HPC for Quanti-Tray

Heterotrophic plate count made easy for bottling and manufacturing plants and on-premise testing


  • Quantifies heterotrophic organisms in a 100 mL format
  • No autoclaving, filtering, or agar
  • No colony counting or interpretation



  • Convenient 100-mL sample size—test source water, transport vehicle water, manufacturing line water, and finished products.
  • Simple procedure needs no special training.
  • Shares the same Quanti-Tray system as ColilertEnterolertand Pseudalert  tests for maximum efficiency.
  • Results valid at 44–72 hours.


How the HPC for Quanti-Tray test works

The HPC for Quanti-Tray test is used for the quantification of heterotrophic organisms in 100 mL of water.

The test is based on the IDEXX proprietary Multiple Enzyme Technology, which detects viable heterotrophic organisms by testing for the presence of key enzymes known to be present in these organisms. The test uses multiple enzyme substrates that produce blue fluorescence when metabolized by waterborne bacteria.

The sample/reagent mixture is added to a Quanti-Tray, incubated, and then examined for fluorescing wells. The number of fluorescing wells corresponds to a most probable number (MPN) of total heterotrophic organisms in the original sample.

The HPC for Quanti-Tray test detects organisms at 1 cfu/100 mL after 44–72 hours of incubation.



How to use


Step 1

Add reagent to sample (sample will turn pink).

Step 2

Pour into Quanti-Tray or Quanti-Tray/2000.

Step 3

Seal using a Quanti-Tray Sealer; incubate for 44 hours.

Step 4

Read under ultraviolet light; count blue fluorescent wells and refer to MPN table.

Frequently asked questions

Which water types can be tested?

The HPC for Quanti-Tray test is designed specifically for bottled-water samples. Bottled-water samples are defined as samples taken from any point in the bottled-water manufacturing process (from the original water source, to transportation vehicles, to the manufacturing line, to the finished product).

What is the sample incubation time and temperature?

Water samples are incubated at 36ºC (± 2ºC) for 44 hours, and results are valid up to 72 hours.

What is the detection limit?

The HPC for Quanti-Tray test detects heterotrophic organisms at 1 cfu/100 mL.

Does the test include a comparator?

There is no comparator for the HPC for Quanti-Tray test. Use a negative control for comparison when you interpret results.

Are results valid prior to 44 hours?

Yes, if the results are positive. An inoculated HPC for Quanti-Tray test sample that is positive before 44 hours is a confirmed positive test. However, for an accurate quantitative determination of heterotrophic count in a sample, the results should be read between 44 and 72 hours of incubation.

Are results valid after 72 hours?

Yes, if the results are negative. If an inoculated HPC for Quanti-Tray test sample is inadvertently incubated over 72 hours, lack of fluorescence is a valid negative test. However, a fluorescent read after the 72 hours is not valid and should be repeated or verified.

Can either a 51-well or a 97-well Quanti-Tray be used?

Yes, both the Quanti-Tray and Quanti-Tray/2000 can be used with the HPC for Quanti-Tray test in the 100-mL format.

What are the recommended test storage conditions?

What should be the color and consistency of the test powder?

The HPC for Quanti-Tray test reagent powder should be pink in color and of a free-flowing, granular consistency. Direct any concerns about the color or integrity of the powder to IDEXX Technical Service at 1-800-321-0207 or [email protected].

How should customers dispose of a positive HPC sample?

Check with your local, state, and/or federal authorities for proper disposal of bacteriological biohazard materials at your facility.

Can the HPC for Quanti-Tray test be used with carbonated water samples?

The HPC for Quanti-Tray test should not be used with carbonated water samples.