CA1263152A - Quadrupole mass filter with unbalanced r.f. voltage - Google Patents
Quadrupole mass filter with unbalanced r.f. voltageInfo
- Publication number
- CA1263152A CA1263152A CA000519373A CA519373A CA1263152A CA 1263152 A CA1263152 A CA 1263152A CA 000519373 A CA000519373 A CA 000519373A CA 519373 A CA519373 A CA 519373A CA 1263152 A CA1263152 A CA 1263152A
- Authority
- CA
- Canada
- Prior art keywords
- voltage
- rods
- pairs
- mass filter
- quadrupole mass
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
- H01J49/34—Dynamic spectrometers
- H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
- H01J49/4205—Device types
- H01J49/421—Mass filters, i.e. deviating unwanted ions without trapping
- H01J49/4215—Quadrupole mass filters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/0095—Particular arrangements for generating, introducing or analyzing both positive and negative analyte ions
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Electron Tubes For Measurement (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
ABSTRACT
An unbalanced radio frequency voltage is supplied between two pairs of conductive rods of a quadrupole mass filter of a mass spectrometer system. Means are provided for d.c. voltage polarity reversal for moni-toring positive and negative ions. The d.c. voltage is derived by rectification of the radio frequency voltage.
An unbalanced radio frequency voltage is supplied between two pairs of conductive rods of a quadrupole mass filter of a mass spectrometer system. Means are provided for d.c. voltage polarity reversal for moni-toring positive and negative ions. The d.c. voltage is derived by rectification of the radio frequency voltage.
Description
2 61051-2005 ~ POLE MASS FILTER
WI~ UNBALANC~D R.F. VOLTAGE
QEie3Lon ~.a~
This invention relates to a method of opera~ing a quadrupole mass filter used wlth mass spectrometers.
Backqround Art One type of mass speckrometer that is extensively used ~or ~ualitative and quantitative analysis of chemicals employs one or more quadrupole mass filters. In such spectrometer systems, quadrupole mass filters incorporating ~our conductive metal rods are supported on mounts made of an insulating material. The rods are energized by combined direct current (d.c.) and alternatlng curren~ (a.c.) voltage ~o achieve selective mass focusing. An example of a mass filter is described in U.S. Patent 4~032,782 entitled "Temperature Stable Multiple Mass Filter and Method Therefor" which issuad to the same assignee. The patent discloses a method of maintaining ~ilter stability by thermal matching o~
the rods an~ the mounts.
To obtain accurate readings and interpretations o~
analyses performed by mass spectroscopy, it is highly desirable that the mass peak wave~orms obtained by the scans are smooth and not characterized by spurious spllts or depressions which affect the spectral quality of the data. In prior art systems, it has been observed that such spurlous splits and depressions of the ~nass peaks occur frequently, thus deleteriously a~fecting the interpretation o~ the xesulting data.
.. ~, ~ .
.
'' .::''' "
We have discovered that by unbalancing the r.f. voltages applied to the pairs of quadrupole rod3 that spurious splits and depressiorls are subst.antial.ly reduced.
Summary of the Invention According to a broad aspe~t of the invention there is provided the method of operating a quadrupole mass filter of the type including first and second pairs of conducting rods comprising the steps of:
applying a mass con~rol DC voltage to said pairs of rods to generate an electrical field between said rods whereby to transmi~
a narrow band of ion masses therethrough;
applying an RF voltage to each of said pairs o~ rods; and adjusting the magnitude of the ~F voltage applied to one of said pairs of rods so ~hat it is different from that supplied to the other one of said pairs so that a radio frequency voltage unbalance is produced between said pairs of rods to thereby improve the transmission of ions through said mass filter.
Brief DescriPtion of ~he Drawina The inven~ion will be described with relation to the sole ~igure of the drawing which is a schematic circuit and block diagram of the apparatus of this invention.
:~' . . .
.
