Liquid chromatography-evaporative light-scattering detection-mass spectrometry

J.-P. Mercier, Ph. Morin, M. Dreux and A. Tambute, Liquid chromatography analysis of phosphonic acids on porous graphitic carbon stationary phase with evaporative light-scattering and mass spectrometry detection, J. Chromatogr. A, 849, 197-207 (1999). 

As a result of advances in detection technology, newer HPLC detection techniques may be utilized. For example, evaporative light-scattering detection and refractive index detection may be used to quantify impurities with poor or no UV chromophore. Conductivity detection may also be used. In some cases, when no chromophore is present, chemical derivatization may be used to add a chromophore. Increasingly, tandem techniques such as liquid chromatography mass spectrometry (LC-MS) and GC-MS are utilized for impurity characterization. The highly selective nature of LC-MS ensures that few impurities are undetected. 

Abbreviations DCM, dichloromethane DIC, 1,3-diisopropylcarbodiimide DIEA, diiso-propylethylamine DMAP, 4-dimethylaminopyridine DMF, IVJV-dimethylformamide ELSD, evaporative light scattering detection HOBt, hydroxybenzotriazole IR, infrared LC/MS, high-pressure liquid chromatography/mass spectrometry NMM, V-methylmorpho-line NMR, nuclear magnetic resonance PyBop, benzotriazol-l-yloxytripyrrolidino-phosphonium hexafluorophosphate SAR, structure-activity relationship TFP, tetrafluorophenol THF, tetrahydrofuran. 

Detection methods HPLC-DAD, HPLC with diode-array detection. HPLC-(ESI-MS), HPLC with electrospray ionization mass spectrometry. RP-HPLC, revcrsed-phase HPLC. UPLC/Q-TOFMS, UPLC with quadrupole-time of flight mass spectrometry. HPLC-APCI-MS, HPLC with atmospheric pressure chemical ionization mass spectrometry. CE-IT-MS, capillary elecliophoresis-ion-1r mass spectrometry. LC-ESI-ITMS, liquid chromatography-electrospray ionization ion trap mass spectrometry. LC-ELSD, LC with evaporative light scattering detector. DNBZ-Cl, 3,5-dinitrobenzoyl chloride. 

Any of the methods of detection used in liquid chromatography can be used in IC, though some are more useful than others. If the eluent does not affect the detector the need for a suppressor disappears. Common means of detection in IC are ultraviolet (UV) absorption, including indirect absorption electrochemical, especially amperometric and pulsed amperometric and postcolumn derivatization. Detectors atomic absorption spectrometry, chemiluminescence, fluorescence, atomic spectroscopic, refractive index, electrochemical (besides conductivity) including amperometric, coulometric, potentiometric, polaro-graphic, pulsed amperometric, inductively coupled plasma emission spectrometry, ion-selective electrode, inductively coupled plasma mass spectrometry, bulk acoustic wave sensor, and evaporative light-scattering detection. 

Characterization of a new methylated p-cyclodextrin with a low degree of substitution by matrix-assisted laser desorption mass spectrometry and liquid chromatography using evaporative light scattering detection. J. Chromatogr. A, 2005,1083, 106-112. 

Because purity determined by liquid chromatography (LC) or LC-mass spectrometry (LC-MS) with ultraviolet (UV) or evaporative light scattering detector (ELSD) detection represents only relative purity, the presence of impurities such as inorganics, materials with poor chromophores and/or good evaporative properties, and materials that tend to be retained by a guard column cannot be detected. Therefore, we measure the absolute purity of six representative compounds in each library at both optimization and production stages. 

Rocha JM, Kalo PJ, Ollilainen V, Malcata XF. Separation and identification of neutral cereal lipids by normal phase high-performance liquid chromatography, using evaporative light-scattering and electrospray mass spectrometry for detection. J Chromatogr A 2010 1217 3013-25. 

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