[tripton]

Hi, I must analyze total CN in wastewaters. I will receive several samples and I haven´t distillation enough equipments to treat them in the reception day. The expected concentration is between 1 and 200 ppm.
In the Standard Methods for Examination of water & wastewater 20th ed. (APHA, AWWA, WEF) (page 1-33) I found the "recommended storaging time" is 24hs  but the "regulatory" is 14days  .
Someone has experience analyzing this kind of analysis? Can I wait 2 or 3 days before to do the distillation?

Thanks in advance,

Tripton

[AWK]

Why not? The regulatory time is 14 days

[tripton]

Yes, but recomended is 24hs.
Really I´m not sure if after 24hs the cyanide in the samples may suffer some degradation.
I guest the regulatory is 14d because in a real wastewater taked from an industry, it should acceptable if after 14days the CN is under regulation limits. Perhaps because the regulation limits are very stringents contemplating this long analysis time.
In my case, this samples cames from an experiment. Then if I analyze some of them in different days and the Cyanide disappears, I may get wrong conclusions.
What´s your opinion about?

Thanks

[JGK]

Why not test thestability yourself, spike water samples, test a sub-sample immediatelyand store the remainder. Then test at specified storage intervals and compare to the original value.

If you assign an acceptance criterial to the test, you can define your own storage period and have the data to back it up.