JPS6054618B2 - Emission spectroscopy method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention performs repeated discharge between a discharge electrode and a sample, and uses the light produced by the discharge to perform optical emission spectroscopic analysis. This invention relates to an analysis method that allows simultaneous analysis of these elements in a single analysis operation.

In the optical emission spectrometry method, a spark-like or arc-like discharge is generated in a discharge gap formed between a sample and an electrode facing it, and the light emitted by this discharge is detected. For low-pressure spark discharge, which is generally used as a light source for spectroscopy, the discharge duration is in the range of 20 to 100 μsec because the reproducibility of analysis results is good and matrix effects due to sample evaporation are small. .

However, with such a short-time discharge, sensitivity may be low for certain elements contained in trace amounts in the metal of the sample, and sufficient analytical accuracy may not be obtained. In order to increase analytical sensitivity and accuracy for such elements, it is necessary to use arc-like discharge with a long discharge duration of several hundred microseconds or more. For this reason, in some cases, it may be necessary to perform the analysis multiple times for the same type of sample, such as using spark-like discharge to analyze certain elements and arc-like discharge to analyze other elements. . The present invention aims to provide an emission spectroscopic analysis method that can analyze both elements suitable for spark-like discharge and elements suitable for arc-like discharge in a single analysis in the above-mentioned case.

The light source of the emission spectrometer is designed to charge a capacitor with discharge energy, apply a trigger voltage to the discharge gap, and discharge the charge in the capacitor through the discharge gap. By appropriately setting the time constant of discharge, it becomes spark-like discharge or arc-like discharge.

Although they are called spark-like discharge and arc-like discharge, they are not essentially different; they are simply distinguished by the length of the discharge duration, and there is no clear boundary between the two. In the present invention, a plurality of discharge energy storage circuits having different capacitances and discharge time constants are connected in parallel or series to one discharge gap, and a trigger signal is applied to the discharge gap to trigger the discharge. The plurality of energy storage circuits are sequentially discharged so that a spark-like discharge and an arc-like discharge occur successively in one discharge gap, so that an element suitable for spark-like discharge and an arc-like discharge are generated in each discharge. Ensure that the luminescence of both types of suitable elements is obtained,
An analysis method is provided in which such discharge is repeated to complete the analysis of both types of elements in one analysis operation. The present invention will be explained below with reference to Examples. FIG. 1 shows a circuit of an apparatus according to an embodiment of the present invention.

In this embodiment, two energy storage circuits are connected in parallel to one discharge gap G. One of the energy storage circuits is made up of a rectifier circuit 1, a capacitor C1, a resistor R1, a choke coil L1, and a diode D1, and the other energy storage circuit is made up of a rectifier circuit 2 and a capacitor C.
2, a resistor R2, a choke coil L2, and a diode D2. AC is a common alternating current power supply for rectifier circuits 1 and 2, and rectifier circuit 1 rectifies this alternating current power supply voltage to V
A DC voltage of 1 is generated, and a capacitor C1 connected to this rectifier circuit is charged to a voltage of 1. S1 is a charging switch inserted in the charging circuit in series with the capacitor C1, and is closed when the light source is used. Capacitor C1, resistor R1, choke L1, diode D1, choke L3, discharge gap G
A closed circuit of one capacitor C1 is one discharge circuit, and the time constant of this discharge circuit is determined by the capacitance of the capacitor C1, the resistor R1, and the inductance of the chokes Ll and L3. Similarly, the rectifier circuit 2 is connected to the voltage V2. A current voltage is generated and the capacitor C2 is charged to voltage 2. S2 is a switch inserted in the charging circuit in series with the capacitor C2, and is closed when the light source is used, and is equivalent to the switch S1, but S1 and S2 can be opened and closed independently. Sl and S2 are independent. The advantages of this will be discussed later. The energy storage circuit mainly composed of the capacitor C2 and the one mainly composed of the capacitor C1 have exactly the same configuration, and both are connected to each other closer to the discharge gap G than the diodes D1 and D2 and before the choke L3, and both the diodes D1 and D2 are connected to each other in front of the choke L3. The direction is such that conduction is directed toward the discharge gap/gap G. C3 is a capacitor connected in parallel to both energy storage circuits at the connection point between the two energy storage circuits. With the above configuration, the design selection is V1>V2, Cl, C2, Rl
It is set to R2 and L2.

Due to the above relationship, C1 in the two energy storage circuits
The discharge time constant of the energy storage circuit mainly composed of C2 is smaller than the discharge time constant of the energy storage circuit mainly composed of C2. Therefore, the discharge when only the charge of the energy storage circuit mainly composed of C1 is discharged is spark-like, and on the contrary, the discharge of the energy storage circuit mainly composed of C2 is arc-like discharge. Capacitor C1 is charged to voltage V1, C2 is charged to V2, and ■1>
V2, but since there are diodes Dl and D2, Cl and C
2 are charged independently of each other, and the voltage V1 is initially acting on the discharge gap G. In this state, when a trigger voltage is applied to the gap G to trigger discharge, the capacitor C1 is discharged, and as long as the charging voltage of C1 is higher than that of C2, the discharge of C2 is suppressed. When the charging voltage of C1 decreases to 2 or less, C2 also starts discharging, and discharge currents of both Cl and C2 flow through the discharge gap G. FIG. 2 is a graphical representation of the operation described above.

