Atomic spectrometers, control

It should be also pointed out that the robustness of electrothermal atomization enables one to avoid the use of high dilution factors. The sensitivity of ET-AAS to a high percentage of dissolved salts, major elements and/or acids is relatively controllable. Manipulation can be also reduced. Calibration is therefore possible at concentrations where contamination phenomena can be better mastered. Multielement atomic spectrometers have additional advantages of saving time and resources by quantifying simultaneously Cd and Pb. 

The optical detection systems used in MIPs are the same as those used for other atomic spectrometers and can be either single or multichannel. Fourier transform-based spectrometers have also been used. Conventional optical systems are best designed if the plasma is viewed from the exit of the discharge tube, as is possible with the TMqio type cavity, rather than through the walls of the discharge tube, which become etched. The commercially available AED uses a computer-controlled silicon photodiode array detector which has multielement detection capability over segments of spectra. In recent years, MIP sources have also been investigated as ion sources for mass spectrometry. 

This limitation led to the development of laser ablation as a sampling device for atomic spectroscopy instrumentation, where the sampling step was completely separated from the excitation or ionization step. The major benefit is that each step can be independently controlled and optimized. These early devices used a high-energy laser to ablate the surface of a solid sample, and the resulting aerosol was swept into some kind of atomic spectrometer for analysis. Although initially used with atomic absorption - and plasma-based emission techniques, it was not until... 

Atomic Fluorescence System - Millennium Excalibur PSA 10.055 -was used in our work. This system consists of the autosampler, the integrated continuous flow vapour generator and the atomic fluorescence spectrometer with the boosted dischar ge hollow cathode lamp and a control computer. 

The X-ray spectrum observed in PIXE depends on the occurrence of several processes in the specimen. An ion is slowed by small inelastic scatterings with the electrons of the material, and it s energy is continuously reduced as a frmction of depth (see also the articles on RBS and ERS, where this part of the process is identical). The probability of ionizii an atomic shell of an element at a given depth of the material is proportional to the product of the cross section for subshell ionization by the ion at the reduced energy, the fluorescence yield, and the concentration of the element at the depth. The probability for X-ray emission from the ionized subshell is given by the fluorescence yield. The escape of X rays from the specimen and their detection by the spectrometer are controlled by the photoelectric absorption processes in the material and the energy-dependent efficiency of the spectrometer. 

Gill and Fitzgerald [481] determined picomolar quantities of mercury in seawater using stannous chloride reduction and two-stage amalgamation with gas-phase detection. The gas flow system used two gold-coated bead columns (the collection and the analytical columns) to transfer mercury into the gas cell of an atomic absorption spectrometer. By careful control and estimation of the blank, a detection limit of 0.21 pM was achieved using 21 of seawater. The accuracy and precision of this method were checked by comparison with aqueous laboratory and National Bureau of Standards (NBS) reference materials spiked into acidified natural water samples at picomolar levels. Further studies showed that at least 88% of mercury in open ocean and coastal seawater consisted of labile species which could be reduced by stannous chloride under acidic conditions. 

FIA star 5010 Modular, semi- or fully automatic operation. May be operated with process controller microprocessor. Can be set up in various combinations with 5017 sampler and superflow software which is designed to run on IBM PC/XT computer 60-180 samples h Dialysis for in-line sample preparation and in-line solvent extraction.Thermostat to speed up reactions. Spectrophotometer (400-700nm) or photometer can be connected to any flow through detector, e.g. UV/visible, inductively coupled plasma, atomic absorption spectrometer and ion-selective electrodes... 

A comparative study was made between determinations of the 15N content of plant and soil samples, using the methods of the International Atomic Energy Agency Laboratories, based on MS, a novel automatic N analyzer coupled to a mass spectrometer and a microprocessor-controlled emission spectrometer. Although the latter instrument is fast, its precision may be insufficient to determine 15N in soil59. 

Introduction into a DC plasma requires rather more care and attention owing to its inherent design features. As the hydride is being introduced into the plasma, it is necessary to provide a controlled sheath of argon to contain the hydride and direct it into the plasma. This chimney effect significantly improves the sensitivity for hydride-forming elements. This interface has also formed the basis of an introduction system for mercury vapour into an atomic-fluorescence spectrometer as described by Godden and Stockwell [12]. 

In order to determine the dynamics of atoms we have to carry out an inelastic neutron scattering measurement. With a reactor source this can be done with a triple-axis spectrometer, which has an analyzer crystal. Tripleaxis refers to the three axes for the monochromator, sample, and analyzer, all moving independently and controlled by a computer. With a pulsed source we use a mechanical chopper, which is a rotating cylinder with a hole perpendicular to the rotating axis that allows neutrons with a chosen range of velocity to go through. The neutrons scattered by the sample are detected... 

D Commercial COTS controlled by external computer Hybrid systems such as automated dissolution workstation with high-performance liquid chromatography (HPLC) or ultraviolet-visible (UV-Vis) interface Liquid chromatographs, gas chromatographs, UV/Vis spectrophotometers, Fourier transform infrared (FTIR) spectrophotometers, near-infrared (NIR) spectrophotometers, mass spectrometers, atomic absorption spectrometers, thermal gravimetric analyzers, COTS automation workstations... 

More than seventy elements may be detected by standard procedures. Atomic gases, such as O, N, H, He. Ar, Ne, Kr, Xe, and Rn and the halogens are excluded. Nonmetallic substances, such as C, S, and Se. require vacuum path specuometets foi optimum detection and measurement. Analytical ranges may extend from fractional parts per million to about 40% concentration. Computer-controlled photoelectric optical emission spectrometers will output printed percent concentrations for 30 to 50 elements per sample in just a few minutes. This form of analytical instrumentation is used widely in production and quality control, as well as for research studies. 

The mass spectra of the gases evolved from the deuterated SWNT sample heated in vacuum were measured with the MI 1201V mass spectrometer. Gas ionization in the ion source of the spectrometer was produced with a 70-eV electron beam. To obtain the gas phase, the sample was placed in a quartz ampoule of a pyrolyzer that was connected to the injection system of the mass spectrometer through a fine control valve. Then the ampoule was evacuated to a pressure of about 2-x 10-5 Pa in order to remove the surface and weakly bound impurities from the sample. After the evacuation, the ampoule was isolated from the vacuum system and the sample was heated to 550°C in five steps. At each step, the sample was kept at a fixed temperature for 3 h then the fine control valve was open and the mass-spectrometric analysis of the gas collected in the ampoule was performed. After the analysis, the quartz ampoule was again evacuated, the valve was closed, and the sample was heated to the next temperature. The measurements were carried out over the range 1 < m/z < 90, where m is the atomic mass and z is the ion charge. The spectrometer resolution of about 0.08% ensured a reliable determination of the gas-phase components. 

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