Table 1 Highest tolerated concentrations of substances for valid LPS spike recovery, a comparison between EndoLISA and LAL assay.

From: EndoLISA®: a novel and reliable method for endotoxin detection

  Substance Solvent EndoLISA LAL assay
Buffer/pH Acetate (pH 4.0) 100 mM NaCl 50 mM 12.5 mM
  Acetate (pH 5.0) 100 mM NaCl 100 mMa 12.5 mM
  MES (pH 6.0) 100 mM NaCl 100 mMa 5 mM
  Potassium phosphate (pH 7.2) 100 mM NaCl 100 mMa 50 mM
  Imidazole (pH 7.4) Water 500 mM 40 mM
  HEPES (pH 7.5) 100 mM NaCl 100 mMa 100 mMa
  Sodium borate (pH 9.0) 100 mM NaCl 100 mMa 50 mM
Salt NaCl Water 1 M 0.5 M
  KCl Water 1 M 0.25 M
Chaotropic agent Urea Water 6 M 0.5 M
  Guanidinium chloride Water 1 M 0.05 M
Organic solvent Methanol Water 20%a 5%
  Ethanol Water 30% 0.5%
  2-Propanol Water 20% 0.2%
  DMSO Water 10% 2%
Detergent SDS Water 0.05% 0.001%
  CTAB Water 0.004% 0.0001%
  Zwittergent 3-14 Water 0.02% 0.005%
  Tween 20 Water 2% 0.1%
  Triton X-100 Water 0.02% 0.005%
Chelator EDTA (pH 8.0) Water 0.4 mM 0.4 mM
  Citrate (pH 7.5) Water 10 mM 10 mM
Protease inhibitor Benzamidine Water 100 mMa 0.1 mM
  PMSF 2-Propanol 5 mM <0.05 mM
Antibiotic Rifampicin Methanol 3.5 mg/ml 0.04 mg/ml
  Chloramphenicol Ethanol 3.5 mg/ml 0.1 mg/ml
  1. aHighest concentration tested.
  2. The tested substances were dissolved in the respective solvents, and dilution series of the samples were prepared in water or 0.1 M NaCl and subsequently spiked with 5 EU/ml LPS (Escherichia coli O55:B5). EU/ml values and spike recovery (%) were calculated. The validity criterion of spike recovery was 50–200%. CTAB, cetyl trimethylammonium bromide; DMSO, dimethylsulfoxide; MES, methyl ethyl sulfonate; PMSF, phenylmethylsulfonylfluoride; SDS, sodium dodecyl sulphate.