Chromatography Forum

I have been given the task of running to15 analysis at our lab. We are using Entech pre-concentrators with agilent gc/ms. I am using an Entech dynamic diluter to prepare standards in a 6L summa can. The first standard I made had no Ethanol or 2-propanol and very low 1,4-dioxane when analyzed back to back with a standard made previously.

Are there any tricks to making these standards? Should I add h2o (10ul)to the can before prepping?

I did use a verified clean can.

Water (humidity) does have an effect on recovery of polar compounds from Summa canisters, and should be controlled. Deactivation or lack of same can also have an effect on recovery of polar compounds.

So...do I want to add water to the can? In what way does it affect polar compounds? Water good? Water bad? for polar compund recovery?

Water is usually not good. If there is any condensation in the canister that will tend to collect polar compounds and they will not be detected, or the response will be low. Adding water is a tough decision, you want the humidity of the samples and standards to match so the recovery will be the same. I wouldn't add water to standards in Arizona, but I probably would in Florida.

With too much water in the can, water can condense on the inside walls of the canister causing loss of polar compounds due to dissolution of VOCs into the water. On the other hand, with too little water in the can, polar compounds can be adsorbed on the canister walls otherwise occupied by water molecules.

Because all air samples contain moisture, preparation of air standards with humidified air with RH above 20% is desired. Entech diluter has a water reservoir, check and make sure the water level is ok. Extra amount of water can be added to the can prior to the standard preparation. The amount of water to be added can be calculated depending on the RH of the standard.

Is there any way to transfer sample from Summa canister onto thermal desorption tubes?