I try to analyze the drug concentration (absorption at 240 nm) in the solution which released from a drug carrier by using the UV-VIS spectrum. But the degradation product of carrier also has a strong absorption at 200-250 nm. The drug carrier also degrade as time goes on. I had been trying to filter the solution by 0.22 µm pore size filter, but it didn't work well. Even though the background noise are decrease, the absorption intensities of drug are decrease too. I'm not sure that it is the absorption signal from the pure drug or the degradation product. I also worry that I lose some drug after filtration. The drug concentration will not accurate. My lab doesn't have HPLC or other column separation device, and my adviser is extremely worry that we clog the column with insoluble degradation product if we borrow from other lab. Do there have any easy methods to analyze the drug concentration without lose any drug? Thanks!
Study drug release by using dialysis bag method. Only drug will go outside the dialysis bag, It may help you
could you specify the molecular weight of the drug and the contaminants? There is an opinion to clean on centrifugal filter column if there is a discrete difference on Mw... maybe not much will drop the sensitivity of the detection
Avinash Kumar Thanks for your reply. Some literature has descried that the dialysis bag would affect the drug penetrated efficiency, especially the drug has lower solubility and diffusivity. To solve the issue, a higher volume ratio between outer and inner mediums is require. In my experiment, the model drug is dexamethasone and the maximum solubility is 80 ppm. I think the first problem is that my sample is not enough to scale up. Nevertheless, I'll try to scale up the sample, and try to use dialysis bag to do the test. Thank you!
P. V. Ershov Thanks for your reply. In my experiment, the MW of drug is 392 g/mol, while the MW of degradation products of drug carrier are unknown because the drug carrier are also hydrolysis while manufacture processes. I am considering using a 3 kDa centrifuge filter tube to separate the drug and degradation products. But it'll be a big problem if the filter tube can't be reused. My 0.22 um filter would lose function after ten times filtration processes. It's a high cost issue for my lab.
Che Min Lin You are right, but you have to modify the protocol according to your experimental problem, like choice of dialysis bag molecular cut off value. If your drug is less soluble than higher volume ratio between outer and inner mediums is not the only solution. There are some reports to increase the solubility and diffusivity of drugs by using less percentage of surfactant in outer media. Have a look
Che Min Lin 3 or 5 kDa will be enough. I meant, for example, to try centrifuge filters like vivaspin 500.
Insofar the properties (I mean physical and chemical) of your drug and carrier are uncertained, it hard to establish the proper way to decrease the noise level. However, in some cases LLE (liquid-liqud extraction) might be helpful and promising if solubility of compounds and their degradation products are distinguished. The extract with compound of interets is further easily collected and concentrated in many ways. Although, it can be accompanied by a few losses of the target compound (especially if highly diluted solutions) and thereof recommended to accomplish quantitatively, but filtration and dialysis are also fraught with difficulties and even more significant losses.
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