> For the complete documentation index, see [llms.txt](https://help.sbtinstruments.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sbtinstruments.com/measurement-essentials/hit-the-right-concentration.md). # Hit the right concentration BactoBox® has a working range from 30,000 to 5,000,000 objects/mL. Cultures may be as concentrated as 1×1011 cells/mL, that is 100,000,000,000 cells/mL. Therefore, cultures must be diluted prior to BactoBox® measurements. ## Dilutions of bacterial cultures To get conductivity right, the minimal dilution factor when using BactoBox® diluent is typically 1:100. This dilution is done by a single pipetting step and works well for the early growth stages. {% hint style="success" icon="square-bolt" %} ## Dilute at least 1:100 to hit the right conductivity. Most growth media must be diluted at least 1:100 to reach the conductivity range required for BactoBox® measurements (1,500–2,200 µS/cm). {% endhint %} As the cell concentration of a culture changes so does the required dilution. The table below summarizes the dilution factors used for various growth stages.
DilutionGrowth stage
1:100Lag, acceleration and early-exponential
1:1,000Mid- and late-exponential
1:10,000Deceleration, stationary, and decline
## Dilution schemes Below dilution schemes provide an overview of how you obtain the different dilutions. The expandable[^1] (:chevron-right:) in each section reveals step by step videos. The examples show how to hit a final concentration of 1×106 cells/mL. A minimum cells is a great target because you will get fast results with minimal risk of clogging the system. Lower and higher concentrations also work as long as they are within the working range from 30 000–5 000 000 total/mL. ### 1:100 dilutions

1:100 dilution is done by a single transfer of 101 µL culture of 10 mL of diluent.

Hands-on demonstration of 1:100 dilutions (click :chevron-right: to show more) {% stepper %} {% step %} ### **Dilute 1:100 in BactoBox® diluent** The below video demonstrates how to do a 1:100 dilution. * Transfer 101 µL of your sample to 10 mL of diluent. * Suspend ×10 to rinse the pipet tip for residual bacteria * Vortex 10 seconds at maximum speed.
{% endstep %} {% step %} ### **Measure the diluted sample on BactoBox®** The below video demonstrates how to do the bacterial measurement * Transfer the tubing kit to the 1:100 vial. * Press Measure to start a new measurement and wait for the results.
{% endstep %} {% endstepper %}
### 1:1,000 dilutions

1:1,000 dilution is done by two consecutive dilution steps. First a 1:100 and then a sequential 1:1,000 dilution. Note that 1 mL is removed from the second dilution vial before transferring the sample from the 1:100 vial.

Hands-on demonstration of 1:1,000 dilutions (click :chevron-right: to show more) {% stepper %} {% step %} ### Dilute 1:100 Label a dilution vial 1:100 . Vortex sample vial briefly (it has already been thoroughly vortexed when sampling). Transfer 101 µL of your sample to the 1:100 vial. Pipette up and down ×10 in the 1:100 vial to rinse the pipette tip for residual bacteria. Cap tightly and vortex 10 seconds at maximum speed.
{% endstep %} {% step %} ### Dilute 1:1,000 Label a second dilution vial 1:1,000. Aspirate and discard 1 mL diluent from the vial labeled 1:1,000 Transfer 1 mL of the 1:100 vial to the 1:1,000 vial. Pipette up and down ×10 in the 1:1,000 vial to rinse the pipette tip for residual bacteria. Cap tightly and vortex 10 seconds at maximum speed.
{% endstep %} {% step %} ### Measure the diluted sample on BactoBox® Transfer the tubing kit to the 1:1,000 vial. Press Measure to start a new measurement and wait for the results. {% endstep %} {% endstepper %}
### 1:10,000 dilutions

1:10,000 dilution is done by two consecutive dilution steps. First a 1:100 dilution and then a sequential 1:10,000 dilution.

Hands-on demonstration of 1:10,000 dilutions (click :chevron-right: to show more) {% stepper %} {% step %} ### Label two dilution vials Label first dilution vial 1:100. Label second dilution vial 1:10,000.
{% endstep %} {% step %} ### Dilute 1:100 Transfer 101 µL of your sample to the 1:100 vial. Suspend ×10 to rinse the pipette tip for residual bacteria. Vortex 10 seconds at maximum speed.
{% endstep %} {% step %} ### Dilute 1:10,000 Transfer 101 µL of the 1:100 vial to the 1:10,000 vial. Suspend ×10 to rinse the pipette tip for residual bacteria. Cap tightly and vortex 10 seconds at maximum speed.
{% endstep %} {% step %} ### Measure the diluted sample on BactoBox® Transfer the tubing kit to the 1:10,000 vial. Press Measure to start a new measurement and wait for the results. {% endstep %} {% endstepper %}
## Learn the ropes This mini course provided you with the essentials on how to dilute bacterial cultures prior to BactoBox® measurements. Try tutorial 3 for a hands-on example on how to adjust the dilution factors when tracking a growth curve. {% content-ref url="/pages/Kig8Uq7Hw23ovBr65Us0" %} [Track growth curve](/tutorials/measure-vitroid-tm-growth-curve.md) {% endcontent-ref %} [^1]: Expandable hides optional details. Click each expandable to reveal additional information about sample preparation. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://help.sbtinstruments.com/measurement-essentials/hit-the-right-concentration.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.