JP2009092524A - Liquid chromatograph mass spectrometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the capacity of a heater transformer which is used for applying heating current while performing a necessary temperature control, when performing the temperature control by using a plurality of heaters in a liquid chromatograph mass spectrometer. <P>SOLUTION: A zero-cross detecting section 36 detects a zero-cross point in a commercial AC voltage and generates pulses. A control section 37 turns SSRs 32, 33 on and off so as to apply a drive power to either of two heaters 13, 16, by using an interval of the pulses as the minimum unit. A distribution of the drive power between two heaters 13, 16 is determined adaptively from characteristic information such as a difference between a target temperature and an actual temperature detected by temperature sensors 34, 35, a temperature time constant of the heaters 13, 16 and the like. Accordingly, the drive power is not applied to the two heaters 13, 16 simultaneously, thereby the rated capacity of the heater transformer 31 can be made small, and the temperature control at each section is performed so as not to disturb the mass spectrometry. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid chromatograph mass spectrometer, and more particularly, to control for driving a plurality of heaters provided in the liquid chromatograph mass spectrometer.

  For example, in a liquid chromatograph mass spectrometer (LC / MS) using atmospheric pressure chemical ionization (APCI), a nozzle for atomizing a sample liquid from a nozzle connected to the end of a column of the liquid chromatograph into the ionization chamber Alternatively, a plurality of heaters are used, such as a heater that heats the vicinity of the nozzle outlet and a heater that heats a narrow tube for transporting ions generated in the ionization chamber to the next intermediate vacuum chamber having a low gas pressure (for example, (See Patent Document 1).

  As a circuit for supplying heating power to such a plurality of heaters, commercial AC power supplied from a commercial AC power source is supplied to a primary winding of a transformer (heater transformer) to step down, and a plurality of secondary windings of the transformer That supply power to the heaters are known. In conventional LC / MS, in consideration of the case where heating is performed simultaneously by a plurality of heaters, a heater transformer having a rated capacity that is equal to or greater than the sum of the power capacities of the plurality of heaters to be driven is used.

  For this reason, the cost of the heater transformer is high, which is one factor hindering cost reduction of the apparatus. In addition, since the heater transformer with a large rated capacity is large and heavy, it is disadvantageous for making the device smaller and lighter.

JP-A-11-108895

  The present invention has been made to solve the above-described problems, and the object of the present invention is to appropriately heat each part so as not to disturb the analysis while suppressing the rated capacity of the heater transformer as much as possible. The object is to provide a liquid chromatograph mass spectrometer.

A first invention made to solve the above problems is a liquid chromatograph mass spectrometer that performs mass spectrometry by introducing a sample liquid containing a sample component separated in a liquid chromatograph part into the mass analyzer.
a) a plurality of heaters disposed in an ionization unit of the mass spectrometry unit and / or an ion transport unit that transports ions generated in the ionization unit to the subsequent stage;
b) switching means for supplying driving power based on commercial AC power supplied from a commercial AC power supply to one of the plurality of heaters;
c) Zero-cross detection means for detecting the zero-cross point of commercial AC voltage;
d) The distribution of drive power to each heater is determined based on the characteristics and target temperatures of the plurality of heaters, and the supply of the drive power at the position of the zero cross point detected by the zero cross detection means Control means for controlling the switching means to switch the destination;
It is characterized by having.

A second invention made to solve the above problems is a liquid chromatograph mass spectrometer that performs mass spectrometry by introducing a sample solution containing a sample component separated in a liquid chromatograph part into the mass analyzer.
a) a plurality of heaters disposed in an ionization unit of the mass spectrometry unit and / or an ion transport unit that transports ions generated in the ionization unit to the subsequent stage;
b) a heater transformer having a primary winding supplied with commercial AC power supplied from a commercial AC power source and a secondary winding provided corresponding to each of the plurality of heaters;
c) a plurality of power switching means for supplying drive power generated in the secondary winding of the heater transformer to each of the plurality of heaters for a specified period;
d) Zero-cross detection means for detecting the zero-cross point of commercial AC voltage;
e) closing the power switching means at a certain point in a half cycle period between two time-adjacent zero cross points detected by the zero cross detection means, and opening the power switching means at the next zero cross point. Control means for controlling each of the power switching means, wherein the plurality of drive powers within the half cycle period are under the condition that the sum of all the drive powers is equal to or less than the prescribed power determined for the heater transformer. Control means for determining the distribution of drive power to each heater based on the respective characteristics and target temperature of the heater, and controlling each power switching means by deciding the timing for closing the power switching means accordingly,
It is characterized by having.

