Preparation of Reference Material 8504, Transformer Oil

A new reference material (RM), RM 8504, has been prepared for use as a diluent oil with Aroclors in transformer oil Standard Reference Materials (SRMs) 3075 to 3080 and SRM 3090 when developing and validating methods for the determination of polychlorinated biphenyls (PCBs) as Aroclors in transformer oil or similar matrices. SRMs 3075-3080 and SRM 3090 consist of individual Aroclors in the same transformer oil that was used to prepare RM 8504. A unit of RM 8504 consists of one bottle containing approximately 100 mL of transformer oil. No additional constituents have been added to the oil.     

Levels of polychlorinated biphenyls (PCBs) in transformer oils from Korea

Using Korean waste official method, polychlorinated biphenyls (PCBs) were analyzed from 33 transformer oils collected under National Institute of Environmental Research (NIER) in Republic of Korea (ROK) and their emission rate in Korea was estimated. Practical quantification limits analyzed by this method were in the ranges of 0.02 and 0.05 mg L(-1), and recovery of samples was in the ranges of 77-97%. The analytical results showed that PCBs in the transformer oils were identified as Aroclor 1242, 1254 or 1260. Twenty-nine samples were determined to contain PCBs of >0.05 mg L(-1) and among these samples, nine samples contained to have >2 mg kg(-1) which is limit of Waste Control Act (WCA) with regard to PCBs in transformer oil from Korea. The concentrations of PCBs in transformer oils were between N.D. (not detected) and 48.33 mg kg(-1). PCBs concentrations did not exceed 50 mg kg(-1) which is generally accepted limit for the definition of waste in POPs Guideline of Basel Convention.     

Quantitative enzyme-linked immunosorbent assay for determination of polychlorinated biphenyls in environmental soil and sediment samples

An enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of Aroclors 1242, 1248, 1254, and 1260 in soil and sediments was developed and its performance compared with that of gas chromatography (GC). The detection limits for Aroclors 1242 and 1248 in soil are 10.5 and 9 ng/g, respectively. The assay linear dynamic range is 50-1333 ng/g. Cross-reactivity of the assay with 37 structurally related potential cocontaminants in environmental soil samples was examined; none of the chlorinated anisoles, benzenes, or phenols exhibited >3% cross-reactivity, with <0.1% cross-reactivity being the norm. Soil spike recoveries of 107% and 104% were obtained for Aroclors 1242 and 1248, respectively, for a spike level of 5 mg/kg, with corresponding relative standard deviations of 14% and 17%. One hundred forty-eight environmental soil, sediment, and paper pulp samples, obtained from two EPA listed Superfund sites, were analyzed by ELISA and standard GC methods. Samples were extracted for ELISA analysis by shaking with methanol. Additional extractions of the same samples were performed either with supercritical carbon dioxide or by Soxhlet extraction with methanol. ELISA results for both the supercritical fluid and the Soxhlet extracts were in close agreement with the GC results, while the ELISA results for the methanol shake extracts were not. The data for the environmental samples demonstrated the capability of the ELISA to provide accurate results and reinforced the dependence of any detection method, including ELISA, on appropriate extraction procedures.     

Development of a NIST standard reference material containing thirty volatile organic compounds at 5 nmol/mol in nitrogen

