High performance liquid chromatography-charged aerosol detection applying an inverse gradient for quantification of rhamnolipid biosurfactants.
A method using high performance liquid chromatography coupled to charged-aerosol detection (HPLC-CAD) was developed for the quantification of rhamnolipid biosurfactants. Qualitative sample composition was determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The relative quantification of different derivatives of rhamnolipids including di-rhamnolipids, mono-rhamnolipids, and their precursors 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) differed for two compared LC-MS instruments and revealed instrument dependent responses. Our here reported HPLC-CAD method provides uniform response. An inverse gradient was applied for the absolute quantification of rhamnolipid congeners to account for the detector's dependency on the solvent composition. The CAD produces a uniform response not only for the analytes but also for structurally different (nonvolatile) compounds. It was demonstrated that n-dodecyl-β-d-maltoside or deoxycholic acid can be used as alternative standards. The method of HPLC-ultra violet (UV) detection after a derivatization of rhamnolipids and HAAs to their corresponding phenacyl esters confirmed the obtained results but required additional, laborious sample preparation steps. Sensitivity determined as limit of detection and limit of quantification for four mono-rhamnolipids was in the range of 0.3-1.0 and 1.2-2.0μg/mL, respectively, for HPLC-CAD and 0.4 and 1.5μg/mL, respectively, for HPLC-UV. Linearity for HPLC-CAD was at least 0.996 (R(2)) in the calibrated range of about 1-200μg/mL. Hence, the here presented HPLC-CAD method allows absolute quantification of rhamnolipids and derivatives.
Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstr. 30, 48149 Münster, Germany.
Beate
B
Behrens
Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstr. 30, 48149 Münster, Germany.
Matthias
M
Baune
Department of Food Chemistry, Faculty of Mathematics and Natural Sciences, University of Wuppertal, Gaussstr. 20, 42119 Wuppertal, Germany.
Janek
J
Jungkeit
iAMB ⿿ Institute of Applied Microbiology, ABBt ⿿ Aachen Biology and Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
Till
T
Tiso
iAMB ⿿ Institute of Applied Microbiology, ABBt ⿿ Aachen Biology and Biotechnology, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany.
Lars M
LM
Blank
Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstr. 30, 48149 Münster, Germany. Electronic address: heiko.hayen@uni-muenster.de.
Heiko
H
Hayen
D000336:Aerosols / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000592:standards; D006017:Glycolipids / Q000032:analysis* / Q000302:isolation & purification / Q000592:standards; D057230:Limit of Detection; D012015:Reference Standards; D052616:Solid Phase Extraction; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry / Q000592:standards
D000336:Aerosols; D006017:Glycolipids; C418382:rhamnolipid
Biosurfactants; Derivatization; HPLC-UV; HPLC-charged-aerosol detection (CAD); Quantification; Rhamnolipids