Quantification Of Contamination Research Articles

Disequilibrium melting during crustal anatexis and implications for modeling open magmatic systems

Contamination of ascending mantle-derived magmas by the continental crust was investigated and modeled for a suite of volcanic rocks and entrained crustal xenoliths from the Central Andes using bulk geochemical compositions for mantle-derived and crustal end-members as dictated by traditional approaches. The assumption that the crustal contaminant in these open magmatic systems is a single composition was assessed through in situ analysis of quenched anatectic melt trapped within its crustal xenolith. Our results show for the first time significant chemical and Sr-isotopic disequilibrium between melt and source over submillimeter-length scales in a natural system. Sampled glass is rhyolitic in nature, enriched in large ion lithophile elements (LILE) and depleted in heavy rare earth elements (HREE). Analysis of the melt for its 87Sr/86Sr composition revealed isotopic heterogeneity ranging from 0.7164 to 0.7276. The isotopic disequilibrium between melt and source is understood to reflect the melting of minerals with different Rb/Sr (and therefore 87Sr/86Sr) more quickly than the isotopic composition can diffusively equilibrate between melt and minerals. Our results suggest that the mechanism of crustal anatexis produces contaminating melts which are geochemically heterogeneous both spatially and temporally. Furthermore, time scales of Sr diffusion and anatectic melt segregation promote the preservation of isotopic disequilibrium at the micro (submillimeter) and macro (crustal) scale. This highlights the need for detailed microscopic investigations coupled with petrogenetic modeling in order to develop more robust characterization and quantification of contamination in open magmatic systems.

Agarose-gel electrophoresis for the quality assurance and purity of heparin formulations

The adulteration of raw heparin (Hep) with a synthetic oversulfated chondroitin sulfate (OSCS) not found in nature produced in 2007-2008 a global crisis giving rise to the development of additional, new and specific methods for its quality assurance and purity. In this study, a simple and sensitive agarose-gel electrophoresis method has been developed for the visualization of OSCS in Hep samples along with other natural glycosaminoglycans possibly present as "process-related impurities", in particular dermatan sulfate (DS) and chondroitin sulfate (CS). Agarose-gel electrophoresis under non-conventional conditions is able to separate OSCS from Hep with its two components, the slow-moving and fast-moving species, DS and CS by performing separation for 15 h (overnight) and under high voltage (100 mA, ∼200 V). Densitometric scanning enabled us to calculate a limit of detection of ∼0.5 μg OSCS with a linear behaviour from 0.1 to 5 μg, comparable to CS/DS. Contaminated samples from Hep manufacturers were analyzed and quantitative data were found comparable to previous studies. Due to its capacity to process many samples in a single run and to the equipment commonly available in laboratories, this analytical method would be suitable for the identification and quantification of contamination by other polysaccharides, in particular OSCS and DS, within Hep preparations and formulations.

Spatial distribution and human contamination quantification of trace metals and phosphorus in the sediments of Chaohu Lake, a eutrophic shallow lake, China

