JP4586738B2 - ICP analyzer - Google Patents

Description

  The present invention relates to an ICP analyzer using an ICP light source that causes plasma emission or ionization of a liquid sample, such as an ICP (Inductively Coupled Plasma) emission analyzer or an ICP mass spectrometer.

  An ICP emission spectrometer is included in a sample by measuring the wavelength and intensity of the atomic spectrum by spectroscopically analyzing the light that is introduced into the plasma and emitted when the excited sample atoms transition to a low energy level. Elemental qualitative or quantitative determination is performed (for example, see Patent Document 1).

  FIG. 3 shows a schematic configuration diagram of a conventional general ICP emission analyzer. This ICP emission analyzer includes a plasma torch wrapped around an induction coil, a power supply unit that supplies high-frequency power to the induction coil, an impedance adjustment unit, a sample introduction unit, a gas flow rate control unit, a spectrometer, a detector, data It consists of a processing unit, a control unit, and the like.

  When analyzing the sample using the ICP emission analyzer, the plasma for introducing the sample is turned on as follows in the stage before introducing the sample as follows: cooling gas from the gas flow control unit to the plasma torch In addition, a predetermined high frequency power is applied to the induction coil while supplying auxiliary gas (usually Ar is used) at a predetermined flow rate, and spark discharge is used to turn on the high frequency induction plasma. By introducing the atomized sample into the plasma, excitation light emission of the sample molecules occurs.

  When the plasma is turned on, the impedance when the induction coil side is viewed from the high-frequency power supply device side (hereinafter simply referred to as “the impedance of the induction coil”) changes greatly.

  Here, in order to efficiently supply power to the plasma, a process of matching the impedance of the high frequency power supply and the impedance of the induction coil is performed (in the present specification, in the case of simply “impedance matching”, Refers to the matching between the impedance and the impedance of the induction coil.) Since the impedance of the high-frequency power supply is normally designed to be 50Ω, impedance matching is performed so that the impedance of the induction coil viewed from the power supply device side is also 50Ω. By properly performing this impedance matching, the incident power is injected into the plasma with as high an efficiency as possible. At this time, the reflected power is minimized. This impedance matching is generally performed by increasing or decreasing the capacity of the variable capacitor in the matching circuit of the impedance adjusting unit.

  By the way, in ICP analysis, it is common to use different plasma torches with different shapes depending on the type and application of the sample to be measured. For example, a high salt torch has a wider shape near the outlet than a standard torch in order to prevent deposition of deposited salt. In addition, the organic solvent torch is expected to have a large internal volume in anticipation of the volatile content of the sample in the torch. On the contrary, the internal volume of the torch for suppressing consumption of the analysis gas is small. In this way, the torch has a different shape and internal volume for each type, and the appropriate values of the incident power and the gas flow rate differ accordingly.

  After the plasma torch is attached or replaced, the operator needs to set the type of torch currently attached to the ICP analyzer. Conventional ICP analyzers do not have a function to identify the actually installed torch, so if the operator makes a mistake in this setting, the incident power and gas amount suitable for a different type of torch are not obtained. As a result, the temperature of the torch was excessively increased, and there was a possibility that it was melted by heat. In addition, the torch not only melts down, but there is a possibility that surrounding parts may be damaged by the heat.

  For example, the type of torch set in the control unit of the ICP analyzer is applied if the internal volume is a standard size torch while actually mounting a small-sized torch with a small internal volume. Since the high frequency power is too large, the temperature of the torch rises and the torch melts. In addition, if the torch type set in the control unit is a small-sized torch while a standard-size torch is installed, the cooling gas flow rate will be insufficient and the torch temperature will rise. Then the torch melts down.

Japanese Patent Laid-Open No. 10-253540

  The problem to be solved by the present invention is to automatically determine whether or not the type of torch actually attached to the analyzer is the same as the type of torch set in the analyzer. It is to provide an ICP analyzer that can be used.

