Histidine

To ensure exact exposure times, and by this exact determination of disinfection efficacy, 3 neutralization media were tested and validated depending on the disinfectant ingredient and its concentration (Table 2): (1) 1% tryptic soy broth (Oxoid, Germany), (2) 0.5% (w/v) sodium sulfite in 1% tryptic soy broth, or (3) 3% tryptic soy broth, 9% (v/v) Tween 80, 0.9% (w/v) lecithin, and 3.0% (w/v) histidine (Carl Roth GmbH, Germany).^{4 (link)} Validation of neutralization media was performed in 3 independent experiments prior to carrier assays according to DIN EN 14347:2005 using the dilution-neutralization method.²⁰

All materials and reagents utilized in this study were of analytical grade and used directly without further purification. 1,10-Phenanthroline (phen) and 3,3′,5,5′-tetramethylbenzidine (TMB) were purchased from Sigma-Aldrich (Sigma-Aldrich, Germany); sodium persulfate, ethanol, ascorbic acid, citric acid, glucose, fructose, sucrose, sodium chloride, potassium chloride, and calcium chloride from Biochem Chemopharma Chemical Industry Co., Ltd (Cosne Sur Loir, France); tyrosine, proline, alanine, histidine, arginine, and lysine from Carl Roth GmbH + Co. KG (Karlsruhe, Germany); and the orange juice and vitamin C tablets from a local market and a pharmacy, respectively, in Kalar, Sulaymaniyah (Iraq).