Distinguishing and quantifying anthropogenic trace metals and phosphorus accumulated in sediment is important for the protection of our aquatic ecosystems. Here, anthropogenic proportion and potential sources of trace metals and phosphorus in surface sediments of Chaohu Lake were evaluated based on the exhaustive geochemical data. The analysis shows that concentrations of major and trace metals, and phosphorus, displayed significant spatial diversity and almost all elements were over the pre-industrial background value, which should be related to the variations of sediment composition partially. Therefore, conservative element normalization was introduced and calculated enrichment factors (EFs) of the elements were referenced highlighting the human contamination. EFs of the major and trace metals, except Zn, Pb, and Cu, were all nearly 1.0, indicating the detrital origin. The EFs of Zn, Pb, Cu and phosphorus were 1.0-10.4, 1.0-3.8, 1.0-4.9, and 1.0-7.6, respectively, showing moderate to significant contamination. Higher EFs of Zn, Pb and Cu occurred in the mouth areas of Nanfei River and Zhegao River, and they decreased to the lake center in the northwest and northeast lake areas, respectively. We deduced that anthropogenic Zn, Pb, and Cu were mainly from urban and industrial point sources and the non-point sources of atmospheric deposition contributed little to their contamination. The EFs of phosphorus showed similar spatial degradation with that of Zn, Pb, and Cu. Moreover, higher EFs (>1) of phosphorus also occurred in other areas adjacent to the river mouths besides Nanfei River and Zhegao River. This indicated that the non-point agricultural source may also be responsible for the contamination of phosphorus in Chaohu Lake in addition to the urban sewage sources. Anthropogenic phosphorus was mainly concentrated in the speciation of NaOH-P, which had higher potential biological effects than the detrital proportion. Concentrations of Zn, Pb and Cu surpassed the threshold effect concentrations (TEC) of consensus-based sediment quality guidelines of freshwater ecosystems, especially in the contaminated northwest area of Chaohu Lake. This highlighted the contributions of anthropogenic contamination to the elevated potential biological effects of trace metals. Though there had been no obvious human contamination of Cr and Ni in Chaohu Lake, concentrations were all over the TECs, which may be due to higher background levels in the parent materials of soils and bedrocks in Chaohu Lake catchment.

Trace metal contamination quantification on Silicon wafers using ToF‐SIMS: RSF determination from deposited droplet standards

AbstractToF‐SIMS is now widely used in the microelectronic industry for contamination monitoring of silicon wafers, particularly for metallic elements. However, the accuracy of the technique is still questioned considering the discrepancies, sometimes up to a factor of 10, observable in existing Relative Sensitivity Factors (RSF) databases. A new standard preparation method using intentionally contaminated dried droplets is studied here. It is applied for Na, Fe, Zn and Mo on native oxide silicon wafers. Large‐area analysis (macroraster) is used to image the entire droplet residue of typically several mm in diameter overcoming heterogeneity or droplet movement difficulties. General agreement is obtained with existing data in the literature, however, with disparities still ranging around a factor of two are likely due to top surface ionization unsteadiness. Copyright © 2010 John Wiley & Sons, Ltd.

Detection of hazardous pollutants in chrome-tanned leather using locally developed laser-induced breakdown spectrometer

Highly toxic contaminants like Cr, As, and Pb were detected in chrome-tanning process of animal skin to produce leather by applying locally developed laser-induced breakdown spectrometer. An Nd-YAG laser with 1,064nm wavelength was focused on the surface of leather samples (natural and manufactured) to generate a plasma spark and spectrally resolved spectra were used for identification and quantification of contaminants. The leather samples were collected from a tannery located in industrial cities of Riyadh and Jeddah, Saudi Arabia. The study was carried out on fully, half manufactured (wet blue leather), and natural hide (skin). To the best of our knowledge, this is the first attempt where laser-induced breakdown spectroscopy (LIBS) technique has been applied for the analysis of leather before and after tanning process. The maximum concentration of different elements of environmental significance like chromium, lead, arsenic, sulfur, magnesium were 199, 289, 31, 38, and 39ppm, respectively, in one of the manufactured leather samples. The limit of detection (LOD) of our LIBS system for chromium, lead, arsenic, sulfur, and magnesium were 2, 3, 1.5,7, and 3ppm, respectively. The safe permissible limit for tanned leather for highly toxic elements like chromium, lead, and arsenic are 1, 0.5, 0.01ppm, respectively, as prescribed in Environmental Regulation Standards for Saudi Industries set by Royal Commission Jubail, Saudi Arabia. The LIBS technique is superior to other conventional techniques like ICP or atomic absorption that a little or no sample preparation is required, no chemicals are needed, multi-elemental analysis is possible for all kinds of samples (natural and anthropogenic materials), microgram of sample is essential, and LIBS could be applied for remote analysis. It is highly selective and sensitivity higher than ICP, and as no sample and chemicals are required, it is cost effective for multi-sample analysis per unit time as compared with other conventional techniques. The concentration of some toxic elements (Cr, Pb, As) is much higher than the safe permissible limits set by Occupational Safety and Health Administration in USA or Saudi environmental regulatory agencies. Results obtained with our LIBS systems were in close agreement with the results obtained using other standard analytical technique such as the inductively coupled plasma atomic emission spectroscopy.

