Reactions of polyethylene surfaces with the downstream products of an air plasma: Gas phase and surface spectroscopic studies

The gas phase downstream products of an air glow discharge have been measured, using absorption and emission spectroscopies, as a function of plasma power, air flow rate, and distance from the plasma. In addition, the reaction of these products with a linear low density polyethylene (LLDPE) polymer surface has been followed using x-ray photoelectron spectroscopy (XPS). At higher air flow rates (>300 sccm), the primary reactive species is confirmed to be O(³P) atomic oxygen. Some O(³P) is generated in the plasma itself, but more appears to be formed in the downstream region, because of dissociation of molecules in their excited states. At low flow rates, the concentration of O(³P) is strongly depleted at the sample position, but other atomic oxygen states become more prominent. O(⁵S) and O(³S) are two states which are identified. XPS studies of the polyethylene surface reacted at high flow rates shows oxygen functionalities that are likely the result of an initiation by hydrogen abstraction. At low flow rates, the products suggest initiation by oxygen insertion. Thus, changes in flow rate can result in major changes to the polymer surface chemistry. © 1996 John Wiley & Sons, Inc.     

An Atomic Absorption Analysis Method for Cyanide

Abstract

An atomic absorption analysis procedure for cyanide has been developed. The procedure is based upon the solubilization of copper(II) from a basic copper carbonate in an alkaline medium. The amount of copper complexed by the cyanide ion is determined by atomic absorption and a calibration curve is constructed concurrently. The stoichiometry of the cyanide-copper complex is 3:1, implying formation of the complex ion Cu(CN)^? ₃, with no formation of CuCN observed at the low concentration of cyanide used. The method is used primarily for analyzing low levels of cyanide; the sensitivity of the method extending down to 2.0 × 10^?5 M CN^?. The most likely interference, iron, is considered. Finally, recovery of cyanide from spiked samples is demonstrated.     

Atmospheric Pressure Plasma Deposition of Polyfuran

The atmospheric pressure radiofrequency (RF) plasma polymerization of furan was carried out with the objective of synthesizing polyfuran thin film. The structure, compositions and morphology of the plasma deposited polyfuran film were investigated by Fourier transform infrared (FTIR), atomic force microscopy (AFM), ultraviolet‐visible absorption spectroscopy (UV‐vis) and thermogravimetric analysis (TGA). The formation of polyfuran was confirmed using FTIR and UV‐visible analysis. The properties of plasma‐deposited polyfuran were compared with those of chemically synthesized polyfuran. Although the plasma deposited thin film polyfuran shows lower thermal stability than that of chemically synthesized polyfuran. It has better solubility in CHCl₃, also. Thin uniform polyfuran films are obtained in plasma assisted polyfuran deposition, while particles are obtained in chemical polyfuran polymerization.     

Dosage DU Mercure Par Spectroscopy D' Absorption Atomique Sans Flamme

Abstract

A method has been developed whereby low levels of mercury can be determined in biological samples. The sample is burned in an air stream and the mercury vapors are collected in a cold trap and determined by flameless atomic absorption spectroscopy.     

Characterization of an argon-hydrogen microwave discharge used as an atomic hydrogen source. Effect of hydrogen dilution on the atomic hydrogen production

This work is devoted to the study of an argon-hydrogen microwave plasma used as an atomic hydrogen source. Our attention has focused on the effect of the hydrogen dilution in argon on atomic hydrogen production. Diagnostics are performed either in the discharge or in the post-discharge using emission spectroscopy (actinometry) and mass spectrometry. The agreement between actinometry and mass spectrometry diagnostics proves that actinometry on the Ha(656.3 nm) and Hβ(486.1 nm) hydrogen Balmer lines can be used to measure the relative atomic hydrogen density within the microwave discharge. Results show that the atomic hydrogen density is maximum for a gas mixture corresponding to the partial pressure ratioP _{H 2}/P _Ar range between 1.5 and 2. The variation of atomic hydrogen density can be explained by a change of the dominant reactive mechanisms. At a low hydrogen partial pressure the dominant processes are the charge transfers with recombinations between Ar⁺ and H₂ which lead to ArH⁺ and H ₂ ⁺ ion formation. Both ions are dissociated in dissociative electron attachment processes. At a low argon partial pressure the electron temperature and the electron density decrease with increasing partial pressure ratio. The dominant mechanisms become direct reactions between charged particles (e, H⁺, H ₂ ⁺ , and H ₃ ⁺ ) or excited species H(n=2) with H₂ producing H atoms.     

Cadmium Determination in Soil Extracts by Furnace Atomic Absorption

Abstract

A method for the direct determination of Cd in soil extracts by graphite furnace atomic absorption spectrosopy (GFAAS) has been developed. Optimum operating conditions, analyte modifiers and matrix interferences have been investigated. Characteristic amounts are 0.34pg for siliceous samples and 0.45 pg for calcareous soils. The precision has been based on ten replicate readings in standards, and was 1.6%. Cd has been determined by the proposed methods and the results have been compared with those obtained by ICP technique.     

