Roger Sperline - Academia.edu (original) (raw)

Papers by Roger Sperline

The surface of the moon is continuously exposed to solar wind ions impacting at velocities varyin... more The surface of the moon is continuously exposed to solar wind ions impacting at velocities varying between 300 and 700 km/s. Silicate minerals on the lunar surface therefore undergo ion-sputtering and ion-implantation at relatively low energies. As a result, very volatile elements such as H, He, C, N, and noble gases, that are extremely depleted on the moon, are found in grains of lunar soils which have been directly exposed to the solar wind. Nuth et al. (1992) suggested that solar wind implantation of hydrogen on the lunar surface could lead to a measurable spectral IR feature between 4.4 and 4.7 mm in both laboratory and telescopic spectra of lunar regolith due to -SiH functional groups. If true, this could lead to an innovative and powerful tool for remote sensing studies of the moon and asteroids for determining volatile implantation and regolith maturity. To test the hypothesis of Nuth et al. we measured the IR spectrum of six lunar soils, without finding any evidence of a feature in the region of interest.

Applied Spectroscopy, 2000

The distortion of band shapes seen in infrared attenuated total reection (IR-ATR) spectro scopy o... more The distortion of band shapes seen in infrared attenuated total reection (IR-ATR) spectro scopy of strongly absorbing m aterials such as water, relative to transmission sampling, is shown here to be due to the anomalous dispersion (AD) of water. This distortion occurs in addition to the normal 1/n dependence, and, contrary to previous rep orts, is shown to not be due to chemical changes of water at the interface between the optical element and bulk solution. IR-ATR spectra of water were modeled with approximation-free calculations. The m odeled spectra are com pared with experimental ATR spectra for different internal re¯ection elements, and the resu lts are discussed in term s of the AD optical effect.

Inorganic Chemistry, 1978

... Chem. Sot., 98, 4455 (1976). (4) JD Miller and FD Oliver, J. Chem. Soc., Dalton Trans., 2473 ... more ... Chem. Sot., 98, 4455 (1976). (4) JD Miller and FD Oliver, J. Chem. Soc., Dalton Trans., 2473 (1972). (5) L. Vaska, L. S. Chen, and WV Miller, J . Am. Chem. Soc., 93, 6671 (1971). ... Chem. Soc., 92, 61 (1970). (15) DH Huchital and AE Martell, Inorg. Chem., 13, 2966 (1974). ...

Journal of Analytical …, 2004

J. Anal. At. Spectrom., 2004, 19, 751-756 DOI:10.1039/B311353A (Paper). Coupling of a gas chromat... more J. Anal. At. Spectrom., 2004, 19, 751-756 DOI:10.1039/B311353A (Paper). Coupling of a gas chromatograph to a simultaneous-detection inductively coupled plasma mass spectrograph for speciation of organohalide and organometallic compounds. ...

Inorganic Chemistry, 1977

Applied Spectroscopy, 1992

FT-IR attenuated total reflection (ATR) spectroscopy was applied to quantitatively determine the ... more FT-IR attenuated total reflection (ATR) spectroscopy was applied to quantitatively determine the extent of bovine serum albumin adsorbed onto a biomedical-grade poly(ether)urethane film deposited on a ZnSe internal reflection element (IRE). The method of adsorption density determination was based on the optical principles for a stratified medium consisting of three layers. The spectral peak area due to bulk solution was less than 1% of total peak area. The measured adsorption density of albumin in a flowing system was 3.9 t~g/cm 2 at a solution concentration of 4.5 g/100 mL.

Solvent Extraction and Ion Exchange, 1992

Colloids and Surfaces A-physicochemical and Engineering Aspects, 1994

An attenuated total reflection (ATR) Fourier transform infrared radiation (FTIR) technique has be... more An attenuated total reflection (ATR) Fourier transform infrared radiation (FTIR) technique has been explored for the in situ quantitative analysis of bovine serum albumin (BSA) adsorption from aqueous solutions onto a segmented poly(ether)urethane film deposited on a ZnSe internal reflection element (IRE) and onto a bare ZnSe IRE surface. The IR spectral area of the amide II band was used for the quantitative analysis of adsorption. BSA adsorption reached equilibrium within 30 min and changed linearly with solution concentration in the range 0.5–6 wt.% and was found to be dependent on the solution pH and substrate type. At the physiological concentration, BSA adsorption densities of 2.4 mg cm−2 and 3.9 μg cm−2 were obtained for ZnSe and polyurethane respectively. The adsorption density was higher at pH 7 than that at pH 3 or 11, and both α-helix and β-sheet structures were present in the adsorbed layer. BSA adsorbed onto these solids appears to adopt an extended conformation and the long axis of the molecule appears to lie in the plane of the interface. Adsorption density was higher on the more hydrophobic polyurethane surface than on the relatively less hydrophobic ZnSe crystal surface.

Journal of Analytical Atomic Spectrometry, 2010

ABSTRACT Isotope-ratio measurements are necessary in a wide range of applications. The precision ... more ABSTRACT Isotope-ratio measurements are necessary in a wide range of applications. The precision of these measurements is of utmost importance because it governs the ability to distinguish differences between samples. Often, simultaneous isotope detection is necessary to reach the precision values needed for an analysis to be conclusive. Furthermore, the more isotope ratios that can be precisely determined at once, the better the chances of distinguishing between samples. Therefore, detector arrays, able to simultaneously monitor a broad range of isotopes, are attractive. Such an array detector, termed the focal plane camera (FPC), has been shown to be capable of achieving impressive precision values (0.02% RSD) within relatively short integration times (200 s). However, because the channels of the FPC array detector are inherently discrete, optimization of peak integration methods is important. This paper compares isotope-ratio precision values based on different peak integration methods of raw and zero-filled interpolated data. Also, problems associated with peak drift are explored and the use of flat-topped peak shapes for improved isotope-ratio precision levels are investigated.

Analytical and …, 2004

The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma ... more The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP–MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP–MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity.

Intl. J. Ion Mobility …, 2002

Analytical …, 2007

In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are d... more In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously and continuously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry.

Analytical …, 2002

A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to... more A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) with an inductively coupled plasma ionization source. The FPC employs an array of gold Faraday cups, each with its own charge-integrating circuit that allows the simultaneous detection of several m/z ratios. The ion-sampling interface of the MHMS has been redesigned to provide better heat transfer away from the sampler and skimmer cones and to reduce the negative effects of turbulent gas flows around the plasma. The instrument has produced limits of detection in the tens to hundreds of parts per quadrillion regime and isotope ratio accuracy and precision of 5% error and 0.007% RSD, respectively. Limits of detection with the FPC are comparable to those obtained with a single-channel secondary electron multiplier (SEM). However, the isotope ratio accuracy and precision are better with the FPC than when the SEM is employed. The dynamic range has been shown to be linear over 7 orders of magnitude.

International Journal of Mass Spectrometry, 2001

A micro-Faraday array detector was evaluated for use as an ion detector for mass spectrometry. Th... more A micro-Faraday array detector was evaluated for use as an ion detector for mass spectrometry. This charge-integrating detector was based upon the merging of technologies from the fields of CCDs and infrared (IR) multiplexers. Measurements were performed by exposing the detector to an Ar+ ion beam of low flux. The array detector responds to both positive and negative charges and preliminary results indicate a detection limit of 100 ions. Current data indicate that the linear dynamic range of the device is over five orders of magnitude. The capability of the device to perform specialized charge read out modes could theoretically both lower the detection limit by a factor of seven and increase the linear dynamic range to nine orders of magnitude using non-destructive read outs.

Analytical …, 2004