TMB Stop Solution

Cat. No.: T616350

Storage

Room temperature

Shipped In

Normal

Specifications

Storage

Room temperature

Shipped In

Normal

Application Protocols

No item-specific, vendor-validated protocols are provided in the Product Data for this SKU. Refer to your assay kit instructions or internal SOPs for ELISA workflows using TMB substrate and a stop solution. General method development guidance is provided under the Reaction Conditions and Reaction & Applications tabs.

Biological Roles

Not a biological macromolecule or metabolite. This material is an assay reagent designed to terminate enzyme-mediated color development in immunoassays.

General context (literature):

• Mode of action in assays: Stops horseradish peroxidase (HRP) activity and stabilizes the oxidized TMB product for endpoint detection.
• Impact on biomolecules: Does not have intrinsic biological roles; transient exposure to strong acid can denature proteins in the well, which is acceptable after signal generation.

No biological pathway, receptor, or metabolic role is associated with this product.

Buffer Applications

This reagent is not a buffer and is not intended to maintain pH; rather, it rapidly acidifies the reaction mixture to terminate HRP–TMB color development.

Practical notes (literature):

• Use standard assay buffers (PBS, TBS) for all washing and incubation steps prior to color development.
• After color development with TMB, add stop solution to shift to a low pH endpoint suitable for 450 nm measurement.

For buffer formulation and pH control in other steps, refer to dedicated buffering agents (e.g., phosphate, Tris, HEPES). This stop solution is not typically used for buffering applications.

Green Alternatives

Environmental and safety considerations focus on acid strength, corrosivity, and neutralization requirements. While item-specific composition is not provided, the following compares common literature options used as TMB stop reagents:

• Sulfuric acid (H2SO4): Widely used; strong, efficient quench and stable yellow endpoint. Downsides: corrosive, generates sulfate-containing waste requiring neutralization.
• Hydrochloric acid (HCl): Effective stopper; potential for corrosive fumes and chloride-induced corrosion; avoid contact with bleach (chlorine gas risk).
• Phosphoric acid (H3PO4): Less volatile; effective stop with somewhat different extinction coefficient; phosphate load may affect wastewater permits.
• Citric acid (C6H8O7): Organic, less hazardous handling compared to strong mineral acids; may provide gentler stop and safer waste stream, though sometimes with altered sensitivity/dynamic range.

Trade-offs (literature):

• Stronger acids give rapid, uniform stopping and robust yellow color but increase PPE/waste burden.
• Weaker/organic acids can improve handling and reduce corrosion but may require re-optimization of incubation times and calibration due to different optical responses.

Greener practice tips:

• Minimize volumes; use calibrated multichannel pipettes to avoid excess.
• Neutralize acidic waste to pH 6–8 before disposal per local rules.
• Consider phosphoric or citric acid systems if they meet assay sensitivity and regulatory needs, validating performance before adoption.

Pharmaceutical Uses

No direct pharmaceutical formulation or excipient role is intended. This product is supplied for laboratory research use only (per product note) and is typically used in analytical immunoassays (e.g., ELISA) rather than in drug products or clinical diagnostics. It is not covered by pharmacopeial monographs in this context.

If adapting assay methods for GMP/QC environments, qualification should include verification of stop kinetics, optical stability, leachables from packaging, and compatibility with validated microplate readers. All such qualifications are user-responsibility and assay-specific.

Physical Properties

Item-specific physicochemical specifications are not provided for this product. Typical properties of TMB stop solutions are given here strictly as literature/general guidance; consult the CoA/SDS for exact values for this SKU.

• Appearance: Not specified for this item; refer to CoA/Spec Sheet.
• Composition/Concentration: Not specified for this item; refer to CoA/Spec Sheet. (Literature: commonly 0.5–2 N mineral acid in water.)
• pH: Not specified for this item; refer to CoA/Spec Sheet. (Literature: strongly acidic, often pH < 1.)
• Density: Not specified for this item; refer to CoA/Spec Sheet. (Literature: near water if dilute; increases with acid normality.)
• Boiling/Melting Point: Not specified for this item; refer to CoA/Spec Sheet. (Literature: aqueous solutions boil near 100 C, dependent on composition.)
• Solubility: Aqueous solution; miscible with water (general/literature).
• UV-Vis behavior (assay context, literature): Upon stopping TMB, absorbance maximum shifts to ~450 nm for the yellow product; measure promptly and consistently.
• Refractive Index, Viscosity, Conductivity: Not specified for this item; refer to CoA/Spec Sheet.

Note: Because this is a formulated assay reagent, conventional single-compound identifiers (MW, SMILES) do not apply. Always rely on the item’s CoA/SDS for quantitative properties.

