Contaminant Peaks Research Articles

A Study of Contamination in Fire Debris Containers

ABSTRACTA survey was conducted to examine the stock of 1L glass mason jars available for use by investigators in the Office of the Ontario Fire Marshal (OFM) to collect fire debris in order to address concerns regarding possible contamination. Two jars were submitted by each of twenty-three investigators, and a minimum of two jars were submitted from six regional storage facilities, each with a brief storage history. Headspace gas chromatography (GC) was performed on all jar contents to ascertain if any contamination could be detected and, if so, to determine its level, nature and possible origin. The majority of mason jars (i.e. those from eighteen investigators and three regional storage facilities) exhibited no appreciable contamination that would interfere with typical fire debris analysis. Approximately one-third of the jars submitted showed trace level contaminant peaks in the range of C8 to C18. These indications would not be positively identified as known ignitable liquid standards using ASTM guideline 1387–95 and would potentially interfere with the analysis of only trace level accelerants made by this laboratory. These data were evaluated in relation to current OFM storage practices and procedures in order to assist in the development of a revised OFM Standard Operating Procedure for mason jar handling prior to use by the investigator.

High-performance liquid chromatography of Pasteurella haemolytica leukotoxin using anion-exchange perfusion columns

An exotoxin, called leukotoxin (LKT), from Pasteurella haemolytica, which had previously proved difficult to purify, was purified by high-performance liquid chromatography using rigid highly hydrophilic microparticulate anion-exchange columns. These anion-exchange stationary phases were employed to overcome difficulties of the relatively hydrophobic LKT interacting with dextran or styrene-based resins. While a short non-porous DEAE column allowed the partial microscale purification of the leukotoxin at pH 7.0, a high capacity strong anion-exchange column of the perfusion chromatography type permitted the purification of LKT on a much larger scale. The purification of the LKT on the large pore strong anion-exchange perfusion column was best achieved when three consecutive linear gradients at increasing NaCl concentration in 20 m M Tris buffer, pH 8.0, containing 6.0 M urea and 0.25% Tween 20 were used. Under these conditions, a better separation was obtained for the tetrameric and aggregate peaks of LKT from the early eluting contaminant peaks. This separation scheme allowed good recovery of activity and purification of the LKT to near homogeneity.

Magnesium salts and oxide: an XPS overview

XPS measurements have been performed on a series of Mg II salts (NO 3 −, CO 3 2−, SO 4 2−, Cl −, CH 3COO −), hydroxides and oxides, these latter compounds are both commercial and prepared in laboratory. The binding energy (BE) of the anionic partner in Mg II salts compares well in any case with literature data for the same anions in other alkaline and alkaline earth compounds. The BE of Mg II appears to be affected by the electroattractive nature of the parent anion. The Mg II spectra, in the case of MgO samples, are not influenced either by the nature of the oxide precursor salt or by the temperature of the oxide preparation (873 K, 1073 K, 1253 K). The BE of Mg 2p ranges between 49.9 eV and 50.2 eV. Oxygen spectra are regular and show the presence of the surface chemisorbed -OH component even at heating temperatures of 1473 K. The choice, as internal reference, of the hydrocarbon contaminant carbon peak is discussed, specifically, in the case of MgO samples with reference to specific lattice and surface properties of the oxide itself.

Reactive Gas Magnetron Sputtering of Lithium Hydride and Lithium Fluoride Thin Films

We report the preparation and structural characterization of lithium hydride and lithium fluoride thin films. These materials, due to their low absorption in the soft x-ray range, may have a role as spacer layers in multilayer mirrors. Theoretical reflection calculations suggest that an epitaxial crystalline multilayer stack of a nitride and a lithium compound spacer layer could produce respectable reflectance for short soft x-ray wavelengths (λ < 10 nm). Lithium targets were magnetron sputtered in the presence of hydrogen or ammonia to prepare the LiH films and nitrogen trifluoride to prepare the LiF films. The films were deposited on room temperature Si (100) or MgO (100) substrates. A near IR–Visible–UV spectrometer indicated a drop in reflectance at ∼250 nm for a 100-nm-thick LiH film. This corresponds to a 5-eV band gap (characteristic of LiH). UV fluorescence indicated characteristic LiH defect bands at 2.5, 3.5, and 4.4 eV. The UV fluorescence characterization also indicated a possible lithium oxide (Li2O) contamination peak at 3.1 eV in some of our thin films. Film surface morphology, examined by scanning electron microscopy, appeared extremely rough. The roughness size varied with reactive gas pressure and the type of substrate surface. A LiH/MoN multilayer was constructed, but no significant d spacing peak was seen in a low angle CuKαXRD scan. It is believed that the roughness of the LiH film prevented smooth, uniform planar growth of the multilayer stack. Possible reasons of rough growth are briefly discussed.

