> 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/troubleshooting/not-in-the-new-structure/what-can-i-measure-on.md).

# What can I measure on?

## 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>

See the [Everyday use](/everyday-use/before-you-measure.md) for basic sample preparation techniques.

## 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.

{% content-ref url="/spaces/eYTtd7c0A325muFr5lMW/pages/t6StrJdpRNXs4kfFtFZz" %}
[Hit the right concentration](/more/how-to-guides/hit-the-right-concentration.md)
{% endcontent-ref %}

{% 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.

See [Focus on target objects](/advanced/advanced-sample-preparation/focus-on-target-objects.md) for how-to guides.
{% endhint %}

Your BactoBox® setup has [microfluidic](https://en.wikipedia.org/wiki/Microfluidics) flow paths. Objects larger than about 5 µm never reach the measurement channel inside the flow cell, so BactoBox® does not count them.

They can still block the flow path. A sample that carries many large objects clogs the [external filter](/item-register/individual-items/external-filter.md) first, and in some cases the flow cell.

Always measure with an external filter fitted, and pre-filter a sample that carries large objects.

{% hint style="success" %}

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

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

## Electrical conductivity

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 an SBT [dilution vial](/item-register/individual-items/dilution-vial.md) or SBT [dilution liquid](/item-register/individual-items/dilution-liquid-5-l.md).

Both have the right electrical conductivity already.

When you [dilute your sample](/more/how-to-guides/hit-the-right-concentration.md) (1:1 000 or more), the conductivity of the diluent dominates over that of your sample. This puts the conductivity within the allowed range.
{% 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](/advanced/advanced-sample-preparation/hit-the-right-conductivity.md) for details.
{% endhint %}

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

Typically, this is because your BactoBox® uses the [BB05 (Original) configuration](/item-register/bactobox-r/bactobox-r-configuration.md). 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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