End-point Titration Research Articles

Comparison of methods for accurate end-point detection of potentiometric titrations

Detection of the end point in potentiometric titrations has wide application on experiments that demand very low measurement uncertainties mainly for certifying reference materials. Simulations of experimental coulometric titration data and consequential error analysis of the end-point values were conducted using a programming code. These simulations revealed that the Levenberg-Marquardt method is in general more accurate than the traditional second derivative technique used currently as end-point detection for potentiometric titrations. Performance of the methods will be compared and presented in this paper.

Improved methylene blue two-phase titration method for determining cationic surfactant concentration in high-salinity brine.

The methylene blue (MB) two-phase titration method is a rapid and efficient method for determining the concentrations of anionic surfactants. The point at which the aqueous and chloroform phases appear equally blue is called Epton's end point. However, many inorganic anions, e.g., Cl(-), NO3(-), Br(-), and I(-), can form ion pairs with MB(+) and interfere with Epton's end point, resulting in the failure of the MB two-phase titration in high-salinity brine. Here we present a method to extend the MB two-phase titration method for determining the concentration of various cationic surfactants in both deionized water and high-salinity brine (22% total dissolved solid). A colorless end point, at which the blue color is completely transferred from the aqueous phase to the chloroform phase, is proposed as titration end point. Light absorbance at the characteristic wavelength of MB is measured using a spectrophotometer. When the absorbance falls below a threshold value of 0.04, the aqueous phase is considered colorless, indicating that the end point has been reached. By using this improved method, the overall error for the titration of a permanent cationic surfactant, e.g., dodecyltrimethylammonium bromide, in deionized (DI) water and high-salinity brine is 1.274% and 1.322% with limits of detection (LOD) of 0.149 and 0.215 mM, respectively. Compared to the traditional acid-base titration method, the error of this improved method for a switchable cationic surfactant, e.g., tertiary amine surfactant (Ethomeen C12), is 2.22% in DI water and 0.106% with LOD of 0.369 and 0.439 mM, respectively.

Electrochemically modified semiconductor gallium arsenide electrodes for the argentometric titration of chlorides with silver nitrate in natural samples

An electrochemical method is proposed for the modification of the surface of semiconductor gallium arsenide sensors. The electrochemical modification of the surface of GaAs-electrodes leads to the improvement of their electrochemical characteristics: an increase in the slope of the electrode function, a decrease in response time, and the extension of the concentration range. Potentiometric titration using unmodified and modified GaAs-electrodes for the determination of chlorides with silver nitrate in soil has been performed. The application of the modified sensors ensures the detection of the titration end-point with a higher accuracy.

Surface-Dried Viruses Can Resist Glucoprotamin-Based Disinfection.

Touching of contaminated objects and surfaces is a well-known method of virus transmission. Once they are attached to the hands, viruses can easily get adsorbed and initiate infection. Hence, disinfection of frequently touched surfaces is of major importance to prevent virus spreading. Here we studied the antiviral activity of a glucoprotamin-containing disinfectant against influenza A virus and the model virus vaccinia virus (VACV) dried on inanimate surfaces. The efficacy of the surface disinfectant on stainless steel, polyvinyl chloride, and glass coupons was investigated in a quantitative carrier test. Vacuum-dried viruses were exposed to 0.25%, 0.5%, and 1% disinfectant for 5 min, 15 min, and 30 min without agitation, and residual infectivity was determined by endpoint titration. Although glucoprotamin was highly active against both viruses in suspension, limited antiviral activity against the surface-dried viruses was detected. Even after 30 min of exposure to 1% disinfectant, VACV was not completely inactivated. Furthermore, influenza A virus inactivation was strongly affected by the surface composition during the 5-min and 15-min treatments with 0.25% and 0.5% disinfectant. The results presented in this study highlight the relevance of practical tests to assess the antiviral activity of surface disinfectants. High virucidal activity in solution is not necessarily indicative of high antiviral activity against surface-dried viruses. In addition, we want to emphasize that the mere exposure of surfaces to disinfectants might not be sufficient for virus inactivation and mechanical action should be applied to bring attached viruses into contact with virucidal compounds.

