The National Institute of Standards and Technology (NIST) recently released SRM 2386 Avocado Powder which has value assignment for over 70 analytes. This material has certified values assigned for 22 analytes and non-certified values assigned for 53 analytes and is intended to be used for the evaluation of methods for the determination of elements, vitamins, amino acids, fatty acids, and proximates in this and similar matrices. The material was purchased pre-packaged from a commercial vendor and data was obtained from NIST and interlaboratory comparison exercises. A description of the material, sample preparations, results, and data analysis are discussed in the following report.

Standard Reference Material (SRM) 916b Bilirubin comprises neat unconjugated bilirubin that is certified as a chemical substance of known purity. It is intended for use in the calibration and standardization of measurement procedures for the determination of bilirubin in clinical samples and for assignment of bilirubin quantity values to in-house control materials. A unit of SRM 916b consists of 100 mg of bilirubin. This publication documents the production, analytical methods, and computations involved in characterizing this product.

Vitamin C is a necessary micronutrient that is involved in many biological processes. In preserved human plasma and serum, vitamin C is most meaningfully analyzed as total ascorbic acid (TAA). From 1993 through 2015, the National Institute of Standards and Technology (NIST) coordinated 40 interlaboratory studies (ILS) devoted to improving the between-participant comparability of TAA measurements. The results from these ILS demonstrate that the concentration of TAA ([TAA]) is stable for at least 20 years in serum diluted 1 + 1 (volume fraction) with 10% mass concentration aqueous metaphosphoric acid (MPA) and stored at −80 °C. The between-participant relative reproducibility precision, expressed as a coefficient of variation (CV), improved from over 16% to under 9% over the course of the studies. Normalization of test samples (i.e., ex post-facto recalibrating the as-submitted results) using participant-prepared serum-free calibration solutions did not improve reproducibility. Normalization to one control sample having a similar serum-based matrix as the test samples improved the CV to 7%; normalization to two such controls reduced the CV to 4%. Multicenter studies that require the highest degree of measurement comparability among the participants should consider calibrating with materials that have a serum-based matrix as similar as possible to that of the samples of interest.

From 1984 to 2017, the National Institute of Standards and Technology (NIST) Micronutrients Measurement Quality Assurance Program (MMQAP) coordinated 79 Round Robin (RR) interlaboratory studies designed to improve measurement comparability among laboratories measuring fat soluble vitamins and carotenoids in human serum and plasma. There were 22 participants in the initial study; participation increased to 58 in 1997 and then declined in stages to 29 by 2017. A total of 138 academic, commercial, governmental, or non-governmental organizations actively participated in at least one RR; two laboratories participated in 77 of the 79 RRs. A total of 350 human serum or plasma samples were distributed in the RRs, typically three to five per RR. One hundred thirty one (131) of these samples were unique materials. While the initial RRs focused on just retinol (vitamin A), ? tocopherol (vitamin E), and ? carotene (provitamin A) over the life of the program 57 vitamin related measurands were reported at least once. Fifteen (15) measurands were reported sufficiently often to enable analysis of measurement performance over time: total retinol, retinyl palmitate, ? tocopherol, ? plus ? tocopherol, total ? carotene, trans ? carotene, total cis ? carotene, total ? carotene, total lycopene, trans lycopene, total ? cryptoxanthin, total lutein, total zeaxanthin, total lutein plus zeaxanthin, and coenzyme Q10. In addition to documenting the number and nature of the MMQAP's participants, measurands, materials, and reported measurements, this report explores the evolution of among-participant concordance and within-participant apparent precision as functions of calendar date documents and the relationships among results reported for materials delivered to participants both as liquid-frozen and lyophilized samples.

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coordinated the Micronutrients Measurement Quality Assurance Program (MMQAP) for laboratories that measure fat-soluble vitamins and carotenoids in human serum and plasma.This report describes the design of and results for the Spring and Fall 1987 MMQAP measurement comparability improvement studies: 1) Round Robin IX Fat-Soluble Vitamins and Carotenoids in Human Serum and 2) Round Robin XI Fat-Soluble Vitamins and Carotenoids in Human Serum.The first participant results for Round Robin IX were received April 22, 1987; the last results were received June 23, 1987.The first participant results for Round Robin XI were received July 8, 1987; the last results were received September 4, 1987.The analytes in Round Robin X were selenium and zinc and are not discussed in this report.

Standard Reference Material (SRM) 968f is intended for use in validating methods for determining fat-soluble vitamins in human serum and plasma and value assigning in-house produced control materials analyzed using those methods.A unit of SRM 968f consists of one vial each of two concentration levels of frozen human serum.This publication documents the production, analytical methods, and statistical evaluations involved in realizing this product.

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately.Such identification is not intended to imply recommendation

Since 1984, the National Institute of Standards and Technology (NIST) has coordinated what is now known as the Micronutrients Measurement Quality Assurance Program (MMQAP) for laboratories that measure fat-soluble vitamins and carotenoids in human serum and plasma.The MMQAP has provided participants with measurement comparability assessment through use of interlaboratory studies, Standard Reference Materials (SRMs) and control materials, methods development and validation, workshops, and tutorials.This report reproduces the printed materials provided to participants in the 1997 Fat-Soluble Vitamin and Carotenoid Analysis Tutorials, the most recent in a series of hands-on training programs for laboratorians involved in fat-soluble vitamin-related analytes.Some of the tutorial material has been updated.