Self-absorption effects on alpha-induced atmospheric nitrogen fluorescence yield

Nitrogen fluorescence induced by radiation can be used to detect the presence of radioactive contamination in the environment. Contamination quantification from the fluorescence signal requires: the source’s effective alpha spectrum; the specific radiation quantum fluorescence efficiency; optical attenuation length in air of the fluorescence signal; the absolute throughput and quantum efficiency of the optical instrumentation; calibration of the instrumentation; and radiation transport modeling of the “effective” array exposure rate given the alpha particle spectrum. Field testing conducted on optical instrumentation measured the nitrogen fluorescence yield generated by 241Am alpha emissions. Laboratory studies of 241Am via alpha spectrometry determined whether the presence of solids on source surfaces produced sufficient self-absorption to decrease fluorescence. Results from the laboratory studies provided correction to the effective alpha-source activity values in a model of the earlier optical-sensor field measurements, and determined the air fluorescence efficiency of alpha particles generated by the 241Am sources used in the field experiments.

Measuring atmospheric nutrient deposition to inland waters: Evaluation of direct methods

Several methodological problems have been noted in analyses of atmospheric phosphorus (P) and nitrogen (N) deposition to inland waters. These include the quantification of contamination, rates of dry deposition of nutrients on wet and dry surfaces, and short‐range dust contamination. On and around a small lake in an agricultural region, we tested bulk and automated dry‐ and wet‐deposition samplers for the presence of insect and dust contamination and presented procedures to eliminate biases. Local (≤100 m) dust deposition appeared negligible, so land‐based measurements could be extrapolated to water; however, on‐ and near‐shore samplers collected more insect contaminants than off‐shore samplers. Insect contamination was large and most significant for estimates of P deposition, but a method to correct for it is proposed. We found that bulk and automated dryand wet‐deposition samplers yielded similar values when contamination was eliminated. Screens for atmospheric deposition samplers were tested and led to lowered insect contamination and similar deposition rates to samplers without them. Bulk sampling can provide acceptable estimates of atmospheric nutrient deposition if contamination is quantified or excluded. A wet surface does not differ significantly from a dry surface for measurement of dry‐fall of P. Short‐range transport of dust‐borne nutrients may be insignificant. Low‐cost bulk samplers yielded accurate measurements of atmospheric nutrient deposition.

Semi-automated relative quantification of cell culture contamination with mycoplasma by Photoshop-based image analysis on immunofluorescence preparations

Mycoplasma contamination in cell culture is a serious setback for the cell-culturist. The experiments undertaken using contaminated cell cultures are known to yield unreliable or false results due to various morphological, biochemical and genetic effects. Earlier surveys revealed incidences of mycoplasma contamination in cell cultures to range from 15 to 80%. Out of a vast array of methods for detecting mycoplasma in cell culture, the cytological methods directly demonstrate the contaminating organism present in association with the cultured cells. In this investigation, we report the adoption of a cytological immunofluorescence assay (IFA), in an attempt to obtain a semi-automated relative quantification of contamination by employing the user-friendly Photoshop-based image analysis. The study performed on 77 cell cultures randomly collected from various laboratories revealed mycoplasma contamination in 18 cell cultures simultaneously by IFA and Hoechst DNA fluorochrome staining methods. It was observed that the Photoshop-based image analysis on IFA stained slides was very valuable as a sensitive tool in providing quantitative assessment on the extent of contamination both per se and in comparison to cellularity of cell cultures. The technique could be useful in estimating the efficacy of anti-mycoplasma agents during decontaminating measures.