An ICP analyzer according to the present invention, which has been made to solve the above problems,
A plasma torch into which a plasma forming gas is introduced, an induction coil arranged around the plasma torch, and a power supply that generates high-temperature plasma in the plasma torch by applying high-frequency power to the induction coil An ICP analyzer comprising: a control unit that controls a high-frequency power, a gas flow rate, and the like according to a preset plasma torch type;
a) an impedance adjustment unit that adjusts the impedance to match the impedance of the induction coil and the output impedance of the power supply unit;
b) a reflected power measurement unit for measuring the reflected power value;
c) For each type of plasma torch, a storage unit in which a standard set value of the impedance adjustment unit and a standard reflected power value that is a value of reflected power in the standard set value are stored;
d) The reflected power value when the set value of the impedance adjusting unit is a standard set value stored in the storage unit corresponding to the type of plasma torch set in the ICP analyzer in advance, and the storage Whether the type of plasma torch set in the ICP analyzer is the same as the type of plasma torch installed in the ICP analyzer by comparing the standard reflected power value stored in the ICP analyzer A torch determination unit for determining
It is characterized by providing.

  In the ICP analyzer according to the present invention, preferably, the type of plasma torch set in the ICP analyzer is different from the type of plasma torch installed in the ICP analyzer by the torch determination unit. In this case, it is desirable to further include a power supply control unit that stops the operation of the power supply unit.

  The ICP analyzer according to the present invention can be applied to various analyzers using an ICP light source, such as an ICP emission spectroscopic analyzer and an ICP mass spectrometer.

  According to the ICP analyzer of the present invention, it is automatically determined whether or not the type of plasma torch actually attached to the ICP analyzer is the same as the type of plasma torch set in advance in the ICP analyzer. Therefore, if the setting is wrong or the wrong torch is installed, improper high-frequency power is applied to the torch, or gas with an inappropriate flow rate is introduced. It is possible to prevent problems caused by being performed.

  In addition, when the result of determination by the torch determination unit is that the type of plasma torch set in advance for the control unit of the ICP analyzer is different from the type of plasma torch installed in the ICP analyzer, the power supply If the power supply control unit is further provided to stop the operation of the part, it is possible to reliably prevent the torch from being melted and to prevent damage to the peripheral part of the torch due to overheating. In using the ICP analyzer, high safety can be ensured.

Hereinafter, an ICP analyzer according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the main part of the ICP analyzer of this embodiment. The ICP analyzer of the present invention includes a plasma torch 1 that can be attached and detached, an induction coil 2 wound around the plasma torch 1, a power supply unit 5 for supplying high frequency power (incident power 21) to the induction coil 2, The impedance adjustment unit 3, the reflected power measurement unit 4 that measures the value of the reflected power returned from the impedance adjustment unit 3, and the control unit 6 are provided. For each type of plasma torch, a storage unit 8 in which a standard set value of the impedance adjusting unit 3 and a reflected power value at the standard set value (details will be described later) are stored is connected to the control unit 6 so as to be accessible. ing. The control unit 6 further includes a torch determination unit 7 that is a function realized by the CPU of the control unit 6 executing a predetermined program (the torch determination unit 7 is configured by hardware by a circuit or the like). It is good.)
In FIG. 1, the description of the other components of the ICP analyzer, such as a spectroscope, a detector, a data processing unit (see FIG. 3), is omitted.

  The control unit 6 is usually composed of a CPU, various memories, a storage device such as a hard disk, and the like, and controls the flow rate of gas (cooling gas, auxiliary gas, carrier gas) supplied from the gas flow rate control unit 10 and timing of introduction. , Performing the control of the amount and timing of the sample supplied from the sample introduction unit 9, and performing various controls such as control of power supply to the power supply unit 5. In addition, the type of plasma torch to be used is previously set in the controller 6 by an operator.

