1. How should the stock solution be prepared?

For dilution and storage, the compound is usually formulated as a stock solution. Before preparing the stock solution, the compound should be centrifuged instantaneously and collected to the bottom of the tube to prevent the compound powder from flying or sticking to the wall when the lid is opened, which may cause loss.

1.1 Calculate the stock solution (storage) concentration of the compound

When preparing stock solution with DMSO, in order to ensure that the final concentration of DMSO has no side effects on living cell culture, it is recommended that the final concentration of DMSO in the culture medium be lower than 0.1%, that is, the concentration of the stock solution prepared is at least 1000 times higher than the concentration of the working solution. For example, if the required working solution concentration is 10uM, then the DMSO stock solution should be at least 10mM. If the compound is water-soluble, the mother liquid can be prepared with a water-based solvent, and the concentration of the mother liquid can be at least 10 times that of the working liquid.

1.2 Choose the right stock solution solvent

The stock solution solvent is usually selected according to the solubility of the compound. If the compound only has high solubility in DMSO, it means that the compound can only use DMSO as the stock solution solvent, not water or other solvents.

1.3 Aliquote stock solution

In order to prevent the stock solution from degrading due to repeated freezing and thawing, it is recommended to dispense the stock solution according to the volume of 5-10 times the amount required for each experiment.

1.4 Working solution preparation

If it is a cell level experiment, you can directly dilute the stock solution in the medium according to the required concentration, and add to the cells after mixing. If it is an animal experiment, please refer to Note 4. It is recommended to use up the working liquid on the same day right before experiment and do not store working solution, so please dilute the mother liquid as needed.

1.5 stock solution storage

It is recommended to wrap the stock solution in tin foil and store it at -20°C or -80°C. Generally, the stock solution can be stored for no longer than 1 months at -20°C and 24 months at -80°C.

1.6 Solid compound preservation

If the amount of the purchased compound is large and cannot be used up in a short time, it is recommended to sub-package the solid and store it at -20°C.

2. Can the compound be directly used in cell experiments? Does it need to be sterilized?

Generally, compounds are produced by chemical processes, so complete sterility cannot be guaranteed. STARK Chemicals recommends that if the stock solution solvent of the compound is DMSO or absolute ethanol, the stock solution can be directly used for cell experiments under the condition of ensuring the sterility of DMSO or absolute ethanol. If the solvent of the stock solution of the compound is water, it is recommended to filter it with a 0.22 micron filter membrane (after filtering, an "air needle" can be applied to the filter membrane twice to filter out the stock solution and prevent residues) before performing subsequent experiments.

If you still need to filter the stock solution prepared with DMSO or absolute ethanol, it is recommended to use a PTFE membrane, because the strong solubility of DMSO will destroy the aqueous phase membrane and the ordinary organic phase membrane.

Please note: High temperature, high pressure or UV sterilization is not recommended for any compound.

3. How to improve the solubility of the compound?

Some compounds have poor solubility under low or normal temperature conditions, but their solubility can be greatly improved under heating conditions. Therefore, in order to obtain higher concentrations, these compounds can be heated in a water bath or mechanical ultrasound at 45 °C~ 50 °C for no longer than 30 min. Improve solubility.

Please note: Be sure to choose an ultrasound system that cleans glassware, not a cell disruptor.

4. How are the compounds used in animal experiments?

If the solubility of the compound in the aqueous solvent can meet your experimental needs, you can dissolve the compound in sterile double-distilled water or deionized water. STARK Chemicals recommends that you use distilled water as a stock solution and diluent with PBS or saline with caution. The reason is that even if some compounds are easily soluble in pure water, there will be obvious solid precipitation in PBS or saline.

For non-water-soluble compounds, it is not recommended to dilute the stock solution directly with water, PBS or physiological saline. Generally, these compounds need to be solubilized with cosolvents or oil solvents, such as polyethylene glycol, Tween 80, propylene glycol, carboxymethyl Sodium cellulose or corn oil, etc. For different compounds, the types and proportions of co-solvents required vary greatly, and the specifics can only be known after actual measurement.

Please note: No matter what proportion of co-solvent is used, be sure to add water in the last step, otherwise it may cause compound precipitation.

5. Transportation of compounds

During transportation, STARK Chemicals will use blue ice to keep the product cold, and during long-distance transportation, the local temperature may cause the blue ice to melt. Since most solid compounds are stable under normal temperature conditions, you can still use the product normally for subsequent experiments.

6. How does STARK Chemicals guarantee the quality of the compound?

Most of STARK Chemicals' compounds are analyzed by NMR to ensure the correct structure of the compound, and analyzed by HPLC to ensure the high purity of the compound. Some products calibrated by special testing methods will be marked in the product report. For some antibiotic products, the potency will be indicated.

7. Why are the properties and solubility of the same product sometimes different?

The same product, due to the improvement of the process, may contain different trace impurities during the production process, and different crystal forms may be formed during the purification process. Therefore, there may be slight differences in product properties, colors, crystal forms, etc. between different batches.

8. Can I split the product after receiving it?

For small-packaged products (such as 5mg, 10mg, etc.), due to their small quality, the powder may stick to the wall, fly up, stick to the spoon or weighing paper during the packaging process, resulting in quality loss and inconsistent stock solution concentration. precise. Therefore, for small packaged products, STARK Chemicals recommends splitting the stock solution instead of the solid.

For large-package products, please refer to 1.6 for the storage method.