Gas chromatograph

• US 6,338,823 B1
• Filed: 04/15/1999
• Issued: 01/15/2002
• Est. Priority Date: 06/30/1998
• Status: Expired due to Fees

• Current Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Original Assignee: Shimadzu Corporation
• Inventors: Furukawa, Masanao
• Primary Examiner(s): Warden, Jill
• Assistant Examiner(s): GAKH, YELENA G
• Application Number:
  US09/292,315
• Time in Patent Office: 1,006 Days
• Field of Search: 422/89, 422/23.22, 73/233.5, 73/233.6, 73/233.9, 73/234.2, 95/12, 95/19, 95/22, 95/23, 95/25
• US Class Current: 422/89
• CPC Class Codes: G01N 2030/025 Gas chromatography
• CPC Class Codes: G01N 2030/324 speed, flow rate
• CPC Class Codes: G01N 30/10 using a splitter
• CPC Class Codes: G01N 30/32 of pressure or speed G01N30/36 takes precedence

Abstract

A gas chromatograph has a pressure sensor measuring a pressure in a sample introduction part, a flow control valve controlling carrier gas flow rate, a flow sensor measuring a flow rate of the carrier gas, a split flow path exhausting part of a carrier gas and sample from the introduction part, an exhaust valve placed in the sprit flow path, and a monitor screen. The controller controls the flow control valve to flow the carrier gas at the designated flow rate into the introduction part, reads an output of the pressure sensor after making the exhaust valve fully open, calculates a flow path resistance of the filter by using an output of the pressure sensor and a flow path resistance of the chromatographic column, and controls the monitor screen to display an indication for exchanging the filter when the calculated resistance reaches the preset value corresponding to a state in which the filter is stuffed.

Claims

1. A gas chromatograph for analyzing elements in a sample by introducing said sample into and separating the elements through a column, comprising:

a chromatograph column with a sample introduction part;

pressure measuring means for measuring a pressure in said sample introduction part;

flow control means, placed in a flow path supplying carrier gas into said sample introduction part, for controlling a flow rate of said carrier gas;

flow measuring means, placed in said flow path, for measuring said flow rate of said carrier gas;

a split flow path, connected to said sample introduction part, exhausting part of said carrier gas and sample from said sample introduction part;

a filter, placed in said split flow path, protecting said split flow path from becoming clogged;

an exhaust valve, having an opening placed in said split flow path downstream of said filter, adjusting a flow rate in said split flow path;

a controller calculating a flow path resistance of said filter based on a flow path resistance of said column, a pressure measured by said pressure measuring means when said exhaust valve is in an opened position, and a flow rate measured by said flow measuring means when said exhaust valve open, said controller controlling a monitor screen to display information based on said filter resistance by which the necessity to exchange said filter can be determined; and

the monitor screen connected to said controller displaying information related to said filter.

2. A gas chromatograph according to claim 1, wherein said controller obtains said column resistance “

r”

based on the following formula, using temperature of the column (t), inside diameter of the column (D), length of the column (L), pressure at the inlet of the column (P1), pressure of the atmosphere (PA), viscosity of said carrier gas (U), and a proportional coefficient (K1);

3. A gas chromatograph according to claim 1, wherein said controller gets said column resistance “

r”

from the following formula based on a flow rate “

f”

measured by said flow measuring means when said exhaust valve is in a closed position and a pressure P measured by said pressure means when said exhaust valve is closed;

4. A gas chromatograph according to claim 1, wherein said controller calculates said filter resistance from the following formula based on said column resistance “

r”

, a pressure “

P”

measured by said pressure measuring means in said exhaust valve when open, and a flow rate “

F”

measured by said flow measuring means in said exhaust valve when open;

5. A gas chromatograph according to claim 1, wherein said controller compares said filter resistance to a clogged resistance corresponding to a state in which said filter is clogged and when said filter resistance becomes greater than said clogged resistance, said controller displays an indication to exchange said filter on said monitor screen.

6. A gas chromatograph according to claim 1,

wherein said pressure measuring means is a pressure sensor sending an output thereof to said controller,

said flow control means is a flow control valve controlled by said controller,

said flow measuring means is a flow sensor sending an output thereof to said controller,

said exhaust valve is controlled by said controller, and

said controller controls said exhaust valve to open, then reads outputs of said pressure sensor, and said flow sensor, and calculates said filter resistance.

7. A gas chromatograph according to claim 1,

wherein said pressure measuring means is a pressure gauge,

said flow control means is a flow valve,

said flow measuring means is a flowmeter, and

said exhaust valve is a needle valve.

