Ok let me pass this by the group and get some feedback.
What I’m thinking to do it get around the salt problem is to add more.
I will also set up 2 controls one will be a fresh mix of saltwater and a tank that has ran for the same amount of time but with no food added.
Lets say if at the end of the test I have 1000ml of wet skimmate and 250ml of dry skimmate what I will do is dilute the dry skimmate to 1000ml till they both have the same volume and
SG there for the only variable will be the dissolved organics. Then I will use either a refractive index or a spectrophotometer to measure the amount of light absorbed by both solutions at a known volume (I.e. 5ml). From this I will be able to tell which one has a higher concentration by the amount of light absorbed.
Once I have this data I can dehydrate both samples and weigh them with the salt content being equal between all samples and controls I can then subtract the controls weight form the samples weight to get a rough volume of dissolved organics. Since I know the
SG of all the samples I can calculate the
PPM/volume and from that I can get the total amount of salt in the samples, therefore hopefully removing the problem of salt content in the sample.
Because I believe the dehydration method is not as precise I will only be using it to back up the refraction test and hopefully get the same greater than or less than result.
