Method for measuring contents of cationic surface active substances by bromothymol blue spectrometry

Abstract

The invention provides a method for measuring contents of cationic surface active substances in solid alkali metal salts, alkaline-earth metal salts or alkaline-earth metal hydroxides by a bromothymol blue spectrometry, which comprises the following steps: using nitric acid to dissolve a sample to be measured to prepare solution of alkali metal or alkaline-earth metal with ion concentration of 0.1 to 0.5 mol / L; adding bromothymol blue solution into the prepared solution, adjusting the pH of the solution to between 7.6 and 7.8 by using monosodium orthophosphate and disodium hydrogen phosphate buffer solution, allowing the solution to stand for 20 to 26 hours, and measuring the absorbency of the sample solution; after the absorbency A of the sample solution is deducted from blank absorbency Ao, forming a linear relation with the content of a complex compound formed by the reaction of the cationic surface active substances and the bromothymol blue in the sample solution; and obtaining the contents of the cationic surface active substances in the sample solution to be measured through a standard curve, and then obtaining the contents of the cationic surface active substances in the solid alkali metal and the alkaline-earth metal salts through conversion. The analysis process is simple and quick, the analysis result accuracy is high, and the repeatability is good.

Description

technical field [0001] The invention belongs to the field of chemical analysis, and relates to a method for measuring the content of cationic surface active substances in alkali metal salts, alkaline earth metal salts or alkaline earth metal hydroxides by spectrophotometry, in particular to a bromothymol blue spectrophotometric method for determination Method for cationic surfactant content in solid alkali metal salts, alkaline earth metal salts or alkaline earth metal hydroxides. Background technique [0002] In the preparation process of solid alkali metal salts, alkaline earth metal salts or alkaline earth metal hydroxides, in order to control the crystallization process, product morphology and particle size distribution, product aggregation state and surface properties, additives are often added to the preparation system, using The additives are mainly surface active substances; the obtained products often contain a certain amount of additives. In order to regulate and ...

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Problems solved by technology

Among these methods, spectrophotometry overcomes the use of toxic solvents in the extraction method, but many metal ions interfere greatly with the determination; two-phase titration is a classic analysis method, international standard ISO-2781 and national standard GB / T5174-2004 adopts the method of two-phase titration

However, the titration end point of this method is difficult to accurately judge, and the operation is cumbersome, time-consuming and laborious. The reagents used are highly toxic and the indicator is expensive.

[0004] In the solid alkali metal salt, alkaline earth metal salt or alkaline earth metal hydroxide, and the determination of cationic surface active substance content in alkali metal, alkaline earth metal ion solution, due to Due to the limitation of salt concentration and the influence of interfering ions, the existing analytical methods cannot be used. At present, there is no mature spectrophotometric method suitable for the content of cationic surface active substances in solid alkali metals, alkaline earth metal salts or hydroxides of alkaline earth metals. Determination of

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