For two decades, the National Institute of Standards and Technology (NIST) and the National Institutes of Health Office of Dietary Supplements have collaborated to develop dietary supplement-matrix reference materials. During the first decade, NIST developed over 20 botanical and non-botanical dietary supplement Standard Reference Materials (SRMs®) using multiple analytical techniques to assign values for selected marker compounds and toxic elements. In the past decade, NIST has expanded the scope of materials available, and other producers of certified reference materials (CRMs) have joined to provide a limited number of additional materials. This review describes briefly the first decade in the development of CRMs for dietary supplements, primarily botanical dietary supplement ingredients (e.g., ginkgo, green tea, saw palmetto, St. Johns' wort, botanical oils, berries, and soy) and a popular multivitamin/multimineral (MVM) SRM. We discuss the analytical challenges in producing these materials and how these materials established a model for the next generation of CRMs. The second generation of dietary supplement CRMs/RMs, consisting primarily of botanical matrices, calibration solutions, and new and replacement MVM CRMs, is discussed in greater detail including improvements based on experiences from the first decade and potential future needs and developments in this emerging reference material research sector.

Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monitor disease, including infectious disease. Despite significant effort dedicated to biomarker identification in case control studies, very few breath tests are established in practice. In this topical review, we identify how gas standards support breath analysis today and what is needed to support further expansion and translation to practice. We examine forensic and clinical breath tests and discuss how confidence has been built through unambiguous biomarker identification and quantitation supported by gas calibration standards. Based on this discussion, we identify a need for multicomponent gas standards with part-per-trillion to part-per-million concentrations. We highlight National Institute of Standards and Technology gas standards developed for atmospheric measurements that are also relevant to breath analysis and describe investigations of long-term stability, chemical reactions, and interactions with gas cylinder wall treatments. An overview of emerging online instruments and their need for gas standards is also presented. This review concludes with a discussion of our ongoing research to examine the feasibility of producing multicomponent gas standards at breath-relevant concentrations. Such standards could be used to investigate interference from ubiquitous endogenous compounds and as a starting point for standards tailored to specific breath tests.

The use of reference materials (RMs) is critical for validating and testing the accuracy of analytical protocols. The National Institute of Standards and Technology (NIST) is in initial stages of developing a glyphosate in oats RM. The first aim of this study was to optimize and validate a robust method for the extraction and analysis of glyphosate and aminomethylphosphonic acid (AMPA). The optimized method was used to screen thirteen commercially available oat products to identify candidate RMs. Glyphosate was detected in all samples, with the highest glyphosate mass fraction of 1100 ng/g; lower levels were measured in grains from organic agriculture. AMPA was quantified in nine samples up to 40 ng/g. The findings of this study led to the identification of candidate RMs, with "high" and "low" glyphosate levels. A preliminary stability study determined that glyphosate is stable in oat material at room temperature for six months.

The Health Assessment Measurements Quality Assurance Program (HAMQAP) was launched in collaboration with the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) in 2017. HAMQAP was established to enable laboratories to improve the accuracy of measurements in samples that represent human intake (e.g., foods, dietary supplements, tobacco) and samples that represent human metabolism (e.g., blood, serum, plasma, urine) for demonstration of proficiency and/or compliance with various regulations. Analytes are paired where possible to represent the full spectrum of health assessment. Exercise 6 of this program offered the opportunity for laboratories to assess their in house measurements of nutritional elements (chlorine, iodine, chromium, molybdenum, and selenium), toxic elements (arsenic, cadmium, lead, and mercury), contaminants (chlorate and perchlorate, glyphosate and aminomethylphosphonic acid (AMPA)), water-soluble vitamins (biotin and vitamin C), fat-soluble vitamins (vitamins A and E), fatty acids (select omega-3 and omega-6 fatty acids), botanicals (anthocyanidins), natural products (caffeine, theobromine, and theophylline), and proximates (fat, protein, carbohydrates, solids, ash, and calories) in foods and dietary supplements, and corresponding biomarkers/metabolites in clinical specimens (human red blood cells).