  As described above, the impedance adjusting unit 3 includes a matching circuit for matching the impedance on the power supply unit 5 side and the impedance on the induction coil 2 side. This matching circuit is usually composed of a semi-fixed variable capacitor, and impedance matching is performed by appropriately changing only the capacitance of the other variable capacitor. However, the configuration of the impedance adjustment unit 3 according to the present invention is not particularly limited to this. The impedance adjustment unit 3 may adjust the impedance on the induction coil 2 side, or may adjust the impedance on the power supply unit 5 side.

  Further, the “set value” in the present invention refers to a set value of one or a plurality of variable capacitors in the impedance adjustment unit 3.

The “standard set value” is a set value set in advance according to the type of the plasma torch, and the value of the reflected power returned when a predetermined high frequency power is applied to the induction coil 2 at the set value. The set value is a value unique to the plasma torch.
Although the reflected power at the standard set value is preferably as small as possible, it is not always necessary to minimize the reflected power at the standard set value.

Next, an embodiment of the plasma torch determination process by the ICP analyzer according to the present invention will be described.
First, when the operator instructs the start of the plasma lighting process by performing a predetermined operation, the control unit 6 accesses the storage unit 8 and acquires a set value corresponding to the type of torch set in the control unit 6 in advance. Then, the set value is output to the impedance adjustment unit 3. The impedance adjustment unit 3 sets the matching circuit based on the set value.

  When high frequency power is applied to the induction coil 2 and the plasma is turned on, the power that was not supplied to the plasma as the incident power 21 is output as the reflected power 22. The reflected power measuring unit 4 measures the value of the reflected power 22 and outputs the reflected power value to the control unit 6.

Next, the torch determination unit 7 in the control unit 6 compares the standard reflected power value stored in the storage unit 8 with the reflected power value output from the reflected power measurement unit 4. When the reflected power value is smaller than the standard reflected power value, it is determined that the type of plasma torch set in the control unit 6 is the same as the type of plasma torch attached to the analyzer.
When the reflected power value is larger than the standard reflected power value, it is determined that the type of the torch that is mounted is different from the set type of torch.

  The above determination can also be made based on whether or not the reflected power value is within a predetermined error from the standard reflected power value.

  If the torch determination unit 7 determines that the type of plasma torch set in the control unit 6 and the type of plasma torch installed in the analyzer are the same, the control unit 6 continues with the sample Install and start analysis. Alternatively, a predetermined message indicating that the torch is set correctly is displayed on a display unit (not shown).

  When the torch determination unit 7 determines that the type of plasma torch set in the control unit 6 is different from the type of plasma torch installed in the analyzer, the control unit 6 is not shown. By displaying a predetermined error message on the display unit or generating a warning sound, the operator is notified that the setting is incorrect. The operator can immediately know that the setting of the torch in the control unit 6 is wrong (or the type of attached torch is wrong) by this error message or warning sound. Appropriate measures such as stopping the supply of electric power can be performed before the torch melts and the surrounding parts are damaged by heating.

  However, depending on the situation, the operator may not be aware of the error message or warning sound or may not be able to take appropriate action quickly. Therefore, the safety can be further improved by providing the power supply control unit 11 in the control unit as shown in FIG. The power supply control unit 11 is a function realized when the CPU of the control unit 6 executes a predetermined program. Of course, the power supply control unit 11 may be configured by a predetermined circuit or the like.

  In the case of this configuration, when the torch determination unit 7 determines that the type of torch set in the control unit 6 is different from the type of torch actually attached to the ICP analyzer, the power supply The control unit 11 transmits a control signal instructing to stop power supply to the induction coil 2 to the power supply unit 5 (or by stopping output of the control signal, Stop supplying.) As a result, overheating of the torch can be prevented without any operator intervention.

