How to perform serial dilutions

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A serial dilution allows you to take a concentrated solution and make a dilute solution through a series of steps. In each step the solution becomes more dilute. You will often need to perform serial dilutions if you need a smaller amount of the solute than you can measure directly from the original solution. Serial dilutions are often used when measuring minute concentrations for chromatography equipment such as in liquid or gas chromatography. For example, you can dilute a solution from 1g/ml to 0.001g/ml.

Place your original solution (the 1g/ml solution) in the test tube rack. Use the permanent marker to label the other test tubes or sample vials with the following labels (you can write directly on the tube or vial): "A 0.1g/ml," "B 0.01g/ml" and "C 0.001g/ml." Line these tubes or vials up in order in the test tube rack.

Place a pipette tip on the pipette. Transfer 9ml of water into Tube A.

Transfer 1ml of the original solution into Tube A. Cap or seal the tube and mix using the vortex mixer for a few seconds or by gently inverting the tube a few times. Tube A now contains a 0.1g/ml solution. Discard the pipette tip.

Place a new pipette tip on the pipette. Transfer 9ml of water into Tube B. Transfer 1ml of the 0.1g/ml solution in Tube A into Tube B. Cap or seal the tube and mix using the vortex mixer for a few seconds or by gently inverting the tube a few times. Tube B now contains a 0.01g/ml solution. Discard the pipette tip.

Place a new pipette tip on the pipette. Transfer 9ml of water into Tube C. Transfer 1ml of the 0.01g/ml solution in Tube B into Tube C. Cap or seal the tube and mix using the vortex mixer for a few seconds or by gently inverting the tube a few times. Tube C now contains a 0.001g/ml solution. Discard the pipette tip.

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