, ''' ' : ' _3_ ~ 3~
Description of the Preferred Embodiment With reference to the drawing, a quadrupole mass filter incorporates two pairs of conductive rods lOa, lOc and lOb, lOd disposed in a configuration that provides a hyperbolic field through which ions of the material under investigation travel. The rods 10, which may be made of molybdenum, are connected to an electrical circuit that provides d.c. voltage and r.f. or alter-nating current (a.c.) voltage. The circuit network includes a tuned circuit that controls the magnitudes of the r.f. and d~c. voltages which are applied to the filter rods. The tuned or r.f. resonant circuit is a low loss, high Q circuit, and the phase relation of the r.f. voltage supplied to the two pairs of rods lCa,c and lOb,d is substantially 180. The rods acts to provide a time varying electrosta~ic field to focus a narrow band of masses.
In operation, a mass control voltage is derived from a control device, such as a computer or sweep generator and applied through an input resistor 12 to a summing point 14. The control voltage is used as a reference that sets the mass to which the mass spectrometer will respond. A feedback voltage V~b is obtained from a measuring device 38, which is coupled to the rod~ ln and to the tuned circuit, as will be described herein-a~ter. If a non-zero voltage appears at the summing point 14, this voltage is amplified by an error voltage amplifier 16 and the amplified voltage is fed to the control input of an r.f. generator 18. The r.f. gen-erator 18 supplies an r.f. signal, having a frequency in the range of 1.0-2.0 MHz for example, to the tuned circuit, which comprises an inductive network consist-ing of inductances 20 ~nd 22 and a capacitive network comprisin~ capacitive elements 34 and 3~. A center coil 24, which preferably has one or two turns, is coupled to the output o~ the generator 18 and is disposed at the center between the two inductances 20 and 22 to supply r.f. power to the tuned circuit.
'' "'''' :' `
, $~2 The capacitive network of the tuned circuit includes the capacitive elements 30 and 32 which represent the capacitances of the wiring, mass filter and cables of ~he system. The capacitances 34 and 36, which are tied to test points TPl and TP2, are selected so that the circuit is resonant at the desired frequency of opera-tion, and so that the r.f. voltages measured at the test points TPl and TP2 have a predetermined unbalance.
The capacitances 34 and 36 may be fixed capacitors of selected value or variable capacitors. In either case, the values of the capacitances are such that they meet the requiremen~s of resonance and r.f. unbalance.
Each inductance 20 and 22 is coupled at one end re-spectively to capaci~ive elements 26 and 28, which are tied to a reference potential such as ground. The other end of each inductance 20 and 22 is coupled to test points TPl and TP2 respectively, which are con-nected to capacitors 34 and 36 respectively. The junction of the inductance 20 and capacitive element 34 is connected to opposins rods lOa and lOc, whereas the junction of the inductance 22 and capacitive element 36 i5 connected to opposing rods lOb and lOd. The induc-tances and capacitive elements form an LC resonant circuit which provides high r.f~ voltage operation, up to 3,000 peak volts ~or example.
Since the precise value~ of some of the capacitive elements of the tuned circui~ are not known, the need for adjustments of the capacitive values of the tuned circuit to effectuate the r.f. unbalance is determined by an r.f. voltage measuring device such as an oscillo-scope. The measuring device is coupled to the test points TPl and TP2, and to the pairs of rods 10. The capaci ors 34 and 36 are adjusted to obtain the desired unbalance. The adjustments may be made manually, or automatically in response to the measurement seen at the measuring device. Al.ternatively the inductors 20 and 22 may be formed with an unequal or different P~41954 :, .
`
: .
'` ' _5_ ~3~
number of turns on opposite sides of the center tap to produce the desired r.f. vol~age unbalance, or may be variable inductances that may be adjusted.
The output feedback Vfb of negative polarity from the measuring device 38 represents the difference in r.f.
voltage between the rod pair lOa, lOc and the rod pair lOb, lOd. This feedback voltage is fed through a feedback resistor 40 to the summing point 14 to be combined with the mass control voltage of positive polarity. As described heretofore, the non-~ero sum of the two voltages provides an error signal that is processed by the feedback loop including the tuned circuit and measuring device 38 to compensate for the error and drive ~he summed voltage at junction 14 towards zero.