Determination of Trace Amounts of Cobalt in Blood

Abstract

The analysis of cobalt in whole blood and blood fractions has been carried out using three different analytical techniques namely, electrothermal atomic absorption spectrometry, inductively coupled plasma mass spectrometry and cathodic stripping voltammetry. This study showed that inductively coupled plasma mass spectrometry was the better equipped technique for conducting such analyses due to its low detection limits and wide linear dynamic range. The results ranged between 0.7 - 2.62 μg/l for plasma, 1.02 - 2.31 μg/l for serum, and 0.66 - 1.28 μg/l for whole blood. The introduction of different forms of cobalt to Wistar rats resulted in a differing distribution of the element between serum and whole blood. This observation suggests that there are at least two modes of Co uptake and transport depending on the administered or taken chemical form.     

The Determination of Silicon in low Alloy Steels by Atomic Fluorescence Spectroscopy in A Separated Nitrous Oxide-Acetylene Flame

Abstract

An atomic fluorescence spectroscopic method is described for the assay of silicon in low alloy steels. The method reported is more sensitive than the corresponding atomic absorption method, the detection limit being 0.7 ppm at 351.6 nm compared to 4 ppm for atomic absorption at the same wavelength.     

Analysis of Borosilicate Catalysts by Inductively Coupled Plasma Atomic Emission Spectroscopy

Abstract

A method was developed for the analysis of borosilicate catalysts. Samples were prepared by fusion technique with potassium hydroxide and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The method was applied to a borosilicate NIST SRM 93 which was analyzed for major and minor elements (aluminum, sodium, silicon and boron). Despite the presence of relatively high concentration of the potassium, no matrix interferences were observed. This method provides precision and accuracy better than ±4% and ±6%, respectively.     

Cadmium Determination in Sedimented Dust by Atomic Emission Spectrometry With a New Radiofrequency Capacitively Coupled Plasma Source

ABSTRACT

A new radiofrequency capacitively coupled plasma source (r.f.CCP) was used for Cd determination in dust samples by atomic emission spectrometry. The plasma torch consists of a molybdenum tube electrode and one or two ring electrodes situated outside the quartz tube. Plasma was operated at 27.12 MHz, at low power (275 W) and low gas consumption (0.4 1 min^? argon flow). The choice of the optimum operating conditions for Cd determination in dust samples dissolved in acids and pneumatically nebulized is presented. The results obtained in such samples were compared with those obtained by flame atomic absorption spectrometry (FAAS). The matrix effect of NaCl and CaCl₂ on Cd emission was also studied depending of the plasma coupling system. The true limit of detection for Cd in dust sample by r.f.CCP-AES is 3 μg g^?1. Concentration of Cd higher than 10 μg g^?1 can be determined by the proposed method with a relative standard deviation within the range 5 - 10%. The recovery is 100 ± 10%.     

Developed Method for Spectroscopic Studies of Viscous Samples

Abstract

In this work, the trace elements in phosphoric acid, which has been considered an example of the proposed viscous sample, were measured accurately by a developed method. Samples were diluted to decrease matrix and background interferences. Quantitative analysis of As, Ca, Cd, Cu, Fe, Hg, K, Mg, Na, Pb, and Zn were carried out using flame atomic absorption spectrometry (FAAS). A comparison with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) proves the validity of the developed method. The change of the electronic transition due to diluted of the viscous samples was demonstrated using UV-VIS spectroscopy.     

Microanalysis For Platinum and Magnesium in Body Fluids and Brain Tissue of Mice Treated with Cis-Platinum Using Graphite Filament Plasma Emission Spectroscopy

Abstract

A method has been developed for the microanalysis of platinum (0.1-500 mg/L) and magnesium (20-40 mg/L) in body fluids and brain tissue using a novel graphite filament plasma (GFP) emission source. Twenty five microliter samples of brain tissue homogenates and body fluids were analyzed without the usual preinstrumental digestion. Calibration standards were prepared in the same matrix as the samples because of the need for matrix matching. The body fluid samples were from mice which received therapeutic doses of the anticancer agent cis-diamminedichloro-platinum(II) (DDP). Platinum levels in urine were initially quite high (400-500 mg/L) due to the bolus method of administration, but lowered substantially within hours. Biphasic elimination of platinum from plasma was observed with half lives of 14 minutes and 32 hours. The equilibration of platinum between the plasma and the erthrocytes was between one and two hours. Hypermagnesia was observed in urine, plasma and whole blood during the twenty-two hour period following DDP injection. In brain tissue of mice given therapeutic doses of DDP singly or in combination with the polar solvent, maturational agent, N-methylformamide (NMF), the platinum levels were at or below the present detection limits of the instrument (0.1 mg/kg fresh tissue).     

