# What can I measure on?

Start with sample prep.

Go to [prepare-your-sample](https://help.sbtinstruments.com/protocols/prepare-your-sample "mention") and pick what applies to your sample.

## Prepare your sample

<table data-column-title-hidden data-view="cards"><thead><tr><th>Common situations</th><th data-card-target data-type="content-ref">Link</th></tr></thead><tbody><tr><td><strong>Clumps and chains</strong><br><mark style="color:$info;">Break up aggregates before measurement.</mark></td><td><a href="../../protocols/prepare-your-sample/break-up-clumps-and-chains">break-up-clumps-and-chains</a></td></tr><tr><td><strong>Large particles</strong><br><mark style="color:$info;">Remove particulate matter above 10 µm.</mark></td><td><a href="../../protocols/prepare-your-sample/remove-large-particles">remove-large-particles</a></td></tr><tr><td><strong>Too concentrated</strong><br><mark style="color:$info;">Dilute into the measurable range.</mark></td><td><a href="../../protocols/prepare-your-sample/hit-the-right-concentration">hit-the-right-concentration</a></td></tr><tr><td><strong>Too dilute</strong><br><mark style="color:$info;">Concentrate your sample before measurement.</mark></td><td><a href="../../protocols/prepare-your-sample/hit-the-right-concentration/concentrate-your-sample">concentrate-your-sample</a></td></tr><tr><td><strong>Conductivity outside range</strong><br><mark style="color:$info;">Adjust conductivity or use a low-conductivity method.</mark></td><td><a href="../../protocols/prepare-your-sample/hit-the-right-conductivity">hit-the-right-conductivity</a></td></tr></tbody></table>

## Sample requirements

<table><thead><tr><th width="199">Parameter</th><th width="210">Allowed range</th><th>Notes</th></tr></thead><tbody><tr><td>Concentration</td><td>&#x3C; 5 000 000 total/mL</td><td>Target 0.5–4 million total/mL. Start low and then move to higher concentrations.</td></tr><tr><td>Particle size</td><td>0.5–5 µm</td><td><em>Equivalent spherical size.</em> BactoBox® detects particles (for example, cells) in this range. BactoBox® does not detect larger objects.</td></tr><tr><td>Electrical conductivity</td><td><code class="expression">space.vars.BB_LIMIT_EC</code></td><td>This is the default range for the <em>BacTotal-v2024-10</em> gating. Custom gating may change the allowed range. The <em>Measure with low conductivity</em> program is one example.</td></tr><tr><td>pH</td><td>5–9</td><td></td></tr><tr><td>Volume</td><td>4–12 mL</td><td>Target 10 mL in your measurement vial.</td></tr></tbody></table>

## Concentration

High concentrations may clog your BactoBox® setup. This is why the 5 000 000 total/mL limit matters.

If the concentration is too high, it may clog the flow cell.

{% hint style="info" %}

## Don't know the concentration of your sample?

Make a dilution series and [**measure the most diluted sample first**](https://help.sbtinstruments.com/protocols/prepare-your-sample/hit-the-right-concentration/dilute-1-100#measure-the-most-diluted-sample-first). This avoids clogging your BactoBox® setup. It also avoids carry-over from your previous sample vial.

Once you are above the lower limit of detection (30 000 cells/mL), target 0.5–4 million cells/mL.
{% endhint %}

{% hint style="danger" %}

## Do not measure on *turbid* sample liquid

If the sample liquid is turbid (not transparent), this strongly indicates that the concentration is too high.
{% endhint %}

## Particle size

{% hint style="info" %}

## BactoBox® counts particles (including cells) in the 0.5–5 µm size range

This includes most bacteria.

Prepare your sample with the [break-up-clumps-and-chains](https://help.sbtinstruments.com/protocols/prepare-your-sample/break-up-clumps-and-chains "mention") and [remove-large-particles](https://help.sbtinstruments.com/protocols/prepare-your-sample/remove-large-particles "mention") guides.
{% endhint %}

Your BactoBox® setup has [microfluidic](https://en.wikipedia.org/wiki/Microfluidics) flow paths. The smallest cross-sectional area is 10×10 µm. That is about one-tenth the width of a human hair.

Even a tiny particle can clog the system.

To avoid that clogging, always use an [external filter](https://help.sbtinstruments.com/encyclopedia/item-register/consumables/external-filter).

{% hint style="success" %}

## Use a 10 µm cell sieve to avoid large particles

Filter the sample liquid with a [10 µm cell sieve](https://help.sbtinstruments.com/encyclopedia/item-register/consumables/cell-sieve-10-m) before you measure on it.
{% endhint %}

## Electrical conductivity

The [electrical conductivity](https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity) of your [sample vial](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/sample-vial) must be within [<code class="expression">space.vars.BB\_LIMIT\_EC</code>](#electrical-conductivity). You control the conductivity of your sample with [diluent](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/dilution-liquid-5-l). Keep the diluent at room temperature!

BactoBox® uses an *electrical* measurement principle. Therefore, the *electrical* conductivity is important for accurate results.

BactoBox® has a built-in conductivity sensor. It gives an error if the conductivity is outside the allowed range.

{% hint style="success" %}

## Use SBT [dilution vial](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/dilution-vial) or SBT [dilution liquid](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/dilution-liquid-5-l)

Use an SBT [dilution vial](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/dilution-vial) or SBT [dilution liquid](https://help.sbtinstruments.com/encyclopedia/item-register/vials-flasks-and-liquids/dilution-liquid-5-l). Both have the right electrical conductivity already.

When you [dilute your sample](https://help.sbtinstruments.com/protocols/prepare-your-sample/hit-the-right-concentration) (1:1 000 or more), the conductivity of the diluent dominates over that of your sample. This puts the conductivity within the [allowed range](#electrical-conductivity).
{% endhint %}

{% hint style="info" %}

## Try the *Measure with low conductivity* program

BactoBox® comes with several gating settings. One of these is part of the *Measure with low conductivity* program. It accepts sample vials in the 500–1 100 µS/cm range.

See [gating](https://help.sbtinstruments.com/encyclopedia/measurements-explained/gating "mention").
{% endhint %}

### Electrical conductivity changes with temperature

{% hint style="success" %}

## Keep your sample vial at *room temperature* to avoid surprises

For example, if your sample is refrigerated, wait for it to warm up.

The electrical conductivity of the diluent changes *a lot* with temperature. A mere 5 °C increase can add about 200 µS/cm.

See [hit-the-right-conductivity](https://help.sbtinstruments.com/protocols/prepare-your-sample/hit-the-right-conductivity "mention") for details.
{% endhint %}

### My BactoBox® uses 1 600–2 100 µS/cm

Typically, this is because your BactoBox® uses the [BB05 (Original) configuration](https://help.sbtinstruments.com/encyclopedia/item-register/bactobox-r/bactobox-r-configuration). This is for an early version of BactoBox®.

We recommend the BB14 (Customizable) configuration for all new BactoBox® devices. [Contact SBT](mailto:customersupport@sbtinstruments.com) for further details.


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