Patent ID: 9739708
Date: 2017-08-22
CPC Classifications: G01N

Claim:
1. A method for measuring chemical composition and/or trace impurities in a compressible fluid sample without the need for a ‘zero’ reference, the method comprising: obtaining a first spectrum for a sample cell containing a sample fluid from a spectroscopic system with the sample fluid at a first pressure in the sample cell; obtaining a second spectrum for the sample cell containing the sample fluid from the spectroscopic system with the sample fluid at a second pressure in the sample cell, wherein the first pressure is different from the second pressure; determining, by a processor of a computing device, a differential absorption spectrum for the sample using the first spectrum and the second spectrum; and identifying, by the processor, one or more constituents of the sample, and/or identifying, by the processor, a concentration of one or more of the one or more constituents of the sample, using the differential absorption spectrum; wherein the sample cell is a flow cell and the sample is drawn from a compressible fluid line, and wherein the compressible fluid line is a natural gas pipeline stream and wherein the one or more constituents of the sample that are identified comprises one or more members selected from the group consisting of CH