Extraction, chromatographic separation, and quantification of low-concentration organic compounds in complex matrices are core challenges for reference material producers and providers of calibration services. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2014 the Organic Analysis Working Group (OAWG) initiated CCQM-K95.1 “Low-Polarity Analytes in a Botanical Matrix: Polycyclic Aromatic Hydrocarbons (PAHs) in Tea”. This was a follow-on comparison from CCQM-K95 which was completed in 2014. The polycyclic aromatic hydrocarbons (PAHs) benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) are considered priority pollutants by U.S. Environmental Protection Agency and are regulated contaminants in food, pose chromatographic separation challenges, and for which exist well-characterized measurement procedures and standard materials. BaA and BaP in a smoked tea were therefore selected as representative target measurands for CCQM-K95.1. Ten NMIs participated in CCQM-K95.1. The consensus summary mass fractions for the two PAHs are in the range of (50 to 70) ng/g with relative standard deviations of (6 to 10) %. Successful participation in CCQM K95.1 demonstrates the following measurement capabilities in determining mass fraction of organic compounds, with molar mass of 100 g/mol to 500 g/mol and having polarity pKow −2, in a botanical matrix ranging in mass fraction from 10 ng/g to 1000 ng/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, (3) extraction of analytes of interest from the matrix, (4) cleanup and separation of analytes of interest from interfering matrix or extract components, and (5) separation and quantification using gas chromatography or liquid chromatography. KEY WORDS FOR SEARCH benz[a]anthracene (BaA), benzo[a]pyrene (BaP), gas chromatography(GC), isotope dilution (ID), liquid chromatography (LC), mass spectrometry (MS), polycyclic aromatic hydrocarbon (PAH), yerba mate tea Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

National Institute of Standards & Technology, Gaithersburg, MD, USA Correspondence Dr. Nino G. Todua, National Institute of Standards & Technology, Gaithersburg, MD 20899, USA. Email: todua@nist.gov This is part 3 from the series “Analytical derivatives in mass spectrometry”, parts 1, and 2 see [1,2]. A method for isolation of enriched fractions of amino acids from human plasma followed by derivatization, gas chromatography separation and mass spectrometry identification is described. The method involves a stepwise extraction of plasma constituents with the use of two solvents: (a) extraction with methanol yields a concentrate of polyols, urea, carbohydrates and most long-chain saturated and unsaturated aliphatic acids, and (b) further solubilization with water produces mainly a concentrate of amino acids. Chemical modification of amino acids with methyl chloroformate/methanol gives rise to methyl esters of methoxycarbonyl derivatives. The derivatization products are stable and quite suitable for gas chromatography with mass spectrometry analysis. The electron ionization mass spectra of the derivatization products reveal specific fragmentation patterns applicable for structure elucidation. The efficiency of the method is demonstrated by gas chromatography with mass spectrometry identification of 19 amino acids as their methyl esters of methoxycarbonyl derivatives in Standard Reference Material 1950 Metabolites in Frozen Human Plasma.

A state-of-the-art, rapid laser-heating technique, referred to as the laser-driven thermal reactor, was used to characterize National Institute of Standards and Technology Standard Reference Material (SRM) diesel and biodiesel fuels, as well as a prototype biodiesel fuel. Also described are the various issues associated with carrying out these measurements under different operating conditions (i.e., temperature, pressure, heating rate, and sample mass). The technique provides measurement of various relevant thermochemical characteristics; for this investigation the focus was on the sample endothermic/exothermic behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, along with integrated optical, gas-supply, and computer-controlled data-acquisition subsystems. At the center of the reactor, the sample and substrate rest on a thermocouple. The reactor is heated from opposing sides by a near-infrared laser to achieve nearly uniform sample temperature. The change in sample temperature with time (i.e., thermogram) is recorded and compared to a baseline (no sample) thermogram obtained prior to the experiment, and then processed (using an equation for thermal energy conservation) for the thermochemical information of interest. Results indicated that the baseline is affected by residue remaining after completion of reactions and a change in the oxide layer of the reactor sphere outer surface. Thus, the sphere must be pre-oxidized in air using the laser prior to any sample or baseline measurement. This investigation provides preliminary evaluation of SRM biodiesel fuels, with the results being consistent with distillation curve work reported in the literature.

A simple approach for preparing standard mixtures of volatile and semi-volatile organic compounds is reported. When placed in a closed container, standard mixture components partition between a polymeric material such as poly(dimethylsiloxane) (PDMS) and headspace to provide constant vapor concentrations. The granular form of heat-conditioned PDMS provides rapid equilibration with the headspace vapor and serves as a standard reservoir. Solid phase micro extraction (SPME) or gas-tight syringe can be used to deliver sample from the headspace to the analytical instrument. Quantitative calibration can be achieved with either active temperature control or by using a previously constructed look-up table. The effects of PDMS form and temperature on equilibrium distribution, initial equilibrium time, and re-equilibrium time after sampling were investigated. With respect to long term use and stability, analytes introduced onto 2.0 g of PDMS in a 7.4 mL vial were sampled more than 114 times during a test period of 43 days, giving chromatographic peak area %RSD values below 4.5% for all compounds. This device was designed to be solventless, quantitative, reproducible, environmentally friendly, and robust for routine evaluation and calibration of gas chromatography-mass spectrometry (GC-MS) systems.

Comprehensive two-dimensional gas chromatography (GC × GC) offers advantages over one-dimensional gas chromatography (GC) including, high peak capacity, signal enhancement, and structured chromatograms. These advantages have been exploited to solve several analytical problems that are difficult to achieve in GC. In this review, qualitative and quantitative approaches of GC × GC are explored, including targeted, non-targeted, group, and fingerprinting analysis.

