Resuspension Calculator

Resuspension turns a measured dry material into a liquid stock solution by adding a suitable solvent. In molecular biology and chemistry laboratories, synthesized oligonucleotides, primers, probes, peptides, and small compounds often arrive as a dry pellet or film with the amount reported in nanomoles. Choosing the solvent volume from the desired concentration makes subsequent pipetting and dilution straightforward. This calculator uses the relationship concentration equals amount divided by volume. With amount entered in nanomoles and target concentration in micromolar, the convenient laboratory conversion is volume in microliters = amount in nanomoles × 1,000 divided by concentration in micromolar. The factor of 1,000 reconciles the metric prefixes. For example, 25 nmol prepared at 100 µM requires 250 µL of solvent. The result is the final solution volume, which is normally approximated by the volume added when the dry material contributes negligible volume. Target concentration should be selected for the downstream workflow. A 100 µM stock is common for DNA primers because simple tenfold dilutions produce 10 µM working stocks, but the appropriate value depends on assay design, stability, solubility, and laboratory protocol. Very small calculated volumes may be difficult to pipette accurately. In that situation, prepare a lower concentration or use a staged dilution rather than relying on a volume below the reliable range of the available pipette. Solvent choice matters as much as arithmetic. Nuclease-free water or a suitable buffered solution may be recommended for oligonucleotides, while other compounds can require a specific aqueous buffer or organic solvent. Follow the supplier's handling instructions, including pH, mixing, temperature, light protection, storage, and freeze-thaw guidance. Confirm that the material is soluble at the chosen target concentration before preparing the stock. After adding solvent, mix using the method appropriate for the material and allow enough time for complete dissolution. Brief centrifugation can collect liquid from tube walls. Label the stock with identity, concentration, solvent, preparation date, and storage conditions. The calculation assumes the supplier's stated nanomole amount is correct and that all material dissolves. For critical quantitative work, account for purity, water content, salt form, recovery, and any concentration verification recommended by the laboratory method.