New tubing, valves and other sample conditioning equipment may be
contaminated with silicate-based substances (oils, dust). These may
contribute to slightly high readings on initial start-up until they are cleaned.
It is recommended the sample line be flushed with sample for one to two
hours before calibration. For an expedient procedure, a dilute caustic
solution such as 1N (5%) sodium hydroxide solution can be injected into the
sample line and forced through to clean sample system components. Injecting
one to four liters of caustic solution into the front end of the sample line and
waiting for the solution to flow through the system and into the analyzer is
usually sufficient.