Variable path length absorption spectrometer having automated continuous slope measurement

A method of determining a concentration of a material in a fluid sample, comprising:

• synchronizing:
• initiating a sample measurement of the fluid sample to determine the concentration, by sending a signal to move an optical probe through a sample vessel containing the fluid sample;
• triggering, at a plurality of instances during a measurement interval, a light source to emit an incident radiation through the optical probe and the fluid sample, wherein a path length L of the incident radiation through the fluid sample is varied;
• and
• receiving, at the plurality of instances during the measurement interval, a measurement of an intensity I of attenuated radiation, derived from the incident radiation after passing through the fluid sample.

A non-transitory computer-readable storage medium storing computer-readable program code executable by a processor to:

• synchronize:
• initiating a sample measurement to determine a concentration of a substance in a fluid sample, by sending a signal to move an optical probe through a sample vessel containing the fluid sample;
• triggering, at a plurality of instances during a measurement interval, a light source to emit an incident radiation through the optical probe and the fluid sample, wherein a path length L of the incident radiation through the fluid sample is varied;
• and
• receiving, at the plurality of instances during the measurement interval, a measurement of an intensity I of attenuated radiation, derived from the incident radiation after passing through the fluid sample.