Influence of climate on pasture infectivity of ovine trichostrongyles in dry pastures.

The pattern of pasture contamination and the influence of some climatic factors on the development of ovine Trichostrongyles have been studied in dry pastures of Castilla-La Mancha (central Spain) during a 3-year period (1986-1988). The main identified genera were Ostertagia and Trichostrongylus, followed by Haemonchus, Cooperia and Nematodirus. Two peaks of pasture contamination were detected: from mid-winter to early-spring and from mid-autumn to early-winter. No significant differences in this pattern were observed during the 3 years except Haemonchus (1986-1988, P < 0.05; 1987-1988, P < 0.001). Seasons differed significantly (spring-autumn, P < 0.05; summer-the rest of the year, P < 0.001). The temperature was negatively correlated with the level of pasture infectivity (except for Trichostrongylus); however, the rainfall was positively correlated with pasture infectivity.

Reactive Gas Magnetron Sputtering of Lithium Hydride and Lithium Fluoride Thin Films

We report the preparation and structural characterization of lithium hydride and lithium fluoride thin films. These materials, due to their low absorption in the soft x-ray range, may have a role as spacer layers in multilayer mirrors. Theoretical reflection calculations suggest that an epitaxial crystalline multilayer stack of a nitride and a lithium compound spacer layer could produce respectable reflectance for short soft x-ray wavelengths (λ < 10 nm). Lithium targets were magnetron sputtered in the presence of hydrogen or ammonia to prepare the LiH films and nitrogen trifluoride to prepare the LiF films. The films were deposited on room temperature Si (100) or MgO (100) substrates. A near IR-Visible-UV spectrometer indicated a drop in reflectance at ~250 nm for a 100-nm-thick LiH film. This corresponds to a 5-eV band gap (characteristic of LiH). UV fluorescence indicated characteristic LiH defect bands at 2.5, 3.5, and 4.4 eV. The UV fluorescence characterization also indicated a possible lithium oxide (Li2O) contamination peak at 3.1 eV in some of our thin films. Film surface morphology, examined by scanning electron microscopy, appeared extremely rough. The roughness size varied with reactive gas pressure and the type of substrate surface. A LiH/MoN multilayer was constructed, but no significant d spacing peak was seen in a low angle CuKα XRD scan. It is believed that the roughness of the LiH film prevented smooth, uniform planar growth of the multilayer stack. Possible reasons of rough growth are briefly discussed.

Characterisation of argon-ion-bombarded and chemically etched Y1Ba2Cu3O7−δ single crystal surfaces

Abstract This XPS surface study shows that it is difficult to “clean” the a-b surfaces of large tetragonal and orthorhombic YBCO single crystals by either chemical etching or argon-ion-bombardment. For both treatments a carbon contamination peak was detected and found to arise from random patches on the large surfaces. However, both chemical etching and low angle ion-bombardment resulted in minimum disruption to the surface atom termination. For the chemically etched surfaces of the YBCO crystals the O 1s emission spectra have been analysed and the origin of the component peak discussed. The pairs of peaks centred at 527.5, 528.2 eV and 527.5, 528.8 eV are considered to be intrinsic to the o- and t-structures. For 45° incidence ion-bombarded surfaces of o- and t-YBCO crystals, both show the O 1s spectrum and the Cu(L 3 VV)-Auger transition to be identical and consequently the surface structures formed are considered to be identical. In fact, these surfaces appear to have Cu 2 BaO 2 formed in the surface region. Valence-band and low energy core level emissions are reported for the chemically etched surfaces of both types of crystals. In the case of the tetragonal crystals the valence-band spectrum is more intense and a significant difference is observed in the shape of the band at ~3 eV compared to that obtained from orthorhombic crystals. After ion-bombardment both spectra were very similar, the valence-bands having a maximum at 3.7 eV, increased intensity relative to the Ba 5p but were almost devoid of fine structure.

