Method of and analyser for the optical analysis of a liquid containing a dissolved gas

An optical analyser, the optical analyser comprising:

• a measurement cell configured to receive a liquid sample, the measurement cell having a transparent wall section configured to permit transmission of optical radiation into the liquid sample;
• an optical radiation source configured to generate the optical radiation;
• a complementary optical radiation detector configured to detect the optical radiation subsequent to interaction of the optical radiation with the liquid sample;
• a liquid flow system having a flow conduit configured in serial flow communication with the measurement cell and including an end configured to be inserted into a reservoir containing a liquid containing a dissolved gas;
• a piston pump in serial fluid communication with the flow conduit at a location between the end and the measurement cell and an in-line back-pressure valve in the flow conduit, the in-line back-pressure valve configured to open in response to a pressure exerted on the in-line back-pressure valve by liquid transferred through the measurement cell exceeding a back pressure, the piston pump configured to generate the back pressure in the measurement cell based on causing liquid to be transferred against the in-line back-pressure valve through the measurement cell;
• and
• a controller that is configured to control an operation of the optical analyser to
• transfer an amount of the liquid containing the dissolved gas from the reservoir into a holder of the liquid flow system, wherein the liquid transferred into the holder contains a first amount per unit of liquid volume of the dissolved gas,
• hold the amount of the liquid containing the dissolved gas in the holder at around ambient pressure based on the holder being open to a waste reservoir for a period of time such that a portion of the dissolved gas is expelled from the amount of the liquid held in the holder to reduce an amount of dissolved gas per unit of liquid volume in the amount of the liquid in the holder from the first amount per unit of liquid volume to a second amount per unit of liquid volume while the holder is open to the waste reservoir,
• transfer at least a portion of the amount of the liquid containing the second amount per unit of liquid volume of the dissolved gas held in the holder under the back pressure above ambient into the measurement cell as the liquid sample, such that the liquid sample contains the second amount per unit of liquid volume of the dissolved gas, and
• perform an optical analysis of the liquid sample from a detection of the optical radiation by the complementary optical radiation detector after interaction of the optical radiation with the liquid sample in the measurement cell while the liquid sample is at the back pressure above ambient within the measurement cell and contains the second amount per unit of liquid volume of the dissolved gas within the measurement cell.