Analytical methods potassium hydroxide

The fermentation-derived food-grade product is sold in 50, 80, and 88% concentrations the other grades are available in 50 and 88% concentrations. The food-grade product meets the Vood Chemicals Codex III and the pharmaceutical grade meets the FCC and the United States Pharmacopoeia XK specifications (7). Other lactic acid derivatives such as salts and esters are also available in weU-estabhshed product specifications. Standard analytical methods such as titration and Hquid chromatography can be used to determine lactic acid, and other gravimetric and specific tests are used to detect impurities for the product specifications. A standard titration method neutralizes the acid with sodium hydroxide and then back-titrates the acid. An older standard quantitative method for determination of lactic acid was based on oxidation by potassium permanganate to acetaldehyde, which is absorbed in sodium bisulfite and titrated iodometricaHy. 

Analytical and Test Methods. The acid number of terephthahc acid discussed above is a titration of a sample dissolved in pyridine, using a sodium or potassium hydroxide titrant. However, specifications on certain impurities are so strict that this test caimot, as a practical matter, be failed. Its use has been discontinued by some manufacturers. 

Analytical Methods. A classical and stiU widely employed analytical method is iodimetric titration. This is suitable for determination of sodium sulfite, for example, in boiler water. Standard potassium iodate—potassium iodide solution is commonly used as the titrant with a starch or starch-substitute indicator. Sodium bisulfite occurring as an impurity in sodium sulfite can be determined by addition of hydrogen peroxide to oxidize the bisulfite to bisulfate, followed by titration with standard sodium hydroxide (279). 

Musumarra et al. [43] identified miconazole and other drugs by principal components analysis of standardized thin-layer chromatographic data in four eluent systems. The eluents, ethylacetate methanol 30% ammonium hydroxide (85 10 15), cyclohexane-toluene-diethylamine (65 25 10), ethylacetate chloroform (50 50), and acetone with the plates dipped in potassium hydroxide solution, provided a two-component model that accounts for 73% of the total variance. The scores plot allowed the restriction of the range of inquiry to a few candidates. This result is of great practical significance in analytical toxicology, especially when account is taken of the cost, the time, the analytical instrumentation and the simplicity of the calculations required by the method. 

KJELDAHL TEST. An analytical method for determination of nitrogen in certain organic compounds. It involves addition of a small amount of anhydrous potassium sulfate to the test compound, followed by healing the mixture with concentrated sulfuric acid, often with a catalyst such ns copper sulfate. As a result ammonia is formed. Alter alkaly/ing the mixture with sodium hydroxide, the ammonia is separated by distillation, collected in standard acid, and the nitrogen determined by back-iilruiion. 

Berthelot45-65 burned rhombic sulfur in oxygen in a bomb at constant volume. The amounts of sulfur dioxide along with the lesser amounts of sulfur trioxide were absorbed and determined by titration with iodine exactly equivalent to the amount of sulfur burned. In another series, Berthelot used aqueous potassium hydroxide to absorb the products of combustion, titrating afterwards with iodine. His data from the two series of experiments yield, respectively, <2=69.4 and 69.1, for the reaction, S (c, rhombic) +02 (g) =S02 (g). Ferguson1 reviewed Berthelot s data and discarded the results of his second series on the grounds of unreliability of the analytical method. 

The hydroxyl number is very important for the synthesis of polyurethane. It is defined as the number of milligrams of potassium hydroxide equivalent to the hydroxyl content of one gram of the sample. The principle of the analytical method is that the hydroxyl group is esterified with a solution of phthalic anhydride in pyridine. The excess reagent is back-titrated with standard sodium hydroxide solution, and a blank is run on the reagents to determine the amount of anhydride consumed. The phenolphthalein is an indicator for the titrate. Because the color of recycled polyol is dark brown, the faint pink endpoint is not clear, so a potentiometric titrate can be applied. 

Potassium hydroxide is a suitable eluant for the determination of inorganic anions with pJC values above 7. Due to the high pH value of the mobile phase, even weak adds are completely dissodated and, thus, may be detected via their conductivity. However, the conductivity of the analytes is lower than that of the mobile phase, so that negative signals are observed for these spedes. This method is called indirect conductivity detection. 

The method consists of separating the lead alkyls on a 10 foot X inch stainless steel column of 10% 1,2,3-tris (2-cyanoethoxy) propane (TCEP) on 80/100 Chromosorb W, hexamethyldisilazane (HMDS) treated. The scrubber section, a 6 inch x inch stainless steel column composed of 20% Carbowax 400 (saturated with silver nitrate) on 30/60 Chromosorb W pre-coated with 8% potassium hydroxide is attached between the analytical column and the detector. 

A very elegant analytical technique for the lead alkyls is that of Ballinger and Whittemore. They combined pressure programming with use of an atomic absorption spectrophotometer as a specific detector to produce a rapid, precise, and sensitive analytical technique. A 10 foot column packed with 20% 1,2,3,-tris-(cyanoethoxy)-propane on 60/80 mesh Chromosorb P coated with 1% potassium hydroxide was operated at 85°C. Flow rates were programmed from 10—00 ml/min., (Figure 159). Analysis of the five lead alkyls was completed in less than one and a half minutes. The amount of lead was determined by the absorption of the lead 2833 S. emission line. The method could detect as little as 20 nanograms of lead as lead alkyl. The application of atomic absorption spectroscopy to the determination of lead alkyls separated chromatography has also been discussed by... 

According to Comman, the principal preparation method was by the acidification of solutions of cobalt salts with acetic acid followed by addition of a concentrated potassium nitrite solution. Cobalt yellow would then slowly precipitate as a yellow crystalline mass. The alternative Hayes method involves nitric acid vapours being passed into a solution of cobalt nitrate and potassium hydroxide (or acetate). Finally, a method where solutions of sodium cobaltinitrite and a potassium salt acidified with acetic acid is used was reputedly devised by DeKoninck and published by Adie and Wood (1900 cf. Cornman) as an analytical test but subsequently used to produce pigmentary grades. 

Kang et al. [61] developed an advanced and sensitive HPLC method for the determination of omeprazole in human plasma. After omeprazole was extracted from plasma with diethylether, the organic phase was transferred to another tube and trapped back with 0.1N sodium hydroxide solution. The alkaline aqueous layer was injected into a reversed-phase C8 column. Lansoprazole was used as the internal standard. The mobile phase consisted of 30% of acetonitrile and 70% of 0.2 M potassium dihydrogen phosphate, pH 7. Recoveries of the analytes and internal... 

---