JPH05151931A - High frequency induction coupling type plasma mass-spectrometer - Google Patents

Abstract

PURPOSE:To provide a plasma mass-spectrometer of high frequency induction coupling type, which can find quickly and set automatically the optimum value of sensor voltage and the optimum setting value of the discrimination level of a pulse height discriminator and which can analyze the elements to be measured as components of a specimen always with the optimum sensitivity. CONSTITUTION:The output of a pulse counter 24 to count output pulses from a pulse height discriminator 23 is monitored, and meantime the optimum value of sensor voltage and the optimum value of the discrimination level setting value in the discriminator 23 are sought using a controller 25 which is to change the voltage of a sensor 21 and the set value on the discriminator 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency wave for supplying a high frequency energy to a high frequency induction coil to form a high frequency magnetic field to generate a high frequency inductively coupled plasma and analyzing the element to be measured in a sample using the plasma. Regarding the inductively coupled plasma mass spectrometer (hereinafter referred to as “ICP-MS”), more specifically, the optimum value of the detector voltage and the optimum setting value of the discriminator level of the pulse height discriminator are automatically calculated in a short time. The present invention relates to an ICP-MS that can be found and set explicitly and can always analyze an element to be measured in a sample with optimum sensitivity.

[0002]

2. Description of the Related Art FIG. 2 is an explanatory view of a general structure of an ICP-MS. In this figure, the argon gas is supplied from the argon gas supply source 3 to the outer chamber 1b and the outermost chamber 1c of the plasma torch 1 through the gas regulator 2, and the inner chamber 1a is filled with solids in the sample introduction device 4. The sample is vaporized by the laser light emitted from the laser light source 5 and then carried in by an argon gas which is a carrier gas. Also, the high frequency induction coil 6 wound around the plasma torch 1
A high-frequency current is applied to the coil 6 by a high-frequency power source 10, and a high-frequency magnetic field (not shown) is formed around the coil 6. In this state, when electrons or ions are implanted in the argon gas in the vicinity of the high frequency magnetic field, the high frequency inductively coupled plasma 7 is instantaneously generated by the action of the high frequency magnetic field.

Further, the inside of the fore chamber main body 11 sandwiched between the nozzle 8 and the skimmer 9 is sucked by a vacuum pump 12. Further, in the center chamber 13, an extraction electrode 14a, an aperture lens 14b, a quadrupole lens 14c, an aperture 14d, and an entrance lens 14e are provided, and the inside of the center chamber 13 is provided. Is sucked by the first oil diffusion pump 15, and the inside of the rear chamber 17 housing the quadrupole mass filter 16 is sucked by the second oil diffusion pump 18.

In this state, the sample vaporized as described above is introduced into the high frequency inductively coupled plasma 7, and ionization and light emission are performed. The ions in the plasma 7 are converged through the nozzle 8 and the skimmer 9 and then between the extraction electrodes 14a and the ion lens system, and are introduced into the quadrupole mass filter 16. In this way, among the ions that have entered the quadrupole mass filter 16, only the ions having the target mass-to-charge ratio pass through the quadrupole mass filter 16 and are guided to the secondary electron multiplier 19 to be detected. The detection signal is sent to the signal processing unit 20 and is calculated and processed to obtain the elemental analysis value of the measured element in the sample.

On the other hand, when tuning the ICP-MS, the value of the detector voltage and the set value of the discrimination level of the pulse height discriminator are input by turning the potentiometer or inputting from the keyboard of the controller. Was taken.

[0006]

However, in the above-mentioned conventional example, due to the deterioration of the detector caused by the normal use of the ICP-MS, the optimum value of the detector voltage and the pulse height discriminator of the pulse height discriminator are reduced. The optimum setting value of the discrimination level was changing daily. Further, in order to search for the optimum value of the detector voltage and the optimum setting value of the discriminator level of the pulse height discriminator, the value of the detector voltage and the pulse of the pulse are detected by trial and error while observing the output of the detector. The set value of the discriminator level of the height discriminator was input.

Since it is complicated to set the optimum value of the detector voltage and the optimum set value of the discrimination level of the pulse height discriminator as described above, the ICP is actually set to the initially set value. -If a phenomenon such as a decrease in detection sensitivity becomes apparent after using the MS for a while, reset the optimum value of the detector voltage or the discriminator level of the pulse height discriminator to the optimum setting value. The method was taken. The present invention has been made in view of such circumstances, and an object thereof is to automatically find an optimum value of a detector voltage or an optimum set value of a discriminator level of a pulse height discriminator in a short time. The purpose of the present invention is to provide an ICP-MS that can be set according to the above conditions and can always analyze the element to be measured in the sample with optimum sensitivity.

