What are stock solutions and how they are prepared?
Stock solutions can best be described as concentrated solutions of known, accurate concentrations that will be diluted for future laboratory use. While you may choose not to prepare stock solutions, doing so can help streamline your operation and save you a lot of time and resources in the process. Since large amounts of solutes are used in preparing stock solutions, a more accurate concentration can be achieved quite easily. As such, chances are slim that you will get erroneous results from your studies.
In addition, stock solutions are generally more stable as compared to working solutions since they do not support bacterial growth. As multiple working solutions can be prepared using a single stock solution, you will also need less storage space in the laboratory.
There are several types of stock solutions that are prepared and used in the laboratory.
Percent (%) solutions. In preparing such solutions, keep in mind that 1% translates to 1 g/100 ml. Scale it up on the percentage (e.g. 20% means 20g/100 ml) and scale to the final volume by multiplying the values by 100 (i.e. 200g/1000ml).
Molar solutions. When tasked to prepare a molar stock solution, you need to know the molecular weight of the solute. Keeping in mind that 1M = 1MW(g)/1000 ml, plug in the appropriate values and scale them up on the required molarity.
X solutions. One of the most common X solutions is 10X PBS (phosphate buffered saline), a buffer solution commonly used in biological research. In preparing such solutions, you need to measure 10 times the amount of each solute to come up with a highly concentrated stock solution.
Tips in Preparing Stock Solutions
Use a proven recipe. This will significantly reduce your prep time and may also save you from the tedious and time-consuming act of adding acids and/or bases if you need to pH your solution.
Use a free online calculator. These tools come in quite handy especially if you are preparing a new stock solution.
Keep your solutions clean. You will want to leave no room for errors.
Mind your labels. Adapt a clear and accurate labelling system in the lab. Be clear on the concentration of your solutions as well.
Now, if you have any buffer requests or would like to ask for stock solution recipes, please leave a comment in the space below and we will provide them as and when needed.
Image By: Sanofi Pasteur