Figure 5 A typical CE-MS system. 1= High-Voltage Supply; 2= Capillary; 3= UV-vis www.selleckchem.com/products/lapatinib.html or PDA detctor; 4 = MS detctor; 5=Buffer solution; 6= PC control Separation is achieved through channels etched on the surface of the capillary (connected to an external high-voltage power supply) that delivers sample to ESIMS. This technique runs in full automation and offers high degree of sensitivity and selectivity. A new type of interface, known as coaxial sheath liquid CE-MS interface, has been developed recently, which allows the use of both LC-MS and CE-MS alternatively on the same mass spectrometer.[20] The necessary sheath liquid is delivered by a pump that floats on the ion sprayer of the MS, avoiding any current flow toward ground. LC-MS and CE-MS modes can be switched within minutes.
To obtain a stable ion spray and to avoid electrical problems, the CE power supply is used to produce the potential for the CE separation and the ESI sprayer tip simultaneously. ESIMS detection technique is generally used in most of the CE-MS systems because ESI is considered to be one of the most powerful on-line tools for the analysis of biomolecules, including natural products, providing both the molecular weight and structural characterization of analytes.[21] The optimization of the interfacing of CE with MS can be a real challenge because of the low flow rates (10�C100 mL/min) required in CE, which is achieved by a make-up liquid. APPLICATION OF HYPHENATED TECHNIQUES IN NATURAL PRODUCT ANALYSIS Rapid identification and characterization of known and new natural products directly from plant and marine sources without the necessity of isolation and purification can be achieved by various modern hyphenated techniques [Figure 6].
Techniques like HPLC coupled to NMR or electrospray ionization tandem mass spectrometry (ESI-MS-MS) have been proven to be extremely powerful tools in natural product analysis, as they permit the fast screening of crude natural product extracts or fractions for detailed information about metabolic profiles, with a minimum amount of material. The combined application of various hyphenated techniques even allows the discovery of new natural product, including complete and conclusive structure elucidation, and relative configurations prior to time-consuming and costly isolation and purification process.
Some examples of the application of hyphenated techniques in natural products analysis are discussed here. Figure 6 Summary of on-line information obtained from hyphenated techniques Isolation and analysis Dacomitinib of natural products Crude natural product extracts, which represent extremely complex mixtures of numerous compounds, can be analyzed successfully by using appropriate hyphenated techniques. Among the various hyphenated techniques, LC-PDA and LC-MS are the two most extensively used for natural product analysis.