Sulfonic acids identification

Principle. By means of potentiometric titration (in nonaqueous media) of a blend of sulfonic and sulfuric acids, it is possible to split the neutralization points corresponding to the first proton of sulfuric acid plus that of sulfonic acid, and to the second proton of sulfuric acid. The first derivate of the titration curve allows identification of the second points the corresponding difference in the volume of titrating agent is used as a starting point in the calculation method (Fig. 4). 

This ESI(+) TIC, however, is dominated by strong and broad signals that eluted between 17 and 31 min, neither observable under APCI(+/—) nor ESI(-) conditions. Even under gradient RP-C18 conditions a strong tailing effect was observed while isocratic RP-C18 failed. The information obtained by ESI—LC—MS(+) was that the compounds could be ionised in the form of [M]+ ions at m/z 230, 258 and 286. ESI-LC-MS-MS(+) resulted in product ion spectra which, by means of a MS-MS library, were found to be characteristic for the amphoteric amine oxide surfactants. These compounds not yet observed in household formulations will be presented later on with the RIC of LC separation (cf. Fig. 2.5.11(d)). After identification as amine oxides, the separation and detection of this compound mixture now could be achieved by an isocratic elution using a PLRP-column and methane sulfonic acid and ESI(+) ionisation with the result of sharp signals (RT = 4-6 min) as presented in Fig. 2.5.11(d). 

In a study aimed at the identification of products of free radical reactions with polystyrene- and aromatic-based PEMs using model compounds, Hiibner and Roduner observed the addition of free radicals to the aromatic rings, preferentially in the ortho position to alkyl- and RO-substituents (in polystyrene- and aromatic-based PEMs, the para position is blocked by the presence of the sulfonic acid group). This study demonstrated the combined ortho-activation by these substituents and the meta-directing effect... 

For the analytical characterization of sulfated tyrosine peptides, spectroscopic methods as well as amino acid analysis and, more recently, mass spectrometry are employed. In Table 2 the spectroscopic data of tyrosine 0-sulfate are compared to those of the related sulfonic acid derivatives as possible byproducts in the chemical sulfation of the tyrosine or tyrosine peptides.[361 In the course of the synthesis of tyrosine 0-sulfate peptides and, particularly in the final deprotection step, desulfation may occur which limits the characterization of the final compounds in terms of quantitative identification of the tyrosine 0-sulfate. This is achieved by amino acid analyses of basic hydrolysates of the sulfated tyrosine peptides or preferably by analyses of the enzymatic hydrolysates with aminopeptidase M or leucine-aminopeptidase. 

The more advanced instrumental methods of analysis, including GC, for the detection and identification of expls are presented (Ref 90) Pyrolysis of expls in tandem with GC/MS was used for the identification of contaminant expls in the environment (Ref 108). Isomer vapor impurities of TNT were characterized by GC-electron capture detector and mass spectrometry (Ref 61). Volatile impurities in TNT and Comp B were analyzed using a GC/MS the GC was equipped with electron capture and flame ionization detectors (Ref 79). The vapors evolved from mines, TNT, acetone, toluene, cyclohexanone and an organosilicon, were analyzed by GC/MS (Ref 78). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-dinitrotoluene, 3- and 4-sulfonic acids (Ref 124). Various reports were surveyed to determine which methods, including GC/MS, are potential candidates for detection of traces of TNT vapors emitted from land mines factors influencing transportability of TNT vapors thru soil to soil/air interface are dis-... 

Suter et al. [73] developed an LC-MS method based on the in-source CID of the aromatic sulfonates a loss of SOj and the formation of the radical ion are observed. Absolute detection limits were 1 ng, similar to UV detection. Unlike UV detection, LC-MS provides a similar response for benzene and naphthalene sulfonates. The method was applied to landfill leachates, and allowed the identification of an unknown aromatic sulfonic acid. 

The identification of the sulfonic acid and sulfonate IR bands is complicated by the fact that there are a number of polystyrene absorbances in the same region in which these absorbances occur. Therefore, band assignments were made not only on the basis of new absorbances, but also from changes in the intensity and breadth of previously existing bands. For example, the band at 1176 cm. in the H-SPS is more intense than the absorbance band at 1182 cm" in polystyrene. Therefore, the peak at 1176 cm- may be the result of contributions from the symmetric stretch of two S 0 bonds and the original absorbance from the polystyrene. Similarly, the absorbance at 907 cm in the U-SPS is much broader than that in polystyrene and may include contributions from an Sj-p bond. New absorbance bands appear at 1125 cm-1 and 1102 cm, which indicate that the benzene ring is disubstituted. The absorbance band at 838 cm indicates that the sample is sulfonated in the para position of the benzene ring. 

Arenesulfonic acids and organic bases often form salts that crystallize readily and have sharp melting points, so that these can be used for identification of the acid.117 Forster and Keyworth,118 for example, describe a process for separating the different naphthalenesulfonic acids by way of their ary-lamine salts. Benzidine and bianisidine salts are also mostly sparingly soluble and can be used for separation and quantitative determination of sulfonic acid mixtures.119... 

Aryl arenesulfonates mostly crystallize readily and are useful for identification of phenols or sulfonic acids they are easily obtained from the acid chlorides and phenols in the presence of alkali689 or a tertiary base690 by the Schotten-Baumann procedure. 

Thallium salts of sulfonic acids also have sharp melting points and have been utilized for identification of sulfonic acids for a long time5. The reactions are illustrated in equations 1-3 and several examples are shown in Table 1. 

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