Primary gravimetric gas cylinder standards containing 30 volatile organic compounds (VOCs) in nitrogen were prepared using a procedure previously developed to prepare gas mixture cylinder standards of VOCs at the 5 nmol/mol level. This set of primary standards was intercompared to existing gas cylinder standards, containing as many as 19 of the 30 volatile organics present in these new primaries, using gas chromatography with a hydrogen flame ionization detector coupled with cryogenic preconcentration. The linear regression analysis showed excellent agreement among the standards for each compound. Similar mixtures containing many of these compounds in treated aluminum gas cylinders have been evaluated over time and have shown stability for as much as 10 years. The development of these 30-component primary standards led to the preparation and certification of a reissue of Standard Reference Material (SRM) 1804 at the nominal amount-of-substance fraction of 5 nmol/mol for each analyte. A lot of 20 cylinders containing the mixture was prepared at NIST following previously demonstrated protocols for preparation of the cylinders. Each cylinder was analyzed against one cylinder from the lot, designated as the "lot standard," for each of the 30 compounds. As a result of the uncertainty analysis, the data showed that rather than declaring the lot homogeneous with a much higher uncertainty, each cylinder could be individually certified. The expanded uncertainty limits ranged from 1.5 to 10% for 28 of the 30 analytes, with two of the analytes having uncertainties as high as 19% in those SRM cylinders certified. Due to stability issues and some high uncertainties for a few analytes in 2 of the samples, 18 of the 20 candidate SRM samples were certified. These volatile organic gas mixtures represent the most complex gas SRMs developed at NIST.     

Simultaneous mass bias and fractionation corrections utilizing isotopic solid standards and laser ablation ICPMS

Homogeneous incorporation of analytes of known isotopic abundance into sol-gel-derived standards that mimic important mineral systems has the potential to contribute significantly to providing solid standard benchmarks for a range of applications. This preliminary study reports on the synthesis of solid glass standards produced via the sol-gel method and their doping with Standard Reference Material (SRM) 981 Common Lead Isotopic Standard and SRM 982 Equal-Atom Lead Isotopic Standard. Custom isotopic materials were also prepared using mixtures of the two isotopic SRMs. Particles from these solid samples were then introduced into an inductively coupled plasma mass spectrometer via laser ablation to determine whether materials of suitable homogeneity could be developed as isotopic reference materials. Preliminary results for Pb isotope ratios show that these solid isotopic reference standards are capable of correcting for instrumental mass bias and laser ablation-induced bias due to fractionation simultaneously. Correction factors generated from the quotient of the certified and measured Pb isotopic ratios in sol-gel disks spiked with SRMs 981 and 982 were successfully applied to produce accurate isotope ratios using comparative control/unknown checks. These correction factors were also used to assign Pb isotopic ratios in NIST SRM 612 Trace Elements in Glass that were in excellent agreement with published measurements, suggesting that tunable matrix sol-gel disks can serve as adequate control matrixes for evaluation of isotope ratios in glass samples.     

Determination of polycyclic aromatic sulfur heterocycles in fossil fuel-related samples

An analytical method is described for the separation, identification, and quantification of a number of polycyclic aromatic sulfur heterocycles (PASHs) in three fossil fuel-related samples including two Standard Reference Materials (SRMs), SRM 1597 (coal tar) and SRM 1582 (petroleum crude oil), and a decant oil. The compounds measured include the 3 possible naphtho[b]thiophenes; dibenzothiophene and selected methyl-, ethyl-, dimethyl-, and trimethyl-substituted isomers; the 3 possible benzo[b]naphthothiophenes; and the 30 methylbenzo[b]naphthothiophenes isomers. Because of the occurrence of polycyclic aromatic hydrocarbons and PASHs together with their large number of possible alkyl-substituted isomers, the analytical method described requires a number of prerequisites: effective sample cleanup, selective stationary phases, and selective methods of detection. The sample cleanup involves solid-phase extraction using aminopropylsilane cartridges with different solvent mixtures followed by normal-phase liquid chromatographic isolation of the PASHs based on the number of aromatic carbons. These aromatic ring fractions are then separated by capillary gas chromatography using two stationary phases with different selectivities, 5% phenyl-substituted methylpolysiloxane stationary phase and 50% phenyl-substituted methylpolysiloxane stationary phase, and analyzed with mass-selective detection and atomic emission detection. A liquid crystalline stationary phase was also used to separate the methylbenzo[b]naphthothiophene isomers in the crude oil sample. Advantages and limitations of each chromatographic and detection technique are discussed.     

