Sample preparation system for an analytical system for determining a measured variable of a liquid sample

An analytical system for determining a measured variable of a liquid sample, comprising:

• a sample preparation system, comprising:
• a first fluid conducting line;
• second fluid conducting line;
• a transport unit with a pump connected with a sample taking location via said first fluid conducting line;
• a sample collecting unit with a container, which serves the analytical system as a staging area for automated removal of liquid samples, based on which the measured variable is determined;
• an analyzer;
• a filter unit arranged between said sample taking location and said transport unit, the filter unit fluidly connected to the sample collecting unit via the first fluid conducting line, and at least one reservoir connected via said second fluid conducting line with said filter unit for providing a cleaning medium for cleaning said filter unit the second fluid conducting line configured to bypass the transport unit, wherein:
• said transport unit is embodied to transport sample liquid from said sample taking location through said filter unit via said first fluid conducting line into said sample collecting unit;
• and the cleaning medium comprises an oxidizing agent;
• and
• an analytic device, comprising:
• a measuring cell;
• at least one liquid container containing a treatment liquid for treating the liquid sample;
• a processing system comprising a transport- and dosing apparatus for transporting and metering the liquid sample from the sample collecting system and the treatment liquid from the liquid container into the measuring cell;
• and
• an optical measuring transducer for providing at least one measurement signal correlated with the measured variable of the liquid sample contained in the measuring cell and treated with the treatment liquid.