  As the switching means in the first invention and the power switching means in the second invention, it is preferable to use a solid state relay using a power transistor, a triac (gate control type semiconductor switch) or the like in the switching unit from the viewpoint of reliability.

  In both the mass spectrometers according to the first and second inventions, the half cycle period from the zero-cross point of the commercial AC voltage waveform to the next zero-cross point is set as a minimum unit, and the control means uses a plurality of heaters in this minimum unit. Distributes drive power. That is, for example, the larger the difference between the target temperature and the actual temperature among the plurality of heaters, the larger driving power can be supplied. Further, even if the temperature difference is the same, a larger driving power may be supplied to the heater that wants to rapidly increase the temperature.

  In the liquid chromatograph mass spectrometer according to the first invention, the control means can adaptively adjust the drive power supplied to each heater according to the difference between the target temperature and the actual temperature, the characteristics of the heater itself, and the like. However, only a maximum of one heater is supplied with driving power at an arbitrary time, and driving power is not supplied to a plurality of heaters simultaneously.

  On the other hand, in the liquid chromatograph mass spectrometer according to the second aspect of the invention, the control means performs power control by so-called phase control, and at a certain point in time, the plurality of power switching means are simultaneously closed and the driving power is simultaneously applied to the corresponding heaters. Although it can be supplied, the sum of all the drive powers when viewed within a half-cycle period is suppressed to a prescribed power set for the heater transformer, generally less than the rated power capacity.

  Therefore, according to the liquid chromatograph mass spectrometer according to the first and second inventions, it is not necessary to increase the rated power capacity of the heater transformer used for heating with a plurality of heaters, and the cost can be suppressed. At the same time, it is advantageous for reducing size and weight. In addition, as described above, the driving power can be distributed adaptively to the heaters that are most important for the analysis at that time, so even if the driving power cannot be supplied to a plurality of heaters at the same time, Even if there is a restriction on the maximum value of the sum of the drive powers, it is possible to achieve good analysis by appropriately heating and temperature controlling each part.

  In particular, according to the liquid chromatograph mass spectrometer according to the first aspect of the invention, when the alternating voltage and alternating current applied to the contact of the switching means are almost zero, the on / off switching operation is performed. It is difficult for an undesirably large inrush current to flow due to this, and it is possible to make it difficult for the switching means to fail or break.

  The drive control of the plurality of heaters as described above can be applied to various heaters provided in the liquid chromatograph mass spectrometer, and in particular, the ionization part of the mass spectrometer is under a substantially atmospheric pressure atmosphere. And a plurality of heaters for transporting the ions generated by the heaters provided in the spraying unit and the ionization unit to a vacuum chamber having the next lower gas pressure. And a heater provided in the thin tube.

[First embodiment]
An LC / MS according to an embodiment (first embodiment) of the first invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of the main part of the LC / MS. This LC / MS uses an atmospheric pressure chemical ionization (APCI) interface, but is not limited to this, and various ionization methods such as an electrospray ionization interface can be used.

  In the liquid chromatograph (LC) unit 1, the liquid feeding unit 3 sucks the mobile phase from the mobile phase container 2 and feeds it to the column 5 while maintaining a constant liquid feeding amount. When a sample is injected into the mobile phase at a predetermined timing by an injector 4 provided in front of the column 5, the sample is introduced into the column 5 on the mobile phase. Various components (compounds) in the sample are separated while passing through the column 5, and are eluted from the outlet of the column 5 with different holding times and introduced into the mass spectrometry (MS) unit 10.

  In the MS unit 10, the sample solution is atomized by a nozzle 12 heated by a heater 13 provided around the sample solution and sprayed into an ionization chamber 11 having a substantially atmospheric pressure atmosphere. A needle electrode 14 is disposed in front of the nozzle 12, and solvent molecules in the sample liquid are ionized by corona discharge from the needle electrode 14, and the solvent ions and sample component molecules undergo a chemical reaction, whereby the component molecules are Ionized. The generated ions are sent to the first intermediate vacuum chamber 17 through a small diameter heating capillary (desolvent tube) 15 heated by a heater 16 which is a block heater, for example.