Simultaneous quantification of polar and non-polar volatile organic compounds in water samples by direct aqueous injection-gas chromatography/mass spectrometry

A direct aqueous injection-gas chromatography/mass spectrometry (DAI-GC/MS) method for trace analysis of 24 volatile organic compounds (VOCs) in water samples is presented. The method allows for the simultaneous quantification of benzene, toluene, ethyl benzene, and xylenes (BTEX), methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA), as well as a variety of chlorinated methanes, ethanes, propane, enthenes and benzenes. Applying a liquid film polyethylene glycol or a porous layer open tubular (PLOT) divinylbenzene GC capillary column to separate the water from the VOCs, volumes of 1–10 μL aqueous sample are directly injected into the GC. No enrichment or pretreatment steps are required and sample volumes as low as 100 μL are sufficient for accurate quantification. Method detection limits determined in natural groundwater samples were between 0.07 and 2.8 μg/L and instrument detection limits of <5 pg were achieved for 21 out of the 24 evaluated VOCs. DAI-GC/MS offers both good accuracy and precision (relative standard deviations ≤10%). The versatility of our method is demonstrated for contaminant quantification in drinking water disinfection (advanced oxidation of MTBE) and for VOC concentration measurements in a polluted aquifer. The wide range of detectable compounds and the lack of labor-intensive sample preparation illustrate that the DAI method is robust and easily applicable for the quantification of important organic groundwater contaminants.

Quantification of Contamination Using Quartz Thickness Monitors

Quantification of Contamination Using Quartz Thickness Monitors

Interactions between poly(vinyl chloride) stabilised with epoxidised sunflower oil and food simulants

Commercial sunflower oil was epoxidised and used as organic co-stabiliser for rigid and plasticised poly(vinyl chloride) (PVC) containing Zn and Ca stearates as primary stabilisers and stearic acid as lubricant. For applications in the packaging of foodstuffs, migration testing must be performed. The detection and the quantification of contaminants migrating from the polymer into the food simulants are essential for the safety assessment of food contact plastic packaging materials. For that purpose, two food simulants were used: olive oil and 15% (v/v) aqueous ethanol. These represent fatty and moist food and beverages, respectively. The test conditions were 12 days at 40 °C. Circular samples of rigid PVC and PVC plasticised with dioctyl phthalate were immersed in a known volume of food simulant. A circular sample and 10 ml of food simulant were taken off every day to be analysed. Each sample was wiped and weighed. The rate of variation of the mass was determined as a function of time. The evolution of the peroxide index of olive oil with time was analysed. The specific migrations of the present additives were investigated by using two analytical methods (atomic absorption spectrometry and Fourier transform infrared spectroscopy). The influence of various parameters such as the nature of food simulant, the presence or the absence of the plasticiser, the agitation and time of contact was considered.

Grazing-Angle Fiber-Optic IRRAS for in Situ Cleaning Validation

Grazing-angle Fourier transform infrared reflection−absorption spectrometry (IRRAS) using a fiber-optic accessory has been investigated as a potential in situ technique for the detection and quantification of contamination by active pharmaceutical agents on glass and metal surfaces. Two methods were used for contamination preparation: one based on smearing a known amount of sample, in solution, onto the substrate and the other by spraying the substrate with an aerosol of the analyte in a volatile solvent. Chemometric calibrations using partial least-squares (PLS) regression are presented and evaluated for acetaminophen on aluminum and glass, and ibuprofen on aluminum and stainless steel. The results indicate that surface loadings of 0.05 μg/cm2 is a readily achievable limit of detection for the IRRAS technique.

Application of mid infrared spectroscopy and iPLS for the quantification of contaminants in lubricating oil

The feasibility of using a narrow spectral range in the mid infrared region for a rapid and conclusive determination of contaminants (gasoline, ethylene glycol and water) in lubricating oil was investigated. A graphically-oriented local multivariate calibration modeling procedure called interval partial least-squares (iPLS) was applied to select a spectral range that provides the lowest prediction error, in comparison to the full-spectrum model. The region from 650 to 784 cm −1, attributed to aromatics, was selected for gasoline determination. The region from 918 to 1052 cm −1, for C−O stretching from glycol, was selected for ethylene glycol determination. Finally, the region from 3598 to 3732 cm −1, absorption from hydrogen bonded OH groups, was chosen for water determination. In the determinations, a root mean square error of prediction (RMSEP) of 0.34% for gasoline, 0.037% for ethylene glycol and 0.023% for water, were obtained after interval selection.

