Q&A for How to Do Serial Dilutions

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How can I compose 2% dextrose saline from 5% dextrose saline?

Community Answer

it depends on the volume of 2% dextrose to prepare: assuming you are to prepare 10ml, use the formula:c1v1=c2v2,where c- concentration and v-volume. 2x10=5xv, 20= 5v, v=4, this implies that you take 4ml of 5% dextrose saline and make up to 10ml by sterile distilled water.

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Question

During serial dilution, why do I need to change the tips and mix well before going to the next dilution?

Community Answer

Change the tips in order to get an accurate dilution. Mix well in order to ensure the solution has equal amounts throughout.

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Question

What happens during the process of dilution?

Community Answer

The molecules are dispersed in water and are farther apart, making the concentration weaker.

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Question

If there was no visible bacterial colony formed on my plate, what can I conclude?

Community Answer

Different things can be concluded. The incubation temperature of your plate might have been too high or too low. The media that was used could also be a problem; some bacteria cannot grow in certain media while others can. In addition, the bacteria might need a longer time than usual to show growth. Any of these could be a possibility, which means more tests need to be done to completely understand and address the issue and come up with a conclusion.

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Question

How can I set up a series of tubes with a 1:4 dilution such that I end up with 3mL of solution in each tube at the end of the procedure?

Community Answer

If you're using 4 tubes, altogether, after dilution, that's 12mL. It's the 3mL times the number of tubes, which is 4. If your dilution is 1:4, then it's a quarter (1/4) of the total after dilution. One quarter of 12mL is 3mL. So, 3mL undiluted to 9mL of water, (or whatever you're using to dilute), 9 + 3 = 12 divided by 4 = 3. This means you should have 3mL in each tube if you divide the total amount into the 4 tubes.

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If I had 2 ml of a substance and then added 4 ml of a dilution, what would my ratio be?

Community Answer

2 ml of substance is your concentrated stock solution, 4 ml is your dilutent, such as water. Volume of concentrated solution/final volume - 2 ml/2 ml + 4 ml = 2/6 = 1/3 or 1:3.

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