The first intermediate vacuum chamber 17 is maintained in a low vacuum atmosphere (for example, about 10 ² [Pa]) by being evacuated by the rotary pump 25. The ions introduced into the first intermediate vacuum chamber 17 are converged by the first ion lens 18 and are fed into the second intermediate vacuum chamber 20 through the orifice at the top of the skimmer 19. The second intermediate vacuum chamber 20 is maintained in a medium vacuum atmosphere (for example, about 10 ⁻¹ to 10 ⁻² [Pa]) by being evacuated by the turbo molecular pump 26 and introduced into the second intermediate vacuum chamber 20. The ions are fed into the analysis chamber 22 while being converged by the octopole-type second ion lens 21.

The analysis chamber 22 is maintained in a high vacuum atmosphere (for example, about 10 ⁻³ to 10 ⁻⁴ [Pa]) by being evacuated by another turbo molecular pump 27, and has a specific mass (strictly, mass to charge ratio m / Only ions having z) pass through the space in the long axis direction of the quadrupole mass filter 23, and ions having other masses diverge midway. Then, the ions that have passed through the quadrupole mass filter 23 reach an ion detector 24 that is a combination of a conversion dynode and a photomultiplier tube, for example, and the ion detector 24 outputs an ion intensity signal corresponding to the amount of ions reached. To do. This output signal is input to a data processing unit (not shown), where a mass spectrum, a mass chromatogram, or a total ion chromatogram is created, and further qualitative / quantitative analysis is performed.

  A nozzle 12 for ionization and a heating capillary 15 for transporting ions to the subsequent stage and evaporating a solvent from fine sample droplets to promote the generation of ions are respectively provided by heaters 13 and 16 attached thereto, respectively. It is heated substantially at an arbitrary temperature within the temperature range. Next, a circuit configuration for driving control of the two heaters 13 and 16 and its control operation will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram of the heater driving circuit.

  AC power supplied from an external commercial AC power supply 30 is applied to the primary winding L1 of the heater transformer 31, and the two secondary windings L2 and L3 of the heater transformer 31 are respectively connected to a solid state relay (SSR) 32, It is connected to the heaters 13 and 16 through 33. The commercial AC voltage is input to the zero cross detection unit 36 before the heater transformer 31, and a zero cross detection signal from the zero cross detection unit 36 is given to the control unit 37. Temperature sensors 34 and 35 are attached to the heaters 13 and 16, respectively, and each temperature detection signal of the temperature sensors 34 and 35 is input to the temperature monitoring unit 38. The temperature monitoring unit 38 calculates the actual temperature based on the temperature detection signal, and gives the temperature values Tr 1 and Tr 2 to the control unit 37.

  The control unit 37 is constituted by a microcomputer including a CPU, for example, and includes a calculation unit that performs calculation processing such as PID control based on a predetermined calculation algorithm, and turns on the two SSRs 32 and 33 according to the calculation result. A drive signal to be turned off is generated. Further, as a parameter for the calculation, heater characteristic information 39 such as a time constant related to the temperature of each heater 13, 16 stored in a memory or the like is given to the control unit 37, and each heater 13, which is a control target, Sixteen temperature set values Tp1 and Tp2 are also given to the control unit 37 according to user settings. The SSRs 32 and 33 are switches that can operate at high speed, and include gate controlled semiconductor switches such as a triac.

  Next, an example of the control operation in the heater drive circuit will be described with reference to FIGS. Prior to the analysis, target temperatures of the nozzle 12 and the heating capillary 15 are set by the user as one of the analysis conditions, and the target temperatures are given to the control unit 37 as temperature setting values Tp1 and Tp2.

  When commercial AC power is supplied from the outside, the zero cross detector 36 generates a pulse signal near the zero cross point of the AC voltage (see FIG. 3). Therefore, two pulse signals are generated in one AC voltage cycle (frequency 50 Hz or 60 Hz). The control unit 37 switches the H / L level of the SSR drive signal with the pulse interval of the zero cross detection signal as a minimum unit.

  The control unit 37 obtains a difference ΔT1 between the actual temperature Tr1 and the temperature set value Tp1 for the heater 13 given from the temperature monitoring unit 38, and a difference ΔT2 between the actual temperature Tr2 and the temperature set value Tp2 for the heater 16, Basically, the heating power supplied to the heaters 13 and 16 is adjusted by controlling on / off of the SSRs 32 and 33 so that the temperature differences ΔT1 and ΔT2 both approach zero. For such control, for example, a well-known PID control can be used.

