Used to help liquids flow through autoanalyzer tubing easier and to help facilitate mixing, surfactant is a necessity for flow analyzers. It has been used for many years since autoanalyzers were constructed and comes in many varieties but I prefer basic Brij-35 and Dowfax 2A1. These two tried and true surfactants were the mainstay for nearly all the Alpkem methods when they were developed for their “new” Expanded Range (ER) detector back in the 90s.
Good surfactants can be hard to find in this day when suppliers tend to outsource everything leading to a loss of control over quality since someone else produces their products. Make sure your supplier is a trusted source that has an active involvement in the production and QC oversight of the surfactant they provide.
I am always surprised at how miserly operators are in the amount of surfactant they use in their reagents. Too little surfactant can seriously degrade performance of an autoanalyzer: The peak shape can be bad as well as poor reproducibility. Too much only can possibly contribute a slight increase in noise to the baseline, if at all. The affects of too little Brij or Dowfax can be catastrophic but using too much is rarely even apparent.
I also strongly suggest only putting surfactant in the container used on a daily basis. If surfactant is put in the stock solutions when they are prepared and stored for any length of time the surfactant starts to break down thus making it less effective and increasingly noisier the longer it sits.
I also suggest not letting the supplies get too old due to degrading of the surfactant chemical integrity. Sometimes labs will buy large amounts to keep in stock in order to save some money but before they can use it up surfactant can go bad. Like milk for our breakfast cereal, surfactant is best bought often in small amounts and used up while it is fresh. Surfactant is a very important ingredient to the success of an autoanalyzer and just pennies a milliliter so I do not suggest being spendthrift or stingy on how much you use. I always like to use at least a milliliter or two per liter of solution, this allows for good flow and does not contribute noise if the surfactant is fresh and from a good clean source.
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