Linearity

If your sample vial follows the requirements, you get great linearity and low variance.

Sample vial requirements

Proper output requires proper input. Make sure that your sample vial follows the requirements. See What can I measure on? and Prepare your sample.

Disaggregate your cells

Some cells tend to form clumps (aggregates), which makes them too big to measure with BactoBox®. Use 3 mm glass beads and a vortex mixer to disaggregate the cells in your sample vial.

BactoBox® does not count particles outside the 0.5–5 µm range.

See Break up clumps and chains for other disaggregation methods.

Linearity

For active cultures, BactoBox® shows great linearity between:

• BactoBox® cells/mL and the dilution factor

• BactoBox® cells/mL and plate counts (CFUs/mL)

This linearity covers the entire range given by the limits of detection.

The table below shows how BactoBox® performs across various particle types. Note that all R² values are very close to 1, which indicates strong linearity across the tested range.

Particle type	Tested range (1/mL)	Linearity with dilution factor	Linearity with plate counts
Staphyloccus epidermidis	30 000–5 000 000	R2=0.9975	R2=0.9982
1 µm silica microspheres	1 000 000–5 000 000	R2=0.9995	N/A

The below figure illustrates the linearity for the Staphylococcus epidermidis linearity-response test.

S. epidermidis linearity response. Concentration of cells for the same primary sample measured at different dilution factors. Each data point represents arithmetic mean of technical triplicates. Error bars represent standard deviation.