Volumetric titrations

The moisture content of cmde sulfur is determined by the differential weight of a known sample before and after drying at about 110°C. Acid content is determined by volumetric titration with a standard base. Nonvolatile impurities or ash are determined by burning the sulfur from a known sample and igniting the residue to remove the residual carbon and other volatiles. 

Non-specific absolute assay methods, e.g. volumetric titration, can be applied to avoid the establishment of a reference substance. This is only appropriate, however, when the monograph describes a separation test for related substances. This approach is certainly valid for the determination of the content of pharmaceutical raw materials but less acceptable for the assay of content of pharmaceutical preparations where the employment of specific assay methods is recommended (ICH Guideline 1994) to take account of decomposition of the active ingredient during the shelf life of the product and to avoid possible interference from excipients. 

Titrations of carbon monoxide and hydrogen sulfide up to 800 torr were performed at 30°C each volumetric titration was composed of two adsorption isotherms the first isotherm was a combination of chemisorption and physisorption. 

In usual practice, the volumetric titrations may be accomplished either by direct titration method e.g., assay of HC1 employing NaOH as the titrant, or by residual titration method e.g., assay of ZnO in which case a known-excess-measured volume of standardised solution of H2S04, more than the actual amount chemically equivalent to ZnO, is added to the sample thereupon, the H2S04 which remain unreacted with ZnO is subsequently titrated (sometimes referred to as back titration or residual titration in the text) employing standardized NaOH solution. 

Thus, most calculations in volumetric determinations (titrimetry) are enormously facilitated by using titer values, which may be seen in the following chapters related to various categories of volumetric titrations. 

Following are the various steps that need to be observed carefully so as to achieve reasonably correct and reproducible results in the volumetric titrations ... 

Conical flasks are considered to be the most suitable vessels meant for volumetric titrations because the mixing can be performed quite rapidly, easily and safely by gently swirling the contents of the flask during the titration,... 

As a number of elements are capable of exhibiting more than one oxidation state, hence volumetric titration methods based on redox reactions are usually employed widely. 

It forms numerous salts, some of which are listed in Ref 4, p 466 L. It has been used for determination of about 40 metals and several anions (Ref 2) also used for decontamination of radioactive surfaces and removal of insol deposits of Ca Mg soaps (Ref 4). Its application in volumetric titrations is discussed in Ref 3. Accdg to Alrose Chem Co, PO Box 1294, Providence, RI, EDTA dissolves Ca oxalate and serves as a sequestrene. The term sequestration may be used for any instance in which an ion is prevented from exhibiting its usual props due to close combination with an added material (Ref 4, p 1013 L) ... 

There are two types of Karl Fisher titrations volumetric and coulometric. Volumetric titration is used to determine relatively large amounts of water (1 to 100. ig) and can be performed using the single- or two-component system. Most commercially available titrators make use of the one-component titrant, which can be purchased in two strengths 2 mg of water per milliliter of titrant and the 5 mg of water per milliliter of titrant. The choice of concentration is dependent on the amount of water in the sample and any sample size limitations. In both cases, the sample is typically dissolved in a methanol solution. The iodine/SCVpyridine (imidazole) required for the reaction is titrated into the sample solution either manually or automatically. The reaction endpoint is generally detected bivoltametrically. 

The aim of an indigo sensor is to keep the leuco-indigo concentration in the solution at a constant value. In the past, different methods were developed for detection of the indigo and sodium dithionite concentration, but up to now with limited success. The sodium dithionite concentration can be determined by volumetric titration with iodine2 22 or with K3[Fe(CN)6]23. The endpoint detection of these titrations can be done visually22,24"25 or... 

Water concentrations in liquid and solid phases were measured by the Karl Fisher method using the Karl Fisher Titrator (Mettler DL 18). Butanol and butyl butyrate were determined by gas chromatography using a 6-ft, 5% DEGS on a Chromosorb WHP, 80/10 mesh column (Hewlett Packard, Palo Alto, CA) and hexanol as internal standard. Acid consumption was monitored by volumetric titration of samples diluted in ethanol employing 0.02 M KOH alcoholic solution and phenolphthalein as pH indicator. Esterification was expressed as molar percent of consumed reactant, according to Eq. 1 ... 

