Toxi-ChromoPad™ Kit
A rapid direct-contact bacterial acute toxicity bioassay for soils, sediments, sludge, and solid waste — no extraction required. The only EBPI acute toxicity test designed specifically for solid matrices. Simple blue colour endpoint; readable visually in minutes.
No Extraction Required — Direct Contact Testing
Unlike aqueous toxicity tests that require costly and time-consuming solvent or water extraction steps, the Toxi-ChromoPad™ allows bacteria to grow in direct contact with the solid sample. This eliminates extraction artefacts, reduces sample preparation time, and provides a more ecologically relevant measure of bioavailable toxicity in the solid matrix.
The Toxi-ChromoPad™ bioassay uses a novel mutant strain of Escherichia coli selected specifically for sensitivity to a wide range of toxic substances and optimised for direct contact testing of solid matrices including soils, sediments, sludge, and solid waste. Bacteria are applied directly to the solid sample on a specialised test pad, eliminating the need for expensive extraction procedures. The chromogenic substrate is pre-embedded in the pad — during incubation, β-galactosidase produced by metabolically active bacteria converts the substrate directly, producing a distinctive blue colour wherever the sample is non-toxic. If the sample is toxic, no colour develops — enzyme activity has been inhibited. The colour endpoint is objective and immediately readable by visual inspection.
Each kit contains all reagents and disposable materials necessary to test at least four samples, including dilutions and controls. The Toxi-ChromoPad™ is ideal for initial acute toxicity screening of solid environmental matrices, dredged material, contaminated land, and industrial waste, providing a rapid pass/fail result without the cost or delay of chemical extraction.
- Test organismEscherichia coli novel mutant strain — selected for broad-spectrum sensitivity to toxic substances
- Sample typeSoils, sediments, sludge, and solid waste — direct contact, no extraction required
- EndpointEnzyme inhibition — blue colour = non-toxic; colourless = toxic
- DetectionVisual qualitative assessment; 8-step 2-fold serial dilution series per disc
- Samples per kitAt least 4 samples including dilutions and controls
- Result typeLowest-observed-effect concentration (LOEC); % toxicity at fixed dilutions
- Unique advantageOnly EBPI acute toxicity test for solid matrices — no extraction, no specialist equipment beyond standard laboratory supplies
📧 Order or Enquire
🍁 Ships from Burlington, Ontario, Canada · International shipping available · Cold-chain packaging included
Simple Direct-Contact Assay Procedure
The Toxi-ChromoPad™ is simple to perform and requires no specialised extraction equipment. The entire procedure from sample preparation to result reading can be completed in a standard laboratory or field setting.
Prepare Sample
Prepare a series of 8 two-fold serial dilutions of the solid sample (soil, sediment, sludge, or solid waste) on the test disc pad, ranging from undiluted to less than 1%
Apply Bacteria
Apply the E. coli mutant bacterial suspension directly onto the sample spots on the pad; bacteria come into direct contact with the solid matrix
Incubate
Incubate the pad under controlled conditions; bacteria grow in contact with the sample, exposing them to bioavailable toxicants. Where uninhibited, β-galactosidase enzyme is produced, converting the pre-embedded chromogenic substrate to a distinctive blue colour during incubation
Read Result
Read the pad visually: blue colour = non-toxic at that concentration; colourless = toxic. Identify the lowest concentration at which toxicity disappears
Reading the Test Disc
Blue — Non-Toxic
The E. coli bacteria have grown successfully and produced β-galactosidase enzyme, converting the pre-embedded chromogenic substrate in the pad to a distinctive blue colour. The sample at this concentration is non-toxic — bacterial metabolism is uninhibited. Blue colour develops around and across the sample spot on the pad during incubation.
Colourless — Toxic
No colour development. Toxic compounds in the sample have inhibited bacterial enzymatic activity or killed the bacteria before they could produce the enzyme. The sample at this concentration is acutely toxic. As the dilution series progresses, colour develops at the point where toxicity is no longer sufficient to inhibit enzyme activity.
Fig. 1 — Toxi-ChromoPad™ Test Disc Results
The photograph below shows two Toxi-ChromoPad™ test discs with different sludge samples run in parallel. Each disc shows an 8-step two-fold serial dilution series, with the centre dot acting as a control. The point at which blue colour develops across the disc identifies the lowest non-toxic dilution of the sample.