[0008]

The present invention is an ICP-M
In S, a pulse amplifier for amplifying the pulse output from the detector, a pulse height discriminator for outputting only when the output of the pulse amplifier exceeds a discrimination level set value, and the pulse height discriminator A pulse counter that counts the output pulses of the pulse counter and a controller that changes the voltage of the detector and the set value of the pulse height discriminator while monitoring the output of the pulse counter, and the controller optimizes the detector voltage. The problem is solved by searching for the optimum value of the value and the set value.

[0009]

The present invention operates as follows. That is, ICP-
After setting both the voltage value of the MS detector and the set value of the discriminator level of the pulse height discriminator to 0 V, the discriminator level of the pulse height discriminator is changed little by little, and the pulse counter of the pulse counter is changed. The part where the output count becomes zero is searched for and used as the set value of the discrimination level. Then, while monitoring a predetermined signal such as the signal of an argon dimer having a mass number of 80, the voltage of the detector is increased until the count reaches a constant count number such as 100 counts per second, and the voltage is increased. The value is the detector voltage.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block circuit diagram of an essential part of an embodiment of the present invention, in which 21 is an ICP-MS detector, 22 is a pulse amplifier for amplifying the pulse output from the detector 21,
Reference numeral 23 is a pulse height discriminator that outputs only when the output of the pulse amplifier 22 exceeds the discrimination level set value, 24 is a pulse counter that counts the output pulses of the pulse height discriminator 23, and 25 is a pulse counter. The controller changes the voltage of the detector 21 and the set value of the pulse height discriminator while monitoring the output of 24. In the embodiment of the present invention composed of such a block circuit of the main part, first, both the value of the detector voltage and the set value of the discrimination level of the pulse height discriminator 23 are set to 0V. Next, the discriminating level of the pulse height discriminator 23 is changed little by little, and a place where the output counter of the pulse counter 24 becomes zero is searched for and set as the set value of the discriminating level. Thereafter, while monitoring a predetermined signal such as a signal of an argon dimer having a mass number of 80, for example, the voltage of the detector 21 is increased until a constant count number such as 100 counts per second is reached. Let the voltage value be the detector voltage.

In this way, while monitoring the output of the pulse counter for counting the output pulses of the pulse height discriminator,
A controller that changes the detector voltage and the pulse height discriminator set value enables you to search for the optimum detector voltage and pulse height discriminator level discriminator level set values. .. The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the following may be adopted. The detector voltage is set to, for example, -1500V.

Mass number 80 amu. A predetermined signal, such as the argon dimer signal of. Discrimination level is, for example, 0.2 mV
Change gradually from the setting value of and record the discrimination level and the number of counts at that time. ∂┯ Calculate the rate of change of the count number at each discrimination level from the data obtained above. This rate of change corresponds to the differential value of the data obtained above and indicates the distribution of the pulse height of the signal. The voltage of the detector 21 is changed little by little, and the above operation is repeated for each voltage. In the distribution chart showing the pulse height of the signal, the detector voltage at which the pulse height with the highest distribution becomes the predetermined value V1 is obtained,
This is the set value. Further, the detector voltage may be set by performing the following operations after the above operations (1) to (3). A distribution chart showing the pulse height of the signal is obtained, and in the distribution chart, the detector voltage is set so that there are almost no pulses near 0 mV and most of the pulses exist at 1 mV or higher.

[0013]

According to the present invention as described in detail above, the output of the pulse counter can be automatically changed while automatically changing the detector voltage and the set value of discrimination without using any other measuring device. The optimum values of the discriminator level setting value and the detector voltage can be searched for and set in a short time by monitoring the output and performing signal processing on the output to determine. Therefore, according to the present invention, the optimum value of the detector voltage and the optimum setting value of the discriminator level of the pulse height discriminator are automatically found and set in a short time, and the optimum value of the sample in the sample is always detected with the optimum sensitivity. ICP-MS that can analyze the element to be measured is realized.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an essential part of an embodiment of the present invention.

FIG. 2 is a general configuration explanatory diagram of an ICP-MS.

[Explanation of symbols]

 21 detector 22 pulse amplifier 23 pulse height discriminator 24 pulse counter 25 controller

Claims (1)

[Claims] 1. A pulse amplifier for amplifying a pulse output from a detector, a pulse height discriminator for outputting only when the output of the pulse amplifier exceeds a discrimination level set value, and the pulse height. A pulse counter that counts the output pulses of the discriminator, and a controller that changes the voltage of the detector and the set value of the pulse height discriminator while monitoring the output of the pulse counter, and the detector is used by the controller. A high frequency inductively coupled plasma mass spectrometer, which is configured to search for an optimum value of voltage and an optimum value of the set value.