The feedback voltage V~b provided by the detector or measuring device 38 is also used to produce the posi-tive and negative d.c. voltages which are applied to the rods 10 in order to produce the mass filtering action of the ~uadrupole. The feedback voltage is fed through a resolution controls circuit 40 which controls the slope and intercept of the d.c. signal, and thus allows for proper adjustment of mass resolution. The d.c. voltage is applied through parallel channels, one of which incorporates a phase inverting amplifier 44, to a d.c. rod polaritv reversible switch Sl. The switch Sl, which is operated manually, or under com-puter control if so desired, reverses he d.c. voltage polarity to enable detection of positive or negative ions by the quadrupole filter. In actual operation, it is desirable to switch rapidly between positive ion anal~sis and negative ion analysis, and in such cases computer control is employed.
The positive and negative d.c. signals are passed respectively through voltage amplifiers 46 and 48, and applied to the junctions between the inductances 22 and :.
: . , . ~:
. ~
20 and the bypass capacitors 28 and 26, for application through the tuned circuit to the xod pairs 10.
Although the use oE the switch Sl at the input o~ the voltage amplifiers 46 and 48 is a preferable imple-mentation because it does not require switching of highvoltage, bipolar d.c. rod voltage amplifiers are re-quired to enable supplying either positive or negative output signal~ from each amplifier. In an alternative approach, a swi~ch S2 is used at the output of the voltage amplifiers 46 and 48, and each amplifier needs only to supply a single polarity d.c. signal, one positive and the other negative.
With the implementation disclosed herein, the d.c. rod voltages are delivered to the quadrupole rods through the inductive coil structure. In such case, the center tap of coil 24 is isolated from the system ground and the r.f. circuit is completed by use of grounded bypass capacitors 26 and 28 which serve to complete the r.f.
circuit while preventing excessive r.f. voltage from reaching the d.c. rod voltage amplifiers 46 and 48~
We have observed that with an unbalance of the r.f.
voltages that are applied to the rods, the shapes of the mass peaks become smooth and a~ford a significant improvement in mass spectroscopy operation, particu-larly in ~uantitative analysis of high mass chemicals.There is a clear separation between adjacent mass peaks wi~hout the spurious si~nals that are experienced in prior art systems and affect the accuracy of the spec-troscopic readout. To obtain the desired unbalance, one or both of the capacitive elements are adjus~ed so that they are different in value. Similarly, the inductive elements may be adjusted to a different value, or adjustment6 both of inductance and capaci-tance may be made to achieve the required imbalance of r.f. voltages. In a preferred implementation, the r.f.
.
' ~Z~63~5:~
voltage at one pair of rods, say lOa, lOc is approxi-mately 1.4 times that at other pair of the rods lOb, lOd.
~ ~ .
.. .. . .
.
WI~ UNBALANC~D R.F. VOLTAGE
QEie3Lon ~.a~
This invention relates to a method of opera~ing a quadrupole mass filter used wlth mass spectrometers.
Backqround Art One type of mass speckrometer that is extensively used ~or ~ualitative and quantitative analysis of chemicals employs one or more quadrupole mass filters. In such spectrometer systems, quadrupole mass filters incorporating ~our conductive metal rods are supported on mounts made of an insulating material. The rods are energized by combined direct current (d.c.) and alternatlng curren~ (a.c.) voltage ~o achieve selective mass focusing. An example of a mass filter is described in U.S. Patent 4~032,782 entitled "Temperature Stable Multiple Mass Filter and Method Therefor" which issuad to the same assignee. The patent discloses a method of maintaining ~ilter stability by thermal matching o~
the rods an~ the mounts.
To obtain accurate readings and interpretations o~
analyses performed by mass spectroscopy, it is highly desirable that the mass peak wave~orms obtained by the scans are smooth and not characterized by spurious spllts or depressions which affect the spectral quality of the data. In prior art systems, it has been observed that such spurlous splits and depressions of the ~nass peaks occur frequently, thus deleteriously a~fecting the interpretation o~ the xesulting data.
.. ~, ~ .
