Confirmation of the chemical formula of heat/light sensitive compounds using field desorption coupled with high-resolution mass spectrometry
MSTips No. 403
Field desorption (FD) is a soft ionization technique useful for producing molecular ions in an MS ion source. The combination of high-resolution time-of-flight mass spectrometry (HRTOFMS) and FD is useful for direct MS measurement of a sample, and provides information for identifying the chemical formula of synthetic compounds and confirming the molecular weight. Since FD-HRMS vaporizes and ionizes a sample rapidly in a vacuum, and does not use a gas chromatograph, it has advantages for measuring unstable compounds, such as those sensitive to heat and light.
The FD emitter consists of carbon whiskers on a tungsten wire, and is inserted into the ion source using a probe. After coating the emitter with a sample solution and installing the probe to MS, FD measurement is performed by turning on the high voltage in the mass spectrometer. The most common method for coating the FD emitter is using a micro-syringe. This application note reports the syringe sampling procedure, and measurement results of example compounds that are sensitive to heat and light.