DE3303400A1 - Method for producing ions from non-volatile substances by means of ultra-short current pulses - Google Patents

Abstract

The invention relates to a novel, simple method for generating ions in a pulsed manner from non-volatile substances, for analysis in propagation-time mass spectrometers by rapid energy dissipation on the solid body surface. This is carried out by means of a very short current pulse which reaches around 100 A in a few nanoseconds, which current, in one mode of the method, flows on a thin wire on which the substance which is to be excited to form ions is applied. In another mode of the method of the invention, local initiation is achieved in such a manner that the current pulse is applied to a planar sample via a wire which can be moved relative to the sample surface, and is dissipated over said sample. The current pulse is caused by rapidly switching off a high voltage via a capacitor. The sample wire can, optionally, additionally be heated via an inductively protected DC source.

Description

Process for generating ions from non-volatile substances by

Ultrashort Current Pulses Ultrashort Current Pulses The invention relates to a novel, simple process for the pulse-like generation of ions from non-volatile ones Substances for analysis in transit time mass spectrometers through rapid energy dissipation on the solid surface.

Different methods of generating ions from non-volatile Substances are known in mass spectrometry. But they are consistently very expensive, if it applies, also from thermolabile non-volatile substances, such as for example peptides, nucleotides, alkaloids, molecular ions and structure-specific To obtain fragment ions in sufficient intensity. The bombardment of the solid surface Such secondary ions are capable of using ions of different energies or atoms trigger. The same can be achieved by irradiating the light in a Q-switched manner Lasers have a similar effect. Since the light can and must be focused, a spatial resolution of a few wum is achieved on planar samples. These procedures consistently have the disadvantage that the generation of ions is very expensive.

This disadvantage is avoided by the present invention in that that the necessary coupling of energy into the solid surface area to be analyzed simply by a very short, about a few nanoseconds, strong electric Current of up to one hundred amperes is accomplished.

The invention consists of two partial inventions.

On the one hand, this new process can be used to generate ions Substance as such can be examined by applying it to the surface from a solution a wire as in Example 1, Figure 1, is spent.

This can either be done using the state of the art electrospray technique done or by simply drying the solution with a micropipette was applied. The current pulse described, which is practical because of the skin effect flowing only along the surface of the wire then causes the generation of molecular and fragment ions from the deposited substance layer. To facilitate the formation of ions in the case of very poorly volatile but not very thermally unstable substances, such as especially Inorganics, static heating of the wire is also provided as an option. Mineralogical and petrological samples can be put on the wire after pulverization be applied.

On the other hand, the high spatial resolution of planar Samples as observed, for example, in the competing LAMMA (31000 process can also be achieved with the simple method of this invention, as described in Example 2, Figure 2. In this case one investigates planar samples such as metals, semiconductors or metals with a locally more or less structured substance layer which, if thin, is not electrical needs to be conductive. Instead of the extraordinarily complex beam guidance one Laser light bundle or an ion or electron beam for precise and reproducible Determining the location of the energy transfer to the surface can be done with the method described here The current pulse is locally defined and traversed using a movable wire tip can be reproducibly brought to the location selected for ion formation.

In both cases the ions become instantaneous with the course of the current pulse educated. Time-of-flight mass spectrometry is therefore always suitable for analysis, the state of the art and available for example in the LAMMAt device on the market is. The wire or the surface adjacent to the wire tip is affected by the current pulse slightly heated. This creates a very small but up to millisecond long-lasting thermionic stream of alkali ions or also thermally producible organic ions. However, this interferes with the recording of transit time mass spectra not.

Belseiel, l In Figure 1 is an embodiment of the invention Procedure, procedure mode 1, indicated: The sample holder is one with two conductive ones Ceramic cylinder (2) (N8 mm) provided with a spacing of 5 mm on pins (1) (1 mm), for example a standard field ion emitter. There is a tungsten wire between the pins of 10 μm diameter (3), which serves as a sample carrier for the formation of ions, clamped. One of the contact pins (I) is directly earthed. The other contact pin is over a capacitor of 5 nF with the high voltage output of a fast switchable High-voltage device (4), for this purpose a Pockels cell supply device, 0 - 5 kV, serve.

Via protective inductances, a direct voltage source (5) optionally the wire (3) can be preheated. The one tapped from the high-voltage device (4) The trigger signal (6) is synchronized with the high-voltage discharge process and becomes required to control the transit time mass spectrometer, for example to control it a Biomation transient recorder for the purpose of recording the time-dependent ion current.

Example 2 In Figure 2 is an embodiment of the invention Procedure, procedure mode 2, indicated: The sample holder is on a ceramic rod (7) mounted metal block (8) that is directly earthed. Relative to this, a Tungsten wire tip (9) embedded in a ceramic holder (10) on the desired location on the sample. This wire will, as in example 1, connected to the high-voltage output via a capacitor.

Claims (5)

PATENT CLAIMS Process for generating ions from non-volatile Substances by ultrashort current pulses Claims 1. A method for generating Ions from non-volatile substances, not shown t that a large number of ions from the surface area, which is itself electrical conductive or non-conductive, an electrical conductor due to the short-term, A strong electric current flows over this conductor for nanoseconds is obtained. 2. A method for generating ions according to claim 1, d a d u r c h e k e n n n n e i n e t that as a sample carrier and conductor of the current pulse a short, thin metal wire is used. 3. A method for generating ions according to claim l, as an alternative to Claim 2, d a d u r c h g e k e n n n z e i c h n e t that as a sample carrier planar piece of metal is used and as a feed line for the electrical current pulse sharpened metal wire, whereby either the sample carrier or the wire can be moved is so that a preselected point on the sample surface through the wire tip can be touched for the purpose of ion formation from the adjacent sample area. 4. The method for generating ions according to claim I for the method modes 2 and 3, it is not shown that the necessary for ion formation ultrashort current impulses of a few nanoseconds in duration and up to 100 A amperage is achieved by briefly switching off a high voltage to which the sample conductor is capacitively coupled. 5. The method for generating ions according to claim 1 and 2, d a d u r c h e k e k e nn n n e i n e t that to facilitate the formation of ions from Optionally, the wire serving as an ion source through non-thermolahile substances an inductively protected direct current source can be heated, so that the effect of the current pulse according to claim 1 is improved.