Separation of Harmala Alkaloids by CZE: Optimization, Calculation of Analytical Figures and Method Transfer between Different CE Instruments

MARCOS TASCÓN; NORA VIZIOLI; FERNANDO J. BENAVENTE MORENO; LEONARDO G. GAGLIARDI

Ciudad Autonoma de Buenos Aires

Simposio; 18th Latin-American Symposium on Biotechnology, Biomedical, Biopharmaceutical and Industrial Applications of Capillary Electrophoresis and Microchip Technology (LACE 2012); 2012

LACE Scientiffic Comitee

P { margin-bottom: 0.21cm; direction: ltr; color: rgb(0, 0, 0); text-align: left; widows: 2; orphans: 2; }P.western { font-family: "Times New Roman",serif; font-size: 12pt; }P.cjk { font-family: "Times New Roman",serif; font-size: 12pt; }P.ctl { font-family: "Times New Roman",serif; font-size: 12pt; } There have been many attempts to improve the limits of detection (LOD) of CE methods. On-line concentration based on solid phase extraction have been carried out since many years with excellent results [1,2]. However, the use of temperature to further improve SPE-CE systems has not been investigated. This approach can be explored easily with commercial instruments. Since the microcartridge SPE is placed near the inlet end of the separation capillary but within the cassette is possible to scan the temperatures of the loading and elution using just the internal temperature control of the cassette [1,2]. However, the use of localized thermostatting systems provide better results and allow to study wider temperature ranges than the using the internal standard control of the instruments. The aim of this work was to investigate the influence of temperature on SPE-CE using microcartridges packed with commercial C18 stationary phases and opioid peptides as model compounds. Opioid peptides are a group of neuropeptides of biomedical interest, which are usually present in biological fluids at extremely low concentrations, typically subnanomolar. Firstly, we had evaluated the thermal stability of these analytes to 95 ° C. Secondly, we have studied the effect of changing temperature from 25 to 60° C, on the sample loading, on elution and on the separation using the internal thermostatting of the commercial instrument. Therefore, we designed a “micro”-water bath to control the microcartridge temperature at any value between 0 and 100° C. We found several uncompatibilities of materials for the microcartridges assemblies with the high temperatures. After many trials and as a result of the introduction of several changes we achieved a robust system which was used with excellent results. In order to normalize the sample volumes introduced hydrodynamically at the different temperatures into the SPE-CE microcartridges proper corrections have been made considering, basically, the change in viscosity with temperature. The increase of temperature causes an unexpected variety of effects depending on the analyte properties. In most of the cases to increase the microcartridge temperature during the sample loading improve significantly the LOD. This demonstrates the potential of the temperature to further improve sensitivity in SPE-EC.