TAL/LAL Reagent (Tachypleus Amebocyte Lysate/Limulus Amebocyte Lysate Reagent) is a core consumable for bacterial endotoxin detection, and its biological activity is highly sensitive to storage conditions. Whether it is TAL/LAL Reagent of different types (such as gel-clot method, kinetic chromogenic method) or the supporting Control Standard Endotoxin (CSE), slight deviations in the storage process may lead to degradation of active components, reduced sensitivity, and ultimately affect the accuracy of detection results. It is necessary to sort out the storage key points throughout the entire life cycle of the reagent to ensure stable performance.
I. Basic Storage of Unopened TAL/LAL Reagent: Focus on the Core of "Temperature-Timeliness-Environment"
(I) Temperature Control: Strictly Adhere to the 2~8°C Refrigeration Range
All unopened TAL/LAL Reagent and supporting CSE must be stored in a refrigerator at 2~8°C—this is a critical prerequisite for maintaining reagent activity. This temperature range protects the structural stability of biological macromolecules such as Factor C, proclotting enzyme, and coagulogen in the reagent: it prevents component denaturation and degradation due to excessively high temperatures, and avoids irreversible inactivation caused by excessively low temperatures (freezing). At the same time, it ensures that the potency of CSE (usually 10-100 EU/vial) in lyophilized powder form is not lost, preventing inaccurate detection benchmarks due to substandard standards.
In practical operation, note the following: Do not place the reagent in the freezer compartment of the refrigerator or near the refrigerator door (where temperature fluctuates frequently); if there are uncooled heat-generating equipment or reagents in the refrigerator, maintain a distance of at least 10 cm from the TAL/LAL Reagent to prevent local temperature exceeding the standard.
(II) Timeliness Management: The 24-Month Shelf Life Relies on Standardized Storage
The shelf life of unopened TAL/LAL Reagent and CSE is 24 months from the date of manufacture, but this period is only valid if the storage conditions are fully met. The shelf life will be significantly shortened or even invalidated if any of the following occurs:
Temperature fluctuations: Short-term exposure to room temperature (exceeding 8°C) for more than 2 hours, or repeated "refrigeration-room temperature" cycles;
Packaging issues: Damaged sealing film on reagent vials, damp outer packaging, leading to moisture absorption and caking of the lyophilized powder;
Contamination risks: Mixing with endotoxin-containing samples (such as bacterial cultures) or non-pyrogen-free utensils, resulting in potential cross-contamination.
Upon receiving the reagent, promptly record the "date of manufacture" and "expiration date" on the label, and arrange the reagents in accordance with the "first-in, first-out" principle. Prioritize the use of batches approaching the expiration date to avoid waste due to expiration.
(III) Environmental Support: Light Protection, Moisture Protection, and Contamination Prevention
The active components of TAL/LAL Reagent are sensitive to light and humidity; additional precautions should be taken during storage:
Light protection: In accordance with the "keep away from light" indication on the label, store the reagent in the light-proof layer of the refrigerator or an opaque storage box to avoid direct sunlight or prolonged exposure to LED lights inside the refrigerator;
Moisture protection: Choose a dry area inside the refrigerator (away from places where condensation occurs), and replace the packaging with dry material promptly if the outer box becomes damp;
Contamination prevention: Store TAL/LAL Reagent and CSE separately, and do not mix them with non-pyrogen-free glassware, contaminated samples, etc. Wash hands and disinfect the workbench before use.
II. Transportation Link: The "Critical Transition" Connecting Storage
Transportation is an extension of the storage chain. Improper protection during transportation will make it impossible to restore reagent activity even with subsequent refrigeration. Focus on the following two aspects of protection:
(I) Temperature Maintenance: Full-Process Monitoring at 2~8°C
Use a professional insulated box for transportation, with sufficient ice packs inside (wrapped in cushioning material to avoid direct contact with reagent vials causing freezing) to ensure the temperature inside the box is stable at 2~8°C. For long-distance transportation, it is recommended to choose logistics services with real-time temperature recording functions. After receiving the goods, check the temperature log—if the temperature exceeds the standard (>8°C or <2°C) for more than 1 hour during transportation, the reagent must first undergo sensitivity verification (e.g., verifying the reaction effectiveness of 2λ, λ, 0.5λ, and 0.25λ concentrations using the gel-clot method) and can only be used after confirming that the activity meets the standards.
