I cannot run my total organic carbon (TOC) test right after sampling; can I preserve the sample and measure it later?
Preserving a sample for later Total Organic Carbon analysis
If immediate analysis is not possible, cool the sample to 4 °C with no headspace. Cooled samples can be stored for several days. Acid preservation is not recommended because it results in poor digestion efficiency and low recovery. For the best accuracy, however, samples should be analyzed as soon as possible to prevent consumption of organic carbon by bacteria. Bacteria consume some organic molecules such as glucose much faster than others.