As a Reference Materials Producer (RMP), WHRM has developed a Certificate Of Analysis (COA) characterization protocol utilizes its own carefully established characterization data in conjunction with data supplied by qualified independent laboratories for its Certified Reference Material pin standard products. This establishes a COA that statistically represents both a carefully established view to the SI unit, and also analysis data from various qualified external laboratories for both the estimated true value and its associated uncertainty. This process was utilized during the production of NIST SRM 2453a and NIST SRM 2454a as well as our other products.
Our Internal Quality Control (IQC) utilizes a Production Tracking Document (PTD) that controls and documents the process of production of our titanium pin standards from receipt of candidate RM material through the entire process of acceptance, analysis, certification and the eventual re-testing for stability analysis and re-issuance/revision of expired COAs.
WHRM bases its methods on ASTM E1447 (Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion Thermal Conductivity/Infrared Detection Method) and ASTM E1409 (Standard Test Method for Determination of Oxygen and Nitrogen in Titanium and Titanium Alloys by Inert Gas Fusion). For determination of the elemental analysis of the hydrogen, oxygen, nitrogen and carbon interstitial gas components. As the methods are designed for analysis in a production environment, they do not provide sufficient data to fully characterize material slated for top-tier Reference Material (RM) or Certified Reference Material (CRM) titanium pin standard production.
To meet our highest client expectations, we have developed a robust in-house Standard Test Method (WHRM STM) based on ASTM E1447 and ASTM E1409 along with a robust statistical analysis protocol that provides data that not only compares the samples to the SI unit for true value estimation, but also provides extensive data that enables the statistician to carefully evaluate the equipment's performance during use to for signs of issues such as drift and poor precision that would compromise the integrity of the data. As a Reference Material Producer certifying reference material for international distribution, WHRM considers this work to be of paramount importance.
WHRM QMS IQC utilizes a step-wise characterization protocol. Upon receipt of the candidate material, a homogeneity study is performed which not only evaluates the homogeneity, but also provides data to evaluate the stability of the content of Hydrogen, Oxygen Nitrogen and Carbon gas elements in the interstitial regions of the titanium. A second analysis is performed after sufficient time has passed to allow any analytes that are not chemically bound to dissipate into the environment. If a bias is determined to exist between the two analyses, a third analysis is performed to evaluate if the lot has stabilized, or if it should be rejected.
To carefully establish our in-house comparison to the SI unit for the analytes reported for our Certified Reference Materials (CRMs), we have established a comprehensive Internal Quality Control system (IQC) and integrated it into our Quality Management System (QMS). There are two distinct comparisons made to the SI unit that we use:
1. We utilize a gas dose instrument which has been calibrated by comparison directly to the SI unit. The calibrator doses the instrument under test with variable amounts of the analytes to match the concentration of the samples under test. It's precision and bias levels are better than 1.0E-07 grams of analyte (< 0.5ppm). Coupled with carefully profiled and standardized recovery rate factors, this provides a precise comparison directly to the SI unit for samples under test and, in addition, demonstrates to our staff an additional quality control measurement of the instrument's fitness to perform analyses.
2. Our characterizations also incorporate analysis data that is indirectly traceable to the SI by comparing with select reference materials according to the following order of priority:
a. NIST SRM or other National Metrology Institute (NMI) reference materials traceable to the SI unit whenever available
b. CRMs which are traceable through an unbroken chain of comparisons to national or international standards.
c. CRMs which have been thoroughly characterized and accepted in the industry.
Our Standard Test Method and robust analysis protocol requires the analyst to continually take a statistical view of the measurement data being generated during an analysis run, so the analyst can spot trends of increasing random errors, or systematic effects that may indicate instrument performance degradation. Each possible indicator of degradation of the process is monitored continually and statistically analyzed. Our IQC protocol sets a high standard for the quality of our analytical data, beyond that required by ASTM E1447 (Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion Thermal Conductivity/Infrared Detection Method), ASTM E1409 (Standard Test Method for Determination of Oxygen and Nitrogen in Titanium and Titanium Alloys by Inert Gas Fusion), ISO/IEC 17025 (Testing Laboratories) or ISO/IEC 17034 (Reference Materials Producer) (RMP).
With this data in perspective and having compared it with prescribed control limits, our analytical chemist is informed to either accept a result or group of results as fit for purpose or reject the results and repeat the analysis (after completion of corrective action, if deemed appropriate).
Production laboratories are advised to bracket their analyses at least every 10 samples with a check standard. Our protocol goes beyond that in various ways.
An integral feature of our IQC involves the inclusion of Quality Control Materials (Check Standards, Control Samples, Drift Standards, etc.) interleaved into the analytical sequence along with NMI produced SRM or CRM as calibration RMs typical to the diagram below. Critical points in the process are identified as QC decision points (labeled 1-15) that must be evaluated before proceeding with the characterization.
This protocol goes beyond that required by either ASTM E1447 (Standard Test Method for Determination of Hydrogen in Titanium and Titanium Alloys by Inert Gas Fusion Thermal Conductivity/Infrared Detection Method) or ASTM E1409 (Standard Test Method for Determination of Oxygen and Nitrogen in Titanium and Titanium Alloys by Inert Gas Fusion).
The analytical results of gas dose, blanks, control samples and calibration samples (used to establish a certified value of an RM or CRM) are statistically analyzed at strategic intervals to identify the instrument's suitability for operation, and to identify the possible development of random and/or systematic degradation during the lot's analytical test cycle.
The two paths of traceability of our reference materials (control samples and calibration samples) are from different lots and have been independently characterized. With the addition of the gas dose data, our IQC detects any significant inaccuracy stemming from instrument performance and sample preparation and handling of the calibration samples (if necessarily performed).
When using our in-house IQC STM to characterize a candidate RM or CRM for hydrogen, oxygen, nitrogen and/or carbon, a set of samples from a single lot of test materials are analyzed under repeatability conditions. (The reagents, the instrument and its settings, the analyst, the day, and the operating procedure remain unchanged during the analysis of a lot.) Operating our characterization process under these conditions affords this internal quality control system of statistical analysis the ability to detect out of control conditions during the characterization process. For example, the reagents in the instrument may become expended during a run, the instrument may have drifted or developed a leak or other problem, requiring attention. The effect of these issues may not be caught without applying the statistics and plotting a control chart at integral QC checkpoints during the analysis phase of RM or CRM titanium pin standard production.
With the application of this IQC process, we obtain a clear perspective on the quality of the characterization data for the RMs and CRMs we produce through robust statistical analysis. With that perspective and the quality decision points and our built-in nonconformance protocols, we obtain a high level of confidence in the data. The declared characterizations we supply for our RMs and CRMs allow our clients to understand and calculate the usability of our titanium pin standard products for their purposes.
As a Reference Materials Producer (RMP), our goal is to provide products with a Certificate Of Analysis backed by a defensible statistical view of the characterization data. Our QMS and IQC process affords us with that ability in compliance with ISO/IEC 17025 (Testing Laboratories) or ISO/IEC 17034 (Reference Materials Producer) (RMP) requirements.