DE2205713A1 - DOUBLE ION BEAM METHOD FOR QUANTITATIVE (ABSOLUTE) MASS SPECTROMETRIC MEASUREMENTS - Google Patents

Description

Double ion beam method for quantitative (absolute) mass spectrometry see measurements There are already several methods and mass spectrometric devices known who work with two ion beams, a * a., in which two Ion beams are sent through the same analyzer system or systems, wherein the ion beams are generated in the same or in two separate ion sources will.

The main advantages of the already known 2-twin-jet process or The two-jet process in general consists of getting an unknown Can examine substance with a known substance at the same time and. so much easy identification of the unknown substance or the individual components direct comparison with the components of the known substance (reference substance or Standard) is possible.

Above all, this can be done relatively easily and nevertheless precise statements about the mass numbers of the unknown components (peaks) be made by taking as reference substances substances for which the situation the individual components are exactly known - such as

Perfluoro kerosene et al.

It is also possible to use the double ion beam method to investigate the same substance (sample) under two different conditions at the same time and thus to hold on to the relief much more strikingly.

A major disadvantage of the double ion beam methods known up to now It is, however, that a direct and quantitative comparison of the components of the Sample with one or more components of the reference substance only with the help of Computers, with relatively great effort and only with precise knowledge of the inflow volume or the pressure of both the sample and the reference substance is possible.

The subject of this invention is a double ion beam process, This allows, among other things, quantitative comparisons between Components of the reference substance and components of the unknown substance must be stirred. At the same time, the process allows very quick comparative analyzes to be carried out, as for quantitative statements in many cases, especially when using Eichlecke or precisely known reference substances, the knowledge of the inflow quantity or the pressure of the sample is not absolutely necessary.

The generation of the two ion beams (sample and P. eSerence) can also in this process similar to the double ion beam processes known up to now, i.e., in one or two separate ion sources and is similar to known methods are sent through the same analyzer system at the same time.

Of the two ion beams (sample and reference), the respective Ion spectra (after the analyzer system) simultaneously - e.g. in the same way as with the already known Doppelauffängerverfahren- with the help of appropriate Panel systems Separated two masses each, namely a so-called Secondary ion, which are chosen so (large peaks) that they can also be used with less sensitive Detection methods (e.g. direct ion current measurement) can be recorded.

From the ion spectrum of the sample is a so-called second mass. Main ion (possibly also several main ions) separated.

In some cases, e.g. for isotope analyzes or routine measurements where the sample and standard are the same substance, the spectrum of the Reference substance a main ion (or several main ions) separated. The main ion or the main ions can be measured with highly sensitive detection methods.

But while the ion beam of the reference substance (standard) according to known Procedure -S.B. in the case of electron impact ion sources through emission stabilization (stabilization electron emission through appropriate regulation of the heating) or through regulation the ionization according to the total ion flow (keeping the total ion flow constant by regulating the heating) - is kept constant, the Keeping the ion beam of the sample material (sample) constant in the sense of the present Invention not according to the above methods, but the ionization of the ion source - with the help of a control voltage, formed by comparing the measured values of the two secondary ions so - ###### regulated that the measured values of the two secondary ions au automatically become the same size.

This makes a direct and absolute comparison of the two main ions or the main ions of the sample and the secondary ions of the standard with little effort easily possible.

However, it is possible to keep the ion beam of the sample material constant within the meaning of the present invention are also carried out so that in each case the Sunme of two or more components from the standard with the sum of two or several components from the sample remains the same size.

This procedure is especially useful for some isotope examinations of interest.

More details as well as some advantages of the procedure can also be found can be seen from some possible applications of the method.

1. Use of the double ion beam method to measure isotope ratios The sample (ion source I and ion beam I) is made with a standard which is the same Contains isotopes (ion source II, ion beam II), the frequent isotopes are secreted as secondary ions, compared electronically and automatically brought to the same size.

The rare isotopes of the sample and the standard are separated separated from the respective ion spectrum and measured individually.

The calculation can take into account the necessary corrections can be made directly from the measured values of the rare isotopes. The evaluation can easily be done with a microcomputer.

Further advantages of the new process compared to the conventional one Isotope measuring methods, such as double gas inlet methods, are that the measuring process can be carried out in a much shorter time, the memory ect (caused by staying of sample or standard gas residues in the apparatus) is much smaller, the drifts the Electronics can be partially compensated by the comparison measurements becomes, due to the electronic equality of the common isotopes, a far higher Measurement accuracy can be achieved and absolute quantitative statements are possible are.

