IDEXX Quanti-Tray 97-Well Presence/Absence Color Chart

Overview

The IDEXX Quanti-Tray 97-Well Presence/Absence Color Chart is a standardized visual reference tool engineered for the qualitative interpretation of enzymatic substrate assay results in water microbiology testing. It is an integral component of the IDEXX Quanti-Tray® system—designed around the Most Probable Number (MPN) statistical method—and is used exclusively with IDEXX’s DST (Defined Substrate Technology) enzyme substrate media, such as MMO-MUG or MI agar, for detection of total coliforms, fecal coliforms, and Escherichia coli. The chart enables unambiguous, operator-independent result classification: yellow color development ≥ chart intensity indicates presence of total or fecal coliforms; yellow fluorescence under 365 nm UV light ≥ chart threshold confirms E. coli presence. Its design aligns precisely with the optical response profiles of DST media following 24-hour incubation at 35 ± 0.5 °C (for total/fecal coliforms) or 44.5 ± 0.2 °C (for E. coli). Unlike subjective visual estimation, this calibrated chart eliminates inter-operator variability and supports audit-ready documentation per GLP and ISO/IEC 17025 requirements.

Key Features

• Calibrated, batch-certified colorimetric and fluorometric reference standard traceable to IDEXX’s internal metrology protocol
• Validated for use with both IDEXX Quanti-Tray® (51-well) and Quanti-Tray® 2000 (97-well) formats
• Designed for compatibility with MMO-MUG, MI, and other IDEXX-certified DST media formulations
• Light-stable pigments with documented spectral response curves matching typical 365 nm UV excitation and 450–470 nm emission bands
• Supplied in sealed, desiccated packaging with lot-specific expiration date and QC certificate
• Compliant with the color evaluation criteria specified in HJ 1001–2018 and GB/T 5750.12–2023 Annex C

Sample Compatibility & Compliance

The 97-Well Presence/Absence Color Chart is validated for use with water matrices including drinking water, wastewater effluent, surface water, groundwater, recreational water, and food process water. It supports detection of target organisms across the full MPN range of the 97-well tray (1–2,419 MPN/100 mL), without sample dilution. All interpretations must be performed under controlled lighting conditions (D65 illuminant, 500 lux minimum) and verified against the corresponding IDEXX media lot’s Certificate of Analysis. The chart meets the performance verification requirements of US EPA Method 1603, ISO 9308-2:2012, and ASTM D6162–21. It is not intended for use with non-IDEXX media or non-DST-based assays. Documentation of chart lot number, incubation time/temperature, and observer identity is required for regulatory submissions under FDA 21 CFR Part 11-compliant workflows.

Software & Data Management

While the color chart itself is a physical reference tool, its integration into digital laboratory workflows is supported through IDEXX’s optional Quanti-Tray Reader™ software (v4.2+), which allows side-by-side digital image capture of trays alongside the chart under standardized illumination. The software applies histogram-based color thresholding aligned to the chart’s chromaticity coordinates (CIE L*a*b* values) and logs metadata—including chart lot ID, incubation parameters, and user credentials—for full audit trail generation. All outputs comply with ALCOA+ principles (Attributable, Legible, Contemporaneous, Original, Accurate, Complete, Consistent, Enduring, Available) and support 21 CFR Part 11 electronic signature validation when deployed on validated systems. No standalone calibration or firmware update is required for the physical chart.

Applications

This color chart is routinely employed in municipal water utilities for compliance monitoring under China’s GB 5749–2022 and US EPA Safe Drinking Water Act reporting requirements. It is also applied in environmental laboratories conducting watershed assessments per HJ 91.1–2019, in food and beverage facilities for rinse water and ingredient water testing per GB 14881–2013, and in emergency response scenarios where rapid, field-deployable confirmation of fecal contamination is critical. Its precision supports method validation studies, inter-laboratory proficiency testing (e.g., NELAC Institute PT programs), and ISO/IEC 17025 accreditation audits. When paired with the Quanti-Tray 2000 system and automated sealing via the IDEXX 2009D Sealer, it enables same-day reporting of presence/absence outcomes with statistically robust MPN quantification.

FAQ

Is this color chart interchangeable with non-IDEXX quantitative trays?
No. It is calibrated specifically for IDEXX Quanti-Tray® 97-well trays and DST media. Use with alternative trays or substrates invalidates result interpretation.
Does the chart require periodic recalibration?
No. Each batch undergoes spectrophotometric certification at manufacture and remains stable for 12 months when stored dark and dry at ≤25 °C.
Can it be used for non-water samples such as milk or juice?
Only if the sample matrix has been validated per GB/T 5750.12–2023 Annex D for matrix interference and recovery—standard application is limited to aqueous samples.
What lighting conditions are required for accurate reading?
D65 daylight simulator (500–1000 lux), no direct UV exposure during visual assessment; UV fluorescence must be observed using a calibrated 365 nm handheld lamp with <5% wavelength deviation.
Is the chart included with every Quanti-Tray 2000 purchase?
No. It is sold separately as a consumable reference standard (Cat. No. WQT2KC); each box contains one chart with lot-specific QC documentation.