Limit Tests 1,4-Dioxane

Dioxane Determine as directed under 1,4-Dioxane Limit Test, Appendix IIIB. 

Dioxane Limit Test, 757 Diphenylamine TS, 851 Diphenylcarbazone TS, 851 Diphenyl Ether, (S3)70, 98 Diphenyl Ketone, 458 Diphenyl Oxide, (S3)70 Diphenylthiocarbazone, 860 Dipotassium Monophosphate, 324, (S1 )38 Dipotassium Phosphate, 324, (S1 )38 a,a -Dipyridyl TS, 851 Disodium Dihydrogen Pyrophosphate, 350, (Sl)39, (S2)30, (S3)52 Disodium Edetate, 125 Disodium EDTA, 125 Disodium EDTA, 0.05 M, 856 Disodium Ethylenediaminetetraacetate, 125... 

Method. 0.2 ml of an ethanolic solution of hydrochloric acid (0.65 ml of concentrated hydrochloric acid per litre of absolute ethanol) is added to the dry keto steroid in a small test-tube [103,104]. 0.2 ml of a solution of DNS-hydrazine (2 mg/ml in absolute ethanol) is then added. The contents of the test-tube are heated in a bath in boiling water for 10 min for hydrazone formation. The tube is cooled and 0.2 ml of sodium pyruvate (5 mg/ ml in absolute ethanol) is added to destroy the excess of DNS-hydrazine. The tube is permitted to stand at room temperature for 15 min. 6 ml of diethyl ether and 3 ml of Q.5-N aqueous sodium hydroxide are then added and the tube is shaken. The diethyl ether layer is removed and evaporated to dryness. The residue is dissolved in a small volume of chloroform (0.2-0.5 ml) for TLC analysis. The keto steroid derivatives are separated on layers of Alumina G (Woelm) (thickness, 250 fim) which have been activated at 120 °C for 30 min. The solvent consists of dioxane-chloroform (1 9). The separated derivatives are observed under UV light at 366 nm. The limits of detection are in the 1-2 nmole range for each steroid. 

The United States Pharmacopeia (USP) test (467) describes three different approaches to measuring organic volatile impurities in pharmaceuticals. Method I uses a wide-bore coated open tubular column (G-27, 5% phenyl-95 % methylpolysiloxane) with a silica guard column deactivated with phe-nylmethyl siloxane and a flame-ionization detector. The samples are dissolved in water and about 1 p is injected. Limits are set for benzene, chloroform, 1,4-dioxane, methylene chloride, and trichloroethylene. Methods V and VI are nearly identical to method I except for varying the chromatographic conditions. For the measurement of methylene chloride in coated tablets, the headspace techniques described above are recommended. 

The mean ionic activity coefficients of hydrochloric acid in water and in dioxane-water mixtures, at an ionic strength of 0.001, together with the corresponding temperatures and dielectric constants are given below. Use the data to test the Debye-Hilckel limiting law, with particular reference to the effect of temperature and dielectric constant. 

Ref. (2)]. While a dependence of e" on solvent dipole moment or dielectric constant has been refuted for numerous experimental adsorption systems [c.g.. Ref. (7)], the belief that dielectric constant defines both solvent strength and sample adsorption energy continues to find support by many workers. The dependence of e values on solvent dielectric constant is tested in Fig. 8-13 for adsorption on alumina. There is a tendency for solvent strength to follow solvent dielectric constant, but the exceptions to this relationship are both numerous and large (e.g., dioxane, e = 0.56 and dielectric constant = 2.2, versus methylene chloride, e = 0.42 and dielectric constant = 9.1). Consequently, the dielectric constant of the solvent is quite limited in its ability to predict solvent strength. The data of Fig. 8-13 do not support any fundamental relationship between solvent strength and dielectric constant. 

System 2 involves development over 8.5 cm (20 min) with a mixture of 10.6% chloroform, 9.9% ethyl acetate, 9.0% dioxane, 70,6% hexane 0.5 acetic acid was added as a modifier. The system is an example of a mobile phase developed and optimized by the PRISMA model using the most common pigments from rhubarb as a test mixture. The system produces sharp bands, but the resolution of the components is not significantly better than in S3rstem 1. Only a limited area of the plate surface is utilized, and the system is not recommended for preparative separations. 

Dioxane 100 25 >30 5 Limited resistance Solef Solvay Polymers Specimen Solef 1008, 1010 and 1012, 2 mm thick test pieces... 

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