What can I measure on?

Sample requirements

Parameter	Allowed range	Notes
Concentration	< 5 000 000 total/mL	Target 0.5–4 million total/mL. Start low and then move to higher concentrations.
Particle size	0.5–5 µm	Equivalent spherical size. BactoBox® detects particles (for example, cells) in this range. BactoBox® does not detect larger objects.
Electrical conductivity	1 500–2 200 µS/cm	This is the default range for the BacTotal-v2024-10 gating. Custom gating may change the allowed range. The Measure with low conductivity program is one example.
pH	5–9
Volume	4–12 mL	Target 10 mL in your measurement vial.

See the Measurement essentials 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.

Hit the right concentration

Do not measure on turbid sample liquid

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

Particle size

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

This includes most bacteria.

See Focus on target objects for how-to guides.

Your BactoBox® setup has microfluidic 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.

Use a 10 µm cell sieve to avoid large particles

Filter the sample liquid with a 10 µm cell sieve before you measure on it.

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.

Use an SBT dilution vial or SBT dilution liquid.

Both have the right electrical conductivity already.

When you dilute your sample (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 changes with temperature

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 for details.

My BactoBox® uses 1 600–2 100 µS/cm

Typically, this is because your BactoBox® uses the BB05 (Original) configuration. This is for an early version of BactoBox®.

We recommend the BB14 (Customizable) configuration for all new BactoBox® devices. Contact SBT for further details.