Quantitative measurement of carbon nanotubes in rat lung

Despite their numerous possible applications, the potential impact of carbon engineered nanomaterials (CEN) on human health, especially after inhalation exposure, is still questioned. Quantification of CEN in the respiratory system is a recurring issue and deposition and pulmonary biopersistence data are essential for toxicological evaluation. In this context, a fully validated standard method for CEN quantification in lung tissue is therefore imperative. The present method, based on the National Institute for Occupational Safety and Health 5040 method for atmospheric elemental and organic carbon analysis as well as on previous developments on biological matrices, involves a simple thermogravimetric analysis (TGA) of lyophilized samples, possibly preceded by a step of chemical digestion of the tissues depending on the nature of CEN investigated. The analytical method was validated for 4 CEN (carbon black as well as 3 long and thick or short and thin carbon nanotubes) for selectivity, linearity, detection and quantification limits, bias, and within-batch and between-batch precision. Calibration curves show linearity in the range of 1-40 mg/g lyophilized lung. Limits of detection for the different CEN range from 6 to 18 µg in 20 mg dry test sample. On average, within-batch precision was kept below 20 and 10% for analysis with or without a prior digestion step, respectively, whereas the corresponding between-batch precision levels reached almost 20 and 15%, respectively. The method was successfully applied to toxicological investigations for the quantitative analysis of CEN contents in rat lung exposed by inhalation.