In order to verify the influence of the internal volume of a solenoid valve on chromatographic analytical accuracy, a research project was performed using two different valve types:

• Standard Valve
• Zero-Dead-Volume Valve

The internal volume of the standard solenoid valve is composed of a flow path and a valve chamber. Media in the flow path are not trapped, but there is space where such media are apt to be structurally trapped in the valve chamber. This space is called the 'Dead-Volume.' It sometimes causes a decline in the media's purity and cleanliness, negatively affecting analysis accuracy. The Zero-Dead-Volume valve has a unique design that eliminates the internal volume in the valve chamber. We compared the analytical accuracy obtainable using the different valves in this test.

• Zero-Dead-Volume Valve

The details of the research and the results are as follows:

Comparative Table of the Internal-Volume

Diagram 1: Results of the Measurements

Note: Details such as specifications, etc., may be changed without notice.

Diagram 1 shows the results of a standard sample gas analysis using a Zero-Dead-Volume valve and a standard valve. As can be seen from the diagram, the peaks obtained using the standard valve are obtuse. In addition, the roots of each peak are broad, and there are parts in which some ingredients mix. In comparison, the heights for the Zero-Dead-volume valve are acute, and the widths of the roots of each peak are not wide. The acuteness of the peaks shows that the performance in separation was of high quality. As a result, we can confirm that the Zero-Dead-volume valve improves the performance of a gas sampling control device and the accuracy in chromatographical analysis.

• Zero-Dead-Volume Valve

Details of the Measuring Method

Sample gas was collected by low-temperature condensation at the concentrator (a trap made of stainless steel) in a gas sampling control device and then placed in an analyzer after heating and removal from the concentrator. Ideally, the flow path from the concentrator to the analyzer should be zero.

The circuit for fluid control is composed of solenoid valves as follows:

Separation Circuit Chart

Note: Details such as specifications, etc., may be changed without notice.

Details of the Separation Conditions:

• Column: HP-INNOWAX (Inner Diameter: 0.25 mm, Length: 30 m, and Cross-Linked Polyethylene Glycol Stationary Phase of 0.25 μm)
• Carrier Gas: He (Pressure: 79 kPa)
• Column Temperature: 45°C
• Gas Chromatograph (Detector): GC-17A (Method: FID)
• Standard Sample: Acetone, Ethanol, and Methanol (1 ng Injection)

Note 1: Details such as specifications, etc., may be changed without notice.

Note 2: The gas sampling control device used for the above experiment was developed in a joint research project with the Nagoya Institute of Technology.

Note 3: The above experiment was conducted in a joint research project with the Nagoya Institute of Technology.

Reference: 'Chromatography-Mechanism of Separation and Application' Takao Tsuda, 2^nd Edition, Maruzen, 1995 (Published in Japanese)