QUANTITATIVE ANALYSIS OF VERY WEAK ACID AND BASE BY pH-FIXED TITRATION METHOD

pH-fixed titration method for the determination of weak acids and bases has been studied in this paper.It is not necessary to know the ionization constant of weak acid or base and the concentration of titrant. This method had been applied to determine phenol,4-aminoantipyrine and glycine,whose ionization constants range from 10^(-10)to 10^(-12).The results were satisfactory.

Titration Method Validation of Live Vaccines against Infectious Bursal Disease

Validating a method of analysis goes through different steps, which aims at testing the normality of measurements distribution, estimating the uncertainty of the components of a measurement （i.e., accuracy and correctness）, and finally, define the control tests of non degradation of the method performances. This paper outlines the steps for validating a biological method of analysis. It involves the construction of an experimental design, a statistical model, and the preparation of an interne laboratory reference material （pilot vaccine）. The latter is used to study the impact of deviation and variation factors, in order to, optimize the analytical method, to evaluate the bias （random error）, and to calculate the uncertainty of measurement, and make the control charts. This method is applied in the titration of live viral vaccines of Gumboro disease on chicken＇s embryos fibroblasts. The experimental results show that potential influence factors related to the titration method had no significant influence on the obtained results. Taking into account these results, an operating mode has been elaborated. The finalized method proved to be faithful to standard deviation of repeatability and reproducibility of 0.21 and 0.22, respectively, with a confidence level of 95%. The calculated uncertainty of measurement is equal to 0.2, which represents the average error level of a titer. A homogeneous stock of interne laboratory reference vaccine （MRIL）, with an average titer of 5.9 log DIT 50, was produced and the control chart set in away to provide the laboratory with an important tool of control and monitoring of the viral titers evolution in time, as well as, the mastery of the validated titration method performances.

Numerical Method for Determination of Composition of Weak Acid Mixtures by Potentiometric Titration

An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixtures were determined. The advantages of this treatment were demonstrated by analyzing binary mixtures of chloroacetic, formic and acetic acids.

Assessment of Calcimetric and Titrimetric Methods for Calcium Carbonate Estimation of Five Soil Types in Central Sudan

Despite the CaCO3 estimation using titration method was not reliable, but up to the present time, some soil laboratories in Sudan still used this method. The objective of this study was to compare and assess the results of calcimetric and titrimetric methods of quantitative estimation for soil calcium carbonate of different soils in Sudan. 26 soil samples from five soil profiles were collected from different climatological and ecological regions in central Sudan. CaCO3 equivalent was estimated using calcimeter and titration methods in order to find accurate, rapid and suitable method for soils of Sudan. The results revealed that there are no significant differences between calcimeter and titration methods for calcium carbonate estimation in all studied samples except in samples from Gedaref area. We concluded that when the Calcimeter method used for CaCO3 estimation, the differences between one person and another in detecting titration end point would be avoided, rapid and accurate results would be obtained compared to titration method. Additionally, time would be saved;fewer amounts of chemicals would be used. From this study, we highly recommend using calcimeter method for CaCO3 estimation for soils of Sudan.

Microcalorimetric Study on the Oscillating System of Two-phase Reaction of Aqueous Acid with Primary Amine in Chloroform

It has been found that the two-phase reactions of aqueous HCl, HOAc or H_3PO_4 with primary amine N_ 1923 in chloroform are oscillating reactions. Their power-time curves were measured by the titration microcalorimetric method, and the induction period (t_ in). The first oscillating period (t_ p.1) and the second oscillating period (t_ p.2) were determined. The apparent activating parameters and the orders of the oscillating systems were calculated and the following relationships were established: for the oscillating system of hydrochloric acid t_ in∝c 0.147_ HClexp(1.35×10 3T), t_ p.1∝c 0.241_ HCl· exp(4.33×10 3T), t_ p.2∝c 0.290_ HClexp(5.59×10 3T); for the oscillating system of acetic acid, t_ in∝c 0.883_ HOAcexp(2.32×10 3T), t_ p.1∝c 0.399_ HOAc· exp(4.50×10 3T), t_ p.2∝c 0.301_ HOAcexp(5.88×10 3T); for the oscillating system of phosphoric acid, t_ in∝c 1.14_ H_3PO_4exp(7.70×10 4T), t_ p.1∝c 1.42_ H_3PO_4exp(1.14×10 4T), t_ p.2∝c 1.47_ H_3PO_4exp(1.27×10 4T).

A new strategy based on acid-alkali complexation for rapidly and accurately fishing phytochemicals in Sennae Folium

Objective:There are some anthraquinones,anthraquinones and flavonones in Sennae Folium which exhibited significant acidity,such as sennoside A/B and sennoside C/D.The current strategies used in separating these components are mainly based on conventional column chromatography which is time consuming,laborious and costly.This study is aimed at exploring a method of precipitation extraction of acid components in Sennae Folium.Using alkaloid as a"hook",it is reasonable to use the principle of"acid-alkali complexation"to"fish"the acidic components in Sennae Folium.Methods:Isothermal titration calorimeter(ITC)was used to measure the extraction efficiency of different alkaloids.Then,alkaloid determined by ITC was mixed with extracting solution of Sennae Folium to form complex.High performance liquid chromatography coupled with mass spectrometry(HPLC-MS2)was used to investigate the ingredients"fished"by berberine(Ber).The mechanism of"fishing"process was explained by ITC,optical activity,fluorescence spectrometry and scanning electron microscope.Results:The ITC results proved that the choice of"hook"was particularly important in the process of"fishing".Among the hooks,the fishing efficiency of the isoquinoline alkaloids(Ber)was the highest,reaching 10.3%.Nine ingredients were detected and determined by HPLC-MS2,and the main components were sennoside A/B and sennoside C/D.Based on ITC test of Ber and sennoside A,the combination mechanism of the two ingredients was a chemical reaction with a nearly binding ratio(2:1).Fluorescence and optical properties of the active ingredients were changed after complexation.By scanning electron microscope,we found that two types of components had obviously self-assembled behavior during the formation process.Conclusion:Ber successfully"fished"the main acidic components,sennoside A/B and sennoside C/D,from Sennae Folium.Combined with different characterizations,the"fishing"process was determined as a chemical association reaction induced by electrostatic interaction orπ-πstacking.Therefore,with special identification ability,the"fishing"process had the potential of practical application.