Dioxane test sample

Procedure Place the vial containing the 1,4-Dioxane Standard Preparation in the automated sampler, and start the operating sequence so that each vial is heated at 90° for a minimum of 30 min. Using appropriate headspace sampler settings, inject the 1,4-Dioxane Standard Preparation, and measure the peak area for 1,4-dioxanc. Similarly, place the vial containing the Test Preparation in the automatic sampler, obtain a chromatogram as done for the 1,4-Dioxane Standard Preparation, and measure the peak area for 1,4-dioxane. The sample passes the test if the peak area of the Test Preparation is not greater than that of the 1,4-Dioxane Standard Preparation. 

Lineshape and resolution tests on other nuclei follow a similar procedure to that above. Not all nuclei available with a given probe need be tested and typically only tests for inner and outer coil observations on multinuclear probes are required. This means the second test will often involve carbon-13 for which two samples are in widespread use the ASTM (American Society for Testing and Materials) test sample (40% p-dioxane in deuterobenzene also used for the sensitivity test) or 80% benzene in deuteroacetone. In either case on-resonance continuous-wave (CW) decoupling of protons should be used as this provides improved results for a single resonance relative to broadband decoupling. Rather long (30-40 s) acquisition times will be required for a well shimmed system. 

The course of the fermentation is tested by removal of samples, which are extracted with methyl isobutyl ketone. The extract is analyzed by paper chromatography in a system of dioxane toluene/propylene glycol. 

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. 

Iodoform test. Place 5 drops of each sample into separate clean, dry test tubes (150 X 18 mm). Add to each test tube 2mL of water. If the compound is not soluble, add dioxane (dropwise) until the solution is homogeneous. Add to each test tube (dropwise) 2mL of 6 M NaOH tap the test tube with your finger to mix. The mixture is warmed in a 60°C water bath, and the prepared solution of I2-KI test reagent is added dropwise (with shaking) until the solution becomes brown (approximately 25 drops). 

Test Preparation Transfer 5.0 g of sample, accurately weighed, into a 22-mL pressure headspace vial, and seal the cap and crimp as directed for the 1,4-Dioxane Standard Preparation. 

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. 

A simple test for free epoxy groups, either in epoxy monomers or in only partially reacted resins, is the reaction with 2.4-dinitrobenzene sulfonic acid. In the presence of piperazine, the resulting ester gives an intensive yellow coloration. For this test, about 0.5 g of the sample is dissolved in a few ml of dioxane, and then a 1 % solution of 2.4-dinitrobenzene sulfonic acid in dioxane is added. After about 1 hr, add a 1 % solution of piperazine in dioxane. The yellow color is specific for free epoxy groups. 

Dioxane can form shock- and heat-sensitive peroxides that may explode on concentration by distillation or evaporation. Samples of this substance should always be tested for the presence of peroxides before distilling or allowing to evaporate. Dioxane should never be distilled to dryness. 

Procedure To the sample (100 mg) dissolved in 1 ml of water (insoluble substances should be dissolved in methaaol or dioxane) are added 3 ml of 10% NaOH and then, dropwise, a 10% iodine solution in 20% aqueous potassium iodide until it is in excess. The test tube is then immersed in water at 60 °C. Additional iodine solution is added until its color persists for 2 min followed by dropwise addition of alkali until the brown color fades. The test tube is taken out of the water bath and 10 ml of water are added to it. Iodoform separates as a yellow solid of characteristic odor, the melting point of which is 120 °C. If the separated iodoform is not lemon-yellow, it is separated by filtration, suspended in 2 —3 ml of dioxane, and shaken with 1 ml of 10% NaOH. 

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