Definitive method certification of clinical analytes in lyophilized human serum: NIST Standard Reference Material (SRM) 909b

The National Institute of Standards and Technology (NIST) has developed several Standard Reference Materials (SRMs) based on human serum. NIST SRM 909b, Human Serum, is a lyophilized human serum material with concentrations for seven organic and six inorganic analytes at two levels certified solely by definitive methods (DMs). This material provides the vehicle by which high precision, high accuracy measurements made with DMs at NIST can be transferred through the measurement hierarchy to other laboratories. Isotope dilution gas chromatographic-mass spectrometric (GC-IDMS) methods were applied to measure cholesterol, creatinine, glucose, urea, uric acid, triglycerides, and total glycerides. Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used for determination of lithium, magnesium, potassium, calcium, and chloride. In addition, chloride was determined by coulometry, providing a comparison between two DMs. Sodium, which lacks a stable isotope that would permit isotope dilution mass spectrometric (IDMS) measurement, was determined by gravimetry. SRM 909b includes certified values for total glycerides and triglycerides, which were not certified in the previous lot of this material (SRM 909a). Improvement in uniformity of vial fill weight in the production of SRM 909b resulted in smaller certified uncertainties over previous freeze-dried serum SRMs. Uncertainties at the 99% level of confidence for relative expanded uncertainty (%) for certification of the organic analytes on a mmol/L/g basis ranged from 0.44% for urea (level II) to 5.04% for glucose (level II). (In-house studies have shown glucose to be a relatively unstable analyte in similar lyophilized serum materials, degrading at about 1% per year.) Relative expanded uncertainties (99% C.I.) for certification of inorganic analytes on a mmol/L/g basis ranged from 0.25% for chloride (level I) to 0.49% for magnesium (level II). Received: 30 July 1997 / Revised: 24 October 1997 / Accepted: 31 October 1997     

Definitive method certification of clinical analytes in lyophilized human serum: NIST Standard Reference Material (SRM) 909b

The National Institute of Standards and Technology (NIST) has developed several Standard Reference Materials (SRMs) based on human serum. NIST SRM 909b, Human Serum, is a lyophilized human serum material with concentrations for seven organic and six inorganic analytes at two levels certified solely by definitive methods (DMs). This material provides the vehicle by which high precision, high accuracy measurements made with DMs at NIST can be transferred through the measurement hierarchy to other laboratories. Isotope dilution gas chromatographic-mass spectrometric (GC-IDMS) methods were applied to measure cholesterol, creatinine, glucose, urea, uric acid, triglycerides, and total glycerides. Thermal ionization isotope dilution mass spectrometry (TI-IDMS) was used for determination of lithium, magnesium, potassium, calcium, and chloride. In addition, chloride was determined by coulometry, providing a comparison between two DMs. Sodium, which lacks a stable isotope that would permit isotope dilution mass spectrometric (IDMS) measurement, was determined by gravimetry. SRM 909b includes certified values for total glycerides and triglycerides, which were not certified in the previous lot of this material (SRM 909a). Improvement in uniformity of vial fill weight in the production of SRM 909b resulted in smaller certified uncertainties over previous freeze-dried serum SRMs. Uncertainties at the 99% level of confidence for relative expanded uncertainty (%) for certification of the organic analytes on a mmol/L/g basis ranged from 0.44% for urea (level II) to 5.04% for glucose (level II). (In-house studies have shown glucose to be a relatively unstable analyte in similar lyophilized serum materials, degrading at about 1% per year.) Relative expanded uncertainties (99% C.I.) for certification of inorganic analytes on a mmol/L/g basis ranged from 0.25% for chloride (level I) to 0.49% for magnesium (level II).     

