The process of standard preparation begins with the use of the highest-purity source materials. For preparation of alkali, alkaline earth, or rare earth metals, we use the metal, salt, or oxide. For this material, the stoichiometry of each salt or oxide is first checked. The purity of each material is checked by optical emission spectrometry. Source materials that do not meet required purity levels are discarded.

Before weighing the high-purity material, the analytical balance is checked with NIST calibrated weights. The calibration of all volumetric vessels is checked by weight to five significant figures. Before use, the Teflon beakers and volumetric vessels are pre-cleaned in 20% HNO3 and rinsed with copious amounts of 18 megaohm high-purity water and air dried in a Class 100 area. Salts are dried to a constant weight and oxides are ignited to a constant weight.

The material is weighed on an analytical balance to one part in ten thousand. The sample is transferred to a clean Teflon beaker and dissolved in high-purity subboiling acids. The solution is transferred to a volumetric flask. An appropriate amount of high-purity acid is added and the solution is diluted to near calibrated volume. The solution is allowed to come to ambient temperature, and then diluted to the calibrated volume. Finally the solution is transferred to clean natural high-density polyethylene (HDPE) or low density polyethylene (LDPE) laboratory grade bottles.

In the evaluation of plastic containers for the Certified Reference Material (CRM) spectrometric standard solutions, our studies have shown that the concentrations of aqueous solutions change by 0.5% to 1% per year due to transpiration in low-density polyethylene bottles. The use of HDPE laboratory grade bottles reduces the change to only 0.1% to 0.2% per year. Only Teflon containers have been found to be more impervious than the HDPE laboratory grade containers. Commercial grade HDPE or LDPE materials are never used in the preparation of HPS solutions.

HPS single-element and multielement standard solutions are certified against the NIST OSRM 3100 series spectrometric standard solutions prior to shipment. The HPS standard solution must agree with the NIST standard within the acceptable limits of the method. The single-element standard solutions are marketed at 1000 ± 3 µg/mL and 10.00 ± 0.03 mg/mL in 100, 250, and 500 mL HDPE or LDPE laboratory grade bottles. Certification data are included in the Certificate of Analysis that is sent with every product.

Prior to shipping, the plastic bottle is double sealed in plastic bags. Each element is shipped with a Material Safety Data Sheet.

High-Purity Standards is committed to continual improvement of our quality system that governs our manufacturing processes. To accomplish this we have embarked upon implementing changes that would result in ISO 9001:2000 certification. We anticipate completion of this goal by April 2006. ISO 9001:2000 is one of several quality guidelines that we use in our manufacturing processes. Spectrometric standards prepared in our laboratory meet or exceed all of the requirements in the ISO/IEC Guide 25 for traceability, calibration, and testing.