title: The uncertainty of reference standards--a guide to understanding factors impacting uncertainty, uncertainty calculations, and vendor certifications.
abstract: Certified solution standards are widely used in forensic toxicological, clinical/diagnostic, and environmental testing. Typically, these standards are purchased as ampouled solutions with a certified concentration. Vendors present concentration and uncertainty differently on their Certificates of Analysis. Understanding the factors that impact uncertainty and which factors have been considered in the vendor's assignment of uncertainty are critical to understanding the accuracy of the standard and the impact on testing results. Understanding these variables is also important for laboratories seeking to comply with ISO/IEC 17025 requirements and for those preparing reference solutions from neat materials at the bench. The impact of uncertainty associated with the neat material purity (including residual water, residual solvent, and inorganic content), mass measurement (weighing techniques), and solvent addition (solution density) on the overall uncertainty of the certified concentration is described along with uncertainty calculations.
authors.affiliation: Cerilliant Corporation, Round Rock, Texas 78665, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Gates
authors.forename: Ning
authors.initials: N
authors.lastname: Chang
authors.forename: Isil
authors.initials: I
authors.lastname: Dilek
authors.forename: Huahua
authors.initials: H
authors.lastname: Jian
authors.forename: Sherri
authors.initials: S
authors.lastname: Pogue
authors.forename: Uma
authors.initials: U
authors.lastname: Sreenivasan
mesh_terms: D002568:Certification; D002623:Chemistry Techniques, Analytical / Q000592:standards; D003284:Contract Services / Q000592:standards*; D004865:Equipment and Supplies, Hospital / Q000592:standards*; D005069:Evaluation Studies as Topic; D053593:Forensic Toxicology / Q000592:standards*; D006801:Humans; D012015:Reference Standards; D035501:Uncertainty