Streaming potential and groundwater contamination

Measurements of streaming potential can provide a means for the detection and quantification of contaminants in groundwater prior to remediation. However, laboratory determinations of specific electrolyte properties are required for an adequate analysis of the hydraulic gradient in complex situations. Data obtained for the King River in Tasmania confirm a linear relationship linking streaming potential data and hydraulic gradients. Laboratory samples at low concentration (0.001M KC1) indicate values in the range 20-80 mV/cm of water pressure, while for higher concentrations (0.01M KC1) values are less than 25 mV/cm. Similar ion concentrations are observed in the King River, consistent with field correlations indicating values for streaming potential close to 15 mV/cm. In-situ fluid samples are required for more detailed analysis of local anomalies that may be associated with variations in recharge and migration of contaminants.

Quantification of contaminants to incoherent nuclear resonant scattering

We calculate the contribution of inelastic electronic x-ray scattering to inelastic incoherent nuclear resonant scattering measurements. We discuss the propagation of plane waves in a medium with a strong energy-dependent index of refraction and treat the inelastic electronic scattering in the kinematical approximation. In experimentally relevant situations, the electronic admixture proves negligible. We conclude that inelastic incoherent nuclear resonant scattering provides partial, vibrational densities of states for the resonant nuclei.

Use of spin‐coated TXRF reference samples for ToF‐SIMS metal contaminant quantification on silicon wafers

Among the emerging techniques able to reveal the metals contaminating the wafer surface in the manufacturing processes of microelectronic devices, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is considered very promising. Despite the potentialities of this analytical tool, some of the phenomena that affect the signal intensity are not fully investigated and still hinder the use of the technique. To evaluate the capabilities of ToF-SIMS to detect quantitatively metal traces on silicon wafers, we analyzed contaminated reference samples produced by spin coating. These standards were also characterized by total reflection x-ray fluorescence spectroscopy (TXRF), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The comparison between results obtained by TXRF and ToF-SIMS allowed us to evaluate the metal detection sensitivities and to estimate the detection limits for most of the elements that produce detrimental effects on device yield. We prove that the metals' secondary ion yields are governed by silicon oxide matrix effects and that a linear relationship between the ToF-SIMS signal intensity and the elemental areal density holds for most of the considered elements for changes in the uppermost layer composition ranging over more than three orders of magnitude. Besides, it is shown that although spin-coating is commonly employed to produce reference samples, the lateral distribution and the physical status of the contaminants produced by this technique may seriously affect the results obtained by both ToF-SIMS and TXRF. Copyright © 2000 John Wiley & Sons, Ltd.

Use of spin-coated TXRF reference samples for ToF-SIMS metal contaminant quantification on silicon wafers

Among the emerging techniques able to reveal the metals contaminating the wafer surface in the manufacturing processes of microelectronic devices, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is considered very promising. Despite the potentialities of this analytical tool, some of the phenomena that affect the signal intensity are not fully investigated and still hinder the use of the technique. To evaluate the capabilities of ToF-SIMS to detect quantitatively metal traces on silicon wafers, we analyzed contaminated reference samples produced by spin coating. These standards were also characterized by total reflection x-ray fluorescence spectroscopy (TXRF), x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The comparison between results obtained by TXRF and ToF-SIMS allowed us to evaluate the metal detection sensitivities and to estimate the detection limits for most of the elements that produce detrimental effects on device yield. We prove that the metals' secondary ion yields are governed by silicon oxide matrix effects and that a linear relationship between the ToF-SIMS signal intensity and the elemental areal density holds for most of the considered elements for changes in the uppermost layer composition ranging over more than three orders of magnitude. Besides, it is shown that although spin-coating is commonly employed to produce reference samples, the lateral distribution and the physical status of the contaminants produced by this technique may seriously affect the results obtained by both ToF-SIMS and TXRF.