Continuous Hydride Generation with Direct Current Plasma Emission Spectroscopic Detection for Total Arsenic Determinations (HY-DCP)

Abstract

Total arsenic determinations in complex food matrices can be performed with a high degree of accuracy and precision using an initial hydride formation step followed by direct current plasma (DCP) emission spectroscopic detection¹. The hyphenated technique, HY-DCP, uses a continuous flow hydride formation step with dual mixing of the hydride forming reagents, followed by on-line, continuous introduction of the aqueous arsenic sample. The final aqueous solution of arsine, excess sodium borohydride, and sample components, is directly introduced into the conventional spray chamber of the DCP instrument. Calibration plots for both arsenate and arsenite have been determined, together with linearities and minimum detection limits (MDLs) The overall methods for total arsenic determination have been applied to spiked water and tunafish samples. Accuracy and precision determinations have been performed for these total arsenic analyses, and compared with continuous hydride formation-flame atomic absorption (FAA) detection, as well as sequential hydride formation-FAA methods. All of these results are then compared, with the individual advantages and disadvantages o f each approach summarized.     

A New Highly Sensitive Preconcentrating Sampling Technique for Flameless Atomatic Absorption Spectroscopy

Abstract

A new technique for sampling metal ions in solution for flameless atomic absorption has been developed. A tungsten alloy wire loop is soaked in the sample solution for a specified period of time. Metal ions are concentrated on the surface of the wire loop apparently by an ion exchange mechanism. The wire loop is then used as an electrically heated atomizer for atomic absorption spectroscopy. Detection limits of 4 × 10^?14 grams for cadmium and 2 × 10^?11 grams for lead have been achieved.     

Cavity Ring-Down Spectroscopy coupled with helium microwave-induced plasma for fluorine detection

Cavity Ring-Down Spectroscopy with a tunable diode laser has been used for the detection of fluorine at trace levels. A homemade experimental setup was constructed to accommodate the microwave-induced plasma glow discharge inside the optical cavity. The energy delivered by helium plasma discharge was successfully used not only for the dissociation of fluorine molecules but, more importantly, also for the excitation of fluorine atoms into their metastable level 3s⁴P_5/2. The absorption observed at the 3s⁴P_5/2–3p⁴D^o_7/2 transition (corresponding to a 685.603-nm atomic line) was used for fluorine atom detection. Good agreement between theoretical and measured absorption line shapes confirmed the selectivity of fluorine atomic absorption. We observed an absorption coefficient of 4 ? 10⁻⁶ cm⁻¹, corresponding to a detection of F(3s⁴P_5/2) atoms at about 1.5 ? 10⁶ atoms cm⁻³. These data demonstrate that we achieved a detection limit of 100 ng g⁻¹ under the conditions of our initial homemade experimental setup. However, the optimization of the system may lead to the improvement of the detection limit by approximately two orders of magnitude.     

INDIRECT ATOMIC ABSORPTION SPECTROMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

Abstract

An indirect atomic absorption spectrometric method for arsenic has been developed on the basis of heteropoly chemistry. Molybdoarsenic acid is formed, extracted and stripped by a basic buffer solution. The resulting molybdate, which is equivalent to a specific amount of arsenic, is determined by atomic absorption spectrometry.     

Indirect Determination of Vanadium by Atomic Absorption Spectrometry

Abstract

An indirect atomic absorption spectrometric method for vanadium has been developed on the basis of heteropoly chemistry. Molybdovanadophosphoric acid is formed, extracted and stripped by a basic buffer solution. The resulting molybdate, which is equivalent to a specific amount of vanadium, is determined by atomic absorption spectrometry.     

Drag on an ellipsoid particle in free-molecular plasma flow

Based on the analysis of molecular gas dynamics, the drag and moment acting on an ellipsoid particle of revolutionX ²/a ²+Y ²/a ²+Z ²/c ²=1, as an example of nonspherical particles, are studied under the condition of free-molecular plasma flow with thin plasma sheaths. A nonzero moment which causes nonspherical particle self-oscillation and self-rotation around its own axis in the plasma flow—similar to the pitching moment in aerodynamics—is discovered for the first time. When the ratio of axis lengthc/a is unity, the moment is zero and the drag formula are reduced to the well-known results of spherical particles. The effects of the particle-plasma relative velocity, the plasma temperature, and the particle materials on the drag and moment are also investigated.     

Temporally resolved laser diagnostic measurements of atomic hydrogen concentrations in RF plasma discharges

Ground-state atomic hydrogen produced in radio-frequency plasma discharges (20 KHz-5 MHz) has been detectedin situ using two-photon absorption laser-induced fluorescence (TALIF). Atomic ground-state concentration measurements have demonstrated excellent spatial resolution in the interelectrode gap of a planar discharge configuration with 10 nsec temporal resolution at all phases of the RF driving voltage waveform. Concentrations were measured in gas mixtures of helium and hydrogen down to 2×10¹³ H atoms/cm³.     

INDIRECT DETERMINATION OF MERCURY BY ATOMIC ABSORPTION SPECTROPHOTOMETRY USING ZINC HOLLOW CATHODE LAMP

Abstract

An indirect atomic absorption spectrophotometric method for mercury has been developed on the basis of solvent extraction chemistry. Mercury(II) was converted into a bromo-complex anion and extracted into 1,2-dichloroethane with the 2,2′-bipyridyl-zinc chelate cation. The resulting zinc in the extract, which was equivalent to a specific amount of mercury, was determined by atomic absorption spectrophotometry. The sensitivity for the determination of mercury could be enhanced to the level of zinc by the proposed method.