System response matrix calculation using symmetries for dual‐head PET scanners

Positron emission tomography (PET) scanner with dual‐head geometry offers better spatial resolution and higher sensitivity for dedicated application when compared with conventional full‐ring PET scanners. However, this configuration suffers from limited‐angle projection and depth‐of‐interaction (DOI) effects. Accurate modeling of the system response matrix (SRM) and its incorporation into iterative methods can help to obtain images with better quality. In this paper, we proposed a line‐of‐response (LOR) based symmetry approach to calculate the SRM of PET scanners with dual‐head geometry. Both Monte Carlo (MC) and analytically computed SRMs were obtained and named MC SRM and geometrical SRM respectively, with their performances been compared using simulated phantom studies. The point source study shows that the resolution in directions parallel to the detector is rather uniform, with a full width at half maximum (FWHM) of 0.6～0.7 mm and 0.6～0.8 mm using MC and geometrical SRMs respectively. While the spatial resolution in the direction perpendicular to the detector is much worse, when moving towards the detector panel from the field‐of‐view (FOV) center, the FWHM changes from 1.5 mm to 1.8 mm and 2.4 mm to 3.1 mm using MC and geometrical SRMs, which is caused by the missing of projection views. Images generated using MC SRM also show better stochastic quality and quantitative performance. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 205–214, 2013     

Massic Activity Ratios of the NBS/NIST Tritiated-Water Standards Issued Between 1954 and 1999

As part of the preparation and calibration of three new National Institute of Standards and Technology (NIST) tritiated-water radioactivity Standard Reference Materials (SRMs), the massic-activity (activity of the sample divided by the mass of the sample) ratios of all of the available NBS/NIST tritiated-water SRMs issued between 1954 and 1999 were measured using liquid-scintillation (LS) counting. Four of the tritiated-water standards (SRMs 4361, 4926B, 4927C, and 4927D) were not available for measurement. All of the other tritiated-water standards (SRMs 4361B, 4361C, 4926, 4926C, 4926D, 4926E, 4927, 4927B, 4927E, and 4927F) were available, having been stored in flame-sealed glass ampoules. Where possible, massic-activity ratios measured by liquid-scintillation counting are compared with massic-activity ratios calculated from gravimetric dilution factors. The agreement is well within the stated uncertainties. For two of the tritiated-water standards that were not available for measurement (SRMs 4361 and 4926B), massic-activity ratios calculated from gravimetric dilution factors are available.     

Determination of polycyclic aromatic hydrocarbons with molecular weight 300 and 302 in environmental-matrix standard reference materials by gas chromatography/mass spectrometry

An analytical approach based on gas chromatography/ mass spectrometry (GC/MS) is presented for the measurement of polycyclic aromatic hydrocarbons with molecular weight (MW) 300 and 302 in environmental samples. Three different GC stationary phases [5% and 50% phenyl methylpolysiloxane and dimethyl (50% liquid crystalline) polysiloxane] were compared, and retention indexes (RI) are given for 23 individual MW 302 isomers. Identification of MW 300 and 302 isomers in four environmental-matrix Standard Reference Materials (SRMs) (SRM 1597, coal tar extract; SRM 1648 and SRM 1649a, air particulate matter; and SRM 1941, marine sediment) was based on the comparison of RI data and mass spectra from authentic standards. Dibenzo[a,l]pyrene, which is of considerable interest because of its high carcinogenicity, was identified and quantified in the four environmental-matrix SRMs. A total of 23 isomers of MW 302 and four isomers of MW 300 were quantified in four different environmental-matrix SRMs, and the results are compared to previously reported results based on liquid chromatography with fluorescence detection.     

DSP-Based Automated Error-Reducing Flux-Linkage-Measurement Method for Switched Reluctance Motors

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus, it has become a popular research topic in the field of variable-speed drives as well as servo drives. Research on SRMs mainly includes their design, modeling and performance analysis, control, as well as applications. However, for verification of design, performance prediction, as well as development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate and fully automated digital method for the measurement of the magnetic characteristic of SRMs, which includes online offset-error removal and winding resistance estimation. In this method, a digital-signal-processor-based virtual instrumentation for measurement of flux linkage is developed. Then, the results of the measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing with that found via a magnetic analyzer. Finally, the various sources of errors and their contributions to the errors are discussed. The scheme can also be used, in general, for transformers or inductors.     

