During the experiment, there were some problems. It was thought that the original sample might be too dirty, which caused the collapse of the sieve plate. Is there a problem with membrane selection? Stuffed heart! It is not clear what is right or wrong. The only way to protect the chromatographic column and liquid injection system is to continue to strictly control the sample pretreatment.
For analysis, sample pretreatment is not only an essential link but also a technical work. Regardless of ultrasound or oscillation, the liquid phase system should be filtered after the solution of the main drug is guaranteed. The role of the membrane filter is very important. Today we’re going to talk about membrane filters.
Syringe filter is the most commonly used for dissolution and liquid phase sample pretreatment. A day does not know how many times, small makeup today to tell some of the tips that we usually pay little attention to.
Before inhaling the sample, suck about 1ml of air into the syringe to minimize liquid residue. Inhale the sample into the syringe, invert the syringe, wipe the residue on the top, connect the syringe filter to the syringe, and gently tighten it to ensure good sealing.
Filter the sample in the syringe and inject it into the bottle. Remove the filter, inhale the air into the syringe, reconnect the filter head, and press the pushrod to filter out all residual samples. Maximize sample recovery.
Tips: During the filtration process, it is better not to use a syringe less than 10ml to avoid liquid leakage caused by excessive pressure.
Design of membrane filter adsorption test
The membrane filter should be inspected before use to determine whether it has an adsorption effect on the measured components. No matter the dissolution, or the content, or the relevant substances, if the membrane filter has an effect, it will lead to the subsequent output results are wrong. Whatever the drug’s structure, it is always right to examine it before the trial begins. According to different analyses and test items, the determination of membrane filter adsorption and verification methods are slightly different.
Determination of dissolution
Before the dissolution test, the membrane filter adsorption test must be carried out.
The membrane filter adsorption test method is as follows: take the reference solution and compare the absorbance/peak area value after direct injection without filtration and filtration according to the prescribed method. Or the use of raw materials and blank auxiliary materials to configure the solution. High speed centrifugation and membrane filter were used respectively.
The absorbance/peak area of the centrifugal supernatant and the filtered solution were compared. The primary filtrate of different volumes was discarded. The above methods are for reference only, different operation methods of actual projects are different, please adjust them according to the actual situation.
The Use of Microporous Membrane
Laboratory workers use a membrane to filter two phases. Actually, the membrane is a kind of media. According to different aperture sizes, filter membranes can be divided into the microporous membrane, ultrafiltration membrane, nanofiltration membrane and reverse osmosis membranes. Specifically, the microporous membrane is commonly used in laboratories with an aperture size of 0.1 to 1 micron. Talking about microporous membrane, it is mainly made from refined nitrocotton with moderate cellulose acetate, acetone, n-butyl alcohol, ethyl alcohol, etc. It is important to filter solvent and samples with the microporous membrane in the laboratory, basically, there are two reasonable concerns. One is to protect the chromatographic column and instrument. The other is to prevent pollution from affecting the analysis results. For example, for the ultraviolet detector, if sample concentration is low to a certain degree, the particle will cause serious noise to interfere with normal signals and finally decrease the SNR (Signal to Noise Ratio) and affect the test results.
Choose of Microporous Membrane
PTFE: Apply to all solvent, acid and salt. Nylon: Apply to the most organic solvent and hydro solvent. RC: Apply to water-soluble sample and an organic solvent. PES: Apply to water-soluble sample.
Caution against Using of Microporous Membrane
1. Using a syringe with volume of fewer than 10 ml may cause burst due to high pressure. 2. Different membrane materials will produce different absorption efficiency, but do remember to choose the microporous membrane in accordance with the recommendation in operation specification.