  Importantly, in the above control, it is prohibited to energize the two heaters 13 and 16 simultaneously. Therefore, SSR 32 and SSR 33 are not turned on at the same time, either one is turned on, or both are turned off together. Further, for example, when there is the same temperature difference between the heaters 13 and 16, the priority is set so that the heater 13 is preferentially heated. This is because raising the temperature of the nozzle 12 is indispensable for ionization, and the heater 13 has a larger heat capacity than the heater 16 and the temperature is less likely to rise.

  Therefore, in general, at the time of starting up the apparatus after the start-up and when the analysis is first performed (that is, when the initial temperature of both the nozzle 12 and the heating capillary 15 is normal temperature), the temperature difference ΔT1 is greater than a predetermined value. In the state where the heating by the heater 13 is preferentially performed and the temperature difference ΔT1 on the heater 13 side is reduced to some extent, energization to both the heaters 13 and 16 is permitted, and the drive power is distributed. Decide. Specifically, according to the temperature differences ΔT1 and ΔT2 between the heaters 13 and 16, and the heater characteristic information 39, the number N of times the heater 13 is energized in units of the zero-cross interval during a certain period and the heater 16 The number M of energizations is determined.

  For example, in the example shown in FIG. 4, the number of times N is applied to the heater 13 under the condition of N + M ≦ 8, assuming that the zero-crossing interval corresponding to four cycles of the power supply voltage waveform, that is, eight times is one power distribution cycle, and the heater The number M of energizations 16 is determined. In the example of FIG. 4, N = 3 and M = 5, and more heating power is supplied to the heater 16 than to the heater 13. If the temperature differences ΔT1 and ΔT2 are reduced, the power supplied to the heaters 13 and 16 is reduced by decreasing the values of both N and M, and the temperature differences ΔT1 and ΔT2 are stably shifted as close to zero as possible. So that control continues. When the actual temperatures Tr1 and Tr2 of both the nozzle 12 and the heating capillary 15 are settled near the target temperatures Tp1 and Tp2, the sample liquid is supplied at a constant flow rate, and the ambient temperature is maintained substantially constant, the substantially constant control is continued. That's fine.

  However, the control unit 37 can adaptively determine the distribution of power to the heaters 13 and 16. In other words, the power distribution cycle as described above is not fixed. If the actual temperature suddenly changes due to a disturbance such as a large change in ambient temperature or a change in the flow rate of the sample liquid, Therefore, the power supply for such correction can be prioritized even during the power distribution period. Depending on the characteristics of the heater, it is not appropriate to set the minimum power supply switching unit to a half wave of commercial AC power. For example, power is continuously supplied for a period of half wave × 2 or half wave × 3. In some cases, the temperature can be raised more appropriately. However, such a case can be dealt with by performing PID control with such a constraint as one of the conditions.

  In the above-described embodiment, the case where drive control of two heaters is performed has been described, but the same technique can be applied to three or more heaters.

[Second Embodiment]
Next, an LC / MS according to an embodiment (second embodiment) of the second invention will be described with reference to the drawings. The overall configuration of the LC / MS and the schematic configuration of the heater drive circuit according to the second embodiment are basically the same as those of the first embodiment, and thus the description thereof is omitted. In the second embodiment, the control operation of the control unit 37, specifically, the control program is different from that of the first embodiment. The operation of the heater drive circuit performed under the control of the control unit 37 will be described with reference to FIG.

  Here, the drive power supplied to the heaters 13 and 16 is controlled by phase control. That is, the SSRs 32 and 33 are turned on at a certain point in a half cycle period of the AC voltage, that is, a period between two zero cross positions adjacent in time, and the SSRs 32 and 33 are turned off at the next zero cross position. The waveform area of the drive voltage supplied to the heaters 13 and 16 through the SSRs 32 and 33 changes depending on the timing when the SSRs 32 and 33 are turned on, and the area corresponds to the drive power to the heaters 13 and 16.

  Similar to the first embodiment, the control unit 37 provides the difference ΔT1 between the actual temperature Tr1 for the heater 13 and the temperature set value Tp1 given from the temperature monitoring unit 38, and the actual temperature Tr2 and the temperature set value Tp2 for the heater 16. The drive power supplied to the heaters 13 and 16 is basically adjusted so that the temperature differences ΔT1 and ΔT2 both approach zero. However, in this case, when the driving power supplied to the heaters 13 and 16 during the half-cycle period is Pa and Pb, the sum Pa + Pb of the two is kept below the rated power capacity P determined for the heater transformer 31. In other words, a condition such that P ≧ Pa + Pb is imposed. If the drive power Pa and Pb are determined in this way, the timing for turning on the SSRs 32 and 33 and t1 and t2 in FIG. 5 are determined, and the control unit 37 drives the SSRs 32 and 33 accordingly.

