This document provides methods for the determination of residual elements other than carbon in samples of carbon nanotubes at Single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT) by induced plasma mass spectrometry (ICP-MS). The purpose of this document is to provide optimized SWCNT and MWCNT sample preparation and digestion procedures to enable accurate and quantitative determination of elemental impurities by ICP-MS analysis.