.
'' .::''' "
We have discovered that by unbalancing the r.f. voltages applied to the pairs of quadrupole rod3 that spurious splits and depressiorls are subst.antial.ly reduced.
Summary of the Invention According to a broad aspe~t of the invention there is provided the method of operating a quadrupole mass filter of the type including first and second pairs of conducting rods comprising the steps of:
applying a mass con~rol DC voltage to said pairs of rods to generate an electrical field between said rods whereby to transmi~
a narrow band of ion masses therethrough;
applying an RF voltage to each of said pairs o~ rods; and adjusting the magnitude of the ~F voltage applied to one of said pairs of rods so ~hat it is different from that supplied to the other one of said pairs so that a radio frequency voltage unbalance is produced between said pairs of rods to thereby improve the transmission of ions through said mass filter.
Brief DescriPtion of ~he Drawina The inven~ion will be described with relation to the sole ~igure of the drawing which is a schematic circuit and block diagram of the apparatus of this invention.
:~' . . .
.
, ''' ' : ' _3_ ~ 3~
Description of the Preferred Embodiment With reference to the drawing, a quadrupole mass filter incorporates two pairs of conductive rods lOa, lOc and lOb, lOd disposed in a configuration that provides a hyperbolic field through which ions of the material under investigation travel. The rods 10, which may be made of molybdenum, are connected to an electrical circuit that provides d.c. voltage and r.f. or alter-nating current (a.c.) voltage. The circuit network includes a tuned circuit that controls the magnitudes of the r.f. and d~c. voltages which are applied to the filter rods. The tuned or r.f. resonant circuit is a low loss, high Q circuit, and the phase relation of the r.f. voltage supplied to the two pairs of rods lCa,c and lOb,d is substantially 180. The rods acts to provide a time varying electrosta~ic field to focus a narrow band of masses.
In operation, a mass control voltage is derived from a control device, such as a computer or sweep generator and applied through an input resistor 12 to a summing point 14. The control voltage is used as a reference that sets the mass to which the mass spectrometer will respond. A feedback voltage V~b is obtained from a measuring device 38, which is coupled to the rod~ ln and to the tuned circuit, as will be described herein-a~ter. If a non-zero voltage appears at the summing point 14, this voltage is amplified by an error voltage amplifier 16 and the amplified voltage is fed to the control input of an r.f. generator 18. The r.f. gen-erator 18 supplies an r.f. signal, having a frequency in the range of 1.0-2.0 MHz for example, to the tuned circuit, which comprises an inductive network consist-ing of inductances 20 ~nd 22 and a capacitive network comprisin~ capacitive elements 34 and 3~. A center coil 24, which preferably has one or two turns, is coupled to the output o~ the generator 18 and is disposed at the center between the two inductances 20 and 22 to supply r.f. power to the tuned circuit.
'' "'''' :' `
, $~2 The capacitive network of the tuned circuit includes the capacitive elements 30 and 32 which represent the capacitances of the wiring, mass filter and cables of ~he system. The capacitances 34 and 36, which are tied to test points TPl and TP2, are selected so that the circuit is resonant at the desired frequency of opera-tion, and so that the r.f. voltages measured at the test points TPl and TP2 have a predetermined unbalance.
The capacitances 34 and 36 may be fixed capacitors of selected value or variable capacitors. In either case, the values of the capacitances are such that they meet the requiremen~s of resonance and r.f. unbalance.
Each inductance 20 and 22 is coupled at one end re-spectively to capaci~ive elements 26 and 28, which are tied to a reference potential such as ground. The other end of each inductance 20 and 22 is coupled to test points TPl and TP2 respectively, which are con-nected to capacitors 34 and 36 respectively. The junction of the inductance 20 and capacitive element 34 is connected to opposins rods lOa and lOc, whereas the junction of the inductance 22 and capacitive element 36 i5 connected to opposing rods lOb and lOd. The induc-tances and capacitive elements form an LC resonant circuit which provides high r.f~ voltage operation, up to 3,000 peak volts ~or example.
