High‐performance liquid chromatography of some basic drugs on a n‐octadecylphosphonic acid modified magnesia‐zirconia stationary phase

Abstract

The high-performance liquid chromatographic behavior of some basic drugs was studied on a n-octadecylphosphonic acid modified magnesia-zirconia (C18PZM) stationary phase. The effect of mobile phase variables such as methanol content, ionic strength, and pH on their chromatographic behavior was investigated. The retention mechanism of basic drugs on the stationary phase was elucidated. The results indicate that both hydrophobic and cation-exchange interactions contribute to solute retention under most chromatographic conditions. The inherent Brönsted-acid sites and also the adsorbed Lewis base anionic buffer constituents on accessible ZM surface Lewis acid sites play a role in the retention of ionized solutes by cation-exchange interaction. However, especially at high mobile phase pH, the retention of basic drugs depends mainly on hydrophobic interactions between solutes and support. Separations of the basic drugs on the C18PZM phase by a predominantly reversed-phase retention mode were very promising. The mixed-mode retention feature on this phase, as a result of the adsorbed Lewis base anionic buffer constituents acting as sites for cation-exchange, could also be very useful, e.g. for enhancing the chromatographic selectivity of such analytes. The C18PZM seems to be an excellent alternative to silica-based reversed-phase stationary phase for the separation of strongly basic solutes.

Facile synthesis of magnetic mesoporous titania and its application in selective and rapid enrichment of phosphopeptides

“…The peaks at 2850 and 2930 cm −1 can be assigned to the symmetric and asymmetric stretching vibrations of −CH 2 − groups of the alkyl chains on EDTMPA [9]. Additionally, the peaks at 1230 and 951 cm −1 corresponding to the groups of P¼O and P−O−H can be also found, further verifying the existence of EDTMPA [12].…”

Simultaneous determination of pharmaceutical components in dietary supplements for weight loss by capillary electrophoresis tandem mass spectrometry

“…The matrix effects of all analytes ranged from 0.87 to 1.18, suggesting that co-eluting endogenous substances did not interfere with the ionization of the analytes. Satisfactory recoveries, Figure 1), 0.5 mg/g (4,8,12,14,15,17,20), 2.5 mg/g (5,7,11,19), 6.25 mg/g (6,9,10,18), 12.5 mg/g (1,2,3). IS concentration; 10 ng/μl.…”

“…To achieve the simultaneous determination of 20 compounds, the pH condition of BGE was optimized first. [18] There were differences in migration time between these two compounds at pH 5.0 and 8.0. At low pH, the electro-osmotic flow (EOF) was very slow, which caused prolonged migration time and peak broadening.…”

“…Mazindol has two pKa values of 2.9 and 8.6 [17] , while diazepam has a pKa value of 3.4. [18] There were differences in migration time between these two compounds at pH 5.0 and 8.0. At pH 10.0, both compounds were migrated as neutral species at the same velocity.…”

Liquid chromatographic behavior of two alanine-substituted calix[4]arene-bonded silica gel stationary phases

“…The C 18 stationary phase has been most widely used in daily liquid chromatographic analysis, but its single hydrophobic separation mechanism makes it behave badly when it comes to separating positional isomers, alkali, and ionic samples . Thus, many researchers have been devoting continuous efforts to the design and synthesis of novel functionalized stationary phases , such as charge‐transfer type stationary phases, multiple interactions mode stationary phases, host–guest inclusion stationary phases, and monolithic stationary phases for rapid analysis, etc.…”