A laser microprobe mass spectrometer (LMMS), also laser microprobe mass analyzer (LAMMA), laser ionization mass spectrometer (LIMS), or laser ionization mass analyzer (LIMA) is a

mass spectrometer Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...

that uses a focused

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

for

microanalysis Microanalysis is the chemical identification and quantitative analysis of very small amounts of chemical substances (generally less than 10 mg or 1 ml) or very small surfaces of material (generally less than 1 cm2). One of the pioneer ...

. It employs local ionization by a pulsed laser and subsequent mass analysis of the generated ions.

Methods

In laser microprobe mass analysis, a highly focused laser beam is pulsed on a micro sample usually with a volume of approximately 1 microliter. The resulting

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s generated by this laser are then analyzed with

time-of-flight mass spectrometry Time-of-flight mass spectrometry (TOFMS) is a method of mass spectrometry in which an ion's mass-to-charge ratio is determined by a time of flight measurement. Ions are accelerated by an electric field of known strength. This acceleration result ...

to give composition, concentration, and in the case of

organic molecule In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ...

s structural information. Unlike other methods of microprobe analysis which involve ions or electrons, the LMMS microproble fires an

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

pulse in order to create ions.

Advantages

LMMS is relatively simple to operate compared to other methods. Furthermore, its strengths include its ability to analyze biological materials to detect certain compounds (such as metals or organic materials).

Sample preparation

LAMMA is particular about the sample which is used. The sample must be small and thin. Ionization of too much material results in a large

microplasma A microplasma is a plasma of small dimensions, ranging from tens to thousands of micrometers. Microplasmas can be generated at a variety of temperatures and pressures, existing as either thermal or non-thermal plasmas. Non-thermal microplasmas that ...

whose time spread and ion energy distribution entering the mass spectrometer can result in undesired peak deformation.

References

{{reflist Mass spectrometry Scientific techniques

Methods

Advantages

Sample preparation

See also

References