A mathematical formulation for a gravimetric approach to the univariate standard addition method (SAM) is presented that has general applicability for both liquids and solids. Using gravimetry rather than volumetry reduces the preparation time, increases design flexibility, and makes increased accuracy possible. SAM has most often been used with analytes in aqueous solutions that are aspirated into flames or plasmas and determined by absorption, emission, or mass spectrometric techniques. The formulation presented here shows that the method can also be applied to complex matrixes, such as distillate and residual fuel oils, using techniques such as X-ray fluorescence (XRF) or combustion combined with atomic fluorescence or absorption. These techniques, which can be subject to matrix-induced interferences, could realize the same benefits that have been demonstrated for dilute aqueous solutions.

Two coal certified reference materials (CRMs) for mercury content were blended, and their results checked, resulting in National Institute of Standards and Technology (NIST) traceable standards at mercury concentrations intermediate to parent certified values. How are CRM blends checked? Intervalrepeatability is a new statistic that can be employed as a quality control test to identify incorrectly prepared working standards or nonlinear instrument response over a targeted concentration interval based upon the established repeatability limit (r) of the analytical method used. It is applicable to working standards prepared by CRM dilution, as well as those prepared by CRM blending. Interval-repeatability is unique because it measures the precision between standards of different concentrations. For the measurements of standards to comply with the method precision requirements, the absolute value of observed intervalrepeatability must be less than or equal to the analytical method's calculated interval-repeatability limit for a given concentration interval. Interval-repeatability can provide valuable information to the CRM user regarding the internal consistency of standards, measurement precision, the success of standard sample preparation, and instrument linearity. The theory behind this approach is discussed, detailed instructions on its implementation are given, and interval-repeatability quality control test data for mercury in coal standards created by the CRM user are presented.

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The standard reference material (SRM) for fineness of cement, SRM 114, is an integral part of the calibration material routinely used in the cement industry to qualify cements. Being a powder, the main physical properties of cement, prior to hydration, are its surface area and particle size distribution (PSD). Since 1934, NIST has provided SRM 114 for cement fineness and it will continue to do so as long as the industry requires it. Different lots of SRM 114 are designated by a unique letter suffix to the SRM number, e.g., 114a, 114b, …. ,114q. A certificate that gives the values obtained using ASTM C204 (Blaine), C115 (Wagner) and C430 (45 µm sieve residue) is included with each lot of the material. The supply of SRM 114p, which was released in 1994, was depleted in 2004. Therefore, a new batch of SRM 114 needed to be developed. This process included selection of the cement, packaging the cement in small vials, and determination of the values for the ASTM tests reported. In this case, the Blaine, Wagner and 45 µm sieve residue were the tests used. Later the particle size distribution (PSD) will be added. The purpose of this report is to provide a detailed description of the process used to package and certify SRM 114q. All measurements used for the certifications are provided along with descriptions of the statistical analyses.