(II) Physical Protection: Avoid Vial Damage
Most TAL/LAL Reagent vials are made of glass. Fill the transportation packaging with cushioning materials such as foam and bubble wrap to prevent vial breakage and seal failure due to jolting. Immediately after receiving the goods, check: whether there are cracks in the reagent vials, and whether the lyophilized powder is in a loose white or off-white state (yellowing, shrinkage, or caking indicates abnormality). Do not use the reagent if abnormalities are found, and contact the supplier for handling in a timely manner.
III. After Opening and Reconstitution: Short Timeliness and Strict Protection
The activity of TAL/LAL Reagent is extremely prone to loss after opening or reconstitution. Follow the usage specifications strictly according to the reagent type:
(I) Gel-Clot TAL/LAL Reagent: Single-Use, No Storage
Gel-clot TAL/LAL Reagent is for single use. Each vial needs to be reconstituted with 1.1 mL of pyrogen-free water, and the entire volume must be added to the reaction tube at one time—storage is not allowed. If temporary storage is needed due to operational suspension, use the reagent within 10 minutes at room temperature (15~25°C) and do not return it to the refrigerator. Repeated temperature changes will lead to activity inactivation and may introduce microbial contamination.
(II) Kinetic Chromogenic TAL/LAL Reagent: Use Within 24~48 Hours After Opening
For multi-dose components of kinetic chromogenic TAL/LAL Reagent (e.g., 96-well kit), such as R1 main reagent and R4 reconstitution solution, seal the vial tightly with parafilm after opening, store it back in the refrigerator at 2~8°C, and use it within 24~48 hours. Immediately close the cap tightly after each use to prevent pH changes caused by the reagent contacting air; use pyrogen-free pipette tips for sampling to avoid introducing exogenous endotoxins.
(III) Supporting CSE: Immediate Use After Dissolution
CSE is also for single use. After dissolving and diluting with pyrogen-free water, any unused solution must be discarded directly—refrigerated storage is not allowed. Use pyrogen-free centrifuge tubes and pipettes during the dissolution process to prevent CSE contamination from affecting the accuracy of the standard curve.
IV. Abnormal Handling: Judgment and Response After Improper Storage
If the reagent is found to have abnormal storage conditions (e.g., accidentally left at room temperature for too long, frozen, or damaged packaging), do not use it directly for detection. Handle it according to the following steps:
Appearance Inspection: Observe whether the lyophilized powder is caked, yellowed, or discolored—discard it directly if abnormalities are found;
Sensitivity Verification: For reagents with normal appearance, conduct sensitivity verification (e.g., prepare endotoxin standard solutions of 2λ, λ, 0.5λ, and 0.25λ concentrations using the gel-clot method). If the measured sensitivity λc is within the range of 0.5~2λ, it can be used temporarily; otherwise, discard it;
Priority Discard Scenarios: If the reagent has been frozen, exposed to room temperature for more than 4 hours, or has damaged vials or failed seals, discard it directly even if the appearance is normal. This avoids false negative or false positive detection results caused by reagent inactivation.
In summary, proper storage of TAL/LAL Reagent requires covering the entire process of "unopened-transportation-opened and reconstituted". With 2~8°C refrigeration as the core, combined with light protection, moisture protection, and contamination prevention measures, and strictly following the usage timeliness and abnormal handling principles, only by ensuring the standardization of the storage process can the stable activity of the reagent be maintained, laying a solid foundation for the accuracy of bacterial endotoxin detection results.
