[stasiu]

Hi, I'm trying to figure out where the analytical sensors science is today w.r.t. 'instantaneous' detection of low level stuff in water.
Particularly, I'd like to track a simple ketone, let's say acetone for illustration purposes, at 100-200ppm levels in an aqueous matrix, and to complicate it even further in a flow system
Do know of any smart sensors allowing for that? (v.short response time).
Of course I can go online with GC or build some sort of head-space interface and run MS on it but these seem cumbersome and the response time would be slow.

Many thanks,

S.

[subro]

It's only an idea, but you can use FTIR and look for the carbonyl band (1700 nm more or less). FTIR has a good response time and low LOQ.

I've found a paper about using FTIR in water samples.

http://pubs.rsc.org/en/content/articlelanding/1999/ac/a901196j/unauth#!divAbstract

[marquis]

There is a whole lot more information needed. 

But, if the solution is the ketone and water only, you might be
able to get by with a UV detector (similar to a hplc uv/vis detector).

Another option would be a total organic carbon detector used in
purified water testing.  Some can go to high levels.  Again, whether this
would be usable depends on what else is in the water.

Good luck.

[stasiu]

@subro  Thanks for that comment. Yes, I considered that. I actually had a quick look-see at reactIR with ATR probe but the lowest I could see was .5%, not even close to what I need.

Also, I'll have a few other things in the sample (sub % levels) and they are IR active.

[stasiu]

@ marquis    Sure, I just didn't want to overdo the initial post with too much detail.
There will be other stuff (sub % level) and it will be UV and IR active.

Not an easy thing.

Considering now some sort of headspace analysis -my ketone is the only voc - but this would come with a penalty of fairly complex engineering.

A 'miracle' liquid sensor tuned to my keton would be a nice thing, but I'm not holding my breath for that though:)

Thanks for your comments, by the way.

[GCMASTER]

I think that using of GC for this purpose may be a good solution in couple with:
direct injection - 0.5uL is enough for 100-200 ppm conc. levels using FID detector
short middle polarity column (624 or VRX)
isothermal oven programme
backflush in case of non volatile contaminants in matrix
This way you can approach retention time of some minutes with conventional GC or even less than 1min. in fast GC