Quantitative Methods: Part 1. Solutions and Dilutions
Prepare a Solution in Moles/Liter
The first step in the preparation of any solution is to decide how much to make. To simplify the calculations, express the desired volume in liters. For example, if you want to prepare 200 milliliters of a solution, express the volume as 0.2 liter.
Your formula may describe the concentration in moles per liter. For example, 0.25M means 0.25 moles/liter. It may call for a millimolar (mM) solution, a micromolar (µM) solution,a nanomolar (nM) solution, or even a picomolar (pM) solution. One mM, one µm, one nM, and one pM are 1/1000, 1/1,000,000, 1/1,000,000,000, and 1/1,000,000,000,000 mole/liter, respectively. Whatever prefix is used to describe the desired molar concentration, it is easier to do the calculation by converting the concentration to moles/liter. For example, 25 µM can be expressed as 0.000025M, or 2.5 x 10-5M.
If you know the desired concentration in moles/liter and the formula weight of the substance, you can multiply these numbers and obtain mass per liter (moles/liter X grams/mole = grams/liter). And if you know the volume you need in liters, you then can multiply mass per liter times the desired volume to figure the amount to weigh (grams/liter X volume in liters = grams to weigh).
Remember that extreme precision is seldom either necessary or practical. It usually is good enough to get the actual concentration to within 1% of the desired concentration.
- Farone, M. B. & Farone, A. L. (1999). Dilution Solutions. Kendall-Hunt. [This work is a practical student guidebook and workbook that includes descriptions of types of formulas and how to conduct dilutions, problem sets, and chapters on working with cells, viruses, nucleic acids, and proteins].
- Gerstein, A. (Ed.). (2001). Molecular Biology Problem Solver. John Wiley & Sons, Inc.
- Reed, R., Holmes, D., Weyers, J., & Jones, A. (2003). Practical Skills in Biomolecular Sciences (2nd ed.). Pearson/Prentice Hall.
- Scopes, R. K. (1994). Protein Purification: Principles and Practice (3rd ed.). Springer-Verlag.
- Seidman, L. A. & Moore, C. J. (2000). Basic Laboratory Methods for Biotechnology. Prentice-Hall. [This handbook thoroughly describes a broad range of laboratory methods and is written at a level suitable for students. It serves as a good general reference for laboratory techniques]
Your slide tray is being processed.