In Vitro Virucidal Effect of Mouthrinse Containing C31G on Seasonal Influenza Viruses

C31G is a potent antimicrobial agent and can disrupt the microbial membrane by the alkyl portion of the molecule. The objective of this study was to evaluate the virucidal effectiveness of C31G and mouthrinse containing C31G (Sense-Time) on seasonal influenza viruses. Evaluation of the virucidal activity against influenza viruses was performed with end-point titration in 10-day-old chicken embryos and Madin-Darby canine kidney cells. In vitro studies demonstrated that C31G and Sense-Time inhibited the growth of seasonal influenza viruses even in the presence of 5% organic material. Gargling with C31G or Sense-Time would enhance oropharyngeal hygiene, which would be helpful for reducing influenza transmission.

A novel method for the determination of the degree of deacetylation of chitosan by coulometric titration

A novel method to determine the degree of deacetylation of chitosan is described. In this method, the coulometric titrant OH− is generated by the electrolysis of water. The OH− reacted with the residual hydrochloric acid in chitosan solution and the degree of deacetylation was obtained by Faraday's law. The optimized experimental parameters in this study were 1.0mol/L KCl as supporting electrolyte, 15.00mA as the intensity of constant current, composite glass electrode as indicating electrode couples, double platinum generated electrode-platinum wire auxiliary electrode as working electrode pairs, pH 3.80 as the titration end-point. The degree of deacetylation in the four samples, which varied from 70 to 95% were measured. The results were similar to those from 1H NMR and the standard deviations were lower than 0.5%. With merit of simplicity, convenience, quickness, high accuracy and precision, automatic detection of titration end-point and low-cost, the proposed method will be very useful in the industrial production.

Precise determination of hypochlorite in commercial bleaches with established traceability using automatic potentiometric titration

A measurement procedure is proposed for precisely determining hypochlorite in commercial bleaches, with established traceability and a full description of its uncertainty sources. The procedure is based on automatic volumetric titration with potentiometric detection and was evaluated in the analysis of several commercial bleach samples, with Na-hypochlorite mass fractions in the range 0.002–0.027 g g−1, with an average expanded uncertainty (k = 2) of 0.00027 g g−1 and an average relative standard deviation between measurement triplicates of 0.36 %. Compared with a standard procedure based on manual volumetric titration with visual colorimetric detection, the improved procedure produced equivalent results with a lower average expanded uncertainty (0.00029 g g−1 as compared to 0.0015 g g−1 for the standard procedure). This was related to better precision of the volume measurement using an automatic buret and to better precision of the titration endpoint determination using potentiometric detection. Compared with other studies reported in the literature, the improved procedure presented a lower average relative standard deviation between measurement replicates (0.36 % as compared to 1.00–11.53 %).

Proving a concept: An in vitro approach

In vitro techniques to predict the feeding value of feedstuffs should be quick, accurate, and cheap. A 2-step in vitro assay to simulate gastric and intestinal digestion was shown to predict AME value for roosters fairly accurately in cereals, cereal by-products, and oil. In general, in vitro techniques are optimized to estimate the maximum nutrient digestibility, using adult roosters for calibration. Prediction of absolute feeding values of feedstuffs by in vitro assays can be highly erroneous, and techniques describing the rate of degradation (dynamics of digestion) seem more promising than such end-point titrations. Moreover, the value of adult roosters as models for meat- or egg-producing birds is questionable. Although, dynamic in vitro assays and near infrared reflectance look to be promising tools, large data sets are required to improve the validity of these in vitro predictions. Such assays will certainly be helpful to correct tabulated feeding values when deviant feedstuff batches are being used.

An improved titration model reducing over estimation of total volatile fatty acids in anaerobic digestion of energy crop, animal slurry and food waste

Titration methodologies have been used for the many years for low cost routine monitoring of full scale anaerobic digestion plants. These methodologies have been correlated to indicate the carbonate alkalinity and the volatile fatty acids (VFA) content within digesters. Two commonly used two end-point titration methods were compared using a dataset of 154 samples from energy crop and animal slurry digestates and were shown to be inaccurate in the estimation of tVFA. Using this dataset correlated with HPLC VFA analysis, two empirical bivariate linear regression equations were derived, where the validation dataset showed an absolute tVFA mean error improvement from ±3386 and ±3324 mg kg−1 tVFA to ±410 and ±286 mg kg−1 tVFA, respectively. The same equation was then applied to a food waste dataset where an absolute tVFA mean error was improved from ±3828 to ±576 mg kg−1 tVFA. The newly derived titration equations can provide greater confidence in digester performance monitoring and are tools that can improve digester management.

