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Gamewizard's Content

There have been 15 items by Gamewizard (Search limited from 19-February 19)

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#176545 Advice on test results (microbiological challenge test)

Posted by Gamewizard on 27 August 2015 - 02:33 AM in Microbiology

Hi everyone,


I need a bit of advice on the results I have obtained from my experiment.


So I conducted a microbiological challenge test also called PET/AET. 


What i have observed is that there are no log reductions but the bacterial colonies (cfu/ml per plate) have still reduced. The log reductions are like 0.7 or 0.1, or 0.3 which is basically nothing.


Thus i am having hard time analysing results as I do not know whether the preservative system/product in question can be passed off as an effective antimicrobial or not


So how can this be possible ?   has anyone else experienced this too  



#176043 Preparing buffers for pH testing

Posted by Gamewizard on 24 July 2015 - 01:47 AM in Microbiology

grams NaOH:

m = M * c * V

mass (g) = molar mass (39.99 g/mole) * concentration (0.3 moles/L) * volume (1 L)


m= 11.99 grams (or better 12 g because the NaOH pellets are quite hygroscopic and it won't be that exact anyway (and be not too slow with weighing).


You cannot make an "undilution",i.e. you cannot concentrate a solution out of a more diluted one (except you invest in equipment and efforts which is compared to getting a more concentrated solution, useless, and with HCl almost impossible).


And finally, for me these are an acid and a base and not buffers.


Thank you for explaining that formula so well.  I am just worried about the HCl now,  this means I would have to obtain a a 0.3 M HCl solution then.

#176026 Preparing buffers for pH testing

Posted by Gamewizard on 23 July 2015 - 07:56 AM in Microbiology



I need to prepare some buffers, namely HCl and NaOH. I  want to prepare them at concentrations higher than 0.1M. The NaOH i have is just in pellet form and does not have a concentration or anything.  The HCl is in liquid form and is 0.1 M.   My question is can i use this 0.1M HCl to make    0.3 M HCl ?  i need about 1 litre. And also the NaOH, how much will i have to add to make 0.3 M solution (1 litre)?


Please help

#176020 Determining MIC

Posted by Gamewizard on 23 July 2015 - 03:16 AM in Microbiology

thank you so much,  can you check if i hav calculated the concentrations for the solids correctly?   they are in my previous post




#175963 Determining MIC

Posted by Gamewizard on 19 July 2015 - 11:31 AM in Microbiology

Sorry my bad,  yes  it is g/ml.  I have just found out that the density for my liquids is 1.26g/ml,(it was listed on a paper I had, I should have looked harder before)  but I still don't know how I will use this to calculate concentration of the raw materials in each of the well ?   is there any formula I can use



thank you 

#175928 Determining MIC

Posted by Gamewizard on 16 July 2015 - 12:39 PM in Microbiology

Thank you so much for your reply. You have explained it very well.   So, starting from the first original well, where the initial concentration is 500,000 ug/ml, then 250, 000 ug/ml,

125000 ug/ml, 62500 ug/ml, 31,250 ug/ml, 15625 ug/ml, 7812.5 ug/ml, 3906.25 ug/ml, 1953.125 ug/ml, 976.5625 ug/ml, 488.28125 ug/ml, 244.140625 ug/ml.  Is that correct?  


For the liquids, you determine the density by weighing out the liquid in question and then dividing its mass (g) by volume to get the density right ?   but I don't know what volume you use when weighing it out  ? 


And when you have your density how do you calculate grams/ml ?



#175892 Determining MIC

Posted by Gamewizard on 15 July 2015 - 08:16 AM in Microbiology

Hi all

I basically need some help with interpreting my MIC results.


I have carried out a MIC test on some raw materials against my bug. Bacterial inoculum was at 0.6 OD. Used a 96 well A to H microtire plate.

Obviously made serial dilutions of the raw materials, now some of my raw materials were liquid so i used them straight away (100%) but some were solids so i had to dilute them first with with sterile water.


