Where do I buy a preservative (sodium carbonate) for Porphyrins test?

[Guest guest]

Hi Listmates,

For those familiar with the Porphyrins test -- the major problem is

getting accurate results. As Andy Cutler stated, incompetence of

labs handling samples is a major problem. Andy Cutler and others

have advised to use a preservative to protect the sample.

Specifically, Andy Cutler advises the use of sodium carbonate [Na(2)

CO(3)] as a preservative. I've been battling with labcorp to get

them to use this preservative as it is one they have the option of

using. These guys are just @!# -- anyway ...

Rather than dealing with Labcorp, I'm considering buying sodium

carbonate and adding it to the urine container.

Does anyone know where I can buy sodium carbonate? Is it expensive?

Thanks to all in advance.