Accelerated, Spleen-Based Titration of Variant Creutzfeldt-Jakob Disease Infectivity in Transgenic Mice Expressing Human Prion Protein with Sensitivity Comparable to That of Survival Time Bioassay

The dietary exposure of the human population to the prions responsible for the bovine spongiform encephalopathy (BSE) epizooty has led to the emergence of variant Creutzfeldt-Jakob disease (vCJD). This fatal, untreatable neurodegenerative disorder is a growing public health concern because the prevalence of the infection seems much greater than the disease incidence and because secondary transmission of vCJD by blood transfusion or use of blood products has occurred. A current limitation in variant CJD risk assessment is the lack of quantitative information on the infectivity of contaminated tissues. To address this limitation, we tested the potential of a transgenic mouse line overexpressing human prion protein (PrP), which was previously reported to propagate vCJD prions. Endpoint titration of vCJD infectivity in different tissues was evaluated by two different methods: (i) the "classical" bioassay, based on the appearance of clinical symptoms and the detection of pathological prion protein in tissues of the inoculated mouse, and (ii) a shortened bioassay based on the detection of the protein in the mouse spleen at defined time points. The two methods proved equally sensitive in quantifying infectivity, even after very-low-dose inoculation of infected material, but the time schedule was shortened from ~2.5 years to ~1 year with the spleen bioassay. Compared to the "gold-standard" RIII model routinely used for endpoint titration of vCJD/BSE prions, either method improved the sensitivity by >2 orders of magnitude and allowed reevaluating the infectious titer of spleen from a vCJD individual at disease end stage to >1,000-fold-higher values. Here, we provide key reevaluation of the infectious titer of variant CJD brain and spleen tissues. The highly sensitive, accelerated spleen-based assay should thus constitute a key advance for variant CJD epidemiological and risk assessment purposes and should greatly facilitate future titration studies, including, for example, those aimed at validating decontamination procedures. The overlooked notion that the lymphoid tissue exhibits a higher capacity than the brain to replicate prions even after low-dose infection raises new questions about the molecular and/or cellular determinant(s) involved, a key issue regarding potent silent carriers of variant CJD in the lymphoid tissue.

A single-beam titration method for the quantification of open-path Fourier transform infrared spectroscopy

This study introduced a quantitative method that can be used to measure the concentration of analytes directly from a single-beam spectrum of open-path Fourier Transform Infrared Spectroscopy (OP-FTIR). The peak shapes of the analytes in a single-beam spectrum were gradually canceled (i.e., “titrated”) by dividing an aliquot of a standard transmittance spectrum with a known concentration, and the sum of the squared differential synthetic spectrum was calculated as an indicator for the end point of this titration. The quantity of a standard transmittance spectrum that is needed to reach the end point can be used to calculate the concentrations of the analytes. A NIST traceable gas standard containing six known compounds was used to compare the quantitative accuracy of both this titration method and that of a classic least square (CLS) using a closed-cell FTIR spectrum. The continuous FTIR analysis of industrial exhausting stack showed that concentration trends were consistent between the CLS and titration methods. The titration method allowed the quantification to be performed without the need of a clean single-beam background spectrum, which was beneficial for the field measurement of OP-FTIR. Persistent constituents of the atmosphere, such as NH3, CH4 and CO, were successfully quantified using the single-beam titration method with OP-FTIR data that is normally inaccurate when using the CLS method due to the lack of a suitable background spectrum. Also, the synthetic spectrum at the titration end point contained virtually no peaks of analytes, but it did contain the remaining information needed to provide an alternative means of obtaining an ideal single-beam background for OP-FTIR.

A Size‐Exclusion Nanocellulose Filter Paper for Virus Removal

This is the first time a 100% natural, unmodified nanofibrous polymer-based membrane is demonstrated capable of removing viruses solely based on the size-exclusion principle, with a log10 reduction value (LRV) ≥ 6.3 as limited by the assay lower detection limit and the feed virus titre, thereby matching the performance of industrial synthetic polymer virus removal filters.

PrP Expression Level and Sensitivity to Prion Infection

Mice overexpressing the prion protein (PrP) sequence from various host species are widely used for measuring infectious titers in prion disease. However, the impact that the transgene expression level might have on the susceptibility to infection raises some concerns about the final biological relevance of these models. Here we report that endpoint titration of a sheep scrapie isolate in sheep and in mice overexpressing the ovine PrP results in similar estimates of the infectious titer.