Since the precise value~ of some of the capacitive elements of the tuned circui~ are not known, the need for adjustments of the capacitive values of the tuned circuit to effectuate the r.f. unbalance is determined by an r.f. voltage measuring device such as an oscillo-scope. The measuring device is coupled to the test points TPl and TP2, and to the pairs of rods 10. The capaci ors 34 and 36 are adjusted to obtain the desired unbalance. The adjustments may be made manually, or automatically in response to the measurement seen at the measuring device. Al.ternatively the inductors 20 and 22 may be formed with an unequal or different P~41954 :, .
`
: .
'` ' _5_ ~3~
number of turns on opposite sides of the center tap to produce the desired r.f. vol~age unbalance, or may be variable inductances that may be adjusted.
The output feedback Vfb of negative polarity from the measuring device 38 represents the difference in r.f.
voltage between the rod pair lOa, lOc and the rod pair lOb, lOd. This feedback voltage is fed through a feedback resistor 40 to the summing point 14 to be combined with the mass control voltage of positive polarity. As described heretofore, the non-~ero sum of the two voltages provides an error signal that is processed by the feedback loop including the tuned circuit and measuring device 38 to compensate for the error and drive ~he summed voltage at junction 14 towards zero.
The feedback voltage V~b provided by the detector or measuring device 38 is also used to produce the posi-tive and negative d.c. voltages which are applied to the rods 10 in order to produce the mass filtering action of the ~uadrupole. The feedback voltage is fed through a resolution controls circuit 40 which controls the slope and intercept of the d.c. signal, and thus allows for proper adjustment of mass resolution. The d.c. voltage is applied through parallel channels, one of which incorporates a phase inverting amplifier 44, to a d.c. rod polaritv reversible switch Sl. The switch Sl, which is operated manually, or under com-puter control if so desired, reverses he d.c. voltage polarity to enable detection of positive or negative ions by the quadrupole filter. In actual operation, it is desirable to switch rapidly between positive ion anal~sis and negative ion analysis, and in such cases computer control is employed.
The positive and negative d.c. signals are passed respectively through voltage amplifiers 46 and 48, and applied to the junctions between the inductances 22 and :.
: . , . ~:
. ~
20 and the bypass capacitors 28 and 26, for application through the tuned circuit to the xod pairs 10.
Although the use oE the switch Sl at the input o~ the voltage amplifiers 46 and 48 is a preferable imple-mentation because it does not require switching of highvoltage, bipolar d.c. rod voltage amplifiers are re-quired to enable supplying either positive or negative output signal~ from each amplifier. In an alternative approach, a swi~ch S2 is used at the output of the voltage amplifiers 46 and 48, and each amplifier needs only to supply a single polarity d.c. signal, one positive and the other negative.
With the implementation disclosed herein, the d.c. rod voltages are delivered to the quadrupole rods through the inductive coil structure. In such case, the center tap of coil 24 is isolated from the system ground and the r.f. circuit is completed by use of grounded bypass capacitors 26 and 28 which serve to complete the r.f.
circuit while preventing excessive r.f. voltage from reaching the d.c. rod voltage amplifiers 46 and 48~
We have observed that with an unbalance of the r.f.
voltages that are applied to the rods, the shapes of the mass peaks become smooth and a~ford a significant improvement in mass spectroscopy operation, particu-larly in ~uantitative analysis of high mass chemicals.There is a clear separation between adjacent mass peaks wi~hout the spurious si~nals that are experienced in prior art systems and affect the accuracy of the spec-troscopic readout. To obtain the desired unbalance, one or both of the capacitive elements are adjus~ed so that they are different in value. Similarly, the inductive elements may be adjusted to a different value, or adjustment6 both of inductance and capaci-tance may be made to achieve the required imbalance of r.f. voltages. In a preferred implementation, the r.f.
.
' ~Z~63~5:~
voltage at one pair of rods, say lOa, lOc is approxi-mately 1.4 times that at other pair of the rods lOb, lOd.
~ ~ .
.. .. . .