Production and certification of NIST Standard Reference Material 2372 Human DNA Quantitation Standard

Modern highly multiplexed short tandem repeat (STR) assays used by the forensic human-identity community require tight control of the initial amount of sample DNA amplified in the polymerase chain reaction (PCR) process. This, in turn, requires the ability to reproducibly measure the concentration of human DNA, [DNA], in a sample extract. Quantitative PCR (qPCR) techniques can determine the number of intact stretches of DNA of specified nucleotide sequence in an extremely small sample; however, these assays must be calibrated with DNA extracts of well-characterized and stable composition. By 2004, studies coordinated by or reported to the National Institute of Standards and Technology (NIST) indicated that a well-characterized, stable human DNA quantitation certified reference material (CRM) could help the forensic community reduce within- and among-laboratory quantitation variability. To ensure that the stability of such a quantitation standard can be monitored and that, if and when required, equivalent replacement materials can be prepared, a measurement of some stable quantity directly related to [DNA] is required. Using a long-established conventional relationship linking optical density (properly designated as decadic attenuance) at 260 nm with [DNA] in aqueous solution, NIST Standard Reference Material (SRM) 2372 Human DNA Quantitation Standard was issued in October 2007. This SRM consists of three quite different DNA extracts: a single-source male, a multiple-source female, and a mixture of male and female sources. All three SRM components have very similar optical densities, and thus very similar conventional [DNA]. The materials perform very similarly in several widely used gender-neutral assays, demonstrating that the combination of appropriate preparation methods and metrologically sound spectrophotometric measurements enables the preparation and certification of quantitation [DNA] standards that are both maintainable and of practical utility. Figure NIST Standard Reference Material (SRM) 2372 Human Quantitation Standard     

血清中葡萄糖的测量比对-ID-LC—MS／MS法

利用同位素稀释-液相色谱-质谱法-（ID-LC-MS／MS）准确测定血清中葡萄糖含量。以[13C6]葡萄糖为内标,用重量法准确地与血清混合,离心沉淀蛋白后在碱性条件下与1．苯基-3-甲基-5-吡唑酮反应,以ZORBAXRX-SIL色谱柱分离,以乙腈-水（体积此25：75）为流动相,使用电喷雾三重四极杆串联质谱多重反应监测模式（MRM）测定,同位素稀释的括号法进行定量。采用美国NIST的血清标准物质SRM965b进行了确证,并用该方法参加JCTLM关于血清中葡萄糖含量的国际比对,测量值与均值的相对偏差分别为1．1％（A样）．1．8％（B样）,结果在等效范围内。     

Certification of NIST standard reference material 2389a, amino acids in 0.1 mol/L HCl—quantification by ID LC-MS/MS

An isotope-dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) measurement procedure was developed to accurately quantify amino acid concentrations in National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 2389a—amino acids in 0.1 mol/L hydrochloric acid. Seventeen amino acids were quantified using selected reaction monitoring on a triple quadrupole mass spectrometer. LC-MS/MS results were compared to gravimetric measurements from the preparation of SRM 2389a—a reference material developed at NIST and intended for use in intra-laboratory calibrations and quality control. Quantitative mass spectrometry results and gravimetric values were statistically combined into NIST-certified mass fraction values with associated uncertainty estimates. Coefficients of variation (CV) for the repeatability of the LC-MS/MS measurements among amino acids ranged from 0.33% to 2.7% with an average CV of 1.2%. Average relative expanded uncertainty of the certified values including Types A and B uncertainties was 3.5%. Mean accuracy of the LC-MS/MS measurements with gravimetric preparation values agreed to within |1.1|% for all amino acids. NIST SRM 2389a will be available for characterization of routine methods for amino acid analysis and serves as a standard for higher-order measurement traceability. This is the first time an ID LC-MS/MS methodology has been applied for quantifying amino acids in a NIST SRM material.     

Determination of fortified and endogenous folates in food-based Standard Reference Materials by liquid chromatography-tandem mass spectrometry

The National Institute of Standards and Technology (NIST) is developing a wide variety of Standard Reference Materials (SRMs) to support measurements of vitamins and other nutrients in foods. Previously, NIST has provided SRMs with values assigned for the folate vitamer, folic acid (pteroylglutamic acid), which is fortified in several foods due to its role in prevention of neural tube defects. In order to expand the number of food-based SRMs with values assigned for folic acid, as well as additional endogenous folates, NIST has developed methods that include trienzyme digestion and isotope-dilution liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis. Sample preparation was optimized for each individual food type, but all samples were analyzed under the same LC-MS/MS conditions. The application of these methods resulted in folic acid values for SRM 1849a Infant/Adult Nutritional Formula and SRM 3233 Fortified Breakfast Cereal of (2.33?±?0.06) μg/g and (16.0?±?0.7) μg/g, respectively. In addition, the endogenous folate vitamer 5-methlytetrahydrofolate (5-MTHF) was detected and quantified in SRM 1849a Infant/Adult Nutritional Formula, candidate SRM 1549a Whole Milk Powder, and candidate SRM 1845a Whole Egg Powder, resulting in values of (0.0839?±?0.0071) μg/g, (0.211?±?0.014) μg/g, and (0.838?±?0.044) μg/g, respectively. SRM 1849a Infant/Adult Nutritional Formula is the first food-based NIST SRM to possess a reference value for 5-MTHF and the first certified reference material to have an assigned 5-MTHF value based on LC-MS/MS. The values obtained for folic acid and 5-MTHF by LC-MS/MS will be incorporated into the final value assignments for all these food-based SRMs.     