An improved method for the determination of saturationcharacteristics of switched reluctance motors

Experimental determination of magnetization characteristics of switched reluctance motors (SRMs) is quite important in their accurate performance prediction. Over the last decade, various experimental procedures have been used to obtain these characteristics. Every evolved new method has its own limitations and constraints. This paper describes an improved, simple and cost effective experimental procedure and an equally simple post-experimental data processing to obtain the flux-linkage-current curves at varying rotor positions of the SRM. The experimental results on a 4 kW, four-phase, 8/6 pole SRMs show the effectiveness of the method and the results compare well with the previously results compare well with the previously published results of similar and higher rating SRM's     

On site PCB analysis in support of a transformer rebuilding project

In December 1997, Emergencies Science Division (ESD) was contracted by Natural Resources Canada (NRCAN) to perform on-site analyses in support of a transformer-rebuilding project at Sault Ste-Marie, Ont. Using a gas chromatograph with electron capture detector (GC/ECD) mounted in a mobile laboratory, PCB analyses were conducted on the original transformer oil, surface wipes, Varsol rinsing of the transformer tank interior and cooling fins. To assess the efficiency and validity of the decontamination process, PCB contamination was monitored closely on the rinse solvent. Surface wipe samples after wash down showed surface concentration of several hundred microg Aroclor 1254/100 cm(2), well below the acceptable limit of 8000 microg/100 cm(2). Because of the relatively large percentage of the internal surface area, the fin banks had to be rinsed exhaustively to meet the decontamination criteria. Final rinses of each of the seven fin banks of transformer 1 still showed presence of PCB, ranging from 80 to 590 ppm (microg/ml) with a mean value of 280 ppm. Upon completion of rebuilding, analysis of the R-Temp retro fill fluid showed 5 ppm at the initial power-up, increasing slightly to 16 ppm after 1 year of operation, which was far below the regulatory limit 50 ppm. The second transformer, by comparison, had a lower mean concentration of 54 ppm in the final fin rinse during decontamination. However, the backfill R-Temp showed an initial concentration of 38 ppm and remained essentially unchanged at 32 ppm after approximately 10 months of operation. Extensive comparison of GC and the quick test Clor-N-Oil kit were also carried out and showed generally good agreement. The use of an on-site GC was crucial in providing rapid and accurate analysis on-site, thus, enabling quick modifications to the decontamination strategies in order to meet the target PCB level. For projects of this nature, a GC/ECD was far superior to quick test kits by providing the selectivity and sensitivity for the diverse nature of the sample media.     

Cocarcinogenesis between cadmium and Aroclor 1254 in planarians is enhanced by inhibition of glutathione synthesis.

Asexual Dugesia dorotocephala planaria continuously exposed to 50 micrograms/beaker of Aroclor 1254 (A1254) and cadmium (Cd) developed tumors after 11 days of continuous exposure to 0.65 or 1.3 mg/liter Cd and after 23 days to 0.13 mg/liter Cd. The tumor rate at 14 days averaged 53% for the survivors in both 0.65 and 1.3 mg/liter Cd + A1254 and 40% at 0.13 mg/liter Cd + A1254. Other groups were either preexposed or coexposed to L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of glutathione synthesis. In the presence of A1254 (50 micrograms/beaker), animals continuously exposed to BSO and 0.13 mg/liter Cd first developed tumors at 18 days, with a tumor yield equal to 41% of the survivors. Tumors developed by 6 days at 0.65 mg/liter Cd, with a yield equal to 75% of survivors. At 1.3 mg/liter Cd, BSO did not change the rate or frequency of planarian tumor production. Continuous BSO always produced high mortality over 20 days. In contrast, a 24-h preexposure to BSO caused little mortality. In these groups, tumor yields increased with cadmium concentration (0.13, 0.25, 0.65 mg/liter), and the large cocarcinogenic effect of A1254 was clearly evident. No tumors developed in animals exposed only to 50 micrograms/beaker of Aroclor 1254 or continuously only to 1 mM BSO.     