Sources of plant sterol contaminants encountered in low level steroid analysis

During development of an analytical method to characterize ligands to new members of the steroid hormone receptor superfamily, a persistant contaminant profile was observed during gas chromatographic analysis of reagent blanks. Mass spectrometric analysis identified three of the contaminant peaks as cholesterol and the plant sterols stigmasterol and sitosterol. Laboratory articles made of natural rubber, i.e. pipette fillers and latex gloves, were found to be the source of these and other compounds in the reagent blank profile.

Characterization of contaminants in EMS-associated L-tryptophan samples by high-performance liquid chromatography.

To identify chemical contaminant(s) associated with eosinophilia-myalgia syndrome (EMS), case and control lots of tryptophan were analyzed by HPLC with both UV and FL detection. Numerous contaminant peaks appeared on the chromatograms and some of them were identified as 5-hydroxytryptophan, indol aldehyde, indol, etc; from the retention time of authentic compounds. Among these, three peaks were significantly associated with case lots. One corresponds to di-tryptophan aminal of aldehyde (peak E). Others are unknown contaminants, UV-5 (FL-7) and UV-28 (FL-36). The structural elucidation and toxicological implication of UV-5 (FL-7) are currently in progress.

Contamination of commercially available quisqualic acid by glutamate-like and aspartate-like substances

Six different batches of the glutamic acid analogue quisqualic acid were analyzed with high-pressure liquid chromatography (HPLC). All batches examined showed contaminant peaks. Different batches had different contaminant peaks and differing amounts of each contaminant. Every batch of quisqualic acid tested demonstrated a contaminant peak which co-eluted with exogenously added glutamic acid. Certain batches possessed a contaminant which co-eluted with aspartic acid. The levels of glutamate-like contamination ranged from 0.08 to 0.60%, and the levels of aspartate-like contamination ranged from undetectable amounts to 0.80%. The amount of combined glutamate- and aspartate-like contamination of each batch of quisqualate correlated very highly with the ability of that batch to interact with non-quisqualate receptors in an autoradiographic binding assay. These non-quisqualate receptors are likely N- methyl- d-aspartate (NMDA) receptors. Thus, when high concentrations of quisqualate are used experimentally, contamination is likely to produce spurious effects at non-quisqualate glutamate receptors. Quisqualate itself may be a more specific agonist than assumed previously.

Assessment of concentration peaks in setting exposure limits for air contaminants at workplaces, with special emphasis on narcotic and irritative gases and vapors.

In various countries, concentration peaks of gaseous air contamination are assessed by a standard formula. Toxicologic data are not sufficient to warrant occupational short-term exposure limits for the majority of substances. In this article the literature on exposure to concentration peaks is reviewed, and the problem is analyzed from general toxicokinetic and physicochemical points of view. Several ways are suggested to achieve better standards. One straightforward and reasonably simple method is summarized in the following three points, which should be considered in the setting of occupational exposure limits: (i) For substances with fast or moderately fast action, only ceiling limits should be considered; (ii) when structure analogy is justified for narcotic and irritating gases, the correct way is to set the limits at the same thermodynamic activity (relative saturation) of the substances in question and not at the same concentration; (iii) for substances absorbed and eliminated slowly time-weighted exposure limits, combined with rules for excursions, or short-term exposure limits derived from such rules are appropriate, but the possible accumulation of large absolute quantities of the substances should be considered. This point is particularly important when the critical effect is narcosis or irritation, as the thermodynamic equipotency means that the effective concentration of water-soluble gases and vapors is higher than that of substances with low water solubility.