Recent developments in food-matrix Reference Materials at NIST

Since 1996, the National Institute of Standards and Technology (NIST) has developed several food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, and SRM 2383 Baby Food Composite. Three additional materials--SRM 1946 Lake Superior Fish Tissue, SRM 2384 Baking Chocolate, and SRM 2385 Spinach--are in preparation. NIST also recently assigned values for proximate (fat, protein, etc.), individual fatty acid, and total dietary fiber concentrations in a number of existing SRMs and reference materials (RMs) that previously had values assigned for their elemental composition. NIST has used several modes for assignment of analyte concentrations in the food-matrix RMs, including the use of data provided by collaborating laboratories, alone and in combination with NIST data. The use of data provided by collaborating food industry and contract laboratories for the analysis of food-matrix RMs has enabled NIST to provide assigned values for many analytes that NIST does not have the resources or analytical expertise to measure.     

Differences between propane in nitrogen versus air matrix analyzed using gas chromatography with flame-ionization detection

New US Federal low-level automobile emission requirements, such as Zero Level Emission Vehicle (ZLEV), for hydrocarbons and other species have resulted in manufacturers need for new certified reference materials. The new emission requirement for hydrocarbons requires the use, by automobile manufacturing testing facilities, of 100 nmol/mol (ppb) propane in air gas standard. Emission measurement instruments are required, by Federal law, to be calibrated with the US National Institute of Standards and Technology (NIST) traceable reference materials. A NIST Standard Reference Material (SRM) containing 100 nmol/mol propane has been developed. During the development of this SRM a critical question arose as to the matrix of the primary propane standards. The automobile companies make their measurements using total hydrocarbon analyzers with flame-ionization detectors which integrate all hydrocarbons in a sample. NIST uses gas chromatography/flame-ionization detection (GC/FID) with a column to separate all components. Since the SRM mixtures were in air, the question as to the effect of oxygen on the detector arose. To investigate this effect, two suites of propane primary standards were developed: one in air and the other in nitrogen. The two suites of primary standards were analyzed using NIST methods, and the concentration of propane in an air mixture was determined. The results show that there was a difference of 0.63% in the propane concentration determined versus air and nitrogen suites.     

Analysis of carcinogenic polycyclic aromatic hydrocarbons in complex environmental mixtures by LC-APPI-MS/MS

Here we developed a highly sensitive, fast and reliable liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the detection and analysis of 16 different polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs that have been identified as carcinogens and classified according to their biological potency. Comparison to standard analysis procedures based on gas chromatography-mass spectrometry (GC-MS) instrumentation demonstrated an improved easiness of sample preparation and sensitivity of detection achieved with the new LC-MS/MS method employing an atmospheric pressure photoionization (APPI) source attached to an API 4000 mass spectrometer (LC-APPI-MS/MS). The favorable outcome could be confirmed by analyzing complex mixtures such as certain Standard Reference Materials (SRMs) obtained from the National Institute of Standards & Technology (NIST), i.e., SRM 1975 and SRM 2975, and several diesel exhaust soots provided by the German automobile industry. Certified concentrations of individual analytes provided by NIST not only could be confirmed, but additional extremely potent carcinogens such as several isomeric hexacyclic dibenzopyrenes (DBPs), 5-methylchrysene (5-MC), and others have been detected in these crude samples in a concentration range down to below 1 ng g(-1) raw material.     