Speciation of elements in NIST particulate matter SRMs 1648 and 1650

X-ray absorption fine structure (XAFS) spectra for S, Cl, V, Cr, Mn, Cu, Zn, As, Br, Cd and Pb and Mossbauer spectra for Fe have been obtained for two National Institute of Standards and Technology (NIST) particulate matter (PM) standard reference materials (SRMs): urban PM (SRM 1648) and diesel PM (SRM 1650). The spectral data, complemented by information on elemental concentrations from proton-induced X-ray-emission (PIXE) spectroscopy, were used to interpret the speciation of these elements in these complex materials. It appears that all the metallic elements investigated occur in oxidized forms, principally as sulfates in the diesel PM SRM and as sulfates, oxides, and possibly other forms (e.g. clays?) in the urban PM. A minor fraction of the sulfur and major fractions of the halogens, Cl and Br, occur as organosulfide (thiophene) and organohalide occurrences, respectively, that must be associated with the abundant carbonaceous matter that constitutes the major component of the two PM SRMs. Most of the sulfur, however, occurs as sulfate in the urban PM and as bisulfate in the diesel PM. In addition, elemental oxidation states have been determined directly by the spectroscopic techniques. Such information is often the key parameter in determining the toxicity and solubility of specific elements in PM, both of which are important in understanding the threat that such elements may pose to human health. For the two HAP elements, Cr and As, for which the toxicity depends greatly on oxidation state, the XAFS data showed that both elements are present in both SRMs predominantly in the less toxic oxidation states, Cr(III) and As(V). The potential of the XAFS spectra for use as source apportionment signatures is illustrated by reference to chromium, which exists in these two PM SRMs in very different forms.     

Achieving 0.2% relative expanded uncertainty in ion chromatography analysis using a high-performance methodology

A high-performance (HP) technique that was originally developed for inductively coupled plasma optical emission spectrometry (ICP-OES) has been successfully translated to ion chromatography (IC) to enable analyses with extremely low uncertainty. As an example application of the HP-IC methodology, analyses of several National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) in the SRM 3180 series of anion standard solutions are reported. The relative expanded uncertainty values expressed at 95% confidence for these analyses range from 0.087% to 0.27% and average 0.18%. Strong correlation between analyte and internal standard anion peak heights or peak areas, as well as the use of a unique drift-correction approach, is shown to be important for attaining such low uncertainty.     

Summarizing the effectiveness of supercritical fluid extraction of polycyclic aromatic hydrocarbons from natural matrix environmental samples

A summary of the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from four natural matrix Standard Reference Materials (SRMs) is presented. The work involved the investigation of the effects of extraction fluid [carbon dioxide (CO(2)), chlorodifluoromethane (R22), and 1,1,1,2-tetrafluoroethane (HFC134a)], fluid modifier (dichloromethane and aniline), temperature (60, 150, and 200 °C) and added water on the SFE recoveries of PAHs compared to certified results from Soxhlet extractions. For SRM 1649a (Urban Dust/Organics), R22 yielded excellent recoveries (>90% of certified concentrations) of all PAHs measured, while results for the same SRM using HFC134a as the fluid were typically <80% of the certified concentrations for most of the PAHs measured. For SRM 1941a and 1944, both aquatic sediments with similar physical and chemical compositions, extractions of the wet materials with dichloromethane-modified CO(2) (10%, v/v) yielded quantitative recoveries of all PAHs for SRM 1944 but an obvious trend of lower recoveries for higher molecular weight PAHs (≥228 amu) for SRM 1941a. Results of SFEs of SRM 1650 (Diesel Particulate Matter) showed that this material is the most refractory of the SRMs investigated in this study, with recoveries of indeno[1,2,3-cd]pyrene and benzo[ghi]perylene at <20% of the Soxhlet results.     