A simple method to detect and differentiate Bacillus anthracis (BA), Bacillus thuringiensis (BT), Bacillus atrophaeus (BG), and Bacillus cereus (BC) endospores using biomarker compounds, including dipicolinic acid methyl ester (DPAME) and fatty acid methyl esters (FAMEs), has been developed The method is based on thermochemolysis methylation (TCM) of the endospores and gas chromatography-mass spectrometry (GC-MS) of the reaction products A suspension of the sample mixed with sulfuric acid (H2SO4) and tetramethylammonium hydroxide (TMAH) in methanol (MeOH) at room temperature is sampled using a coiled wire filament (CWF) device, which consists of a tiny platinum helical wire coil attached to a retractable plunger that moves the coil in and out of a syringe needle housing Sampling is accomplished by dipping the CWF in an endospore sample suspension, evaporating the suspension liquid, and then introducing the CWF into the injection port While DPAME can be used for the general detection of endospores, specific saturated and unsaturated C-15, C-16, and C-17 fatty acid methyl esters provide additional information for differentiating various Bacillus species grown at different temperatures and in different media. DPAME could be detected in samples containing as few as 6000 endospores, and the GC-MS peak area percent reproducibility for FAMEs varied from 3 to 13% (RSD). Better than 97% correct predictability of Bacillus species identity was obtained from a blind experiment consisting of 145 samples

Abstract The U.S. Environmental Protection Agency is promoting the development and application of sampling methods for the semicontinuous determination of fine particulate matter (PM2.5, particles with an aerodynamic diameter <2.5 µm) mass and chemical composition. Data obtained with these methods will significantly improve the understanding of the primary sources, chemical conversion processes, and meteorological atmospheric processes that lead to observed PM2.5 concentrations and will aid in the understanding of the etiology of PM2.5-related health effects. During January and February 2007, several semicontinuous particulate matter (PM) monitoring systems were compared at the Utah State Lindon Air Quality Sampling site. Semicontinuous monitors included instruments to measure total PM2.5 mass (filter dynamic measurement system [FDMS] tapered element oscillating microbalance [TEOM], GRIMM), nonvolatile PM2.5 mass (TEOM), sulfate and nitrate (two PM2.5 and one PM10 [PM with an aerodynamic diameter <10 µm] ionchromatographic-based samplers), and black carbon (aethalometer). PM10 semicontinuous mass measurements were made with GRIMM and TEOM instruments. These measurements were all made on a 1-hr average basis. Source apportionment analysis indicated that sources impacting the site were mainly urban sources and included mobile sources (gasoline and diesel) and residential burning of wood, with some elevated concentrations because of the effect of winter inversions. The FDMS TEOM and GRIMM instruments were in good agreement, but TEOM monitor measurements were low because of the presence of significant semi-volatile material. Semi-volatile mass was present dominantly in the PM2.5 mass.

A simple device for field sampling and concentration of analytes for subsequent introduction into an injection port for gas chromatographic (GC) analysis has been developed. It consists of a tiny, coiled platinum wire filament (CWF) that is attached to a retractable plunger wire, which fits inside a syringe needle housing. Sampling is accomplished by dipping the end of the CWF in a liquid sample, which is drawn into the wire coil by capillary action, and introducing it into the injection port either before or after allowing the solvent to evaporate. The CWF can be used with or without a nonvolatile chemical coating. A major advantage of this sampling device is that nonvolatile sample matrix components remain on the wire coil, reducing the required injection port and liner cleaning frequency and contamination of the head of the chromatographic column. The coil itself can be easily cleaned between analyses by rinsing and/or burning off residual material in a small flame. The sampling coil facilitates specifically designed chemical reactions in the injection port, such as thermochemolysis and methylation. Applications demonstrated in this work include: (1) direct introduction of samples with little or no pre-treatment, (2) simultaneous thermochemolysis and methylation of lipid-containing samples such as bacteria and bacterial endospores for analysis of biomarkers, and (3) solid phase micro-extraction (SPME) using temporary wire coatings. The CWF allowed for significant reduction in sample preparation time, in most cases to less than a few minutes. The peak shapes examined for polycyclic aromatic hydrocarbon analytes (PAHs) were significantly better (asymmetry factors <1.3) when using the CWF sampling technique compared to splitless and on-column injection techniques (asymmetry factors >1.3). Extraction efficiencies for SPME (especially for high boiling point components such as PAHs) improved by an average of 2.5 times when using the CWF compared to the performance of commercially available SPME fibers. Coiled wire filaments and GC injection port liners were used for more than 100 Bacillus endospore thermochemolysis methylation analyses without the need for cleaning or replacement.