The Experts below are selected from a list of 7746 Experts worldwide ranked by ideXlab platform

Bonner M Denton - One of the best experts on this subject based on the ideXlab platform.

  • high precision simultaneous analysis of pt pd and rh in catalytic converter samples by carius tube dissolution and inductively coupled plasma atomic emission spectroscopy with Charge Injection Device detection
    Applied Spectroscopy, 2001
    Co-Authors: Frank M Pennebaker, Bonner M Denton
    Abstract:

    A robust method of analysis that uses multichannel array detector technology is presented for high-precision, accurate measurement of Pt, Pd and Rh in catalytic converters. Catalytic converter samples, National Institute of Standards and Technology (NIST) reference standards, and a fresh converter sample are dissolved and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Complete dissolution of sample sizes up to 2 g of NIST reference standards is achieved with the use of high-pressure, high-temperature carius tubes. Carius tube dissolution of a modern catalytic converter sample is found to be incomplete because of the presence of higher concentrations of Ce, Ni, and Zr. For this sample, the addition of FeCl3 increases the dissolving power of the carius tube for base metals and noble metals, particularly Rh. Although interference problems are encountered in samples bearing high concentrations of Fe, use of a high-resolution ICP-AES system alleviated these problems. Precise quantitation of Pt, Pd, and Rh is accomplished by using the method of standard additions, with high accuracy and a precision of 1–2% RSD (relative standard deviation). This analysis also confirmed the values determined by NIST by using isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) for standard reference materials (SRMs) 2556 and 2557.

Frank M Pennebaker - One of the best experts on this subject based on the ideXlab platform.

  • high precision simultaneous analysis of pt pd and rh in catalytic converter samples by carius tube dissolution and inductively coupled plasma atomic emission spectroscopy with Charge Injection Device detection
    Applied Spectroscopy, 2001
    Co-Authors: Frank M Pennebaker, Bonner M Denton
    Abstract:

    A robust method of analysis that uses multichannel array detector technology is presented for high-precision, accurate measurement of Pt, Pd and Rh in catalytic converters. Catalytic converter samples, National Institute of Standards and Technology (NIST) reference standards, and a fresh converter sample are dissolved and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Complete dissolution of sample sizes up to 2 g of NIST reference standards is achieved with the use of high-pressure, high-temperature carius tubes. Carius tube dissolution of a modern catalytic converter sample is found to be incomplete because of the presence of higher concentrations of Ce, Ni, and Zr. For this sample, the addition of FeCl3 increases the dissolving power of the carius tube for base metals and noble metals, particularly Rh. Although interference problems are encountered in samples bearing high concentrations of Fe, use of a high-resolution ICP-AES system alleviated these problems. Precise quantitation of Pt, Pd, and Rh is accomplished by using the method of standard additions, with high accuracy and a precision of 1–2% RSD (relative standard deviation). This analysis also confirmed the values determined by NIST by using isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) for standard reference materials (SRMs) 2556 and 2557.

Zakharov Y. - One of the best experts on this subject based on the ideXlab platform.

  • Analytical measurement in electrothermal atomic absorption spectrometry - How correct is it?
    2020
    Co-Authors: Gilmutdinov A., Nagulin K., Zakharov Y.
    Abstract:

    The detection system for atomic absorption spectrometers based on the use of photomultiplier tubes (PMTs) is analysed from the point of view of its ability to provide accurate analytical information. It is shown that absorbance recorded by the system depends not only on the number of absorbing atoms but also on their distribution in the furnace volume. The typical non-uniformity of atomic distribution that occurs in graphite furnaces and its impact on the recorded signal are discussed. The cross-sectional distribution of the intensity of the radiation beam from a primary source was measured at different locations of the spectrometer for different source operating conditions. The distribution is rather non-uniform and can be described by the Gaussian function. An analysis of the joint effect of the radiation and analyte non-uniformity on the absorbance measured is given. The shape of the radiation beam cross-section changes from a circle to an ellipse with increasing lamp current. A new detection system based on the use of a solid-state detector (photodiode array, Charge coupled Device, Charge Injection Device) instead of PMTs is proposed. The solid-state detector is located vertically along the monochromator exit slit and allows the detection of spatially resolved absorbances. It is shown that the analytical signal recorded by this new system is proportional to the number of absorbing atoms irrespective of the non-uniformities described above

Gilmutdinov A. - One of the best experts on this subject based on the ideXlab platform.

  • Analytical measurement in electrothermal atomic absorption spectrometry - How correct is it?
    2020
    Co-Authors: Gilmutdinov A., Nagulin K., Zakharov Y.
    Abstract:

    The detection system for atomic absorption spectrometers based on the use of photomultiplier tubes (PMTs) is analysed from the point of view of its ability to provide accurate analytical information. It is shown that absorbance recorded by the system depends not only on the number of absorbing atoms but also on their distribution in the furnace volume. The typical non-uniformity of atomic distribution that occurs in graphite furnaces and its impact on the recorded signal are discussed. The cross-sectional distribution of the intensity of the radiation beam from a primary source was measured at different locations of the spectrometer for different source operating conditions. The distribution is rather non-uniform and can be described by the Gaussian function. An analysis of the joint effect of the radiation and analyte non-uniformity on the absorbance measured is given. The shape of the radiation beam cross-section changes from a circle to an ellipse with increasing lamp current. A new detection system based on the use of a solid-state detector (photodiode array, Charge coupled Device, Charge Injection Device) instead of PMTs is proposed. The solid-state detector is located vertically along the monochromator exit slit and allows the detection of spatially resolved absorbances. It is shown that the analytical signal recorded by this new system is proportional to the number of absorbing atoms irrespective of the non-uniformities described above

Gert Cauwenberghs - One of the best experts on this subject based on the ideXlab platform.

  • Charge mode parallel architecture for vector matrix multiplication
    IEEE Transactions on Circuits and Systems Ii: Analog and Digital Signal Processing, 2001
    Co-Authors: Roman Genov, Gert Cauwenberghs
    Abstract:

    An internally analog, externally digital architecture for parallel vector-matrix multiplication is presented. A three-transistor unit cell combines a single-bit dynamic random-access memory and a Charge Injection Device binary multiplier and analog accumulator. Digital multiplication of variable resolution is obtained with bit-serial inputs and bit-parallel storage of matrix elements, by combining quantized outputs from multiple rows of cells over time. A prototype 512/spl times/128 vector-matrix multiplier on a single 3 mm /spl times/3 mm chip fabricated in standard 0.5-/spl mu/m CMOS technology achieves 8-bit effective resolution and dissipates 0.5 pJ per multiply-accumulate.