FAQs 

Topic: Contamination Control

Question: Can you advise us on how to reduce contamination problems when handling high purity reagents?
Answer: Contamination control for high purity reagents is essential for ensuring the integrity of the subsequent analysis. A chemical handling/storage technique that has worked well to prevent the contamination of high purity reagents in the clean room laboratory environment is outlined here.

1. Add 20 mL of an ultra-pure 1% nitric acid solution to a PTFE 125 mL container that has been cleaned according to the procedure described in Section 8, “Inert Labware Cleaning”. Shake the container vigorously, and leave to settle for 10 minutes.
2. Go to the sensitivity tune screen in the Agilent ICP-MS ChemStation software, aspirate the solution and monitor the analytical masses associated with environmental contamination. These would include, but not be limited to, sodium 23, aluminum 27, magnesium 24, potassium 39, calcium 40, iron 56, and zinc 66. If the observed count rates are equivalent to those of the UPW alone, this would indicate no contamination in the cleaned bottle. If the count rates show that the vessel is contaminated, return it to the beginning of the cleaning cycle. It's worth noting that PTFE is the best material to work with when performing low-level analysis. PTFE is the easiest material to clean to low background levels both when new and when reused.
3. If the bottle is contaminant free, transfer the reagent to be used into the bottle. The 125 mL container will serve as a “secondary” reagent storage container. This will allow the original, or parent 500mL reagent container to be opened only 4 times in its useful lifetime, and thereby minimizing its probability of contamination.
4. If using Tama chemicals, please note that they will arrive with a set of instructions for minimizing contamination. The instructions are helpful with the following suggested modifications:
   • Each TAMA chemical comes in a PTFE container that is double bagged with one of the bags having the adhesive chemical label attached to it. The instructions suggest that the user reinsert the unlabeled bottle into the labeled bag each time it is used. It has been found that the reuse of the bag, which is often set on the working surface of the hood, can carry contamination to the container. It has been found that peeling the label off the bag and attaching it to the Teflon container is a better practice.
   • Each TAMA chemical comes in a PTFE container that has an additional PTFE insert in the neck of the bottle. These inserts should be disposed of when the container is first opened, and not replaced to the neck of the container since it also acts as a mechanism of contamination transport to the reagent container.

Extract taken from Agilent’s Semiconductor Laboratory Startup & Contamination Control Guide" (73 kbytes)

Topic: Contamination Control

Question: Can anyone suggest any references which would serve as a primer for someone considering setting up a clean room for ICP-MS analysis? What sort of things should one consider in choosing equipment or in designing the lab layout? Is there any data on "typical" blank values which can be achieved in a given class of clean room- Class 100 vs. Class 10,000 for example?

Posted on the PlasmaChem Listserver 11/5/01

Answer: Please refer to Agilent’s "Semiconductor Startup and Contamination Control Guide" that addresses some of your questions. In addition, you might find some of the contamination control literature references useful.