Assay by non-aqueous titrations

Neutralization with KOH in aqueous THF gave the desired poly(styrene-b-potassium methacrylate) (S-b-MA.K). The carbonyl band in the IR spectrum is replaced with a strong, broad carboxylate absorption centered near 1566 cm 1 (Figure 2c). The carboxylate and potassium contents were assayed by non-aqueous titration and ICP, respectively. The resulting values of 0.91 meq COj /g and 0.98 meq K/g indicate essentially quantitative conversion to the potassium methacrylate. S-b-MA.K obtained in this manner is easily dissolved in solvents such as THF and dichloromethane, in contrast to the... 

Pyridoxine, HC1 has been assayed by non-aqueous titrations, using 0.1 N perchloric acid in the presence of mercuric acetate and crystal violet indicator (4,6, 10, 87). 

Triamterene is assayed by non-aqueous titration. 7 The method used is as follows. Transfer about 0.5 g of triamterene, accurately weighed, to a 400 mL beaker, and dissolve in 250 mL of a solvent previously prepared by mixing, in the order named and with cooling prior to use, 1 volume of formic acid, 1 volume of acetic anhydride, and 2 volumes of... 

The substance can be assayed by non-aqueous titration (p. 792) and forms an insoluble compound with ammonium reineckate. 

The assay of the alkaloidal base in this salt follows the conventional lines of extraction with chloroform from ammoniacal solution and titration of the dried alkaloid using methyl red as indicator. 1 ml 0 05N acid = 0 01781 g CieHgjOaNjHBr. It can be assayed by non-aqueous titration (p. 792) using 0 5 g. 1 ml 0 1 N perchloric acid — 0 03563 g. Homatropine methylbromide, Ci7H2403NBr, Mol. Wt. 370 3 can also be assayed by this method. 1 ml 0 1 N perchloric acid == 0 03703 g. 

Assayed by non-aqueous titration with 0-lN perchloric acid in the presence of mercuric acetate (see p. 792). 1 ml 0-lN perchloric acid = 0-02477 g. 

Papaverine hydrochloride, C2oH2i04N,HCl, Mol. Wt. 375-9 and papaverine sulphate, (C2oH2i04N)2,H2S04,5H20, Mol. Wt. 867-0, can be assayed by non-aqueous titration (see p. 792) the base may be also extracted by chloroform or carbon tetrachloride from alkaline solution and weighed after drying at 105 1 g residue - 1-107 g of C2oH2i04N,HCl, 1-144 g of... 

Little analytical chemistry has been applied to these compounds. The bases can be extracted with solvent and titrated with standard acid. They can also be assayed by non-aqueous titration after extraction (see p. 792). 

A number of compounds of similar pharmacological action are available. They are all assayed by non-aqueous titration with perchloric acid (see p. 792) although their injections are determined gravimetrically as reineckates (or from the iodide content in the case of gallamine triethiodide injection). 

Assays of various pharmaceutical substances either in pure form or in dosage form may be assayed successfully by non-aqueous titrations. For the sake of convenience these typical titrations can be categorized into two broad groups, namely ... 

How would your assay Niclosamide and Chlorthalidone using tetrabutyl-ammonium hydroxide either potentiometrically or titrimetrically by non-aqueous titrations. 

Numerous assay procedures for phenytoin in pharmaceutical preparations have been devised, based on the separation of phenytoin from phenobarbital by ion exchange chromatography or solvent extraction procedure, followed by non-aqueous titration.4 ... 

Codeine is extracted from alkaline solution by chloroform and assay of its salt and galenicals is effected by normal alkaloidal extraction technique. Codeine phosphate, Ci8H2i03N,H3P04,l H20, Mol. Wt. 424-4, is official in the5.P., but the U.S.P, salt is a hemihydrate, Mol. Wt. 406-4, and this is the more usual commercial product. It may be determined by non-aqueous titration (see p. 792). 1 ml 0-1N perchloric acid = 0-03974 g Ci8H2i03N,H3P04 or 0 02994 g C,3H2i03N. 

The base is assayed by solution in excess of standard acid and back-titration of the excess with bromocresol green as indicator, 1 ml 0-01N = 0-01992 g C23H30O4N2. It can also be determined by non-aqueous titration (p. 792). 

Levallorphan tartrate, Ci9H250N,C4Hg0e, Mol. Wt. 433-5, is assayed in the B.P.C. by non-aqueous titration of the extracted base ... 

The official methods are not consistent. In the B.P. about 0 2 g is dissolved in 40 ml of dimethylformamide and titrated with OTN lithium methoxide using quinaldine red as indicator precautions are taken against the effect of carbon dioxide and a blank is determined with the lithium methoxide. The B.P.C. uses considerably less solvent, 15 ml, for about 0 4 g of substance, thus providing a more suitable titration volume, but requires no protection against carbon dioxide. The latter conditions are in keeping with the findings of Ryan et al Prior neutralisation of the titration system as given under the Appendix on non-aqueous titration should always be carried out. However, in our opinion, the conditions for titration of barbitones by non-aqueous methods are so critical that as an assay for determination of purity they are not justified. 

Pethidine hydrochloride can be determined by direct non-aqueous titration and is assayed in the U.S.P, by this method. 

The official sulphonamides are all derivatives of sulphanilamide and the assay for all members of the group by diazotisation follows that of the parent substance either directly or after preliminary hydrolysis or reduction (para-nitrosulphathiazole) except for sulphafurazole and sulphafurazole diethanolamine. Sulphafurazole cannot be diazotised quantitatively since the product consumes more than one equivalent of nitrous acid. Non-aqueous titration can also be applied. 

Nakazawa and Tanaka described a potentiometric titration of salts of organic bases in non-aqueous solvents with the addition of bismuth nitrate [16], The base halide or hydrohalide (0.7 mequiv.) is dissolved in 40 mL of anhydrous acetic acid, and then 40 mL of 1,4-dioxane and 2.5 mL of 5% Bi(N03)3 solution in acetic acid are added. The Bi(N03)3 prevents interference by the halide. The solution is titrated to a potentiometric endpoint with 0.1 M HC104 (a blank titration is also carried out). Results of purity assays of acetylcholine chloride and other compounds were tabulated, and it was found that the coefficient of variation was 0.18%. 

The non-aqueous potentiometric titration of amine hydrochloride salts, introduced by Pifer-Wollish and used in the assay of various phenothiazine derivatives can be applied to the determination of propiomazine hydrochloride. The procedure involves initial reaction of the amine hydrochloride group with mercuric acetate in an acetic acid medium. The halide is tied up as undissociated HgClg and the acetate ion liberated can be titrated as a base with perchloric acid, hercuric acetate is essentially undissociated in acetic acid and the excess, therefore, does not interfere. 

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