The combination of HPLC and MS can be used as an offline technique, that is, fractions are collected and then a mass spectrum of each obtained. Much greater sensitivity, however, may be achieved by having an online interface, but this is much more difficult to achieve than with GC. The vapour flow in HPLC is much greater than in GC and there may be problems with electrical breakdown in high voltage instruments. HPLC may be operated in either normal or reversed-phase modes and the mobile-phase composition may be either isocratic or gradient. Different-sized columns are available (analytical, microbore and capillary), leading to a wide range of operational flow rates. The various possible configurations complicate the interfacing to MS.

The development of LC-MS has a history of more than 20 years and many interfaces have been reported, although only a small number have become commercially successful. Each method has its advantages and disadvantages (i.e. there is no universal interface). All facilitate the transition of analyte from solution into the gas phase with either simultaneous or sequential ionization. Those interfaces that have stood the test of time and are (or have been)

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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