JPH0527216B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to atmospheric pressure ionization mass spectrometers, particularly the shapes of the needle electrode and the counter electrode, and is particularly applicable to introducing a large amount of gas or atomizing a solution sample. The present invention relates to an atmospheric pressure ionization mass spectrometer having a needle electrode and a counter electrode suitable for introduction.

[Background of the invention]

Atmospheric pressure ionization mass spectrometry is known as a highly sensitive ionization method, but attempts have also been made to atomize and analyze not only gas samples but also solution samples.
[For example, Anal, Chem., 54, 143 (1982)] In all of these methods, a sample is ionized using corona discharge from a needle electrode. The prior art will be explained based on FIG. The needle electrode 1 has a straight shape, and its tip faces a pore 4 of a flat counter electrode 3 for passing ions to an analysis section. With such a shape of the needle electrode 1, when a solution is atomized, large droplets (several 100 μm) directly hit the pores 4 (40 to 100 μm in diameter) of the counter electrode 3.
There was a drawback that the pores 4 became clogged, making it difficult to observe ions. Further, as shown in FIG. 1, the flat counter electrode 3 has the drawback that excess gas near the pores 4 has difficulty escaping to the outlet 2, making it easy to cause clogging.

[Purpose of the invention]

The purpose of the present invention is that even if a large amount of gas from an atmospheric pressure ion source is introduced or a solution sample is atomized and introduced,
It is an object of the present invention to provide a corona discharge needle electrode and a counter electrode shape that are unlikely to cause clogging.

[Summary of the invention]

When a solution sample is atomized, large mist droplets tend to fly away quickly, but to prevent large mist droplets from directly hitting the pores of the counter electrode, the tip of the needle electrode should be bent in a dogleg shape. It was bent so that the pores were hidden by the needle electrode. An obstacle was also placed in front of the hole to prevent large particles from hitting it. Also,
In order to prevent excess gas from remaining in the vicinity of the pores of the counter electrode, the shape of the counter electrode was changed from the conventional flat plate shape to a skimmer shape.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The sample introduced from the gas inlet is 500V~
It is ionized by the corona discharge needle electrode 7 applied with a voltage of 1000V, and the pores 4 (40 to 40) of the counter electrode 3 are ionized.
100 μmφ) and subjected to mass analysis in the analysis section of an atmospheric pressure ionization mass spectrometer. A solution sample is atomized using an ultrasonic vibrator, or a few μmφ
Sometimes the diameter is 100μmφ when sprayed from the pores of
Larger mist droplets may occur. In order to prevent such large mist droplets from directly hitting the pores 4, the tip of the needle electrode 7 was bent about 3 mm into a dogleg shape.
The tip of the needle electrode 7 is in the normal direction to the counter electrode 3, and the distance between the electrodes 3 and 7 is 3 to 5 mm.
The large mist droplets that fall from the center of the pipe become fine as they hit the needle electrode 7, and the opposite electrode 3
The problem of clogging of the pores 4 is reduced. Also,
The needle electrode 7 may be provided with a ball 8 (FIG. 4), or the needle electrode 7 may be provided with an obstacle 9 behind it (FIG. 3).

Further, at this time, the counter electrode 3 is of a skimmer type, and the inclination of the cone is about 30°. In this way, if the counter electrode 3 is made into a skimmer type, surplus gas that is not sampled from the pores 4 can easily escape to the surplus gas outlet 2 through the wall of the counter electrode 3. In particular, the effect of the shape of the counter electrode 3 appears when a sample in a solution is atomized and introduced, and has the effect of making the pores 4 less likely to become clogged.

〔Effect of the invention〕

According to the present invention, since large mist droplets do not directly hit the pores, the problem of pore clogging can be greatly alleviated. Furthermore, since excess gas is less likely to stay near the pores of the counter electrode, clogging can be mellowed out.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an atmospheric pressure ion source using a conventional flat plate type pore electrode, and Fig. 2 is a block diagram of an atmospheric pressure ion source using a cone shaped pore electrode according to the present invention. FIGS. 3 and 4 are sectional views showing other embodiments of the needle electrode for corona discharge according to the present invention. DESCRIPTION OF SYMBOLS 1... Needle electrode for corona discharge, 2... Excess gas outlet, 3... Counter electrode, 4... Pore, 5... Atmospheric pressure ion source block, 6... Insulator for supporting needle electrode for corona discharge, 7... Needle electrode for corona discharge, 8...
Ball, 9...obstacle.

Claims (1)

[Claims] 1. A corona discharge electrode that ionizes the sample is provided in the passageway into which the gas into which the gaseous or liquid sample is atomized is introduced, and a corona discharge electrode is provided in the counter electrode facing the tip of the corona discharge needle electrode. In an atmospheric pressure ionization mass spectrometer that samples an ionized sample into the analysis section of the mass spectrometer, the counter electrode has a cone shape, and the pore is provided at the tip of the counter electrode. The needle electrode for corona discharge is provided with a bent part or a branched part near the tip thereof, and the needle electrode for corona discharge is provided with a bent part or a branched part near the tip of the needle electrode, and A bead-like member is provided in the part, and the bead-like member is arranged to cover the pore when viewed from the direction in which the atomized gas is introduced, and the tip of the corona discharge needle electrode is located close to the pore. An atmospheric pressure ionization mass spectrometer, characterized in that the atmospheric pressure ionization mass spectrometer is disposed between the ball-shaped member and the pore in the normal direction of the ionization mass spectrometer.