Preparation and value assignment of standard reference material 968e fat-soluble vitamins, carotenoids, and cholesterol in human serum

Standard Reference Material 968e Fat-Soluble Vitamins, Carotenoids, and Cholesterol in Human Serum provides certified values for total retinol, γ- and α-tocopherol, total lutein, total zeaxanthin, total β-cryptoxanthin, total β-carotene, 25-hydroxyvitamin D₃, and cholesterol. Reference and information values are also reported for nine additional compounds including total α-cryptoxanthin, trans- and total lycopene, total α-carotene, trans-β-carotene, and coenzyme Q₁₀. The certified values for the fat-soluble vitamins and carotenoids in SRM 968e were based on the agreement of results from the means of two liquid chromatographic methods used at the National Institute of Standards and Technology (NIST) and from the median of results of an interlaboratory comparison exercise among institutions that participate in the NIST Micronutrients Measurement Quality Assurance Program. The assigned values for cholesterol and 25-hydroxyvitamin D₃ in the SRM are the means of results obtained using the NIST reference method based upon gas chromatography-isotope dilution mass spectrometry and liquid chromatography-isotope dilution tandem mass spectrometry, respectively. SRM 968e is currently one of two available health-related NIST reference materials with concentration values assigned for selected fat-soluble vitamins, carotenoids, and cholesterol in human serum matrix. This SRM is used extensively by laboratories worldwide primarily to validate methods for determining these analytes in human serum and plasma and for assigning values to in-house control materials. The value assignment of the analytes in this SRM will help support measurement accuracy and traceability for laboratories performing health-related measurements in the clinical and nutritional communities.     

Development of a new standard reference material: SRM 1955 (homocysteine and folate in human serum)

Total homocysteine (tHCY) and folate are interrelated biomarkers for arteriosclerosis and coronary heart disease. Although many different methods for both tHCY and folate are clinically available, the intermethod and interlaboratory results are often poor, resulting in the need for a matrix reference material and reference methods. The National Institute of Standards and Technology (NIST) has developed isotope dilution liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/ tandem mass spectrometry (LC/MS/MS) methods for determination of tHCY and several folate forms including 5-methyltetrahydrofolic acid (5MT) and folic acid (FA). Additionally, a method for simultaneous measurement of tHCY, 5MT, and FA has been developed and validated. In collaboration with the Centers for Disease Control and Prevention (CDC), mass spectrometric methods and methods used in clinical laboratories have been applied to characterize a new Standard Reference Material (SRM), SRM 1955, "Homocysteine and Folate in Human Serum," containing low, medium, and high levels of tHCY and 5MT. Additionally, FA, 5-formyltetrahydrofolic acid (5FT), vitamin B12, and total folate values are provided. Use of the new SRM should improve clinical measurements and will permit traceability to internationally recognized certified reference materials, as described by European Directive 98/79/EC on in vitro diagnostic medical devices.     

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge

Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02 μg g⁻¹ for As and Se, respectively, in original soil and sludge samples.     

Determination of trace elements in human serum by inductively coupled plasma atomic emission spectrometry with flow injection

An analytical method for the simultaneous determination of some trace elements (Au, Fe, Mg, Li, Sr, Zn) in human serum by inductively coupled plasma atomic emission spectrometry (ICP-AES) with flow injection is described. Physical interference caused by the change of sample viscosity is discussed. When 100 μl of serum was injected, the relevant recoveries of > 99% for Li, > 98% for Cu and Mg, > 95% for Fe were obtained for an NIST SRM with R.S.D. > 1.3% using optimized flow injection parameters. The prepared lyophilized control serum for routine analysis in clinical laboratories was analyzed and verified for the validity of the technique employed in this experiment using NIST SRM 909 as a primary reference material.     

New NIST sediment SRM for inorganic analysis

NIST maintains a portfolio of more than 1300 standard reference materials (SRM), more than a third of these relating to measurements in the biological and environmental fields. As part of the continuous renewal and replacement efforts, a set of new marine sediments has been recently developed covering organic and inorganic determinations. This paper describes the steps taken in sample preparation, homogeneity assay, and analytical characterization and certification with specific emphasis on SRM 2702 inorganics in marine sediment. Neutron activation analysis showed the SRM to be highly homogeneous, opening the possibility for use with solid sampling techniques. The certificate provides certified mass fraction values for 25 elements, reference values for eight elements, and information values for 11 elements, covering most of the priority pollutants with small uncertainties of only several percent relative. The values were obtained by combining results from different laboratories and techniques using a Bayesian statistical model. An intercomparison carried out in field laboratories with the material before certification illustrates a high commutability of this SRM.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Application of laser ablation multicollector inductively coupled plasma mass spectrometry for the measurement of calcium and lead isotope ratios in packaging for discriminatory purposes

