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Topic: Awkward Analyte - Some Suggestions?  (Read 511 times)

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Offline rjb

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Awkward Analyte - Some Suggestions?
« on: January 03, 2022, 01:55:43 PM »
I am currently working with a very awkward analyte which consists of both dissolved organic compounds and also insoluble metallic micro-particulate within an organic solvent. The particulate has a particle size of between 0.5 and 10um and is present at a concentration of about 120,000 particles/ml. Because of its density, I suspect that it will most likely not form a suspension for any reasonable length of time and is likely to settle out pretty rapidly.

I would like to be able to consistently pipette low microlitre volumes (~10-50ul) of this analyte from the stock material for analysis and with this in mind, I would be grateful for your thoughts on the following aspects.   
 
To achieve a reasonably consistent sample for analysis, I will need to ensure a reasonable level of homogeneity within my stock at the point at which I take a sample, which is a problem as it settles out. I have considered the following methods for achieving a reasonable level of homogeneity and would be grateful of your thoughts on the appropriateness of these )and for any other suggestions that you might have).

•   Simple magnetic stirrer
•   Vortex
•   Ultrasonic Bath

Pipetting small volumes of a suspension is also an issue and I had considered either:

•   Gilson Microman – Positive displacement pipette
•   A Hamilton Syringe – Probably with 22 gauge needle (ID 0.168mm)

Does anyone foresee any issues with either of these?

Many thanks for taking the time to consider this

Kind Regards

R

Offline wildfyr

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Re: Awkward Analyte - Some Suggestions?
« Reply #1 on: January 03, 2022, 04:16:09 PM »
Have you considered one of the bazookas of chemistry, Nitric acid, to dissolve the metal then measure the metal content? The organic analysis can then be done totally seperately.

Offline rjb

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Re: Awkward Analyte - Some Suggestions?
« Reply #2 on: January 03, 2022, 04:48:33 PM »
Hi Wildfyr,

Good call, alas, I failed to mention in my question that my particulate must remain 'as is'.
The particulate will undergo subsequent SEM-EDX analysis and its morphology, size and elemental composition are key factors which means that Nitric acid would be a no-no :(

Thanks for your reply nevertheless :)

Kind Regards

R
 

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