In the above embodiment, the torch is determined by comparing the reflected power value with the standard reflected power value based on the reflected power value at the standard setting value. In many cases, the reflected power value obtained at a certain standard setting value is close between a plurality of torches, and the determination accuracy of the torch may be lowered.
Therefore, in order to further improve the accuracy of determining the type of plasma torch, a fluctuation value (reflected power fluctuation value; details are described based on a change in the reflected power value when the set value is changed from the standard set value by a predetermined range. The torch can also be determined as described below.

  In the case of this configuration, the standard reflected power that is a value for comparison with the standard setting value of the impedance adjusting unit, the change range for changing the standard setting value, and the reflected power fluctuation value for each type of plasma torch in advance in the storage unit 8. Save the fluctuation value.

  When the start of the plasma lighting process is instructed, the control unit 6 accesses the storage unit 8 to acquire a set value corresponding to the type of torch set in the control unit 6 in advance, and the set value is used as the impedance adjustment unit. 3 is output. The impedance adjustment unit 3 sets the matching circuit based on the set value. Next, a predetermined high frequency power is applied to the induction coil 2, and the plasma is turned on. The reflected power measurement unit 4 measures the value of the reflected power 22 and outputs the reflected power value to the torch determination unit 7 of the control unit 6.

  The control unit 6 changes the set value output to the impedance adjustment unit 3 based on the change range of the standard set value stored in the storage unit 8. As the set value of the impedance adjusting unit 3 changes, the magnitude of the reflected power 22 returned from the induction coil 2 also changes. The reflected power measurement unit 4 outputs the reflected power value to the torch determination unit 7.

  The torch determination unit 7 calculates the reflected power fluctuation value based on the change in the reflected power value output from the reflected power measurement unit 4. The reflected power fluctuation value may be a difference between the maximum value and the minimum value of the reflected power value, or may be a standard deviation of the reflected power value at a plurality of setting values. Of course, the calculation method of the reflected power fluctuation value is not limited to these, and various numerical calculation methods can be used.

The torch determination unit 7 compares the calculated reflected power fluctuation value with the standard reflected power fluctuation value stored in the storage unit 8 in advance, and the type of plasma torch set in the control unit 6 and the analyzer It is determined whether or not the type of plasma torch attached to the is the same.
Since the reflected power fluctuation value obtained when the set value is changed in a certain range differs depending on the type of torch, more accurate determination can be performed by determining the torch by this method.

  The ICP analyzer according to the present invention has been described above. However, each of the above-described embodiments is merely an example, and modifications and modifications as appropriate within the spirit of the present invention are included in the scope of the claims of the present application. Obviously.

  Note that the set value when the high frequency power is first applied to the induction coil 2 may be different from the standard set value that is the set value for determining the torch.

  In the above embodiment, the torch determination is performed before the sample is introduced into the torch, but the torch determination may be performed after the sample introduction.

  Further, in the above embodiment, the torch determination unit 7 and the power supply control unit 11 are included in the control unit 6, but of course these may be provided outside the control unit 5.

The principal part block diagram of the ICP emission spectroscopy apparatus which concerns on this invention. The principal part block diagram of the other Example of the ICP emission spectroscopy apparatus which concerns on this invention. 1 is a schematic configuration diagram of a conventional ICP emission spectrometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plasma torch 2 ... Induction coil 3 ... Impedance adjustment part 4 ... Reflected electric power measurement part 5 ... Electric power supply part 6 ... Control part 7 ... Torch determination part 8 ... Memory | storage part 9 ... Sample introduction part 10 ... Gas flow rate control part 11 ... Power supply control unit 21 ... incident power 22 ... reflected power

Claims (6)

