CPI International Peak Performance™ Standards are prepared from high-purity starting materials, sub-boiling distilled acids, and 18-mega-ohm de-ionized water. We use only Class A volumetric labware and balances calibrated with Class F NIST-traceable weights. All of our solutions are bottled in either HDPE or LDPE bottles that have been pre-cleaned, pre-leached and secured with heat-shrink seals. Every standard is certified gravimetrically and instrumentally against NIST SRM 3100 series spectrometric solutions. A certificate of analysis and a material safety data sheet are shipped with every standard and the accuracy of single element standards is guaranteed to ±0.3% for 18 months from the date of shipment.