The potential of high‐precision calcium and lead isotope ratio measurements using laser ablation coupled to multicollector inductively coupled plasma mass spectrometry (LA‐MC‐ICP‐MS) to aid distinction between four genuine and five counterfeit pharmaceutical packaging samples and further classification of counterfeit packaging samples has been evaluated. We highlight the lack of reference materials for LA‐MC‐ICP‐MS isotope ratio measurements in solids. In this case the problem is minimised by using National Institute of Standards and Technology Standard Reference Material (NIST SRM) 915a calcium carbonate (as solid pellets) and NIST SRM610 glass disc for sample bracketing external standardisation. In addition, a new reference material, NIST SRM915b calcium carbonate, has been characterised in‐house for Ca isotope ratios and is used as a reference sample. Significant differences have been found between genuine and counterfeit samples; the method allows detection of counterfeits and aids further classification of packaging samples. Typical expanded uncertainties for measured‐corrected Ca isotope ratio values (⁴³Ca/⁴⁴Ca and ⁴²Ca/⁴⁴Ca) were found to be below 0.06% (k = 2, 95% confidence) and below 0.2% for measured‐corrected Pb isotope ratios (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb). This is the first time that Ca isotope ratios have been measured in packaging materials using LA coupled to a multicollector (MC)‐ICP‐MS instrument. The use of LA‐MC‐ICP‐MS for direct measurement of Ca and Pb isotopic variations in cardboard/ink in packaging has definitive potential to aid counterfeit detection and classification. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a 100 nmol mol<Superscript>−1</Superscript> propane-in-air SRM for automobile-exhaust testing for new low-emission requirements

New US federal low-level automobile emission requirements, for example zero-level-emission vehicle (ZLEV), for hydrocarbons and other species, have resulted in the need by manufacturers for new certified reference materials. The new emission requirement for hydrocarbons requires the use, by automobile manufacturing testing facilities, of a 100 nmol mol(-1) propane in air gas standard. Emission-measurement instruments are required, by federal law, to be calibrated with National Institute of Standards and Technology (NIST) traceable reference materials. Because a NIST standard reference material (SRM) containing 100 nmol mol(-1) propane was not available, the US Environmental Protection Agency (EPA) and the Automobile Industry/Government Emissions Research Consortium (AIGER) requested that NIST develop such an SRM. A cylinder lot of 30 gas mixtures containing 100 nmol mol(-1) propane in air was prepared in 6-L aluminium gas cylinders by a specialty gas company and delivered to the Gas Metrology Group at NIST. Another mixture, contained in a 30-L aluminium cylinder and included in the lot, was used as a lot standard (LS). Using gas chromatography with flame-ionization detection all 30 samples were compared to the LS to obtain the average of six peak-area ratios to the LS for each sample with standard deviations of <0.31%. The average sample-to-LS ratio determinations resulted in a range of 0.9828 to 0.9888, a spread of 0.0060, which corresponds to a relative standard deviation of 0.15% of the average for all 30 samples. NIST developed its first set of five propane in air primary gravimetric standards covering a concentration range 91 to 103 nmol mol(-1) with relative uncertainties of 0.15%. This new suite of propane gravimetric standards was used to analyze and assign a concentration value to the SRM LS. On the basis of these data each SRM sample was individually certified, furnishing the desired relative expanded uncertainty of +/-0.5%. Because automobile companies use total hydrocarbons to make their measurements, it was also vital to assign a methane concentration to the SRM samples. Some of the SRM samples were analyzed and found to contain 1.2 nmol mol(-1) methane. Twenty-five of the samples were certified and released as SRM 2765.     