Comparison of isotope dilution mass spectrometry methods for the determination of total homocysteine in plasma and serum

Two independent methods have been critically evaluated and applied to the measurement of total homocysteine in serum and plasma: solid-phase anion extraction (SPAE) gas chromatography/mass spectrometry (GC/MS) and protein precipitation liquid chromatography/tandem mass spectrometry (LC/MS/MS). In addition, analysis of samples prepared by SPAE was accomplished by liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS. These methods have been used to determine total homocysteine levels in several existing serum-based Standard Reference Materials (SRMs) from the National Institute of Standards and Technology and in patient plasma samples provided by the Centers for Disease Control and Prevention. The precision of the homocysteine measurements in serum and plasma was critically evaluated, and method comparisons were carried out using Bland-Altman plots and bias analysis. On the basis of the excellent precision and close agreement of the mass spectrometric (MS) methods, the MS-based methods will be used for certification of a serum-based SRM for homocysteine and folates.     

Analysis and characterization of switched reluctance motors: Part II. Flow, thermal, and vibration analyses

This paper presents new approaches for certain mechanical characterizations, such as thermal and vibration analyses, of switched reluctance motors (SRMs). The paper presents, in three parts, the modeling and simulation procedure for three-dimensional (3-D) finite-element analysis (FEA)-based flow analysis, flow-analysis-based thermal analysis, and a realistic vibration analysis. Section I documents a computational fluid dynamics (CFD) flow analysis procedure for the evaluation of the air velocity distribution inside the SRM at any speed. Section II presents a prediction method for steady-state and transient thermal characteristics of an SRM, using 3-D FEA. The convection coefficient at various heat-dissipating surfaces inside SRM, which is not a material property, but a quantity that solely depends on the air velocity at the respective surfaces, is the major parameter to be evaluated for an accurate simulation of heat distribution. The results of CFD analysis are used, for the first time on SRM, for this purpose. Windage loss calculation, one of the other applications of CFD, is introduced. Vibration in electric motors is an inevitable, at the same time undesirable, property that originates from four major sources: mechanical, magnetic, applied loads and, to a smaller extent, the associated electronic devices. Section III presents: 1) a thorough numerical study of vibration analysis in SRMs, using 3-D FEA methodology, covering all the above vibration sources except the electronics; 2) a 3-D modal analysis of SRMs including stator and rotor structures, shaft, end shields, bearings, and housing; 3) an unbalanced rotor dynamics analysis; 4) associated harmonic analysis; and 5) a stress analysis under various loading conditions. The 3-D vibration analyses presented in this paper to examine the vibration in SRM as a whole are new additions to SRM vibration analysis. Section IV concludes the paper. Future work in every section is highlighted.     

Effect of collision energy optimization on the measurement of peptides by selected reaction monitoring (SRM) mass spectrometry

Proteomics experiments based on Selected Reaction Monitoring (SRM, also referred to as Multiple Reaction Monitoring or MRM) are being used to target large numbers of protein candidates in complex mixtures. At present, instrument parameters are often optimized for each peptide, a time and resource intensive process. Large SRM experiments are greatly facilitated by having the ability to predict MS instrument parameters that work well with the broad diversity of peptides they target. For this reason, we investigated the impact of using simple linear equations to predict the collision energy (CE) on peptide signal intensity and compared it with the empirical optimization of the CE for each peptide and transition individually. Using optimized linear equations, the difference between predicted and empirically derived CE values was found to be an average gain of only 7.8% of total peak area. We also found that existing commonly used linear equations fall short of their potential, and should be recalculated for each charge state and when introducing new instrument platforms. We provide a fully automated pipeline for calculating these equations and individually optimizing CE of each transition on SRM instruments from Agilent, Applied Biosystems, Thermo-Scientific and Waters in the open source Skyline software tool ( http://proteome.gs.washington.edu/software/skyline ).