.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The method of operating a quadrupole mass filter of the type including first and second pairs of conducting rods comprising the steps of:
applying a mass control DC voltage to said pairs of rods to generate an electrical field between said rods whereby to transmit a narrow band of ion masses therethrough;
applying an RF voltage to each of said pairs of rods; and adjusting the magnitude of the RF voltage applied to one of said pairs of rods so that it is different from that supplied to the other one of said pairs so that a radio frequency voltage unbalance is produced between said pairs of rods to thereby improve the transmission of ions through said mass filter.
applying a mass control DC voltage to said pairs of rods to generate an electrical field between said rods whereby to transmit a narrow band of ion masses therethrough;
applying an RF voltage to each of said pairs of rods; and adjusting the magnitude of the RF voltage applied to one of said pairs of rods so that it is different from that supplied to the other one of said pairs so that a radio frequency voltage unbalance is produced between said pairs of rods to thereby improve the transmission of ions through said mass filter.
2. The method as in claim 1 which includes the additional step of varying said DC voltage to control the masses of ions passing through said quadrupole mass filter.
3. The method of operating a quadrupole mass filter as in claim 1 including the additional step of sensing the RF voltage unbalance and employing said voltage unbalance to control the RF
voltages.
voltages.
4. The method of operating a quadrupole mass filter as in claim 1 or 2 including the step of reversing the polarity of the DC voltage applied to said rods to control the transmission of positive and negative ion masses through said mass filter.
5. The method of operating a quadrupole mass filter as in Claim 1 wherein the magnitude of the RF voltage supplied to one of said pairs of rods is up to 1.4 times the RF voltage applied to the other pair of rods.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US78251285A | 1985-10-01 | 1985-10-01 | |
| US782,512 | 1985-10-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1263152A true CA1263152A (en) | 1989-11-21 |
Family
ID=25126286
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000519373A Expired CA1263152A (en) | 1985-10-01 | 1986-09-30 | Quadrupole mass filter with unbalanced r.f. voltage |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0217644B1 (en) |
| JP (1) | JP2529219B2 (en) |
| CA (1) | CA1263152A (en) |
| DE (1) | DE3678085D1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6028308A (en) * | 1996-11-18 | 2000-02-22 | Mds Inc. | Resolving RF mass spectrometer |
| US20060163472A1 (en) * | 2005-01-25 | 2006-07-27 | Varian, Inc. | Correcting phases for ion polarity in ion trap mass spectrometry |
| US7491931B2 (en) | 2006-05-05 | 2009-02-17 | Applera Corporation | Power supply regulation using a feedback circuit comprising an AC and DC component |
| JP5778053B2 (en) * | 2012-02-06 | 2015-09-16 | 株式会社日立ハイテクノロジーズ | Mass spectrometer and method for adjusting mass spectrometer |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3321623A (en) * | 1963-05-13 | 1967-05-23 | Bell & Howell Co | Multipole mass filter having means for applying a voltage gradient between diametrically opposite electrodes |
| US3617736A (en) * | 1968-06-19 | 1971-11-02 | Hewlett Packard Co | Quadrupole mass filter with electrode structure for fringing-field compensation |
| US3783279A (en) * | 1971-03-03 | 1974-01-01 | W Brubaker | Hyperbolic field mass filter |
| JPS59123155A (en) * | 1982-12-28 | 1984-07-16 | Jeol Ltd | quadrupole mass spectrometer |
-
1986
- 1986-09-25 DE DE8686307396T patent/DE3678085D1/en not_active Expired - Fee Related
- 1986-09-25 EP EP86307396A patent/EP0217644B1/en not_active Expired - Lifetime
- 1986-09-30 CA CA000519373A patent/CA1263152A/en not_active Expired
- 1986-10-01 JP JP61234262A patent/JP2529219B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0217644B1 (en) | 1991-03-13 |
| JP2529219B2 (en) | 1996-08-28 |
| DE3678085D1 (en) | 1991-04-18 |
| EP0217644A2 (en) | 1987-04-08 |
| EP0217644A3 (en) | 1988-03-16 |
| JPS62188154A (en) | 1987-08-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |