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
• 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