please help me in this method ?

[Newchromatographer]

Hi there ,

I want to study the effect of soil organic matter on the degradation of specific pesticided by HPLC .You know the organic matter from caly soil was sperated by centrifuge so i have clean dark brown solution at the end .Now , i want to take 5% from this dark solution in 100 ml flask contain water and pestcide .

The solution is very very brown dark ( i mean when it conains 5% O.M ) .So i passed 2.5 ml into 0.2 micron PTFE syring filter and measure it by hplc AFTER specific time .The chromatogram look clear after dead volum then my peak is eluted ! .What i am worry about is that the deep dark brown solution will damage my column , am i right ? please help me as i am totally stop my experiment wating for your answer ?

Thanks

[Kostas Petritis]

Maybe yes, maybe no, it is difficult to say.

Your best bet is either use SPE to further clean your sample or use a pre-column which will be the first to go south if indeed your sample is not clean enough.

[Camisotro]

Agreed, SPE seems like a good fit here. What sort of pesticides are we talking about here, how polar? That would determine what kind of cartridges to consider.

If the dark brown is coming from dissolved matter, it should be very easy to spot visually on the SPE cartridge. The question is, of course, when your pesticides elute.

[DSP007]

Hellow
Many methods.
SPE - extraction , extraction in organic solvents end its evaporate , set up safety pre-column on line. May be use any metod of separation and quantificatiln - quantitative TLC or GS (from volature pesticides, such as lindane).

[unmgvar]

some simple approaches are to use
or SPE or TLC made of the about same media you use for your column
if c-18 then get either c-18 SPE or tlc

load a sample on it
then run or wash in several steps that are part of your method
going from 100% buffer/water phase to 100% full organic Meoh or ACN.
see what happens to your sample
does the brown goes out?
does it stay on top? or at base of TLC?
does it simply gets all over the place?

if you are going for the SPE, at the same time, save all the washed out steps and test them by HPLC to test for the feasibility of SPE in your method, check recovery

one more advice that i know from experience is that you can for many pesticides reconcentrate them right on the head of a c-18 column if you run the entire sample on the column at 100% water.
it is done to monitor for pepticides in water for very very low levels, then elease them at the various ACN% with a gradient. so do not worry of a very diluted sample, if you have enough of it you will stil be capable of analysing it in the end