Hepatocyte horseradish peroxidase uptake is saturable and inhibited by mannose-terminal glycoproteins.

In the liver, horseradish peroxidase (HRP) is thought to be taken up via mannose receptor-mediated endocytosis by non-parenchymal cells (NPC) and via fluid-phase endocytosis by hepatocytes. When we attempted to inhibit NPC uptake of HRP with mannan in the whole perfused rat liver, > 80% of HRP uptake was eliminated. Liver cell fractionation revealed that mannan not only inhibited HRP uptake by NPC (91%) but also by hepatocytes (81%). In isolated hepatocytes, HRP uptake was linear over 60 min and saturable in the range of 0 to 200 mg/l (Vmax = 4.3 ng.mg protein-1.min-1; Km = 8.3 mg/l). Mannan inhibited uptake competitively (Ki = 2.0-2.5 mg/l). At high concentrations of HRP, a nonsaturable component of HRP uptake became evident (k = 2.8 pg.mg protein-1.min-1.mg HRP-1.l-1). Hepatocyte uptake of HRP was inhibited by other glycoproteins and glycopeptides with mannose-terminal groups, as well as by mannan, but not by asialofetuin (ASF) or bovine serum albumin. Hepatocyte uptake of 125I-labeled ASF, which is taken up via the asialoglycoprotein receptor, was saturable and not inhibited by mannan. HRP binding to hepatocytes, determined at 4 degrees C, was also inhibited by mannan. Quantification of contamination of the parenchymal cell fraction by NPC by cell counting and by pronase digestibility suggested our results could not be explained by contamination of hepatocytes by NPC. At concentrations used for most morphological studies (1,000-10,000 mg/l), fluid-phase endocytosis accounts for much of HRP uptake. However, at low concentrations, a saturable low-capacity mechanism is responsible for most HRP uptake by the hepatocyte.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of boron isotopes for identifying contaminants such as fly ash leachate in groundwater

The B isotopic ratio of a fly ash leachate can be very different from the B isotopic ratio of a natural groundwater. Mixtures of leachate and groundwater typically result in nonlinear B isotope mixing curves that enable identification and quantification of leachate contamination in a groundwater at much lower levels than possible using concentration analyses alone. Limits on B isotope use for contaminant quantification will exist for some environments such as landfills with multiple ash types, but B isotopic analysis may often remain the preferred method for qualitative identification. 20 refs., 4 figs., 3 tabs.

Estimating mutagen mass in indeterminate mixtures: Micronuclei in Tradescantia

Short-term biological tests are used to evaluate environmental damage caused by toxic chemicals. Risk or damage to an ecological system exposed to chemicals is assessed using ecological studies or inferences derived from biological-effect data after identification and quantification of contaminants. The compositions of environmental contaminant mixtures are generally indeterminate; there are no direct methods for identifying and comprehensively quantifying all the mutagens, carcinogens, and other types of biologically active chemicals in these mixtures. We present a method for using the induction of micronuclei (MCN) in Tradescantia during the tetrad stage of meiosis to estimate the total quantity of active chemicals. Component identification is not needed. The lognormal distributions of the estimated minimum effective dose (EMED) for 23 compounds tested in solution and 11 tested as vapors (Ma, T. H., Harris, M. M., Anderson, V. A., Ahmed, I., Mohammed, K., Bare, J. L., and Lin, G., 1984, Mutat. Res. 138, 157–167) are used to determine the median-mutagen activity for each exposure route. These activities are 203 mg/liter for aqueous exposures and 14,854 ppm-min for vapor exposures. The method is illustrated using the responses of Tradescantia exposed to a hexachloroethane/zinc chloride aerosol for 30 min at 50 and 100 m. The response at 50 m was equivalent to exposure to a median-active mutagen at 365 ppm for 30 min.