Chromatography Forum

Hi people!
I´m analyzing cyproheptadine in an oral suspension, and i´m having problems in order to quantify. The area´s values are very different between a several samples.
I´ve shaked the bottle very before take the sample...but nothing, i´ve heated (just a little) the suspension but i got the same problem...significate differences between samples...
so, does anybody know how should i treat suspensions before quantify.?
is there a standard method to do this?
thanks!!

A few more questions back at you and the community:

How are you testing the samples; whos method are you following?

Is this a procedure which usually works but is playing up today?

Do the areas fluctuate randomly or is there a trend up or down?

Are the results stable when reinjecting the same sample multiple times?

Is shaking sufficient homogenisation for a viscous suspension? Is it common for syrupy products, presumably homogeneous upon bottling, to 'settle out'?

Coquim,

How are you sampling the suspension and how viscous is it?

Ideally you need to sample with a positive displacement pipette and not an air displacements device. Air displacement pipettes are adversly affected by viscous samples and with suspensions, if the particles aggregate, they may not enter the tip and you will prefrentially sample the matrix

Also sampling with volumetrics is to be avoided withviscous samples as the sample will adhere to the internal surface causing irregular sample volumes.

more details would be useful but....

suspensions can be tricky to handle. If they are unsophiticated formulations like in many preclinical studies they can be very difficult or impossible to resuspend and subsample.

Positive displacement pipettes help but you might want to weigh samples and correct for sampling weight variations or at least confirm that you can sample in a reproducible manner. Do you know the density of your formulation? do you correct for this when sampling volumetricly?

the best case is to get your original samples massed into vials from which you can quantitatively transfer or have them massed into volumetrics for subsequent sample prep.

one of the major problems associated with oral suspensions is that during constitution a lot air can be trapped in the solution very unheavenly, this makes it impossible to test.

we always make sure constitute the suspension by slowly shaking or swerling the bottle by hand, sometimes by rolling it on it's side. it can take 15-30 minutes even more sometimes until you do one bottle.

if your method is by volume then the precision is also problematic. it wiser to weight the sample. we have less and less methods by volume for the sample.

Millions of people are handling trillions of blood samples, which are very tricky suspensions. Handling has been standardized.

Millions of people are handling trillions of blood samples, which are very tricky suspensions. Handling has been standardized.

well there you go...

so you can handle a 200ul mouse ocular bleed the same as 5ml human blood sample the same as cyproheptadine in an oral suspension, great!

coquim, just put your samples in a blood tube with Li Heparin and i guess everything will be ok.. oh wait maybe its K2EDTA thats standard?

Your oral suspension is childs play compared to blood.

^^Generalizing and purely from the standpoint of how complex the suspension is I agree.

But i have received both types of samples…

I would rather work with properly sampled and handled blood (read ‘standardized’ procedure) than early stage dosing suspension samples etc. that were not sampled accurately, of sufficient volume, sampled into a suitable container, stabilized, etc. (read ‘non-standardized’ procedures) to allow for successful representative analysis or the original suspension.

Your child’s play statement is relevant because that is origin of most suspension analysis issues. It usually goes like this - “it’s only a simple suspension just take half ml samples with a syringe, put them in 20ml vials, and freeze em till the lab is readyâ€

Blood seems more convenient to you since there are millions of people who have handled it a certain way. If you take a close look at the compromises made here you should be able to apply some to the suspension.