Effect of temp. on phosphate readings

[bethw]

Being Mechanical and not so chemical, I am not sure of this: What effect does sample temperature have on our boiler water phosphate sample tests? Our local operators say temperature does have a bearing on the result. And how about a silica test? I am designing a cooling system for the water samples in our plant.

 

[bimr]

Don't think the temperature of the sample has anything to do with the results. The majority of contaminants in water are completely dissolved, many of them are quite easy to sample for the dissolved constituents.

The majority of the errors involved in sampling and measurement occur in the sampling lines. For example, a high temperature sample saturated with dissolved metal or metal oxide may become supersaturated as it is cooled and the contaminant may plate out on the sampling system surfaces.

It is important to keep the sample flow rate and temperature constant. A change may result in a crud burst that can raise the contaminant concentration by an order of magnitude. Silica monitoring will also require that the samples be continously flowing.

 

[rlancaster]

I have more of lab perspective: your operators are probably commenting on the effect temperature has on their particular test method. Check the Hach manual (if they are using Hach equipment) or "Standard Methods" if they are using one of those methods for temperature info. I have seen several instances when either temp affected results, or a mismatch between the temp of the "standard" or "blank" and the actual "sample" adversely affected results.