Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: rjb on January 03, 2022, 01:55:43 PM
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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
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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.
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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