Liquid chromatographic determination of cyclosporin a in serum with use of a solid-phase extraction: Comparison between high-performance liquid chromatography and radioimmunoassay levels in clinical investigations

A simple reliable liquid chromatographic method for assay of cyclosporin A in serum or urine is described. Samples were cleaned up on a solid-phase extraction system (cyanopropyl column). The system involve a reversed-phase C 18 Ultrasphere column maintained at 72°C and an acetonitrile linear gradient (65 to 95%) in 0.14% triethylammonium phosphate. Liquid chromatographic analysis of radioimmunoassay standards shows that some samples contain a contaminant peak. Comparison of cyclosporin A levels obtained by radioimmunoassay and high-performance liquid chromatography in clinical investigations show that the former values are generally, but not always, higher than the latter, and that cyclosporin A is very differently metabolized depending on the patient, disease and treatment.

A quantitative measure of the reliability of searches of spectral libraries

A quantitative measure of library search reliability has been developed. Applications of the quantitative reliability metric (QRM) for evaluating the reliability of library searches for unknown target spectra and the use of this measure to detect the failure of a library search caused by noise, contaminant peaks and missing library spectra are discussed. The effects of noise and composite infrared spectra of mixtures on the QRM are examined for test sets of 561 infrared spectra. The QRM is also used to evaluate the performance of a search of an infrared library compressed by eigenvector projection.

31P-NMR Monitoring of Ethephon Decomposition in Olive Leaves

Abstract The possibility of using 31P-nuclear magnetic resonance (NMR) spectroscopy to detect ethephon (ET) in olive leaves has been examined. 31P-NMR spectroscopy can be used as a nondestructive technique (tissues excised but not extracted) with the unique attributes of monitoring ET hydrolysis internally and without radiochemicals. A characteristic spectral peak for the parent ET molecule was found 17-21 ppm (a measure of relative frequency, not concentration) downfield from the H3PO4 reference, and a nonreactive, minor contaminant spectral peak was found at 26-27 ppm. Absolute spectral peak location (“chemical shift”) is pH-dependent. The ET hydrolysis product, orthophosphate, produces a spectral peak at 2 to 3 ppm, which coincides with the broad spectral peak attributed to major endogenous phosphate compounds in leaves, such as inorganic phosphate. The lower limit of 31P-NMR detection of ET in solution was 10−3 m; however, spray applications of ET were not detectable in olive leaves unless concentrations of 5 × 10−2 m or more were used, which is far greater than current agricultural use levels for mechanical harvest of olive. Nevertheless, 31P-NMR spectroscopy was useful in following ET uptake and decomposition for more than 48 hr in olive leaves from xylem-fed shoots, and the resolution of the ET spectral peak into separate, adjoining peaks presents the potential to identify and quantify subcellular compartmentalization of ET according to pH-induced chemical shifts. Such knowledge would contribute to understanding long- and short-term in vivo decomposition of ET to ethylene. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).

A new measurement of the 429 keV 15N(p, αλ) 12C resonance. Applications of the very narrow width found to 15N and 1H depth location : II. Applications

The unexpectedly narrow width Γ p = 120 eV or Γ N 15 = 1.8 keV of this resonance opens quite new possibilities for its use in 15N or 1H depth location and for hydrogen adsorption studies using 15N beams. Resonance depth profiling of 15N is possible with much better near-surface depth resolution than thought until recently. In 1H resonance depth profiling the indeep background originating from the surface contamination peak is also much smaller than previously assumed. These features are illustrated by 15N self-diffusion experiments in NbN films and by 15N adsorption experiments on copper single crystals in ultrahigh vacuum. The strong effect of Doppler broadening on the actual ultimate near-surface depth resolution of hydrogen depth profiling with 15N beams is discussed as well as the use of this resonance for the direct measurement, based on the Doppler effect, of the vibration speed distribution of hydrogen atoms adsorbed on clean surfaces.

High-performance liquid chromatography of glucagon and related compounds

Glycerolpropylsilane bonded phases have been found to adsorb peptides and proteins via ionic interactions. In this paper high-performance liquid chromatography separation of glucagon and related compounds, using a Diol-silica matrix, is described. Crystalline, commercial preparations of glucagon, when analyzed on LiChrosorb Diol columns eluted with low-ionic-strength acidic buffers, contained up to four contaminant peaks, in different numbers and ratios. Three of these contaminants, called A, C, and D, were recovered and characterized. Contaminant A, representing a few percent of the total, was a mixture of mono- and didesamidoglucagon, as shown by treatment with bis(I,I-trifluoroacetoxy)iodobenzene, with which it is possible to differentiate between carboxamide and carboxylic acid residues. Contaminant C, ranging from 0 to about 30% of the total, was N-terminal degraded glucagon. Contaminant D, ranging from a few percent to about 25% of the total, was (Met 27 sulfoxide) glucagon.