T is the trigger voltage waveform, and v1 is the charging voltage of the capacitor C1. To be more precise, the cathode side voltage of D1 is saturated.
When the trigger voltage is applied to the discharge gap G, it suddenly drops as a discharge. i1 is the discharge current of capacitor C1.
V2 is the charging voltage of the capacitor C2, more precisely the cathode side voltage of D2, which is saturated at voltage 2. C2 until capacitor C1 starts discharging and its charging voltage becomes less than ■1.
The discharge of is suppressed, but at the time t when v1 becomes ■2
Then capacitor C2 starts discharging. 12 is the discharge current of the capacitor C2.

After time t when capacitor C2 starts discharging, v1 and V
2 and 2 decrease while maintaining the same level, and at time t'' the discharge in the discharge gap G stops, and the capacitors Cl and C
2 charging starts. IO is the sum of the discharge currents of capacitors Cl and C2, and represents the discharge current in the discharge gap G, where the range a corresponds to spark-like discharge, and the range b corresponds to arc-like discharge. Spark-like discharge and arc-like discharge are realized during one discharge in the same discharge gap. By changing the relationship of circuit constants in Fig. 1, C1>C2, Rl>R2,
When Ll>L2, the energy storage circuit mainly composed of capacitor C1 has a larger discharge time constant than the one mainly composed of C2, and under the relationship V1>■2, arc-like discharge starts first, In the middle of the discharge, spark-like discharge overlaps, and the current in the discharge gap G is shown in Figure 2 1.
The shape will be as shown in .

FIG. 3 shows another embodiment of the invention, in which two energy storage circuits are connected in series.

Portions corresponding to those in the example of FIG. 1 are given the same reference numerals, and individual explanations will be omitted. The entire circuit configuration is a series connection of the inverted L-shaped circuit of (1), in which the capacitor is a parallel element and the choke is a series element, and diodes Dl and D2 are connected in parallel with each capacitor Cl and C2 to counter the charging voltage. It is inserted in the direction shown. In this configuration, the inductance is L2>L1
It is assumed that the capacitance of the capacitor is C1≧C2. In the energy storage circuit mainly composed of the capacitor C2, two chokes are connected in series to the discharge circuit, so that the discharge time constant can be made larger than that of the energy storage circuit mainly composed of the capacitor C1. In this circuit configuration, the saturation charging voltages of the capacitors Cl and C2 are equal, and if discharge is now triggered in the discharge gap G, the discharge currents of the capacitors Cl and C2 change as shown in FIG. 4, 11, i2. The change in I2 is determined by the voltage across the Qi yoke L2, and this value is initially small and gradually increases. When the capacitor C1 is discharged and i1 exceeds the maximum value, the voltage at the upper terminal of C1 tends to become negative. The current in choke L1 is blocked by diode D1. The flow is prevented from decreasing. This prevention of current reduction in the choke L1 is provided by the discharge current 12 of the capacitor C2. Therefore, the discharge current in the discharge gap G changes as shown in FIG. 4, with the range a being a spark-like discharge and the range b being an arc-like discharge. The optical emission spectrometry analysis method of the present invention has the above-described configuration, in which a plurality of energy storage circuits are connected to one discharge gap, and these energy storage circuits are sequentially discharged during one light emission. It is possible to achieve both spark-like discharge and arc-like discharge during a single light emission in the gap, and it is possible to simultaneously analyze the same sample for elements suitable for either of the discharge types. It became.

For example, when analyzing cast iron or pig iron, it was difficult to achieve a stable evaporation state of the sample using either spark-like or arc-like discharge alone, but now stable evaporation is possible, and P,
The detection sensitivity of trace element elements such as S, Pb, Sn, and Sb has been greatly improved, and the accuracy of analysis has also improved as the reproducibility of analysis has improved. Note that the switches Sl and S2 are capacitors Cl.
, C2 in series with the capacitors Cl and C2. If one of these switches is left open, the capacitors in series with it are removed from the entire circuit, and the circuit is closed. This is equivalent to a circuit having only one energy storage circuit, and for example, only spark-like discharge or arc-like discharge can be performed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a device according to one embodiment of the present invention, FIG. 2 is a glass for explaining the operation of the above circuit, FIG. 3 is a circuit diagram of another embodiment of the device according to the present invention, and FIG. It is a graph explaining the operation of the circuit. G: discharge gap, 1, 2: rectifier circuit,
Cl, C2... Capacitors that form the main body of the energy storage circuit.

Claims (1)

[Claims] 1. A discharge in which spark-like discharge and arc-like discharge coexist in one period in one discharge gap by connecting multiple types of discharge energy storage circuits with different discharge time constants in parallel or in series in one discharge gap. 1. An emission spectroscopic analysis method characterized in that it enables simultaneous analysis of both elements suitable for spark-like discharge and elements suitable for arc-like discharge.