For instance, if I do serial dilution of microbiology culture with 10^-6 with (100/900 microliter) in place of 1mL/9mL volumes, is it acceptable or is it a bad practise?
Personally I think it is accepted because your dilution factor is still the same..just that you are working with smaller volumes..cheers
Dear Mr. Patil,
I do support Margaret Baekalia. Usually when we do count CFU the formula is - average number of colonies x reciprocal value of the dilution x value to make the inoculated volume to 1 ml (usually CFU is counted as CFU/ml). So, here the lowest amount you are using is not the factor. The factor is the dilution (i.e. it should be 1:10). So, 100ul in 900ul and 1ml in 9ml is the same in terms of dilution.
Good luck
If you want to be efficient, and use less media, and work faster, use 100/900 microliter dilutions. It is very well accepted.
Well, theoretically, its absolutely fine.. No issues and is very well accepted, however if a minor pipetting error is introduced, remember you are going to extrapolate the value to 10^6 the error factor increases in this case. However as we increase the volume the error factor reduces.
To test this you can try to run the same experiment at different volumes and check. If you are an expert in serial dilutions then both the values should be similar.
I am in agreement with Aparna. The only reason to take higher volume is to reduce the pipetting error (handling and instrumental). You can do dilutions with smaller volume but you should make sure that your pipette is well calibrated.
I do appreciate Aparna Pandey and Santosh Kumar Yadav, but I don't think 100ul is that less amount to be so careful. Yes, a well calibrated pipette is important though.
Hello amol,
i use to work with 100ul/900ul dilutions with axenic cultures, but when i'm sampling for search diiferent species of microorganisms, i.e. determinations of phycriphilic,, mesophilic, yeast & moulds, salmnella, listeria and S. aureus in a product, i prefer to use 1mL/9mL dilutions.
In a way, the practice is fine. However, doing in ml instead of microlitres, will theoretically ensure better results, as your sample size will be larger. By sample size, i mean, larger volume is equal to more number of experiments performed. The greater is your sample size, the more the experimental accuracy.
It is better to define a formula using the capacity of equipment used. It is very different expressing 1 mL/9 mL and 1microliter/9 microliter because of the equipment precision used.
Hi there,
If you run your dilution with the suitable equipment it's fine! So for 100µL/900µL, use P100 and P1000 pipetor and for 1mL/9mL, use P1000 and 10mL-pipet. If you have done so, it's perfectly fine! And don't forget the mixing/homogenizing step before pipeting...
It is all about the accuracy of the pipetor. 100ul into 900 should not be a problem, however 1ul into 9ul is not likely to be very accurate.
Hi, like other colleagues rightly stated, you must also be certain that the micropipette tip is dispensing out the right volume. The essence of using small volume for your analysis is just to conserve the materials especially when you have limited quantity. using micropipette also give accuracy to your work especially if you are conversant to its usage. Goodluck.
Hi
In mathematical terms is exactly the same, but, in microbiology terms, it does depend on the purpose of the dilutions.
It does much depend on the purpose of the dilution. If you're starting from a
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