Decay ofV50

A. 4.25-kg sample of vanadium metal was counted with a high purity Ge detector for 135.5 d. Ninety-six peaks were observed in the $\ensuremath{\gamma}$-ray spectrum between 220 and 2615 keV, all but one of which could be assigned to known contaminant radioactivities mostly contained in the V sample itself. After making a 4.0% calculated correction for the intensity of a $^{234}\mathrm{Pa}^{m} \ensuremath{\gamma}$ ray of 1554.1(5) keV, the unassigned peak had an energy of 1553.77(6) keV and contained 1020(70) counts. This energy agrees with a recent precision determination of 1553.768(8) keV for the $\ensuremath{\gamma}$ ray from the first excited state of $^{50}\mathrm{Ti}$ following the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{50}\mathrm{Sc}$. The 1554-keV $\ensuremath{\gamma}$ ray from the V sample is assigned to the electron capture decay of $^{50}\mathrm{V}$ to $^{50}\mathrm{Ti}$. Based on an absolute $\ensuremath{\gamma}$-ray efficiency calibration of the system, a partial half-life ${T}_{\frac{1}{2}}=1.5(3)\ifmmode\times\else\texttimes\fi{}{10}^{17}$ yr and $log{f}_{0}t=23.4(1)$ were derived for the $^{50}\mathrm{V}$ e.c. branch. The expected 783.3-keV $\ensuremath{\gamma}$ ray, which would follow the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{50}\mathrm{V}$ to $^{50}\mathrm{Cr}$, was in an unresolved region of contaminant peaks allowing only an upper limit of 560 counts to be placed on its intensity. This corresponds to ${T}_{\frac{1}{2}}4.3\ifmmode\times\else\texttimes\fi{}{10}^{17}$ yr and $log{f}_{0}t24.0$ for the ${\ensuremath{\beta}}^{\ensuremath{-}}$ branch. The total half-life derived for $^{50}\mathrm{V}$ is ${T}_{\frac{1}{2}}={1.5}_{\ensuremath{-}0.7}^{+0.3}\ifmmode\times\else\texttimes\fi{}{10}^{17}$ yr.

Studies on the mode of bacterial contamination of an operating theatre corridor floor

Bacterial contamination of the floor of a corridor leading into an operating theatre suite was studied in relation to the site chosen for changing footwear. Recovery of bacteria showed a peak at the site of exchange of footwear, and decreased with increasing distance from the site. When the site of exchange was moved further away from the clean area, the peak of contamination moved to the new site and bacterial contamination decreased in the clean area. These results indicate that exchange of footwear should occur as far from the operating theatre as possible.

Improved gas-liquid chromatographic method for the determination of protein amino acids

The gas-liquid chromatographic method previously reported by us was improved with regard to the gas chromatographic columns and their operating conditions. It became possible to perform more accurate quantification of the 22 protein amino acids, including asparagine and glutamine, in less than 25 min on a dual set of columns. At the same time, the method allowed determination of the amino acids in the range 0.5-10 μg of each by eliminating the contaminant peaks derived from solvents and reaction vials. A single sample could be analysed in an overall time of 1 h.

Phthalic ester, an artifactual contaminant in diazomethane prepared from N‐methyl‐N‐nitroso‐p‐toluenesulfonamide for the derivatization of prostaglandins

AbstractDuring analyses of prostaglandin (PG) methoxime methyl trimethylsilyl (MO‐ME‐TMS) ether derivatives by gas chromatography, we consistently observed a contaminant peak which we identified as di‐2‐ethylhexyl phthalate (DEHP). The diazomethane prepared from N‐methyl‐N‐nitroso‐p‐toluenesulfonamide (MNTSA) using the Diazald kit was the major source of DEHP. Several other materials also were significant sources. The concentrations of DEHP in these materials were quantified by gas chromatography‐mass spectrometry.