Interpreting Test Disc Results
The two examples below, taken directly from typical Toxi-ChromoPad™ test runs, illustrate how the dilution endpoint is used to compare the relative toxicity of different solid samples.
🔭 Disc 1 — Sludge Sample A
A series of 8 two-fold serial dilutions were carried out on the pad, ranging from pure sludge to less than 1%. The centre dot is a negative control. Blue colour development appeared across the dilution series, with toxicity disappearing at a concentration of 0.8%.
Toxicity endpoint: 0.8% — High toxicity🔭 Disc 2 — Sludge Sample B
The same dilution series carried out on a different sludge sample from the same facility. In this case, toxicity disappeared at a concentration of 6% — ten times higher than Sample A, indicating this sample was significantly less toxic than Sample A.
Toxicity endpoint: 6% — 10× less toxic than Sample AWhy Use the Toxi-ChromoPad™?
✅ No Extraction Needed
Direct contact testing eliminates costly solvent or water extraction steps, reducing preparation time, cost, and the risk of extraction artefacts masking true bioavailable toxicity.
👁️ Simple Visual Result
Blue = non-toxic; colourless = toxic. The result is immediately readable by visual inspection — no plate reader, luminometer, or specialist detection equipment required.
🌿 Ecologically Relevant
Direct contact testing reflects how organisms in the environment are actually exposed to contaminants in soils and sediments — through bioavailable contact, not extracted fractions.
⚡ Rapid Screening
Provides a rapid pass/fail acute toxicity result for solid matrices, enabling quick prioritisation of samples for more detailed chemical or biological analysis.
🔬 Sensitive Strain
The E. coli mutant strain is selected specifically for sensitivity to a wide range of toxic substances encountered in soils, sediments, and industrial solid waste.
📋 Complete Kit
All reagents and disposable materials for at least 4 samples with dilutions and controls are supplied ready-to-use. No additional reagent preparation required.
Applications for the Toxi-ChromoPad™
Sediment Toxicity
Direct contact toxicity screening of aquatic sediments for contaminated site assessment, dredging material evaluation, and regulatory compliance.
Soil & Contaminated Land
Rapid acute toxicity screening of soil samples from contaminated sites, brownfields, and industrial land prior to remediation planning.
Industrial Sludge & Waste
Toxicity characterization of industrial sludge, biosolids, filter press cake, and other solid or semi-solid industrial waste streams.
Mining Waste & Tailings
Direct toxicity testing of mine tailings, waste rock leachate residues, and acid mine drainage precipitates for environmental impact assessment.
Wastewater Treatment Residuals
Toxicity screening of WWTP sludge, biosolids, and dewatered cake for land application suitability assessment and regulatory compliance.
Battery of Tests
Combine with the SOS-ChromoTest™ or umuC sediment genotoxicity tests for a complete acute toxicity + genotoxicity battery on the same solid sample.
Kit Specifications
| Parameter | Detail |
|---|---|
| Product Number | 5033 |
| Product Name | Toxi-ChromoPad™ Kit |
| Test Organism | Escherichia coli novel mutant strain — selected for sensitivity to a wide range of toxic substances in solid matrices |
| Sample Types | Soils, sediments, sludge, biosolids, filter cake, solid and semi-solid industrial waste — direct contact, no extraction required |
| Endpoint | Enzyme (β-galactosidase) inhibition — blue colour = non-toxic; colourless = toxic (enzyme inhibited) |
| Detection | Visual qualitative assessment; no specialist detection equipment required |
| Dilution Series | 8-step two-fold serial dilutions per test disc (pure sample to <1%); centre dot = negative control |
| Samples per Kit | At least 4 samples including dilutions and controls |
| Result Expression | Lowest observed effect concentration (LOEC) as % v/w of sample at which toxicity disappears; relative toxicity comparison between samples |
| Extraction Required | None — direct contact testing |
| Kit Contents | All reagents and disposable materials ready-to-use for 4 samples with dilutions and controls |
| Manufacturer | EBPI — Environmental Bio-Detection Products Inc., Burlington ON, Canada |
Other Acute Toxicity & Sediment Tests
Contact EBPI for pricing, application guidance, or technical support for the Toxi-ChromoPad™ Kit.