It is easier to analyse what we release to water than what nature releases to its waters. This ”Natural Organic Matter” (NOM) plays a vital role in water usage and we still know almost nothing about it!
Why do we know so little about NOM?
- … cannot be concentrated without beeing destroyed.
- … is present in very small concentrations only.
- … is too hydrophilic to be isolated fully from water.
- … has no specific chemical functionalities.
In this situation, what can be done?
- Take the water sample as it is, inject it into a semipre-parative column filled
with a hydrophilic polymer containing pores for separation according to
speed of diffusion and use a mild buffer at neutral pH as mobile phase.
- Use several detectors for analysis including a DOC-detector for quantification.
- Use custom-made intelligent software for data processing.
- Have an experienced person for data interpretation. This approach is called ”LC-OCD” (Liquid Chromatography – Organic Carbon Detection).
DOC-Labor Dr. Huber has developed this technique and is currently the only service laboratory offering this worldwide to research and industry.
The benefit of LC-OCD?
We are still far away from compound identification, but we are able to separate NOM into 6 fractions to get meaningful results.
Position of LC-OCD in the family of analytical tools for characterisation of NOM
Many researchers use both strategies and have to realise that a large part of DOC remains unidentified.
LC-OCD was developed to fill this analytical ”gap”, at least to some extent. While mass balancing on the basis of DOC is maintained, a lot of information on the qualitative composition of DOC is obtained.
For example, humic substances, which are the most dominating class of compound in natural waters, are quantified and characterised.
Sensitivity of LC-OCD-OND is in the low ppb range: Even organic impurities in very ”pure” waters such as lab waters can be analysed by direct injection of a sample.