Claritas PPT® Multi-Element Standards for ICP-MS SPEX CertiPrep Claritas PPT® standards are a class of Inorganic Certified Reference Standards designed specifically for today's new generation of trace ICP and ICP-MS instrumentation. Based on extensive development, our chemists have formulated this line of high-purity standards for user convenience and stability. Our Claritas PPT® selection of standards includes a complete series of multi-element solutions, many designed for use with US EPA Methods. These solutions are made with the highest purity materials available and are tested on our state-of-the-art ICP-MS. SPEX CertiPrep Certified Reference Materials (CRMs) are manufactured under a quality system complying with the requirements of ISO 9001, ISO/IEC 17025 and ISO 17034. Internal Standards May be used to monitor and correct for changes that occur from differences between standards and samples. Since environmental samples often contain significant amounts of lithium, isotopically enriched 95% 6Li can be analyzed as an internal standard, avoiding the signal from the 7Li peak.