Novel photometric system

• US 4,011,451 A
• Filed: 10/24/1975
• Issued: 03/08/1977
• Est. Priority Date: 07/03/1975
• Status: Expired due to Term

• Current Assignee: Waters Technologies Corporation (Waters Corporation)
• Original Assignee: Waters & Associates PLC
• Inventors: Nelson, Kenneth E.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US05/625,590
• Time in Patent Office: 501 Days
• Field of Search: 250/340, 250/341, 250/343, 250/344, 250/345, 250/346, 250/373, 356/96, 356/246
• US Class Current: 250/343
• CPC Class Codes: G01N 2021/0382 Frustoconical, tapered cell
• CPC Class Codes: G01N 2030/746 detecting along the line of flow, e.g. axial
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 30/74 Optical detectors measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J

Abstract

Novel photometric apparatus advantageously having a conical shaped flow-cell comprising a light source proximate the narrow end and a photosensitive detector at the wider end of the cell. The flow-cell adequately compensates for a lens effect that has been discovered to be a substantial factor in electro-magnetic energy absorption studies on liquid streams.

Claims

1. In a photometer of the type utilizing a light source, a sample cell adapted to transmit a continuously-flowing liquid to be analyzed from an inlet port near one end thereof through a flowpath to an outlet port near the other end thereof, and a means for measuring the absorption of light in said sample cell, the improvement wherein said photometer comprises a light detector forming means to receive substantially all non-absorbed light transmitted from said sample cell, means for eliminating liquid lens effects said means comprising a generally conical sample cell, a smaller end of said sample cell being nearer said light source, such that there is substantially reduced loss of light refracted by said lenses on walls of said sample cell.

2. A photometer as defined in claim 1 wherein said light source and said measuring means are so selected that said photometer is an ultra-violet absorbance detector.

3. A photometer as defined in claim 2 wherein an angle of divergence between an axis of said flowpath and the wall of said flow-cell is from 1°

to 3°

.

4. A photometer as defined in claim 2 wherein said sample cell has a volume of less than 32 microliters and a maximum diameter of less than 2 millimeters.

5. A photometer as defined in claim 4 wherein an angle of divergence between an axis of said flowpath and the wall of said flow-cell is from 1°

to 3°

.

6. A photometer as defined in claim 1 wherein said sample cell has a volume of less than 32 microliters and a maximum diameter of less than 2 millimeters.

7. A photometer as defined in claim 6 where an angle of divergence between an axis of said flowpath and the wall of said flow-cell is from 1°

to 3°

.

8. A photometer as defined in claim 1 wherein an angle of divergence between an axis of said flowpath and the wall of said flow-cell is from 1°

to 3°

.

9. A photometer as defined in claim 8 wherein the length to average diameter ratio of the flowpath is at least 5:

1.

10. In a process for measuring the radiation absorptivity of a flowing liquid sample which comprises a plurality of sequential liquid compositions in a laminar flow mode, the improvement comprising substantially eliminating the interference of dynamic liquid lense with said measuring by

a. feeding said liquid into a generally conical sample cell proximate a smaller cross-sectional end thereof,

b. removing said liquid from said sample cell at a larger cross-sectional end thereof,

c. and measuring the radiation absorptivity of said liquid through said cell, said measurement being carried out by detection at said larger end of said cell, substantially all of the non-absorbed radiation from a source proximate the smaller end of said cell.

11. A process as defined in claim 10 wherein the radiation being measured is ultra-violet light.

12. A process as defined in claim 11 wherein the velocity of the sample liquid is decreased by at least about 50 percent during its movement from the inlet end of said sample cell to the outlet end of said cell.

13. A process as defined in claim 10 wherein the volume of liquid sample in said flow-cell is maintained at less than about 32 microliters and wherein said maximum diameter of said cell is 2 millimeters.

14. A process as defined in claim 13 wherein the velocity of the sample liquid is decreased by at least about 50 percent during its movement from the inlet end of said sample cell to the outlet end of said cell.

15. A process as defined in claim 10 wherein the velocity of the sample liquid is decreased by at least about 50 percent during its movement from the inlet end of said sample cell to the outlet end of said cell.

16. In a liquid chromatographic analytical apparatus of the type having a liquid chromatographic column adapted to emit a liquid stream comprising a series of sequentially-arranged liquid compositions, and means for conducting said stream to a photometer of the type comprising a sample flow-cell forming a conduit for said liquid stream, a means to provide a source of radiation, and a radiation detector arranged with respect to said conduit to form a radiation path therethrough.

the improvement wherein said radiation detector form as means to receive substantially all non-absorbed light transmitted through said sample cell and including means for elminiating distortion of said radiation by dynamic liquid lens effects comprising a flow-cell which forms a truncated, generally conical, flowpath, a smaller end of said cone being nearer said radiation means, such that ther is no substantial loss of refracted radiation on walls of said flow cell.

17. A chromatographic system as defined in claim 16 wherein said light source and said detecting means are so selected that said radiaton detector is an ultra-violet radiation detector.

18. A chromatographic system as defined in claim 17 wherein said flow-cell has a maximum diameter of 2 millimeters.

19. A chromatographic system as defined in claim 18 wherein the angle of divergence between the conical wall and axis of said flowpath is from 1°

to 3°

.

20. A system as defined in claim 19 wherein said flowpath has a length-to-average diameter ratio of at least 5:

1.

21. A chromatographic system as defined in claim 16 wherein said flow-cell has a maximum diameter of 2 millimeters.

22. A chromatographic system as defined in claim 16 wherein the angle of divergence between the conical wall and axis of said flowpath is from 1°

to 3°

.

23. A sample cell having an inlet port, an outlet port and a flowpath therebetween, said flowpath formed of a truncated, generally conical chamber forming means for overcoming refraction of radiation onto walls of said chamber during analysis of liquid passing therethrough, which cell has transparent end members adapting it to serve also as a path for transmitting light, said flowpath having a length-to-average diameter ratio of at least 5:

1.