  As is apparent from FIG. 5, in this case, the driving power is simultaneously supplied to the two heaters 13 and 16, but when viewed in a half cycle period, the sum of the two driving powers is the rated power of the heater transformer 31. Since it falls below the capacity, it is possible to perform heating so that a good analysis can be performed within the range of the rated power capacity.

  Moreover, since the said Example is an example of this invention, even if it changes suitably, amends, and is added in the range of the meaning of this invention, it is clear that it is included by the claim of this application.

The whole block diagram of the principal part of LC / MS by one Example (1st Example) of 1st invention. The schematic block diagram of the heater drive circuit in LC / MS of 1st Example. The schematic waveform diagram for demonstrating operation | movement of a heater drive circuit in 1st Example. The schematic waveform diagram for demonstrating operation | movement of a heater drive circuit in 1st Example. The schematic waveform diagram for demonstrating operation | movement of the heater drive circuit in LC / MS by one Example (2nd Example) of 2nd invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... LC part 10 ... MS part 11 ... Ionization chamber 12 ... Nozzle 13 ... Heater, 16
14 ... Needle electrode 15 ... Heating capillary 17 ... First intermediate vacuum chamber 18 ... First ion lens 19 ... Skimmer 20 ... Second intermediate vacuum chamber 21 ... Second ion lens 22 ... Analysis chamber 23 ... Quadrupole mass filter 24 ... Ion detector 30 ... Commercial AC power supply 31 ... Heater transformer 32, 33 ... Solid state relay (SSR)
34, 35 ... temperature sensor 36 ... zero cross detection unit 37 ... control unit 38 ... temperature monitoring unit 39 ... heater characteristic information

Claims (3)

In a liquid chromatograph mass spectrometer that performs mass spectrometry by introducing a sample solution containing sample components separated in a liquid chromatograph part into a mass spectrometer,
a) a plurality of heaters disposed in an ionization unit of the mass spectrometry unit and / or an ion transport unit that transports ions generated in the ionization unit to the subsequent stage;
b) switching means for supplying driving power based on commercial AC power supplied from a commercial AC power supply to one of the plurality of heaters;
c) Zero-cross detection means for detecting the zero-cross point of commercial AC voltage;
d) The distribution of drive power to each heater is determined based on the characteristics and target temperatures of the plurality of heaters, and the supply of the drive power at the position of the zero cross point detected by the zero cross detection means Control means for controlling the switching means to switch the destination;
A liquid chromatograph mass spectrometer comprising: In a liquid chromatograph mass spectrometer that performs mass spectrometry by introducing a sample solution containing sample components separated in a liquid chromatograph part into a mass spectrometer,
a) a plurality of heaters disposed in an ionization unit of the mass spectrometry unit and / or an ion transport unit that transports ions generated in the ionization unit to the subsequent stage;
b) a heater transformer having a primary winding supplied with commercial AC power supplied from a commercial AC power source and a secondary winding provided corresponding to each of the plurality of heaters;
c) a plurality of power switching means for supplying drive power generated in the secondary winding of the heater transformer to each of the plurality of heaters for a specified period;
d) Zero-cross detection means for detecting the zero-cross point of commercial AC voltage;
e) closing the power switching means at a certain point in a half cycle period between two time-adjacent zero cross points detected by the zero cross detection means, and opening the power switching means at the next zero cross point. Control means for controlling each of the power switching means, wherein the plurality of drive powers within the half cycle period are under the condition that the sum of all the drive powers is equal to or less than the prescribed power determined for the heater transformer. Control means for determining the distribution of drive power to each heater based on the respective characteristics and target temperature of the heater, and controlling each power switching means by deciding the timing for closing the power switching means accordingly,
A liquid chromatograph mass spectrometer comprising:   3. The liquid chromatograph mass spectrometer according to claim 1, wherein the ionization unit of the mass analysis unit includes a spray unit that atomizes a sample solution under a substantially atmospheric pressure atmosphere, and the plurality of heaters are A liquid chromatograph comprising: a heater provided in a spray section; and a heater provided in a narrow tube for transporting ions generated in the ionization section into a vacuum chamber having a lower gas pressure. Mass spectrometer.

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