Chromatography Forum

Hello. I know water is one solvent and it is highly soluble in water and easy to analyze on GC-FID. I have soil and water samples. I want to know, can I use dichloromethane to mix the water samples and separate them in separatory funnel. For the soil mix it with dichloromethane and then filter. Do you guys have any idea how to extract with solvent for both soil and water for GC-FID analysis. Thank you

You have a separate post about glycol assay. Do you mean ethylene glycol or one of the thousands of other gycols? I'm a smart guy, but I have no idea and don't want to wate my time on a guess.

I'd say to use methanol or dilute your aqueous extracts 1:1 with methanol.

Or - if you're going to derivatize to trimethylsilyl product - then use DMF or pyridine.

Consumer Products Guy wrote:
You have a separate post about glycol assay. Do you mean ethylene glycol or one of the thousands of other gycols? I'm a smart guy, but I have no idea and don't want to wate my time on a guess.

I'd say to use methanol or dilute your aqueous extracts 1:1 with methanol.

Or - if you're going to derivatize to trimethylsilyl product - then use DMF or pyridine.

So i am analyzing ethylene glycol. I know water is one solvent i can use to mix glycol with. What about methanol. If we have water conaining glycol. Methanol is high soluable in water how can i seperate water from methanol and attach ethylene glycol to methanol. Thank you

You'd inject the water-methanol mix.

Consumer Products Guy wrote:
You'd inject the water-methanol mix.

Will that work?

Direct inject the water + ethylene and propylene glycol onto a wax column with FID for detection. A 0.5 uL injection should see low ppm concentrations. For soils, extract with water, filter and analyze as a water sample.
It has been a while but this worked well for surface waters.

Steve Reimer wrote:
Direct inject the water + ethylene and propylene glycol onto a wax column with FID for detection. A 0.5 uL injection should see low ppm concentrations. For soils, extract with water, filter and analyze as a water sample.
It has been a while but this worked well for surface waters.

i already know water works, but i want to compare with a solvent how does that do for extraction purposes

sohaib1 wrote:

Consumer Products Guy wrote:
You have a separate post about glycol assay. Do you mean ethylene glycol or one of the thousands of other gycols? I'm a smart guy, but I have no idea and don't want to wate my time on a guess.

I'd say to use methanol or dilute your aqueous extracts 1:1 with methanol.

Or - if you're going to derivatize to trimethylsilyl product - then use DMF or pyridine.

So i am analyzing ethylene glycol. I know water is one solvent i can use to mix glycol with. What about methanol. If we have water conaining glycol. Methanol is high soluable in water how can i seperate water from methanol and attach ethylene glycol to methanol. Thank you

Essentially you can't separate the water from the methanol. The problem you will have with ethylene glycol is the hydrogen bonding. It is going to want to remain in the water more than any solvent that would not be soluble in water.

Acetonitrile can be separated from water by adding Sodium Chloride until you have a saturated solution, but then some will be dissolved in the Acetonitrile and give inlet problems after multiple injections.

James_Ball wrote:

sohaib1 wrote:

Consumer Products Guy wrote:
You have a separate post about glycol assay. Do you mean ethylene glycol or one of the thousands of other gycols? I'm a smart guy, but I have no idea and don't want to wate my time on a guess.

I'd say to use methanol or dilute your aqueous extracts 1:1 with methanol.

Or - if you're going to derivatize to trimethylsilyl product - then use DMF or pyridine.

So i am analyzing ethylene glycol. I know water is one solvent i can use to mix glycol with. What about methanol. If we have water conaining glycol. Methanol is high soluable in water how can i seperate water from methanol and attach ethylene glycol to methanol. Thank you

Essentially you can't separate the water from the methanol. The problem you will have with ethylene glycol is the hydrogen bonding. It is going to want to remain in the water more than any solvent that would not be soluble in water.

Acetonitrile can be separated from water by adding Sodium Chloride until you have a saturated solution, but then some will be dissolved in the Acetonitrile and give inlet problems after multiple injections.

Thank you James very much for your help

Hi Sohaib

Just to summarise

You are analysing for ethylene glycol in both soil and water samples.

For the soil

i already know water works, but i want to compare with a solvent how does that do for extraction purposes .

May I suggest that you just try the above suggestions using methanol or methanol /water and make your own comparisons and let us know how these compare with water only

For the soil mix it with dichloromethane and then filter.

Yes, but just try it for yourself ! and let us know the results . Methanol/water may work better.

Various soil types may have different adsorption properties for ethylene glycol

For the water

I want to know, can I use dichloromethane to mix the water samples and separate them in separatory funnel.

Yes, but you will have the partition co-efficient of the ethylene glycol between water and DCM to consider.

Easy for you to give it try and let us know the results

Why not just try adding some methanol ( 1:1 as previously suggested by CPG to reduce injection problems compared to just injecting the water sample) and filter?

In all cases above you will need to run spiked ( standard or multiple standard addition method ) and unspiked samples for your analysis to determine extraction efficiency.

Please let us know how you get on - it may help future posters with a similar problem

GOM wrote:
Hi Sohaib

Just to summarise

You are analysing for ethylene glycol in both soil and water samples.

For the soil

i already know water works, but i want to compare with a solvent how does that do for extraction purposes .

May I suggest that you just try the above suggestions using methanol or methanol /water and make your own comparisons and let us know how these compare with water only

For the soil mix it with dichloromethane and then filter.

Yes, but just try it for yourself ! and let us know the results . Methanol/water may work better.

Various soil types may have different adsorption properties for ethylene glycol

For the water

I want to know, can I use dichloromethane to mix the water samples and separate them in separatory funnel.

Yes, but you will have the partition co-efficient of the ethylene glycol between water and DCM to consider.

Easy for you to give it try and let us know the results

Why not just try adding some methanol ( 1:1 as previously suggested by CPG to reduce injection problems compared to just injecting the water sample) and filter?

In all cases above you will need to run spiked ( standard or multiple standard addition method ) and unspiked samples for your analysis to determine extraction efficiency.

Please let us know how you get on - it may help future posters with a similar problem

Methanol didn't work at all. Only water worked so for soil i did 1 Soil and 2 water ratio. Methanol didn't work all i go was big methanol peak nothing else

Thank you for the update, feedback and for giving the suggestions a try.

An interesting but slightly perplexing result since I would expect EG to be completely miscible with methanol - please correct me if I am wrong - I need to give it some thought

Admittedly a different matrix (alcoholic beverages) and a different detection technique (MS), but we use ethyl acetate as the solvent. The down side is you need to salt out the aqueous samples.

GOM wrote:
Thank you for the update, feedback and for giving the suggestions a try.

An interesting but slightly perplexing result since I would expect EG to be completely miscible with methanol - please correct me if I am wrong - I need to give it some thought

I would imagine that since ethylene glycol is not retained that strongly it may be lost in the large methanol solvent peak. One reason aqueous injections work better for this on FID.