Capillary electrochromatography‐mass spectrometry of cationic surfactants

Abstract

The CEC-MS of alkyltrimethylammonium (ATMA+) ions with chain lengths ranging from C1-C18 is optimized using an internally tapered column packed with mixed mode reversed phase/strong cation exchange stationary phase. A systematic study of the CEC separation parameters is conducted followed by evaluation of the ESI-MS sheath liquid and spray chamber settings. First, the optimization of CEC separation parameters are performed including the ACN concentration, triethylamine (TEA) content, buffer pH and ammonium acetate concentration. Using 90% v/v ACN with 0.04% v/v TEA as mobile phase, the separation of longer chain C6-C18-TMA+ surfactants could be achieved in 15 min. Lowering the ACN concentration to 70% v/v provided resolution of shorter chain C1, C2-TMA+ from C6-TMA+ although the total analysis time increased to 40 min. Furthermore, variation of both the ACN and TEA content as well as ionic strength has found to significantly influence the retention of longer chain surfactants as compared to shorter chains. The optimum CEC conditions are 70% v/v ACN, 0.04% v/v TEA, pH 3.0 and 15 mM ammonium acetate. Next, the optimization of the ESI-MS sheath liquid composition is conducted comparing methanol to isopropanol followed by the use of experimental design for analysis of spray chamber parameters. Overall, the developed CEC-ESI-MS method allows quantitative and sensitive monitoring of ATMA+ from < or =10 microg/mL down to 10 ng/mL. Utilizing the optimized CEC-ESI-MS protocol, the challenging analysis of commercial sample Arquad S-50 ATMA+ containing cis-trans unsaturated and saturated soyabean fatty acid derivatives is demonstrated.

Trends in CE‐MS 2005–2006

“…Moreover, most of the coupling methods applied are built-up or developed in-house and experience in the fabrication and handling is needed [36]. As has been also reviewed by Klampfl [4], developments of the interface were reported [36,37], although more papers address better solutions for the capillary fabrication such as the use of novel separation materials [38][39][40][41], improvements of the packing method [42] or alternations of the separation capillary [43].…”

“…Separations on a mixed solid phase packed in a tapered capillary by a slurry pressure procedure of cationic [41] and zwitterionic [33] surfactants have been optimized recently for a better understanding of the operation variables in CEC-MS. The parallel separation of cationic, neutral and anionic compounds on a monolithic material applying pressure-assisted electrophoresis has also been developed [40].…”

Determination of carbethopendecinium bromide in eye drops by capillary electrophoresis with capacitively coupled contactless conductivity detection

“…Analogous complex formation of septonex with different natural and modified CDs was studied and confirmed by potentiometry with ion‐selective electrodes 15. MEKC with deoxycholate pseudostationary phase 16 and CEC 17 was also proposed as an effective method for the separation of quaternary ammonium compounds.…”

Development of a fritless packed column for capillary electrochromatography–mass spectrometry

“…The analytes were 0.5 mg/mL in 50/50 ACN/H 2 O injected at 10 mbar for 5 seconds. Taking into account our earlier work with other cationic compounds [7], the CEC-MS analysis of the methylamines were done using a mobile phase of 70% ACN, 15 mM NH 4 OAc, 0.04% TEA pH 3.0 mobile phase with 15 kV applied at 25°C using mixed mode hydrophobic and cation exchange C 6 /SCX packing material (attached to 3 μm, 100 Å silica particles). The methylamines injection was done electrokinetically at 10 kV, 10 s. The sheath liquid used was 70% MeOH 10 mM NH 4 OAc with a flow rate of 7 μL/min.…”