Spectrometer calibrations

Magnesium may conveniently be determined by atomic absorption spectroscopy (Section 21.21) if a smaller amount (ca 4 mg) is used for the separation. Collect the magnesium effluent in a 1 L graduated flask, dilute to the mark with de-ionised water and aspirate the solution into the flame of an atomic absorption spectrometer. Calibrate the instrument using standard magnesium solutions covering the range 2 to 8 ppm. 

Insert the sample probe in the MALDI-TOF mass spectrometer. Calibration is performed in external mode with peptides covering the mass range of 500 Da to 5 kDa (see Note 15). 

One should note that some of the kinetic rate constants in all of these models are derived from Peeters and Mahnen mass spectrometric results therefore, it is not surprising that the theoretical fits to this data are rather good. It is reassuring that the model of Ref. 1 also exhibits overall good agreement with the following laser probe results that are free of mass spectrometer calibration estimates and flame perturbation. 

Calibration can be done every time you start a system up but for general leak detection, calibration is less important. However, whenever any general repair or replacement maintenance is performed, such as replacing the filament on a mass spectrometer, calibration becomes mandatory. See your owner s manual for specific instructions. 

Spectrometer calibration for species such as hydroxyl has been carried out with nitric oxide, which also couples with the electric rather than the magnetic field. Westenberg has calculated the theoretical basis of such calibrations, and used the method in flow-tube studies of hydroxyl reactions . Dixon-Lewis et a/. have measured absolute OH concentrations in a similar way, and used the results to elucidate the kinetics of the reactions OH-)-OH, OH-i-Hj and OH-)-CO. 

American Society for Testing and Materials, Standard Guide for Raman Shift Standards for Spectrometer Calibration, Standard E-1840-96, 1998. 

Figure 10.14. Cyclohexane spectrum following correction with Kopp 2412 glass standard. Horizontal numbers are the peak areas (integrated over the shift range indicated by the horizontal bars), relative to the 801 cm peak area. Vertical numbers are the ASTM frequencies for cyclohexane listed in Table 10.4 and Reference 11. Intensity data is average of two spectrometers calibrated independently, as described in Reference 20. (See footnote e of Table 10.7.)...

There is no single standard procedure for Raman spectrometer calibration, since instrument configurations and applications vary so widely. Nevertheless, it is useful to summarize typical procedures, some of which resulted in the spectral results presented in this chapter. 

Fig. 4. (a) Setup for chip-size spectrometer calibration, (b) Snapshot of CMOS camera. 

Optical methods of spectrometer calibration include laser interferometric methods and Moire fringe counting techniques. Since such methods depend on the accurately known wavelength of light (for example, 6328.1983 A for a He-Ne laser at 293 K under standard conditions), they are independent of any assumptions made in the iron foil technique and, thus, are intrinsically more reliable. Moreover, such methods do not require the acquisition of57 Co Mdssbauer sources and reference materials for iron absorber studies and may thus be attractive... 

The apparatus used for these experiments has been described previously (10). In a typical TPD experiment, 25 mg of sample were placed in a quartz microreactor which was mounted inside a furnace. Following evacuation for 1 h at room temperature, helium was flowed over the sample at a rate of 100 cc/min (STP) and the temperature was raised at 0.5 K/s. During heating, the desorption products were swept from the reactor by the helium stream and monitored downstream with a UTI Model 100 C quadrupole mass spectrometer. Upon completion of each TPD experiment, the mass spectrometer was calibrated for oxygen as described below, and then a TPR experiment was performed using a hydrogen flow rate of 200 cc/min (STP). After each TPR experiment, the mass spectrometer calibration was repeated. 

The stable carbon isotope ratios of dissolved inorganic carbon (DIC) and benthic foraminiferal calcite generally are determined with isotope ratio gas mass spectrometers calibrated via NBS 19 international standard to the VPDB (Vienna Pee Dee Belemnite) scale. All values are given in 8-notation versus VPDB with an overall precision of measurements including sample preparation usually better than +0.06 and +0.1%o for calcite and DIC carbon isotopes, respectively. Except one single-specimen based dataset (Hill et al. 2004), all stable isotope data from papers referred to in this overview are from species-specific multi-specimens analyses. The number of specimens used for a single analysis depended on size and weight of species but usually varied between 2 and 25. 

For spectrometer calibration, the Au 4f7/2-signal at 83,8 eV repeatedly has been controlled. 

Gas-chromatography coupled to mass spectrometry (G.C.-M.S.) was carried out on Rexco and Kuwait branched/cyclic fractions with a Pye IOU chromatograph (WCOT glass-capillary column coated with OV-1) on a Varian MAT hh spectrometer (with SS kk computer) at 70 eV ionization voltage. For Turkish Montan wax and asphaltite, G.C.-M.S. were run with the eutectic packed column on an MS 50 spectrometer. Field-desorption (F.D.) M.S. for Kuwait and Rexco samples were recorded on a Varian CH5D spectrometer (calibrated with perfluorkerosene) linked to a Varian Spectro-system 100 data output. 

ASTM (2007) Standard guide for Raman spectrometer calibration, E1840-96. 

The absolute accuracy of binding energies between different instruments and laboratories varies even for noble metals significantly more than the numerical accuracy with which the peak position in a spectrum can be determined (more than the usually quoted 0.1 eV). This is independent of the method of spectrometer calibration and sample preparation. 

Both gas/solid adsorption and gas/liquid partition chromatography can be used for GC-MS, but GC is by far the most common. Because, in GC, the stationary phase is a liquid, usually a polymer, its vapor pressure will cause a continual low flow, or bleed into the ion source of the mass spectrometer. This bleed, which usually consists of decomposed stationary phase, will produce a spectrum whose intensity increases with column temperature. Stationary phases should therefore be of the high-boiling, low-bleed type. Most currently used stationary phases for routine GC-MS are based on alkyl-polysiloxanes or alkyl-phenyl-polysiloxanes that are chemically bonded to the column wall to increase stability. Columns containing such phases can, in some cases, be used at temperatures of up to 400°C. One advantage, however, to the presence of bleed peaks in the spectrum is that they enable a continual check to be made on the mass spectrometer calibration. For the alkyl siloxanes, ion peaks are present, in decreasing relative abundance, at miz 73, 207, 281, 355, 429,... 

Faced with dilute samples, proper presentation of the sample and accurate spectrometer calibrations are particularly important. The sample should be mobile rather than bound, deoxygenated, and free of particulates. The removal of particulates by filtration makes a significant improvement to spectral quality. High-resolution solution work usually requires dissolution in a deuterated solvent for instrumental locking. However, excellent spectra can often be obtained in protonated solvents in the presence of a concentrically placed sealed capillary tube containing the deuterated solvent. This approach is unsuitable for intact biological samples where the NMR probe and coil assembly is designed around the specimen. 

ISO 17973/17974 - Medium-resolution/high-resolution Auger electron spectrometers - calibration of energy scales for elemental analysis ... 

IS015472—2001. Surface Chemical Analysis - X-ray Photoelectron Spectrometers - Calibration of energy scales 2001. 

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