Pressurized liquid extraction–capillary electrophoresis–mass spectrometry for the analysis of polar antioxidants in rosemary extracts

A method based on capillary electrophoresis–electrospray–mass spectrometry (CE–ESI–MS) was developed to qualitatively characterize natural antioxidants from rosemary (Rosmarinus officinalis L.) in different fractions obtained by pressurized liquid extraction (PLE) using subcritical water. The parameters of CE–ESI–MS were adjusted allowing the separation and characterization of different compounds from rosemary in the PLE fractions. These parameters for CE are kind, pH and concentration of the separation buffer, parameters for ESI–MS are dry gas temperature and flow, nebulizing gas pressure, and make-up flow. The following analytical conditions were found most favorable: aqueous CE buffer (40mM ammonium acetate/ammonium hydroxide, pH 9); sheath liquid containing 2-propanol–water (60:40, v/v) and 0.1% (v/v) triethylamine at a flow rate of 0.24 mL/h; drying gas flow rate equal to 7 L/min at 350 ◦C, nebulizing gas pressure of 13.8 kPa (2 psi), using a compound stability of 50%. Different antioxidant compounds (e.g., rosmarinic acid and carnosic acid) could be detected in the rosemary extracts by CE–ESI–MS without any additional treatment, enabling the determination of variations in the extract composition caused by the different PLE conditions (i.e., 60 and 100 ◦C). The results provide complementary information to HPLC analysis.The authors would like to thank Dr. Gerard Bruin and Novartis Pharma AG (Basel, Switzerland) for the gift of the P/ACE 5500 instrument used in this work. Financial support from a bilateral project Spanish MCYT-University of Vienna (HU2002-0042) and a CICYT-AGL2002-04621- C02-02 Project is acknowledged. M.H. thanks MCYT for an FPI Grant. The grant for B.G. from ERASMUS is acknowledged.Peer reviewe