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Standard Plate Count PT - WS

Proficiency Testing Material


Quality Level


set of 2 ea




food and beverages

shipped in

wet ice

storage temp.


General description

Standard Plate Count (SPC) - Water Supply (WS) proficiency testing material is produced in accordance with ISO/IEC 17043:2010. This sample is manufactured according to TNI requirements. However, please note, this sample may include non-TNI analytes as well. The lower criteria from the TNI tables mimic the levels common to drinking water samples.

Supelco® is a global proficiency testing (PT) provider that manufactures best-in-class environmental and pharmaceutical PT products. Most water PT samples are available as concentrates or ready-to-use volumes giving the end-user flexibility in selecting samples that will fit their exact needs.
These samples are typically provided in duplicate for use in case of lab mishap, for QC purposes, or to analyze multiple methods.

Type of PT Scheme: Water analysis: Water Supply (WS)

Matrix: Water Supply/Drinking water

Analyte/s: Values of analytes vary lot to lot.

All information regarding the use of Standard Plate Count - Water Supply (WS) proficiency testing standard can be found in the reporting packet which will be available to download at PT Portal.


Standard Plate Count - Water Supply (WS) proficiency testing material is designed to test the colony count of heterotrophic bacteria.

Have any questions? Explore our FAQs
For more information on this product, please contact our PT Service Team.

Features and Benefits

We have a vast portfolio of environmental PT schemes with "fit-for-purpose" samples to help you meet the needs of the laboratory.

Our proficiency testing (PT) program is a benchmark to:

  • provide staff with an insight into their laboratory′s performance, to verify the accuracy and reliability of their testing process
  • provide a comparison of performance with that of other laboratories, nationally and internationally
  • test and educate staff, provide a better understanding of the impact of incorrect results and identify areas where there may be problems
  • provide an independent evaluation of laboratory performance
  • demonstrate to clients, colleagues and accreditation bodies that there is a commitment to quality


Set contains 2 sterile screw cap vials each containing a Vitroid (a small disk containing the possible organisms) and 2 - 99mL bottles of phosphate buffer.
(Please note, buffer solution may not be provided with your sample. If this causes any concern, please contact PT Service

Preparation Note


  • This PT sample is designed for the quantitative analysis of heterotrophic bacteria.
  • The PT sample is provided as a stable lyophilized pellet requiring hydration.
  • A 100 mL of sterile hydration fluid is supplied with the PT sample. (Please note, buffer solution may not be provided with your sample. If this causes any concern, please contact PT Service
  • When prepared according to instructions, the concentration range of the sample will be between 5 - 500 CF/mL as per TNI Fields of Testing.
  • The lyophilized sample is stable for a time exceeding the study schedule.

General information

  • Due to the sensitivity of microorganisms and short holding times after hydration, please read the entire instructions prior to preparation. You must follow these instructions exactly to ensure the viability of the lyophilized microorganisms.
  • This sample is a single pellet, and the possible concentration range is quite broad, it may be necessary to analyze the sample in a dilution series.
  • This sample may be analyzed by any method appropriate for heterotrophic plate count.
  • Allow no more than 30 minutes to elapse from the completion of hydration and introduction of the sample to media.

Preparation Instructions

  • Allow the capped sample vial to equilibrate to room temperature. This may take up to an hour.
  • While the sample is equilibrating to room temperature, warm the hydrating fluid in your incubator to 35 - 37 °C. This will take about 60 minutes. This step is not necessary but will aid the dissolution of the Vitroid. If you do not have the capability to warm the hydration fluid, allow it to reach room temperature prior to starting the next step.
  • The hydration fluid is sterile and may be stored at room temperature up to the expiration date listed on the bottom, refrigeration is not necessary for the hydration fluid.
  • Open the sample vial and aseptically transfer the Vitroid to the hydrating fluid.
NOTE: The Vitroid is the colored disk within the cryotube. It will either be on top of cotton with opaque desiccant beads below the cotton or free moving in a cryotube that contains a desiccant tablet within the cap. The opaque desiccant beads and desiccant tablet are to keep the container dry and are not biologicals.
  • Allow the Vitroid to dissolve completely this may take up to 15 minutes. Mix by inverting gently several times, shaking may cause the cap to leak.
  • This represents the sample for analysis. Incubate at the temperature required by your method. Minimum incubation time is 24 hours. Further incubation time may be necessary depending on the method and media. If you have questions please contact
NOTE: Results are based on a 1mL sample from the 100mL preparation, thus units are CFU/mL or MPN/mL, not the full volume. In effect you are diluting the disk 100 fold.

Storage and Stability

Please refer to sample label for expiration date, specific storage temperature, and specific storage conditions.

Specific Batch Notes
For batch LRAC5559, it is vital that all 4 discs provided are used.

Other Notes

Are you new to Supelco® Proficiency Testing? Be sure to register your account details in the PT Portal before placing your order.
This will provide access to data entry, reporting packets and final reports. Registrations will be approved shortly after your order is placed. For further questions, write to us at

When placing your order online, please indicate your study preference under the ′your reference′ column. Available studies can be viewed at the bottom of the page.
Click here to learn more about Quick-Turn Studies (on-demand proficiency tests that are offered depending on lot availability). The Quick-Turn results are released within 48-72 hours whereas scheduled study reports are released within 21 days.

Proficiency testing samples are presented as single blind. No values for the samples are released until the testing period concludes. This PT sample is designed for the quantitative analysis heterotrophic bacteria. The PT sample is provided in duplicate as a stable dehydrated Vitroid requiring hydration. The additional sample is provided for mishaps in the lab. Store the PT sample as directed. The dehydrated Vitroid sample is stable for a time exceeding the study schedule.

Proficiency Testing Schedule (2021-2022)

Drinking Water
WS21-1January 13 - February 26, 2021
WS21-2March 24 - May 7, 2021
WS21-3 July 7 - August 20, 2021
WS21-4 September 22 - November 5, 2021

WS22-1January 12 - February 25, 2022
WS22-2March 23 - May 6, 2022
WS22-3 July 6 - August 19, 2022
WS22-4 September 21 - November 4, 2022

Legal Information

Supelco is a registered trademark of Merck KGaA, Darmstadt, Germany
Vitroid is a trademark of Sigma-Aldrich Co. LLC



    Heterotrophic plate count 5.00 - 500 CFU/mL
    Heterotrophic plate count, MPN 5.00 - 500 MPN

Storage Class Code

11 - Combustible Solids



Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Certificate of Analysis

Enter Lot Number to search for Certificate of Analysis (COA).

Certificate of Origin

Enter Lot Number to search for Certificate of Origin (COO).

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

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