#SERIAL DILUTION PROCEDURE SERIES OF STEPWISE#
#SERIAL DILUTION PROCEDURE FREE TO COPY#
#SERIAL DILUTION PROCEDURE SERIAL DILUTION CONSISTS#

Serial Dilution Procedure Serial Dilution Consists

Serial Dilution Procedure Series Of Stepwise

The concentration of bacteria in a typical undiluted sample is so high that colonies growing on an agar plate prepared from that sample will be far too crowded to permit identification and isolation of unique colony types.A serial dilution consists of a series of stepwise dilutions performed in a sequence that results in a geometric decrease in cell concentration. For example, if you take 1 part of a sample and add 9 parts of water (solvent), then you have made a 1:10 dilution this has a concentration of 1/10th (0.1) of the original and a dilution factor of 10.Problem. The dilution factor is the inverse of the concentration factor. The concentration factor is the initial volume divided by the final solution volume.

Otherwise, we would use a 1 ml pipette to deliver a 1 ml volume. In addition to using the method to reduce the concentration of microscopic organisms, we might use it to prepare calibration standards, obtain working titers of an antibody or drug, etc.NOTE: because we are using these plates solely to obtain bacterial isolates we are not as concerned about pipetting accuracy as we would be if we were quantifying bacterial concentrations. Serial dilutions are a relatively uncomplicated way of optimizing the concentration of a solution or mixture when we don't know the starting concentration, the optimum concentration, or either. At least one dilution will result in well separated colonies, enabling us to collect isolates.Applications.

Next you will take 1 ml of your 1 to 10 dilution and mix it with 9 ml water in a second tube to give a 1 to 100 dilution, and on down to a 1 to 10,000 dilution.Note that all of these procedures must be conducted aseptically. You'll start by preparing dilution blanks, then you will mix 1 ml sample with 9 ml sterile water to give a 1 to 10 dilution. Green Pipette pump and container w/10 ml pipettesYou will use these supplies to make four serial dilutions. Empty 20 mm x 150 mm capped culture tubes, in a plastic rack

(left center) Pipette dipped in sterile water with tip touching the bottom. (left) Supplies needed for making dilutions. Handle a pipette only by the back end, so you don't contaminate the part that goes into a bottle or tube.Figure 1. Try to minimize the time during which a vessel is open and/or a pipette is exposed to the air. To minimize the risk of contaminating your samples, try to work quickly.

Open the pipette container, leaving it on its side, and shake out the pipettes so that they extend a few cm from the end. Loosen the screw cap on the bottle of deionized water so that it can be lifted straight off. (right) To limit the risk of contaminating the contents, remove the cap just long enough to introduce the pipette tip and deliver the liquid.

Hold the pipette pump with pipette firmly attached and place your thumb on the control wheel. We always use some type of pipette aid to draw up and expel liquid. Carefully remove one pipette, trying not to touch the others with your fingers, and fit it snugly into the seal of the pipette pump, in a position such that you can see the numbers when holding the pump. Have the mouth of the can extending slightly over the edge of the bench, so the pipette back ends aren't resting on the bench.

Lift the pipette out and immediately replace the cap on the tube. Place the pipette an inch or so into the tube with the tip touching the glass and expel the liquid from the pipette into the tube by rolling the thumb wheel upward. Lift out the filled pipette, immediately put the cap back on the water bottle, and lift the cap off of one of the dilution tubes. It's easiest to fill it to a little above the desired line, and then move the meniscus down to the desired line by gently rolling the thumb wheel upward. Fill the pipette to the 9 ml mark by rolling the thumb wheel downward. Use the other hand to lift the cap off of the bottle of sterile water and insert the pipette into the water with the tip well below the surface.

As you make dilutions, it's best to set up the tubes so there is an empty space in the rack next to the dilution tubes. Four dilution blanks, labeled and filled. Replace it if you think it is no longer sterile.All of the pipettes that we will be using are 'blowout pipettes.' That is, you fill the pipette to the desired volume and then blow all of the contents out of the pipette to deliver the correct volume.Figure 2. If you don't contaminate your pipette you can continue to use the same one.

Load a fresh sterile pipette into your pipette pump as you did previously. Remove the used pipette and place it into the pipette bucket. You will want a fresh pipette because the first one has been out for awhile. With cap secured, shake up the bottle containing your water sample to mix it thoroughly and then loosen the cap so that you can pull it straight off.

Remove the cap from the first dilution tube and place the pipette into the tube so its tip is just above the surface of the water. Remove the pipette and replace the cap. Pull up 1 ml of sample by moving the thumbwheel downward as you did previously.

Remember: we must not use the same pipette to transfer different solutions or different dilutions of the same solution.We now have four dilutions of our original sample, each approximately ten times more dilute than the previous dilution. Load up a fresh pipette and continue by diluting 1 ml from the first dilution tube into the next dilution tube to make your 1 to 100 dilution, and repeat for the remaining tubes, each time using a fresh pipette. Thoroughly mix the contents of the tube using a Vortex mixer. Lift the pipette out and immediately replace the cap on the tube.

Serial Dilution Procedure Free To Copy

If you don't mind letting me know of such intentions I'll be happy to hear from you. Please feel free to copy and/or modify these materials for use in your own academic or other nonprofit program. Caprette, Teaching Professor, Rice University 21 Dec 16 for the course BIOC 318, Laboratory Studies in Microbiology. At least one dilution will give us a manageable number of individual bacterial colonies.Created by David R.