Quantitation of polyhexamethylene biguanide by photometric titration with Naphthol Blue Black dye

A convenient and reliable method for quantitative determination of polyhexamethylene biguanide in aqueous solutions has been developed, based on complexation of the polymer with Naphthol Blue Black dye. Spectrophotometric titration measuring absorbance at 600 nm leads to characteristic zigzag curves, with the inflexion point at dye to polymer mers molar ratio 1:2. The photometric titration endpoints are characterized with good repeatability, resulting in low variance values. As a result, the limit of polyhexamethylene biguanide determination has been found to be equal to 50 and 150 µmol/dm3 of mers for direct and reverse titration, respectively.

Penetapan Kadar Klorida pada Air Sumur di STIKes Guna Bangsa Yogyakarta Tahun 2013

Background : STIKes Guna Bangsa Yogyakarta was a health college which used well water as source of clean water for many needs, one of them use as drinking water. Contamination the source of water in STIKes Guna BangsaYogyakarta can occur cause activity of waste disposal directly into the land so that can give effect to quality of the water source well. The good water must be having four criteria or parameter. The first is physic parameter involve dissolved solid, turbidity, smell, taste, colour and temperature. Second parameter, biology parameter was involved type and contents of microorganism. Third parameter is radioactive was involved radioactive substance. The fourth there’s chemical parameter, it was involved many types of ion, dissolve oxygen or toxic compounds likes chloride. Chloride ions in the form of inorganic anion Cl- is a lot there in the water. The presence of excessive chloride in water can cause interference with the physical properties of water, disruption of metal pipes, and health problems. Lack of chloride element in body will be bring about the fall in value of the extracellular fluids osmotic and if excess, will be damage the kidney. Therefore, the writer interested to know of chloride rate in well water and choose title “Penetapan Kadar Klorida pada Air Sumur di STIKes Guna Bangsa Yogyakarta”. Examination of chloride in well water conducted to determine howlarge concentration of chloride content in well water, drinking water requirements are allowed in PerMenKes RI No. 492/MenKes/Per/IV/2010.
 Method : Chloride concentration in well water determined by Argentometry Mohr with standard solution of AgNO3 and K2CrO4 indicator, the titration end point is marked with red brick precipitation of Ag2CrO4. This research was descriptive research laboratory test. The sample in study was well water in Guna Bangsa Yogyakarta’s STIKes. Data analysis result of research done descriptively in table or graphic form.
 Result : Chloride concentration in well water of Guna Bangsa Yogyakarta’s STIKes with sample as many as 9 sample showed that accordance with PerMenKes RI 2010 were not exceed the maximum limit was 250 mg/L.
 Conclution : The sample of well water in Guna Bangsa Yogyakarta’s STIKes had chloride concentration were according with allow quality of clean water in accordance with PerMenKes RI No. 492/ Menkes/ Per/ IV/ 2010.

Evaluation of a Virucidal Quantitative Carrier Test for Surface Disinfectants

Surface disinfectants are part of broader preventive strategies preventing the transmission of bacteria, fungi and viruses in medical institutions. To evaluate their virucidal efficacy, these products must be tested with appropriate model viruses with different physico-chemical properties under conditions representing practical application in hospitals.The aim of this study was to evaluate a quantitative carrier assay. Furthermore, different putative model viruses like adenovirus type 5 (AdV-5) and different animal parvoviruses were evaluated with respect to their tenacity and practicability in laboratory handling. To evaluate the robustness of the method, some of the viruses were tested in parallel in different laboratories in a multi-center study. Different biocides, which are common active ingredients of surface disinfectants, were used in the test. After drying on stainless steel discs as the carrier, model viruses were exposed to different concentrations of three alcohols, peracetic acid (PAA) or glutaraldehyde (GDA), with a fixed exposure time of 5 minutes. Residual virus was determined after treatment by endpoint titration.All parvoviruses exhibited a similar stability with respect to GDA, while AdV-5 was more susceptible. For PAA, the porcine parvovirus was more sensitive than the other parvoviruses, and again, AdV-5 presented a higher susceptibility than the parvoviruses. All parvoviruses were resistant to alcohols, while AdV-5 was only stable when treated with 2-propanol. The analysis of the results of the multi-center study showed a high reproducibility of this test system.In conclusion, two viruses with different physico-chemical properties can be recommended as appropriate model viruses for the evaluation of the virucidal efficacy of surface disinfectants: AdV-5, which has a high clinical impact, and murine parvovirus (MVM) with the highest practicability among the parvoviruses tested.