2. Comparative measurement of any two samples of the same composition The test and standard louen rays contain the same components, their composition and concentration (size) is precisely known for the standard, while for the sample, similar to application 1, the size (concentration, partial pressure) by comparison can be determined with the standard.

In contrast to application 1, however, there is the option of not Compare only two components at a time, but any number of components.

For this purpose, the measuring process is carried out in two phases: In the first Phase are any two but identical components from sample and standard as Additional ions selected and set (possibly preprogrammed by mass preselection systems) and by the control method which is the subject of this invention they are regulated to be the same size, creating a direct size relationship between all components of the sample and standard is specified.

In the second measurement phase, the entire spectrum or a part of the spectrum is run through and the individual components are evaluated as under 1 or only the desired components are selected (possibly automatically by mass preselection) and measured.

Do you make or do several measurements of the same sample Measurements over a longer period of time, it is sufficient to take the first measurement phase of time to repeat time as a control. This procedure could be special be suitable for performing quantitative routine analyzes, for quality control analyzes and to process controls and process controls - from chemical industries.

3. Quantitative comparative measurements between a sample and a Reference substance (or from any two samples) of unequal composition As a reference substance a suitable reference substance (standard) is used for which the concentration or the partial pressure of at least one component is precisely known (e.g. also Standard leak) and which serves as a secondary ion.

Any component of the unknown sample is used as a minor ion, which corresponds approximately to the size of the secondary ion of the standard, selected and adjusted. The setting of the secondary ions can also be carried out in the presence of a mass of va'nl be carried out automatically.

In the first measurement phase, the two secondary ions are equated by changing the ionization of the second ion source (the sample), whereby the component of the sample selected as the secondary ion is known quantitatively.

In the second measurement phase, as in 2., the whole is done as required Spectrum or a part of the spectrum examined or

desired components set and measured. The lettere can if a mass preselection is available, this can also be done automatically by pre-programming.

The quantified size of the component chosen as the minor ion of the unknown sample can be used as a comparison factor to determine all or the quantitatively calculate the desired components of the sample.

9 If the size of the secondary ion is preprogrammed (from sample or from Standard) in a microcomputer, the evaluation can also be carried out with minimal resources be carried out automatically.

4. Mass marking, pet matching and mass preselection Using the double ion beam method mass marking and peak matching is easy to carry out or

to check or to recalibrate.

For example, based on the mass position of the secondary ion from the standard the mass position of the secondary ion from the sample or the mass positions of all components of the sample or calculated automatically.

The peak matching can also be checked with the standard secondary ion will.

With automatic control and calibration of the mass marking and the peak-matching, the correction factor can be used at the same time as the comparison factor from Ancillary ion (for the quantitative evaluation of the individual components) is given in the computer will.

With the help of the secondary ion there is also a slight check of the accuracy and reproducibility of the mass preselection possible.

The technical execution of the process as well as some implementation options, which are also intended to form the subject matter of the present invention in detail using the simplest possible application = determination of isotope ratios, which are already briefly outlined under 1. vn «-de shown.

1. Analysis scheme (Fig.1) a. Beam guidance The first gas, e.g. standard gas, is ionized in the ion source (1) and the ion beam is passed through the diaphragm (3), via the sector capacitor (2) and the diaphragm (4) into the magnetic analyzer field (5) headed.

The ion current is kept constant by emission stabilization (14) The gas inlet system (15) is used to introduce the gas into the apparatus consisting of: storage vessel, shut-off valve -for static operation-, valve with adjustable Volume, capillary and needle valve.

The second gas (sample) is ionized in the ion source (1 '), and the generated ion beam is transmitted through the diaphragm (3 '), condenser (2') and diaphragm (4) into the common analyzer field.

This second ray runs above the first ray.

The diaphragms (3) and (3 ') - at the separation point of the ion source - and the joint The aperture (4) can be set in different ways the common aperture (4) as the entrance aperture, i.e. it is placed close together while the diaphragms (3) and (3 ') only serve to limit the rays, i.e. they become wide posed.

The diaphragms (3) and are used for real double-focusing operation (3 ') as entrance screens (placed close together), while screen (4) works as an energy screen (widely put).

b. Ion detection The common double diaphragm (6) - in the second focal point The sector magnet separates two sought-after beams from the split ion beams Ions (isotopes).

