Alkylbenzyl-dimethyl-ammonium

The main difficulties in CE analysis of cationic surfactants arise from their strong adsorption to the capillary wall and their ability to form micelles at low concentrations. The addition of organic modifiers in high amounts or separation in absolutely non-aqueous media disrupt micelle formation within the sample and also effectiveness of the organic modifier to disrupt micelles of alkylbenzyl dimethyl ammonium... 

An improved specificity was observed when FIA-MS-MS in product or parent ion mode was used to perform quantification of the surfactants in the methanolic mixtures. The ions selected for quantitation in product or parent ion mode were C13-AE m/z 71, 85, 99, 113, and 127 from alkyl chain together with 89, 133, and 177 from PEG chain generated from parent ions m/z 394, 526, 658, 790 and 922 alkylbenzyl dimethyl ammonium quat m/z 91 and 58 generated from parent ion m/z 214 FADA m/z 88, 106 and 227 generated from parent ions m/z 232, 260, 288, 316, 344 and 372 while the alkylamido betaine was quantified generating the parent ion m/z 343 obtained from product ion at m/z 240. 

Figure 10.195 Determination of alkylbenzyl-dimethyl-ammonium compounds in a toilet cleaner. Separator column lonPac NS1, 10 pm eluent 8mmol/L HCI/MeCN gradient linear, 0% to 90% MeCN in 15 min flow rate 1 mlV min detection (a) UV (205 nm) and (b)...

As an example of cationic surfactant analysis in finished products. Fig. 9-125 shows the separation of alkylbenzyl-dimethyl-ammonium compounds in a toilet cleaner. As can be seen from the respective chromatogram, this raw material basically consists of two species, the C12- and the Ci4-component. Thus, chromatographic separation is much simpler than shown above for alkyl sulfonates. Because these long-chain quaternary ammonium compounds exhibit a marked hydrophobicity, surface-inactive hydrochloric acid is used as an ion-pair reagent. 

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