Lachat Tech Tips

Staining of tubing, one of the biggest concerns when running the Ammonia Phenolate chemistry, can cause a baseline drift and a potential flow problem. The following tips, courtesy of our Lachat Instruments Tech Team, will help prevent occurrences of staining:

1. Disable the pump’s standby feature when using this chemistry. When the pump goes on standby the flow through the chemistry manifold slows dramatically. This could create flow issues and the likelihood of staining.
   
   
2. Use fresh crystalline phenol to prepare the phenolate solution. Liquefied phenol typically causes staining. Remember to refrigerate the crystalline phenol and only use clear crystals to make the reagent.
   
   
3. Remake the phenolate solution every 3 to 5 days or when it turns brown, whichever occurs first. Even when refrigerated, the reagent does not last long. Remake the solution every 3 to 5 days and refrigerate it when not in use. Given its sensitivity to light, it also helps to prepare the solution in a dark bottle.
   
   
4. Keep tabs on the amount of hydroxide in the buffer or hypochlorite. The pH just before the heater should be between 11 and 12. Staining will likely occur if the pH is too high.
   
   
5. Do not use Clorox® for the hypochlorite solution. Older methods may reference the use of Clorox, however, “regular” Clorox is no longer available. The current Clorox is actually Ultra Clorox, which has additional hydroxide and should not be used. Use a 4-6% hypochlorite solution from Fisher (part # SS290-4 for 4 liters; or -1 for 1 liter).