I made a 1 in 2 dilution so put in 10g of solid raw material in to 20 g water. So thier starting percentage was 50%, and then the serial dilutions were made from Column 2 (total vol of column 2 was 200ul as i had 100ul sterile water and 100ul of raw material in it) by taking 100ul out and transfering to next one and so on. (1 in 2 dilution so the percentage was halved each time like so):-


Raw material A

100%, 50% 25% 12.5%, 6.25%, 3.125%, 1.5625%, 0.78174%, 0.390625%, 0.1953125%, 0.09765625%, and 0.0244140625% for all wells.


Now i need to determine at what concentrations the raw materials inhibited the bacterial growth and I dont know how to figure out the concentration, and i believe the concentration has to be in ug/ml as well ?


Can some one please help me figure this out, I have looked on the internet but it has confused me and I do not understand it.


Thank you for reading


#175799 Preparing buffers for pH testing

Posted by Gamewizard on 10 July 2015 - 08:36 AM in General Lab Techniques

What if i just used Citric acid alone (concentrated citric acid) to adjust the pH of my LB broth ?    

#175784 Preparing buffers for pH testing

Posted by Gamewizard on 09 July 2015 - 11:33 AM in General Lab Techniques

Hi I need help with preparing buffers. I have a pH range that i need to test my bacterium against. and for that i want to make buffers for example at each pH level.

The buffers i want to use are citric acid buffer for pH of 3.5, 4.5, 5.5, and 6.0. 

MES buffer solution for making pH of 6.5

HEPES buffer solution for making pH of 7.0, 7.5, and 8.0   and to adjust pH i will be using HCl and NaOH


So for example to make citric acid buffer at pH of 3.5 (50mM) I need 0.7119% w/v citric acid and 0.3807% w/v sodium citrate     how will i work this out in grams ?  


please help

#175763 calculating concentration from %

Posted by Gamewizard on 08 July 2015 - 10:34 AM in General Lab Techniques

Well obviously, I have done that myself, was not clear and that is why came on here for more straightforward answers. Would not ask on here otherwise

#175762 1 in 2 dilution of a powder help please

Posted by Gamewizard on 08 July 2015 - 10:31 AM in General Lab Techniques

Thank you everyone,  this makes sense now

#175712 calculating concentration from %

Posted by Gamewizard on 06 July 2015 - 07:48 AM in General Lab Techniques



If you know the percentage of a solution   then how can u calculate its concentration  ?  or is it the same thing


for example if you had something diluted 1 in 2 times,  and the percentage of that is 50% ,  how wil u calculate the concentration of it  ?  


help as i am confused



#175711 1 in 2 dilution of a powder help please

Posted by Gamewizard on 06 July 2015 - 07:40 AM in General Lab Techniques

Hi ,  I basically need to make a 1 in 2 dilution of a solid material and i dont know how to do that.  The material is in powder form so i need to make it liquid so that i can use it for a microbiology test in the lab. So this is why i need to dilute it and i have decided to make a 1 in 2 dilution of it with sterile water. But I do not understand how much of the powder i will be putting in to how much water.


if i have 0.10 g  for example, how much would i need of this and how much of water to make a 1 in 2 dilution   ?     


Help needed quick

#175555 Dilution and percentage problem

Posted by Gamewizard on 25 June 2015 - 05:48 AM in Microbiology

Your maths is a bit out: 1:10 is 1/10 = 10% or 0.1 as an integer.

Sorry my bad. You are right. 0.01  is a 1 in 100 dilution not in 1 in 10 !   But do you know the answer to my question   >/ ?   


Or do you know how i can 0.06% concentration from 0.1% concentration. The final volume needs to be 1000 microliters of 0.06%      ?     :(   I need to know this !

#175528 Dilution and percentage problem

Posted by Gamewizard on 23 June 2015 - 11:34 AM in Microbiology



so my question is basically on dilutions which I need to do for carrying out MIC


A 1 in 10 dilution converted to percentage is 0.01,   a 1 in 100 dilution is 0.001, however if I had a 1 in 10 dilution in my microtitre plate in well A1, in which I have added 1ml of bacterial diluent and 9ml of water, how much would I take from this column to the second column to make it 0.06% ?  and how much sterile water would I also add    


please help

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