How can the air be removed from a Lachat PDS200 dilutor?

Document ID

Document ID TE10796

Version

Version 1.0

Status

Status Published

Published Date

Published Date 11/20/2018
Question
How can the air be removed from a Lachat PDS200 dilutor?
Summary
PDS200 air concerns
Answer
If air bubbles are present in the PDS200 chamber it may or may not be affecting dilution results.  One can start by trying to prime the dilutor repeatedly to try and dislodge any bubbles.  If there is a small bubble or small number of stubborn bubbles that are not getting dislodged they are also probably not affecting the volumes drawn and delivered.  An accuracy check comparing auto dilutions with manual dilutions can be performed to verify.

If the air is significant or appears to be affecting the accuracy, there are a couple of measures that can be considered to try and minimize/eliminate the air.  The fittings can be replaced in case air is sneaking in through one of them.  One can also consider using Teflon tape on one or more fittings.

The fittings of concern would be the loop on the front of the dilutor (Tubing Assembly, Number 2 from figure 2 below) and the fittings used for the diluent and probe at the top of the dilutor (Numbers 1 and 2 from figure 4 below). 
  • The loop is a single part Fluidic Tubing Product # 44159 which includes both fittings and tubing.  The tubing is flared at both ends which prevents the fittings from being removed from the tubing so it must be replaced as an assembly.
  • The fittings for the diluent and probe assembly also use a ferrule.  The fittings are available as Product # 29008 and the ferrules as Product # 29009.  Each of these comes as a package of 2.

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