Inhibition of spring viraemia of carp virus replication in an Epithelioma papulosum cyprini cell line by RNAi

Spring viraemia of carp virus (SVCV) is an aetiological agent of a serious disease affecting carp farms in Europe and is a member of the Rhabdoviridae family of viruses. The genome of SVCV codes for five proteins: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and RNA-dependent RNA polymerase (L). RNA-mediated interference (RNAi) by small interfering RNAs (siRNAs) is a powerful tool to inhibit gene transcription and is used to study genes important for viral replication. In previous studies regarding another member of Rhabdoviridae, siRNA inhibition of the rabies virus nucleoprotein gene provided in vitro and in vivo protection against rabies. In this study, synthetic siRNA molecules were designed to target SVCV-N and SVCV-P transcripts to inhibit SVCV replication and were tested in an epithelioma papulosum cyprini (EPC) cell line. Inhibition of gene transcription was measured by real-time quantitative reverse-transcription PCR (RT-qPCR). The efficacy of using siRNA for inhibition of viral replication was analysed by RT-qPCR measurement of a reporter gene (glycoprotein) expression and by virus endpoint titration. Inhibition of nucleoprotein and phosphoprotein gene expression by siRNA reduced SVCV replication. However, use of tandem siRNAs that target phosphoprotein and nucleoprotein worked best at reducing SVCV replication.

Novel method for determination of sodium in foods by thermometric endpoint titrimetry (TET)

A novel yet simple, rapid and robust thermometric endpoint titration (TET) method for the determination of sodium in various foodstuffs is described. Sodium reacts exothermically with aluminium in the presence of an excess of potassium and fluoride ions to form NaK2AlF6 (“elpasolite”). This reaction forms the basis of a ro- bust, reliable analytical procedure suitable for routine process control. The reaction of calcium under similar conditions (to form KCaAlF6) suggests that potentially, calcium may interfere in the determination of sodium in some foodstuffs. Results of an investigation suggest that at molar ratios [Ca]/[Na] < 0.85, an error of <1% of the measured value of sodium is incurred.

Preparation Technology of ITO Composite Oxides Nanopowder

The technological parameters on synthesis rate of ITO nanometer by chemical coprecipitation were investigated. The effects of process parameters on synthesis rate of ITO nanometer powders were discussed by the range analysis of orthogonal experiment design. The dispersion features of ITO nanometer powder by ultrasonic dispersion or without were compared. The results show that the biggest factor that affects the powder synthesis rate is the pH at the titration end-point. Powder synthesis rate increases with the increase of pH value. When pH is 9, the powder synthesis rates are all above 90%. TEM images show that ITO nanometer powders are well dispersed without obviously agglomeration when anhydrous ethanol is used as dispersant. Particles have diversity of shapes, and the particle sizes distribute widely. After Ultrasonic physical dispersion, ITO nanopowders are well dispersed with no obviously agglomeration, narrow particle sizes of 20-30 nm and the approximation spherical particle morphology.

MODELLING PH AND TITRATABLE ACIDITY IN BANANA FRUIT BASED ON ACID AND MINERAL COMPOSITION

pH and titratable acidity are important indicators of banana fruit quality, since they are involved in the perception of sourness and sweetness. To understand which chemical components drive these parameters of acidity in banana pulp, they were modelled by solving a set of equations (conservation, dissociation, and ionic balance) representing acid/base reactions. The weak acids used in the model were malic, citric, oxalic, isocitric and phosphoric acids. Mineral cations taken into account were potassium and magnesium. The mineral anion chloride was taken into account as it neutralizes cations. The pH and titratable acidity were calculated based on the known acid and mineral composition of the 46 banana samples from 17 cultivars. The model was validated by comparing observed and calculated pH. The prediction of pH and titratable acidity by taking organic acids (malic, citric, oxalic, and isocitric acids), phosphoric acids, potassium, magnesium and chloride was insufficient. Adding a weak acid at a content of 1.5 meq 100 g-1 of fresh weight in the model considerably improved the prediction. The titratable acidity was best predicted with the same input data when titration endpoint was at a pH of 6.5 rather than at a pH of 8.1. (Resume d'auteur)