Quality & Grades

• Grade/Purity (item-specific): Not specified for this item; refer to CoA/Spec Sheet.

How quality is typically defined for TMB stop solutions (general guidance):

• Functional QC: Performance is best judged by assay behavior—rapid quenching of HRP activity, reproducible conversion to the yellow chromophore, and stable absorbance during the defined reading window (e.g., 5–30 minutes post-stop; literature).
• Lot-to-lot consistency: Critical for ELISA precision. Vendors often verify stop kinetics against a reference TMB substrate and HRP standard curve.
• Low background: High-quality stop solutions should not introduce plate background, precipitates, or turbidity.
• Container/packaging: Acid-compatible, leach-resistant plastics (HDPE/PP) help maintain integrity over shelf-life.
• Labeling: Concentration and composition (normality, acid type) are typically stated on the label/CoA. For this SKU, composition is not disclosed here—verify on receipt.

Implications for your workflow:

• Use the same lot for full studies when possible to minimize inter-lot variability.
• Standardize the stop-time and plate-read interval across plates and runs.
• If qualifying an alternative stop reagent, re-validate standard curves and dynamic range, as extinction coefficients can differ with acid identity/strength (literature).

Reaction & Applications

Primary application: termination of HRP–TMB color development in ELISA and other HRP-based microplate assays, converting a kinetic readout into an endpoint measurement.

Mechanistic/assay notes (literature/general):

• Chemistry: HRP oxidizes TMB to a blue charge-transfer complex (Amax ~650 nm). Acidic stop protonates this species to a yellow diimine with a strong Amax at ~450 nm, while inactivating HRP.
• Quantitation: After stopping, measure at 450 nm with an optional 620–650 nm reference to correct for plate artifacts.
• Kinetics: Stop solution should be added at a consistent time across wells to control reaction time. The yellow product is relatively stable but can drift; define a fixed read window (e.g., 5–30 minutes post-stop) in method SOPs.
• Volume and mixing: Add an equal volume of stop to the developed TMB (common practice), achieving rapid, uniform mixing by using multichannel pipettes and tapping/shaking the plate briefly.
• Dynamic range: Acid identity and concentration influence molar absorptivity and linear range. If changing stop conditions, re-validate calibration curves and limits of detection/quantitation.
• Interferences: Residual peroxide or metal contaminants are usually irrelevant at stop stage, but strong bases or residual bleach in wash systems can partially neutralize the stop and destabilize signals.

Use cases:

• Endpoint ELISA for cytokines, enzymes, and biomarkers.
• HRP-based antibody/antigen detection in microplates, membranes adapted to plate reading, and high-throughput screening assays.

Reaction Conditions

Guidance below is general/literature for TMB-based ELISA workflows; it does not specify the exact composition of this SKU. Optimize within your assay.

Typical endpoint ELISA stopping conditions (literature):

• Substrate development: Incubate TMB with HRP-coupled analyte for 5–20 min at RT until desired blue color forms (monitor at 650 nm if needed).
• Stopping step: Add stop solution at 0.5–1.0× the TMB volume (commonly equal volume). Dispense quickly and uniformly using a multichannel pipette. Briefly tap or shake to mix.
• Readout: Measure absorbance at 450 nm within a defined window (e.g., 5–30 min post-stop). Use a 620–650 nm reference to correct optical imperfections.
• Temperature: Room temperature operation is standard; maintain consistent temperature between plates to minimize variability.
• Controls: Include a standard curve and blanks on every plate. If switching stop reagents or lots, re-validate the calibration curve (molar absorptivity varies with acid).
• Precision tips: Time the addition across columns/rows to <30–60 s spread when feasible; use automated dispensers for large runs. Read plates in the same order as stopped.
• Interferences: Residual detergent or high buffer capacity can slightly moderate the final pH; ensure wash solutions are adequately removed before TMB addition.

These conditions are provided for method development reference; follow your lab’s SOPs and this product’s SDS/label.

Safety & Handling

Item-specific GHS data are not provided here; consult the product SDS for authoritative hazard classifications and response measures for this SKU.