Determination of Adsorbed Ceric Ion. In determining the amount of ceric ion adsorbed on the graft copolymers the volumetric titration was conducted. Here, a given excess amount of ferrous sulfate solution (0.01 N) was added into the aqueous solution of hydrolysis and then the solution was back-titrated with 0.01 IT ceric ammonium sulfate in a 1 IT sulfuric acid solution using o-phenanthroline as an indicator. In so doing the amount of ceric ion adsorbed on the grafted bamboo sample could thus be determined. 

Barrett AJ, Kennedy JC, Jones RA, Nadeau P, Pottier RH (1990) The effect of tissue and cellular pH on the selective biodistribution of porphyrin-type photochemotherapeutic agents a volumetric titration study. J Photochem Photobiol B Biol 6 309-323... 

In this chapter, we have proposed to use the acid-base properties of proteins as the transducing parameter in a biosensor. The acid-base behavior of proteins can reveal some important properties with respect to both their composition (selectivity) and their concentration (sensitivity). A change in this intrinsic parameter of the protein, when used as binding ligand, must be adequately determined. The classical method of acid-base determination is by volumetric titration. Successful application in a sensor requires another approach. Since the ion-sensitive field-effect transistor (ISFET) is suitable for fast (and local) pH detection, an 1SFET can be used for protein titration. 

The approved variations [14] in the Karl Fischer method include volumetric titration methods to either a visual (excess iodine or addition of an indicator) or volta-metric endpoint detection method. The visual or voltametric endpoint methods usually require 30-40 mg of sample for analysis for freeze-dried biological products containing from 1.0% to 3.0% residual moisture. Coulometric Karl Fischer instruments generate the iodine from potassium iodide for water titration at the electrodes. Only 10-20 mg of freeze-dried sample is required for accurate analysis. 

With ferric salts in solution either of these reagents forms the cherry red ferric thio-cyanate and is the basis of qualitative tests for iron and the use of the thio-cyanate as an indicator in volumetric titrations. Potassium thio-cyanate may be prepared by heating potassium cyanide with sulphur or ammonium sulphide. Ammonium thio-cyanate may be prepared by heating together carbon disulphide and ammonia in the presence of alcohol. 

Water in Crude Oil by Karl Fischer Volumetric Titration IP356/87 ASTM 4377-87, American Society for Testing and Materials Philadelphia, PA, 1987. 

Codeine has been estimated by volumetric titration with mercuric salts [143-5], potentiometric methods [146-7], iodimetrically [148], colorimetrically [149], as silico-tungstate [150] and in other ways [29, 42, 151-9 inc.]. 

A standard solution (or a standard titrant) is a reagent of known concentration that is used to carry out a titrimetric analysis. A titration is performed by slowly adding a standard solution from a buret or other liquid-dispensing device to a solution of the analyte until the reaction between the two is judged complete. The volume or mass of reagent needed to complete the titration is determined from the difference between the initial and final readings. A volumetric titration process is depicted in Figure 13-1. 

Weight titrations are more easily automated than are volumetric titrations. 

The principal use of dichromate is the volumetric titration of iron(II) based on the reaction... 

Currently, the most important uses of hydrodynamic voltammetry include (1) detection and determination of chemical species as they exit from chromatographic columns or a continuous-flow apparatus (2) routine determination of oxygen and certain species of biochemical interest, such as glucose, lactate, and sucrose (3) detection of end points in coulometric and volumetric titrations and (4) fundamental studies of electrochemical processes. 

Standard methods were used for chemical analyses of groundwater samples in the Geology Division Chemistry Laboratory of the Alberta Research Council. Concentrations of Ca, Mg, Na and K ions were determined by atomic absorption spectrometry. Turbidometric and volumetric titration methods were used to determine SO4" and Cl concentrations respectively. Concentrations of HCO3 and CO3 were determined by potentiometric... 

The indium concentration was determined by polarographic and colorimetric methods after previous removal of the selenium, and the thallium concentration by a volumetric titration. The attainment of a constant solubility was checked. 

It is necessary, however, to use other methods, such as atomic absorption, inductively coupled argon plasma emission spectrophotometry, and ion chromatography to determine the composition of the salts present. A method involving application of extraction and volumetric titration is also used (IP 77). 

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