Determination of fat-soluble vitamins and carotenoids in standard reference material 3280 multivitamin/multielement tablets by liquid chromatography with absorbance detection

The concentrations of selected fat-soluble vitamins and carotenoids in Standard Reference Material (SRM) 3280 Multivitamin/Multielement Tablets have been determined by two independent LC methods, with measurements performed by the National Institute of Standards and Technology (NIST). This SRM has been prepared as part of a collaborative effort between NIST and the National Institutes of Health Office of Dietary Supplements. The SRM is also intended to support the Dietary Supplement Ingredient Database that is being established by the U.S. Department of Agriculture. The methods used at NIST to determine the concentration levels of vitamins A and E, and beta-carotene in the SRM used RPLC with absorbance detection. The relative precision of these methods ranged from 2 to 8% for the analytes measured. SRM 3280 is primarily intended for use in validating analytical methods for the determination of selected vitamins, carotenoids, and elements in multivitamin/multielement tablets and similar matrixes.     

Iodination on Tyrosine Residues During Oxidation with Sodium Periodate in Solid Phase Extraction of N-linked Glycopeptides

Solid-phase extraction of N-linked glycopeptides (SPEG) using hydrazide-modified supports has become a common sample preparation procedure in glycoproteomic experiments. We demonstrate that iodination of tyrosine residues occur in SPEG as a side reaction during an oxidation step with sodium periodate. MS/MS analysis of oxidized bovine serum albumin and carbonic anhydrase digests revealed a characteristic shift of m/z 125.9 on all y and b fragment ions containing the modified tyrosine residues. Selected reaction monitoring (SRM) measurements showed that the peak intensity from of the iodinated peptides increased during the course of oxidation. After an hour of oxidation, SRM analysis revealed that the strongest signal from an iodinated peptide was approximately one-tenth of the intensity of the corresponding unmodified peptide. Iodinated tyrosine residues were also identified in serum samples subjected to SPEG and analyzed by LC-ESI-MS/MS. We recommend assessing this side reaction by including iodotyrosine as a variable modification when performing database searches on SPEG experiments. For SRM-based acquisitions, we encourage the avoidance of tyrosine-containing glycopeptides or, if this is not practical, monitoring transitions that contain the potential modified iodinated tyrosine residue to monitor the presence of the iodinated form of the glycopeptide.     

Determination of perfluorinated alkyl acid concentrations in biological standard reference materials

Standard reference materials (SRMs) are homogeneous, well-characterized materials used to validate measurements and improve the quality of analytical data. The National Institute of Standards and Technology (NIST) has a wide range of SRMs that have mass fraction values assigned for legacy pollutants. These SRMs can also serve as test materials for method development, method validation, and measurement for contaminants of emerging concern. Because inter-laboratory comparison studies have revealed substantial variability of measurements of perfluoroalkyl acids (PFAAs), future analytical measurements will benefit from determination of consensus values for PFAAs in SRMs to provide a means to demonstrate method-specific performance. To that end, NIST, in collaboration with other groups, has been measuring concentrations of PFAAs in a variety of SRMs. Here we report levels of PFAAs and perfluorooctane sulfonamide (PFOSA) determined in four biological SRMs: fish tissue (SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue), bovine liver (SRM 1577c), and mussel tissue (SRM 2974a). We also report concentrations for three in-house quality-control materials: beluga whale liver, pygmy sperm whale liver, and white-sided dolphin liver. Measurements in SRMs show an array of PFAAs, with perfluorooctane sulfonate (PFOS) being the most frequently detected. Reference and information values are reported for PFAAs measured in these biological SRMs.

Marine mammal blubber reference and control materials for use in the determination of halogenated organic compounds and fatty acids

The National Institute of Standards and Technology (NIST) has a diverse collection of control materials derived from marine mammal blubber, fat, and serum. Standard Reference Material (SRM) 1945 Organics in Whale Blubber was recertified for polychlorinated biphenyl (PCB) congeners, organochlorine pesticides, and polybrominated diphenyl ether (PBDE) congeners. SRM 1945 has also been assigned mass fraction values for compounds not frequently determined in marine samples including toxaphene congeners, coplanar PCBs, and methoxylated PBDE congeners which are natural products. NIST also has assigned mass fraction values, as a result of interlaboratory comparison exercises, for PCB congeners, organochlorine pesticides, PBDE congeners, and fatty acids in six homogenate materials produced from marine mammal blubber or serum. The materials are available from NIST upon request; however, the supply is very limited for some of the materials. The materials include those obtained from pilot whale blubber (Homogenates III and IV), Blainville’s beaked whale blubber (Homogenate VII), polar bear fat (Homogenate VI), and California sea lion serum (Marine Mammal Control Material-1 Serum) and blubber (Homogenate V).