General safety guidance for TMB stop solutions (literature/typical):

• Hazard profile: Many TMB stop reagents are aqueous strong acids and are typically classified as corrosive. Expect potential for skin/eye burns and metal corrosion. Your item’s exact classification may differ—verify with the SDS.
• PPE: Wear lab coat, acid-resistant gloves (e.g., nitrile), safety goggles or face shield. Use in a well-ventilated area or biosafety cabinet when handling plates.
• Handling: Avoid contact with bases, cyanides, oxidizable metals, and bleach (chlorine gas can form with HCl). Add acid to water when diluting. Prevent splashes and aerosol formation during plate dumping or wash steps.
• First aid (overview): Rinse skin/eyes with copious water for ≥15 minutes. Remove contaminated clothing. Seek medical attention for exposure. If ingested, do not induce vomiting; rinse mouth and get medical help. Follow SDS instructions.
• Spill response: Neutralize small spills cautiously with sodium bicarbonate; absorb with inert material. For larger spills, evacuate area and follow institutional protocols.
• Waste: Collect acidic assay waste separately. Neutralize to pH 6–8 before drain disposal if permitted by local regulations, or dispose as hazardous waste.
• Special assay note: After stopping TMB, signals can drift slowly; read within a consistent time window to ensure reproducibility.

Solvent Selection

This product is a ready-to-use aqueous solution intended for microplate assays; separate solvent selection is generally not applicable.

Useful compatibility notes (general/literature):

• Polarity: Highly polar, water-based.
• Miscibility: Fully miscible with water and typical ELISA wash buffers (PBS, TBS). Avoid mixing with organic solvents within the plate during color development/stop, as they may perturb chromophore stability.
• Materials compatibility: Compatible with polystyrene and polypropylene plates/tubes under normal ELISA conditions; rinse promptly to minimize prolonged contact with strong acids.
• When to choose alternatives: If your detection system or instrument requires a different extinction coefficient or longer read stability, laboratories sometimes opt for milder acids (e.g., phosphoric or citric acid; literature). Validate performance before switching.

Storage & Reconstitution

• Storage conditions (item-specific): Room temperature (per Product Data). Avoid extreme heat and protect container integrity.
• Shipping: Shipped under normal conditions (per Product Data).
• Stability: Not specified for this item; refer to CoA/Spec Sheet. (General: many acidic stop solutions are stable for extended periods if tightly capped and uncontaminated.)
• Reconstitution: Not specified for this item; refer to label. Many stop solutions are supplied ready-to-use; if concentration is indicated on the label (e.g., normality), use directly as directed.
• Handling: Keep container tightly closed to avoid dilution/contamination. Dispense with clean, acid-compatible tips/reservoirs. Do not return used aliquots to stock.
• Freeze/thaw: Not typically applicable to aqueous acid solutions; store as directed above.

Always consult the product label and CoA/SDS for definitive instructions on shelf life, concentration, and handling for this SKU.

Structure & Identity

Product type: Ready-to-use assay reagent for terminating TMB (3,3',5,5'-tetramethylbenzidine) color development in HRP-based ELISA workflows.

• Nature of material: This is a formulated aqueous solution (a “stop solution”), not a single defined chemical entity.
• Intended function: Rapidly converts the transient blue TMB–HRP oxidation product to a stable yellow cation, enabling endpoint measurement at 450 nm (with a 620–650 nm reference, literature).
• Typical compositions (literature, not item-specific): Many TMB stop solutions are strong mineral acid solutions (e.g., ~0.5–2 N H2SO4) or alternative acids (e.g., HCl, phosphoric, or citric acid). Composition for this catalog item is not disclosed.
• Functional groups/features: As a stop reagent, its role is protonation and inactivation of HRP; it does not contribute a defined structural motif to the assay other than high acidity (literature).

Item-specific identifiers:

• CAS: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular Formula: Not specified for this item; refer to CoA/Spec Sheet.
• Molecular Weight: Not specified for this item; refer to CoA/Spec Sheet.
• SMILES / InChI / InChIKey: Not applicable for a formulated mixture; not specified for this item; refer to CoA/Spec Sheet.

2D description in words (general): In ELISA plates, wells contain the blue TMB radical cation complex prior to stopping; addition of an acidic stop solution protonates and converts this to the yellow diimine, fixing the signal for readout.

Synthetic Utility

Not applicable. This is a formulated assay reagent for immunoassays and is not used as a synthetic building block or reagent in preparative organic synthesis. For acid-mediated synthetic transformations, choose defined acids (e.g., H2SO4, HCl, TFA) with specified concentration and purity, and consult their dedicated product pages.

Target Specificity

Not applicable. This product is not an antibody or affinity reagent and has no antigen/epitope specificity. No clone, isotype, or species reactivity data apply.

Frequently Asked Questions

How should this product be stored?

Store at room temperature.

How is this product shipped?

This product ships under standard ambient conditions. No temperature-controlled packaging is required.

What documentation is provided?

Available product documentation, including Certificates of Analysis (COA), Safety Data Sheets (SDS), and specification sheets, is shown in the product document area. Document availability and access follow the current site policy.