Quantitation of Phenolic Benzotriazole Class Compounds in Plasma by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

Phenolic benzotriazoles are used as UV stabilizers in consumer products and have been detected in the environment suggesting potential human exposure. Phenolic benzotriazoles were nominated to the Division of National Toxicology Program for testing based on their potential widespread human exposure and lack of adequate toxicity data. Nine chemicals were selected for toxicological evaluation, representing unsubstituted (2-(2H-benzotriazole-2-yl)phenol, (P-BZT)), monosubstituted (drometrizole; 2-(2H-benzotriazol-2-yl)-4-tert-butylphenol (tBu-BZT); octrizole), disubstituted (2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (diMeEtPh-BZT), 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (ditPe-BZT); 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid, octylester (tBuPrOcEst-BZT) and halogenated trisubstituted (bumetrizole; 2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol (ditBuCl-BZT)) compounds. Different extraction methods were utilized and methods were developed to analyze phenolic benzotriazoles by quantitating free (unconjugated parent) and total (free and conjugated parent) analyte levels in plasma of rats to aid in interpretation of toxicity data, understanding of absorption, distribution, metabolism, and excretion differences. The calibration standard range was 1-500 ng/mL for free analytes and 1-1000 ng/mL for total analytes. The methods were linear (r ≥ 0.99). The accuracy was determined as relative error (RE) and ranged from -18.2 to +17.8, and precision was determined as relative standard deviation (RSD) and ranged from 0.0 to 20.1% for both free and total plasma calibration standards, respectively. The limit of quantitation was ≤ 5.0 and 10.0 ng/mL and limit of detection was ≤ 1.2 and 2.0 ng/mL, for free and total analytes, respectively. These data demonstrate that the methods are suitable for quantitation of free and total analytes in rat plasma.