The two main ions (e.g. the rare isotopes from standard and Sample) are converted into secondary electrons by the wedge (8) and after excitation the scintillators (9), (9 ') with the multipliers (10) and (1o') measured.

With the plate (7), which has an adjustable negative voltage, you can the two main rays are drawn apart.

The two secondary ions (e.g. the common isotopes from standard and sample) are amplified with the catchers (11) and (11 ') and the associated DC voltage amplifiers measured.

c. Evaluation of the measurement results The ionization of the sample and the Standard gases are electronically regulated so that the resulting common isotopes (Secondary ions) are constant and of the same size (same meter). This is enough Comparison of the measured values of the rare isotopes. The comparison of the rare isotopes and the possible consideration of corrections, e.g. 0.17-can be done electronically, so that a direct output of the analysis result is possible.

The equation and constant keeping of the more frequent isototes is done by regulating the heating of the ion source with the by means of the difference in the measured values of the common isotopes; (12) = bridge circuit with amplifier, (13) = control circuit - while the ion source is heated with the is emission-stabilized.

The sector capacitors (2) and (2 ') from Fig.1 and 2, which are simultaneously can also be used for double focusing, can also be arranged in any other way e.g. as in Figure 4, so that they point in the same direction, although an additional beam correction is necessary, e.g. using the two deflector plates (24).

Anal yseachema II (Fig.2) The beam guidance is the same as in Scheme I, however, the rays are not simultaneously, but laterally one behind the other sent through the analyzer with the first beam above the second beam Similar to Scheme I.

In contrast to Scheme I, the rays are passed through two capacitors (16) and (16 '), which act as gat, interrupted or let through, alternately at the rate of the clock (17).

Evidence of the ions may be sufficient.

a multiplier with ion converter (8), (9) and (to) for the main ion (rare isotope) and a catcher with an enhancer for the minor ion (common isotope).

Both detection systems are, however, with two display systems (each for sample and standard). Switching to the respective display systems also happens in the cycle of the clock via the upstream gates (18) and (18 ').

For automatic calculation of the measurement results or for equality and storage elements (19) (19 ') are provided.

Advantage of System II over System I Elimination of the interaction of the two ion beams in the analyzer tube.

Disadvantage The intensity of the beam is only half that of Scher 1 and the control electronics are more complicated.

However, the measurement electronics are more complicated.

Analysis scheme III (Fig.3) The rays are alternating as in scheme II from one ion source and then from the other ion source through the analyzer cleverly and measured and evaluated in a similar manner.

In contrast to Scheme I and II, however, the rays run in the same plane and not offset from one another, so that the height of the cross-section of the beam can be optimally selected according to the analyzer cross-section and thereby a maximum beam intensity can be achieved.

For this purpose, the two sector capacitors (2) from Fig. 1, 2 and 4 replaced by a double sector capacitor (22) (see also Fig. 5), which contains an additional correction capacitor (21). Through this capacitor (21) can determine the direction of the ion beam behind the sector capacitor (22) electronically are adjusted in such a way that the diaphragm (23) is constructed in two parts and isolated and is coupled to the correction capacitor (21) via the control electronics (24).

Advantages of analysis scheme III that higher ion currents are achieved can.

Analysis scheme IV (Fig.4) The rays are as in scheme III one behind the other sent through the analyzer, but only becomes from the respective ion spectrum one beam each singled out. The desired side effects and haps are made through mass preprogramming set and called up in the desired order.

The measuring process is carried out in such a way that the secondary ion is called up from the standard, measured and stored. In the second measurement phase the secondary ion is retrieved from the sample, measured, stored and by comparison equated with the standardion. In the third measurement phase, the hapution or the main statements from the sample (possibly also standard) are called up, saved and evaluated.

the sector capacitors (2), (2 ') and (22) cause the deflection of the rays also have an energy homogenization of the same, so that they are simultaneously only dolphin focusing can be used, If you do without the homogenizing The effect of the sector capacitors is a simplified double ion beam arrangement can be used according to Fig. 4.

The ion beams that arise in two separate ion sources (1), (1 '), are within the meaning of the invention directly to a magnetic sector field (5), which is preferably has a square cross-section, supplied in such a way that the one ion beam enters on side (a) and exits as an ion spectrum on side (b), while the second ion beam enters on the (a) opposite side (c) and that associated spectrum exits on side (d) (((4) inner oil partition) from both ion spectra are then in the sense of the present invention with the help of Orifices (6) or by mass preselection, one auxiliary ion each for compensation and for keeping constant of the Brobe ion beam and, depending on the task, one or more main ions from the sample spectrum and possibly also from the standard spectrum evaluated and proven.

