Blend Tolerance
DEFINITION: The degree of agreement between the Blended Concentration and the Customer Requested Concentration

Blend Tolerance can be affected by many factors. The most common are:

• Blending Method: Partial Pressure vs. Gravimetric
• Mixture component reactivity with impurities, other components, cylinder surfaces and blending equipment.
• The concentration of the mixture components

Matheson uses state-of-the-art blending technology, and cylinder treatment combined with our experienced gas reactivity knowledge to meet and exceed our customers' blend tolerance expectations.

Accuracy
DEFINITION: The degree of statistical agreement between the Analyzed Concentration and the Customer Requested Concentration usually at the 95% Confidence Level.

Many factors affect and influence mixture accuracy. These include:

• The reference standard materials used in the mixture analysis
• Precision of the analytical instrument used in the mixture analysis
• Stability factors of the mixture components
• Raw material purity of the mixture components
• Accuracy of the gravimetric system used in mixture preparation

Matheson has over 70+ years of experience of understanding, controlling and calculating these contributions to the accuracy each mixture. Calculating and lowering any possible errors results in final gas mixtures that are the most repeatable, accurate and precise in the industry.

Traceability
DEFINITION: An unbroken chain of comparisons to the National Measurement System using statistically valid methods.

There are two types of Traceability:

• Direct Traceability: The analysis of a customer mixture against a NIST SRM, NTRM or NMI Standard.
• Indirect Traceability: The analysis of a customer mixture against a lab standard against a NIST SRM, NTRM or Weight Traceability

NOTE:
NIST-NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY
SRM-STANDARD REFERENCE MATERIAL
NTRM-NIST TRACEABLE REFERENCE MATERIAL
NMI-NETHERLAND MEASUREMENT INSTITUTE

The accuracy of the reference standard will have direct impact on the accuracy of the calibration standard. The more direct lineage the calibration standard has to the National Measurement System, the more accurate the calibration standard will be. This has increased significance when proper instrument calibration is required because of environmental regulation, use of analyses in legal proceedings and other critical situations.

Stability
DEFINITION: The ability to maintain a constant concentration value over a defined time within statistical significance.

Factors that affect mixture stability include:

• Cylinder and valve material of construction
• Internal cylinder preparation
• Raw material purity
• Component Reactivity
• Component concentration
• Cylinder pressure
• Delivery systems

Mixture stability has a significant impact on the accuracy and long-term usability of the calibration standard. Matheson manufactures a wide spectrum of low concentration mixtures and guarantees their stability over a defined period of time. Matheson is able to offer guaranteed stability from our R&D group. Mixtures are not considered stable unless they meet the required maturation parameters spelled out by Matheson's Standard Operating Procedures.