8. A gas chromatograph for analyzing elements in a sample by introducing said sample into and separating the elements through a column, comprising:

a chromatograph column with a sample introduction part;

pressure measuring means for measuring a pressure in said introduction part;

flow control means, placed in a flow path supplying carrier gas into said introduction part, for controlling a flow rate of said carrier gas;

flow measuring means, placed in said flow path, for measuring said flow rate of said carrier gas;

a split flow path, connected to said sample introduction part, exhausting part of carrier gas and sample from said sample introduction part;

a filter, placed in said split flow path, protecting a said split flow path from being clogged;

an exhaust valve, having an opening placed in said split flow path downstream of said filter, adjusting a flow rate in said split flow path;

a controller calculating a flow path resistance of said filter based on a flow path resistance of said column, a pressure measured by said pressure measuring means when said exhaust valve is open, and a flow rate measured by said flow measuring means when said exhaust valve is open, said controller connected to a buzzer, which buzzer sounds when the controller determines that an exchange of said filter is necessary based on said filter resistance.

9. A gas chromatograph according to claim 8, wherein said controller obtains said column resistance “

r”

based on the following formula using temperature of the column (t), inside diameter of the column (D), length of the column (L), pressure at the inlet of the column (P1), pressure of the atmosphere (PA), viscosity of said carrier gas (U), and a proportional coefficient (K1);

10. A gas chromatograph according to claim 8, wherein said controller obtains said column resistance “

r”

from the following formula based on a flow rate “

f”

measured by said flow measuring means in said exhaust valve when closed and a pressure “

P”

measured by said pressure means in said exhaust valve when closed;

11. A gas chromatograph according to claim 8, wherein said controller calculates said filter resistance from the following formula based on said column resistance “

r”

, a pressure “

P”

measured by said pressure measuring means when said exhaust valve is in the open position, and a flow rate “

F”

measured by said flow measuring means when said exhaust valve is open;

12. A gas chromatograph according to claim 8, wherein said controller compares said filter resistance to a clogged resistance corresponding to a state in which said filter is clogged and when said filter resistance becomes greater than said clogged resistance, said controller displays on said monitor screen an indication for exchanging said filter.

13. A gas chromatograph according to claim 8,

wherein said pressure measuring means is a pressure sensor sending an output thereof to said controller,

said flow control means is a flow control valve controlled by said controller,

said flow measuring means is a flow sensor sending an output thereof to said controller,

said exhaust valve is controlled by said controller,

said controller controls said exhaust valve to open, then reads outputs of said pressure sensor, and said flow sensor, and calculates said filter resistance.

14. A gas chromatograph according to claim 8,

wherein said pressure measuring means is a pressure gauge,

said flow control means is a flow valve,

said flow measuring means is a flowmeter.

15. A gas chromatograph for analyzing elements in a sample by introducing said sample into and separating the elements through a column, comprising:

a chromatograph column with a sample introduction part;

pressure measuring means for measuring a pressure in said sample introduction part;

flow control means, placed in a flow path supplying a carrier gas into said sample introduction part, for controlling a flow rate of said carrier gas;

flow measuring means, placed in said flow path, for measuring said flow rate of said carrier gas;

a split flow path, connected to said sample introduction part, exhausting part of said carrier gas and sample from said sample introduction part;

a filter, placed in said split flow path, protecting said split flow path from becoming clogged;

an exhaust valve having an opening, placed in said split flow path downstream of said filter, adjusting a flow rate in said split flow path;

a controller calculating a flow path resistance of said filter based on a flow path resistance of said column, a pressure measured by said pressure measuring means when said exhaust valve is in an open position, and a flow rate measured by said flow measuring means when said exhaust valve is in the open position, said controller connected to a light bulb which light bulb turns on when the controller determines an exchange of said filter is necessary based on said filter resistance.

16. A gas chromatograph according to claim 15, wherein said controller obtains said column resistance “

r”

based on the following formula, using temperature of the column (t), inside diameter of the column (D), length of the column (L), pressure at the inlet of the column (P1), pressure of the atmosphere (PA), viscosity of said carrier gas (U), and a proportional coefficient (K1);

17. A gas chromatograph according to claim 15, wherein said controller gets said column resistance “

r”

from the following formula based on a flow rate “

f”

measured by said flow measuring means when said exhaust valve is closed and a pressure P measured by said pressure means when said exhaust valve is closed;

18. A gas chromatograph according to claim 15, wherein said controller calculates said filter resistance from the following formula based on said column resistance “

r”

, a pressure “

P”

measured by said pressure measuring means when said exhaust valve is open, and a flow rate “

F”

measured by said flow measuring means when said exhaust valve is open;

19. A gas chromatograph according to claim 15, wherein said controller compares said filter resistance to a clogged resistance corresponding to a state in which said filter is clogged and when said filter resistance becomes greater than said clogged resistance, said controller displays an indication to exchange said filter on said monitor screen.

20. A gas chromatograph according to claim 15,

wherein said pressure measuring means is a pressure sensor sending an output thereof to said controller,

said flow control means is a flow control valve controlled by said controller,

said flow measuring means is a flow sensor sending an output thereof to said controller,

said exhaust valve is controlled by said controller, and

said controller controls said exhaust valve to open, then reads outputs of said pressure sensor, and said flow sensor, and calculates said filter resistance.