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LabCoda / Knowledge Base / Bacterial endotoxins test (LAL)

💊 Bacterial endotoxins test (LAL)

Pharma Ph.Eur. 2.6.14

In short

Detection and quantitative determination of bacterial endotoxins (lipopolysaccharides LPS) in pharmaceutical products using LAL method (Limulus Amebocyte Lysate). The test is performed according to European Pharmacopoeia 2.6.14; Range: 0.005–50 EU/mL (chromogenic/turbidimetric). The procedure comprises 6 steps (about 2 h in total); it is used for: Quality control of water for injection (WFI), Batch release of injectable and infusion drugs, Testing of medical devices contacting blood.

At a glance

  • Standard: European Pharmacopoeia 2.6.14
  • Category: Pharma
  • Procedure steps: 6
  • Total time of stages: 2 h
  • Test sensitivity (λ): 0.03–0.25 EU/mL (typically)
  • Range: 0.005–50 EU/mL (chromogenic/turbidimetric)
  • WFI limit: <0.25 EU/mL

Overview

Bacterial endotoxins (lipopolysaccharides — LPS) are fragments of Gram-negative bacterial cell walls and among the most potent pyrogens. Even trace amounts of endotoxins in injectable drugs can cause fever, septic shock, and patient death. LAL test (Limulus Amebocyte Lysate) uses lysate from blood cells of horseshoe crab (Limulus polyphemus), which coagulates in presence of endotoxins.

European Pharmacopoeia (2.6.14) defines three test variants: (A) gel-clot — qualitative, (B) turbidimetric kinetic — quantitative, (C) chromogenic kinetic — quantitative. Endotoxin limits: water for injection <0.25 EU/mL, injectable drugs calculated per K/M formula (K = pyrogenic threshold, M = maximum dose).

Method principle

Limulus amebocyte lysate (LAL) contains cascade enzyme (factor C) that is activated by endotoxins (LPS). In gel-clot test, activation leads to firm gel formation (coagulation). In turbidimetric test — to turbidity (coagulin polymerization). In chromogenic test — to chromogenic substrate hydrolysis (p-nitroaniline release — yellow color, measurement at 405 nm). Test sensitivity: 0.005–50 EU/mL.

Applications

Key parameters

ParameterValue
Test sensitivity (λ)0.03–0.25 EU/mL (typically)
Range0.005–50 EU/mL (chromogenic/turbidimetric)
WFI limit<0.25 EU/mL
Injectable drug limitK/M (K=5 EU/kg, M=max. dose/kg/h)
Test time60 min (gel-clot), 15–60 min (kinetic)

Standard

Standard number
European Pharmacopoeia 2.6.14
Title (PL)
Badanie endotoksyn bakteryjnych — Test LAL (Limulus Amebocyte Lysate)
Title (EN)
Bacterial endotoxins

Step-by-step procedure

  1. Workstation preparation

    Work in clean room (class B/C) or in LAF. All glassware pyrogen-free (250°C/30 min). Powder-free gloves.

    ⏱ Time: 15 min

  2. LAL reconstitution

    Add LRW to LAL vial. Mix gently (do not vortex). Prepare within 1 h of reconstitution.

    ⏱ Time: 5 min

  3. Standard preparation

    Prepare CSE dilution series: 50, 5, 0.5, 0.05 EU/mL in LRW (1:10 cascade).

    ⏱ Time: 20 min

  4. Sample preparation

    Dilute sample to MVD (Maximum Valid Dilution = endotoxin limit concentration × LAL sensitivity).

    ⏱ Time: 10 min

  5. Gel-clot test (method A)

    Add 0.1 mL sample/standard to tube with 0.1 mL LAL. Incubate 60 ± 2 min, 37 ± 1°C. Invert 180° — firm gel = positive.

    ⏱ Time: 65 min • 🌡 Temperature: 37°C

  6. Result interpretation

    Gel-clot: gel persists after inversion = (+), disperses = (−). Kinetic: read from calibration curve (EU/mL).

    ⏱ Time: 5 min

Required equipment and apparatus

EquipmentExampleIndicative price
LAL kinetic readerCharles River Endosafe nexgen-PTS, Lonza PyroGene40 000–120 000 PLN
Block incubator 37°CIntegrated in reader or external dry-block5 000–15 000 PLN
Pyrogen-free pipettesEppendorf Research Plus with pyrogen-free tips800–2 000 PLN
Pyrogen-free tubes (depyrogenized)Borosilicate tubes, 250°C/30 min2–5 PLN/pc

Reagents, media and consumables

ReagentCASDetails
LAL reagent—Limulus polyphemus amebocyte lysate, lyophilized (Charles River, Lonza, Fujifilm Wako)
Endotoxin standard (CSE/RSE)—Control Standard Endotoxin, lyophilized, calibrated vs. WHO RSE, e.g., 10 000 EU/vial
LAL Reagent Water (LRW)—Pyrogen-free water, <0.005 EU/mL
Chromogenic substrate (for method C)—Peptide-pNA, hydrolyzed by activated factor

Health and safety (OHS)

Frequently asked questions

Which standard describes this test?

The test is performed according to European Pharmacopoeia 2.6.14 — “Bacterial endotoxins”.

How does this method work?

Limulus amebocyte lysate (LAL) contains cascade enzyme (factor C) that is activated by endotoxins (LPS). In gel-clot test, activation leads to firm gel formation (coagulation).

What is the measuring range and accuracy?

Test sensitivity (λ): 0.03–0.25 EU/mL (typically); Range: 0.005–50 EU/mL (chromogenic/turbidimetric); WFI limit: <0.25 EU/mL; Injectable drug limit: K/M (K=5 EU/kg, M=max. dose/kg/h).

How long does the test take?

The times given for the individual stages add up to approximately 2 h. The procedure comprises 6 steps.

What equipment is required?

LAL kinetic reader, Block incubator 37°C, Pyrogen-free pipettes, Pyrogen-free tubes (depyrogenized). Indicative cost of the core instrument (LAL kinetic reader): 40 000–120 000 PLN.

Where is this test used?

Quality control of water for injection (WFI); Batch release of injectable and infusion drugs; Testing of medical devices contacting blood; Control of dialysis and intravenous fluids; Testing of pharmaceutical raw materials (active substances, excipients).

What safety precautions apply?

Endotoxins — pyrogenic, avoid contamination of samples and reagents; Work in clean room — GMP procedures; LAL from protected species (Limulus) — use economically; Biological waste — autoclave before disposal.

Which laboratory can perform this test?

The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number Ph.Eur. 2.6.14.

🔍 Find a laboratory performing this test