Claims (1)

P a t-e n t a n S p r ü c h e CLAIM (1) Double ion beam method for quantitative mass spectrometry Measurements of two samples, characterized in that of the two total ion beams - those generated in two opposite or adjacent ion sources and e.g. by means of two superimposed sector capacitors to the same analyzer system at the same time, but spatially offset, the one ion beam, e.g. that of the standard fabric, according to the conventional type, -z.3. is maintained by emission stabilization constnat, during the Total ion beam of the sample through a so-called. "Secondary ion control" regulated in this way is that an ion (peak) selected from the spectrum of the sample, called a secondary ion, with an identical or similar secondary ion from the spectrum of the standard ion beam is made the same, for what purpose the two secondary ions mechanically or electronically sorted out, measured, compared with each other and with the one obtained Controlled variable is the ionization of the ion source of the sample - e.g. by changing the issue is influenced accordingly in the case of electron impact ion sources. Claim 2 method according to claim 1, characterized in that the regulation and keeping constant of the total ion beam of the sample is not through the so-called "Minor ion method", i.e., approximation of a minor ion from the Sample at a secondary ion of the standard, but that the scheme is so before themselves goes that the sum of two or more ions from the spectrum of the sample the same size is regulated with the sum of two or more corresponding ions from the spectrum of the reference substance. CLAIM 5 Method according to Claim 1 and 2, characterized in that that from the spectra of the "secondary ion method" according to claim 1 or according to the "sum control method" according to claim 2 aligned ion beams of the sample and the standard, in addition to the secondary ions, one or more main ions each are separated out and their measured values manually-computationally for the purpose of determining their relative frequency or electronically compared with each other. CLAIM 4 Method according to Claim 1 and 2, characterized in that that only one or more main ions manually-individually from the sample beam spectrum or electronically -z.E. selected by mass preprogramming or mass flow-through and the measured values manually-computationally or electronically with one of the two equated and according to size -z.3. Concentration or partial pressure known Secondary ions can be compared quantitatively. CLAIM 5 Method according to Claims 3 and 4, characterized in that the precisely known mass position of the secondary ion from the standard material and the mass position of the secondary ion identified by the standard from the sample for manual or automatic determination of the mass positions of the individual ions in the sample and / or for checking and calibrating the mass marking, mass preprogramming and peak matching. CLAIM 6 Method according to Claims 1-5, characterized in that the ion beams mechanically after leaving the ion sources or the capacitors or electronically interrupted, one after the other in a selected cycle and sent periodically through the same analyzer, then from the two spectra secondary ions and main ions selected in the same cycle and for the purpose of obtaining the controlled variable or the analysis results are measured and compared in such a way that the Measuring results supplies corresponding memories and with the help of an electronic Programmer carries out the comparisons in the necessary order. CLAIM 7 Method according to Claim 6, characterized in that instead of the two individual sector capacitors, a single double capacitor is used, which is designed so that the common middle part the two Plates of the capacitors form with the larger radius, while the plates with the smaller radius, which is attached to both sides of the center piece at a precise distance are and each have an electrically insulated extension that is used for Correction of the two ion beams that periodically and one after the other the central axis the capacitors are supposed to pass through. CLAIM 8 Method according to CLAIM 6, characterized in that the secondary and haputions from the standard or sample spectrum not at the same time, i.e. as two separate ion beams - corresponding to two separate detection systems - are separated, but the secondary and main ions are preselected and according to a specified Measurement program consisting of only one ion beam each - corresponding to only one detection system - can be automatically called up, measured and evaluated. CLAIM 9 Method according to CLAIM 1-6, characterized in that the ion beams of sample and reference substance, which are in two separate ion sources are generated directly in a magnetic analyzer, which is preferably a having square cross-section, are supplied in such a way that the one Entire ion current on one side (a) of the sector field and the associated Ion spectrum or oil spectrum - formed under certain circumstances only from one or more ejected single ion beams to one lying on the right or left to (a) Side (b) or (d) emerges, while the second total ion beam at one of the side (a) opposite side (c) arrives and the ion spectrum belonging to it or partial spectrum on a left or right side on (e) adjacent side (d) or (b) emerges and that the regulation and evaluation of the ion beams according to one of the methods of CLAIMS 1-6, which are the subject of this invention, is carried out.