A plasma torch into which a plasma forming gas is introduced, an induction coil arranged around the plasma torch, and a power supply that generates high-temperature plasma in the plasma torch by applying high-frequency power to the induction coil An ICP analyzer comprising: a control unit that controls a high-frequency power, a gas flow rate, and the like according to a preset plasma torch type;
a) an impedance adjustment unit that adjusts the impedance to match the impedance of the induction coil and the output impedance of the power supply unit;
b) a reflected power measurement unit for measuring the reflected power value;
c) For each type of plasma torch, a storage unit in which a standard set value of the impedance adjustment unit and a standard reflected power value that is a value of reflected power in the standard set value are stored;
d) The reflected power value when the set value of the impedance adjusting unit is a standard set value stored in the storage unit corresponding to the type of plasma torch set in the ICP analyzer in advance, and the storage Whether the type of plasma torch set in the ICP analyzer is the same as the type of plasma torch installed in the ICP analyzer by comparing the standard reflected power value stored in the ICP analyzer A torch determination unit for determining
ICP analyzer characterized by comprising. In the storage unit, for each type of plasma torch, the standard setting value of the impedance adjustment unit, a change range in which the standard setting value is changed, and a change in reflected power value when the standard setting value is changed by the change range Standard reflected power fluctuation value based on is stored,
When the torch determination unit changes the set value of the impedance adjustment unit within a predetermined range from the standard set value stored in the storage unit corresponding to the type of plasma torch set in the ICP analyzer in advance The reflected power fluctuation value is calculated based on the change in the reflected power value, and the reflected power fluctuation value is set in the ICP analyzer by comparing the reflected power fluctuation value with the standard reflected power fluctuation value stored in the storage unit. The ICP analyzer according to claim 1, wherein it is determined whether or not the type of the plasma torch is the same as the type of the plasma torch attached to the ICP analyzer. e) Stops the operation of the power supply unit when the torch determination unit determines that the type of plasma torch set in the ICP analyzer is different from the type of plasma torch installed in the ICP analyzer. The ICP analysis apparatus according to claim 1, further comprising a power supply control unit for causing the power supply control unit to operate. A plasma torch into which a plasma forming gas is introduced, an induction coil arranged around the plasma torch, and a power supply that generates high-temperature plasma in the plasma torch by applying high-frequency power to the induction coil An ICP analyzer comprising: a control unit that controls a high-frequency power, a gas flow rate, and the like according to a preset plasma torch type;
The setting value of the impedance adjustment unit that adjusts the impedance to match the impedance of the induction coil and the output impedance of the power supply unit is a standard setting value that is stored in advance in the storage unit,
Obtain the reflected power value when a predetermined high frequency power is applied to the induction coil,
The plasma set in the ICP analyzer is compared by comparing the reflected power value with a standard reflected power value stored in advance in the storage unit corresponding to the type of plasma torch set in the ICP analyzer. A method for determining a plasma torch for an ICP analyzer, comprising: determining whether or not the type of torch and the type of plasma torch attached to the ICP analyzer are the same. A plasma torch into which a plasma forming gas is introduced, an induction coil arranged around the plasma torch, and a power supply that generates high-temperature plasma in the plasma torch by applying high-frequency power to the induction coil An ICP analyzer comprising: a control unit that controls a high-frequency power, a gas flow rate, and the like according to a preset plasma torch type;
The impedance adjustment unit that adjusts the impedance to match the impedance of the induction coil and the output impedance of the power supply unit is set to the induction coil while changing the set value of the impedance adjustment unit by a predetermined range from the standard setting value stored in the storage unit in advance. Obtain the reflected power value when a predetermined high frequency power is applied to the
Calculate the reflected power fluctuation value based on the change in the reflected power value,
The reflected power fluctuation value is set in the ICP analyzer by comparing the reflected power fluctuation value with the standard reflected power fluctuation value previously stored in the storage unit corresponding to the type of plasma torch set in the ICP analyzer. A method for determining a plasma torch for an ICP analyzer, comprising: determining whether or not the type of plasma torch installed is the same as the type of plasma torch attached to the ICP analyzer. When the plasma torch determination method according to claim 4 or 5 determines that the type of plasma torch set in the ICP analyzer is different from the type of plasma torch installed in the ICP analyzer, A method of controlling an ICP analyzer, wherein the operation of the power supply unit is stopped.

Images