What can I measure on?

Start with sample prep.

Go to Prepare your sample and pick what applies to your sample.

Prepare your sample

Clumps and chains Break up aggregates before measurement.

Break up clumps and chains

Large particles Remove particulate matter above 10 µm.

Remove large particles

Too concentrated Dilute into the measurable range.

Hit the right concentration

Too dilute Concentrate your sample before measurement.

Concentrate your sample

Conductivity outside range Adjust conductivity or use a low-conductivity method.

Hit the right conductivity

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.

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.

Don't know the concentration of your sample?

Make a dilution series and 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.

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.

Prepare your sample with the Break up clumps and chains and Remove large particles 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

The electrical conductivity of your sample vial must be within 1 500–2 200 µS/cm. You control the conductivity of your sample with diluent. 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.

Use SBT dilution vial or SBT dilution liquid

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.

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.

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.