Single collector instruments

Inductively Coupled Plasma Mass Spectrometry Handbook 

Sensitivity (single collector) Instrumental detection limit (single collector) 

Linear dynamic range (single collector with SEV detector) 

4 Velocity of an ion in a magnetic field m m mass of the ion B magnetic field strength 

5 m/z with respect to the field strength m ore z 2V r radius of the magnetic field 

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Detection systems. Prior to the past decade, most instruments used for uranium-series analysis were single-collector instruments, for which ion beams of the various isotopes are cycled onto a single low-intensity detector, usually with electronics operating in pulse counting mode (Chen et al. 1986 Edwards et al. 1987 Bard et al. 1990 Goldstein et al. 1989 Volpe et al. 1991 Pickett et al. 1994), in order to measure the low-intensity ion beams of °Th, Pa, Pa, Ra and Ra. Daly detectors and... 

This sample preparation method is not instrument specific but was developed using a Thermo Fisher Element 2 MS-ICP-MS. Whatever instrument is used, the instrument should be mass calibrated. Although it is preferable for the sake of accuracy that all uranium isotopes be acquired in the same detector mode, cross-calibration should be up to date for single collector instruments, as should detector dead time. Since the Thermo Fisher magnetic sector instrument with a low-resolution ion slit in good condition produces data with flat top peaks, and automatically updates detector crosscalibration after acquisition of peak data with sufficient intensity, frequent recalibrations will not be necessary on this instrument or on the Thermo Fisher multicollector instruments. Detector dead time is relatively stable on this instrument but should be up to date. 

Single-collector instruments also prove very usefid for mass content determinations via isotope dilution, as carefiil estimation of all quantities that influence the uncertainty budget demonstrates that the precision on the isotope amount ratio is typically not the dominant factor for high-precision measurements. Often, the accuracy of a mass content measurement will hardly improve through the use of MC-ICP-MS instruments as other influence quantities, such as uncontrolled spectral interferences and sample inhomogeneities, typically deserve more attention. 

Restrictions on the use of ICP-MS in magnesium metabolic studies arise primarily from the limits on precision. Single-collector instruments, irrespective of whether they are equipped with a quadrupole filter, with or without an additional... 

By using single-collector instruments equipped with a collision/reaction cell [248, 251] or double-focusing sector field instrumentation [248], it is possible to determine selenium isotope ratios at a precision and even accuracy of 0.2-0.5% RSD for most selenium isotope ratios. This level of performance can be considered sufficient for metabolic studies in humans and compares well with what can be achieved with NTIMS, although with much lower sample requirements. 

Table 2.1 Selected figures of merit of a magnetic sector field ICP-MS (single-collector instrument)...

Accomplishing mass scans in single-collector instruments... 

Whereas multi-collector devices are operated at a constant magnetic field and collect the isotopes of interest simultaneously in different detectors, single-collector instruments have to scan over... 

Internal correction has the advantage of simultaneous (MC instmments) or quasi-simultaneous (single-collector instruments) correction, but in this case obviously the measured isotope ratio cannot be corrected by using the same isotope ratio. In ICP-MS the mass discrimination for a limited mass range (< 10 mass units) only depends on the mass difference. Other dependencies have not yet been observed. Thus the mass discrimination for a certain isotope ratio in the first approximation can be calculated from a different isotope ratio close to the target one. In practice another isotope ratio of the same element with a constant universal value is used or the sample... 

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