values of sperm and vagina are important for successful fertilization. In this investigation this fact was confirmed, and the goal was to investigate the role of pH values through whole reproductive tract of male and female individuals: testis, rete testis, epididymis, ductus deferens, Cowper's gland, vesicula seminalis, prostata, corpus cavernosus, corpus spongiosus, epitel tissue of penis tube, sperm, vagina, uterus, horn of uterus, oviduct, fimbrie ovarica, ovarium, follicular fluid. Measurement was performed in reproductive active males as well as before and after ovulation in females. Porcine reproductive tracts (per 15 female and male individuals) were collected from institute's slaughterhouse, immediately post mortem dissected, homogenised and pH values were measured (according to method Rede&Rahelic (1969)). Ovarium and follicular liquid have the highest pH values (7,4) in females, but a small peak in preovulatory oviduct is also present and corresponded to pH of sperm of reproductive fully active male individuals (pH=app.7,2). After fertilization pH in surrounding of zygot (through depolarisation of its membrane) in oviduct, and zygot which then has external decreased pH value moves to less pH values regions by the same principle, that means to uterus, (pH between 7,2 (horn) and 7,07(cervix)) in postovulatory female reproductive tract, where nidation of blastocyst occurs. This investigation could help to elucidate knowledge about reproductive physiology in vivo, giving importance to role of pH values along reproductive tract of male and female individuals.

scholarly journals LABORATORY TRIAL OF PROTEIN DETERMINATION IN URINE USING DIFFERENT PH VALUES OF ACETIC ACID AND ACETATE BUFFER METHOD

2020 ◽  
Vol 2 (1) ◽  
pp. 34-41
Author(s):  
Dinar Rahayu ◽  
Tuti Rustiana
Keyword(s):  
Acetic Acid ◽  
Clinical Examination ◽  
Ph Value ◽  
Urine Ph ◽  
Protein Determination ◽  
Ph Values ◽  
Significant Difference ◽  
Laboratory Trial ◽  
Acidic Urine

Abstract The determination of protein in urine is important in clinical examination along with other parameters in urine. The presence of protein in urine can be interpreted that there is a disorder in kidney. Acid and heat coagulations method is still widely used in many areas to determine protein in urine. In this method, the characteristic of protein that will precipitate in the presence of acid or if exposed to heat is deployed to gain information about the amount of protein. The greater amount of protein, the more prominence is the coagulation. Urine pH also varies according to the condition, classic acidosis will give an acidic urine and the presence of ammonium producing bacteria can cause basic urine. In this research acetic acid method with 6% of CH3COOH and pH value of 2,9 and buffer acetic with pH 4,5 are used to determine the certain amount of protein (+3 value, corresponds with 2-4 mg/dL protein in urine) in varied pH values of urine samples. To compare the results, first in control urine with pH 6,8 the results of both methods is compared and shows no significant different, then the Kruskall-Wallis test is used to compare the results in other pH values to control and the test is shown also there are no significant difference. This shows that either acetic acid at pH 2,9 or acetic buffer at pH 4,5 can be used to determine protein amount in urine.

scholarly journals Manipulating Ratio Spectra for the Spectrophotometric Analysis of Diclofenac Sodium and Pantoprazole Sodium in Laboratory Mixtures and Tablet Formulation

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Nejal M. Bhatt ◽  
Vijay D. Chavada ◽  
Mallika Sanyal ◽  
Pranav S. Shrivastav
Keyword(s):  
Diclofenac Sodium ◽  
Pharmaceutical Preparations ◽  
Spectrophotometric Analysis ◽  
Control Analysis ◽  
Anova Analysis ◽  
Spectrophotometric Methods ◽  
Ich Guidelines ◽  
Mean Centering ◽  
Significant Difference

Objective. Three sensitive, selective, and precise spectrophotometric methods based on manipulation of ratio spectra, have been developed and validated for the determination of diclofenac sodium and pantoprazole sodium.Materials and Methods. The first method is based on ratio spectra peak to peak measurement using the amplitudes at 251 and 318 nm; the second method involves the first derivative of the ratio spectra (Δλ=4 nm) using the peak amplitudes at 326.0 nm for diclofenac sodium and 337.0 nm for pantoprazole sodium. The third is the method of mean centering of ratio spectra using the values at 318.0 nm for both the analytes.Results. All the three methods were linear over the concentration range of 2.0–24.0 μg/mL for diclofenac sodium and 2.0–20.0 μg/mL for pantoprazole sodium. The methods were validated according to the ICH guidelines and accuracy, precision, repeatability, and robustness are found to be within the acceptable limit. The results of single factor ANOVA analysis indicated that there is no significant difference among the developed methods.Conclusions. The developed methods provided simple resolution of this binary combination from laboratory mixtures and pharmaceutical preparations and can be conveniently adopted for routine quality control analysis.

scholarly journals Application of membrane filters in determination of the adsorption of tetracycline hydrochloride on graphene oxide

Pharmacia ◽  
2020 ◽  
Vol 67 (4) ◽  
pp. 339-345
Author(s):  
Mirza Dedic ◽  
Sanjin Gutic ◽  
Armina Gicevic ◽  
Ervina Becic ◽  
Belma Imamovic ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Adsorption Process ◽  
Ph Value ◽  
Tetracycline Hydrochloride ◽  
Time Intervals ◽  
Membrane Filters ◽  
Ultrasonic Bath ◽  
Ph Values ◽  
Unique Approach

This paper shows the use of membrane filters in adsorption of solution of tetracycline hydrochloride on graphene materials. The adsorption process was monitored at different wavelengths, different pH values ​​at certain time intervals. The absorbances of the solutions were measured by UV-Vis spectrophotometry at two wavelengths (275 nm and 356 nm), and three pH values (pH 4, pH 7 and pH 10) every 90 minutes for 6 hours of monitoring, with constant stirring in an ultrasonic bath. The results showed decrease in absorbance at both wavelength and in all three pH values which proved the adsorption of tetracycline hydrochloride on GO and rGO. The largest decrease in absorbance was 98.1%. The most suitable pH value for adsorption was pH 4. This paper used a unique approach to filtration through membrane filters, which in the future could lead to the development of membrane filters based on graphene materials.

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