Single ion detection

A second use of arrays arises in the detection of trace components of material introduced into a mass spectrometer. For such very small quantities, it may well be that, by the time a scan has been carried out by a mass spectrometer with a point ion collector, the tiny amount of substance may have disappeared before the scan has been completed. An array collector overcomes this problem. Often, the problem of detecting trace amounts of a substance using a point ion collector is overcome by measuring not the whole mass spectrum but only one characteristic m/z value (single ion monitoring or single ion detection). However, unlike array detection, this single-ion detection method does not provide the whole spectrum, and an identification based on only one m/z value may well be open to misinterpretation and error. 

For measurement of local ion intensities in the direct imaging mode (see Fig. 3.19), amplification ensuring laterally uniform-single ion detection is necessary. Depending on the sensitivity of the detector a single or double channel plate is used. Two imaging devices are in use ... 

The atom-probe field ion microscope is a device which combines an FIM, a probe-hole, and a mass spectrometer of single ion detection sensitivity. With this device, not only can the atomic structure of a surface be imaged with the same atomic resolution as with an FIM, but the chemical species of surface atoms of one s choice, chosen from the field ion image and the probe-hole, can also be identified one by one by mass spectrometry. In principle, any type of mass analyzer can be used as long as the overall detection efficiency of the mass analyzer, which includes the detection efficiency of the ion detector used and the transmission coefficient of the system, has to be close to unity. 

The significance of inorganic mass spectrometry in precise isotope ratio measurements will be further increased for sector field mass spectrometers with multiple ion collector systems and also for mass spectrometers with single ion detection or quadrupole based instruments with and without a collision cell. 

Single ion detection (SID) also allows detection of PGS down to 10 ng or even lower (27, 28, 29, 30). However, focusing on one ion may introduce errors. The amount of the particular ion... 

Lee, M. G., and Millard, B. J. (1978). The quantification of mepyramine using an homologous internal standard plus a deuterated carrier with a gas chromatographic-mass spec-trometric system operating in single ion detection mode. Ado. Mass Spectrom. 7B 1551-1554. 

In double-focusing sector field ICP-MS spectrometers with single ion detection, the best abundance sensitivity with a mass difference of two is observed at medium mass resolution m/Am = 4400 (9 x 10 ). At low mass resolution mlAm = 400) an abnndance sensitivity for °Sr determination of 2 x 10 was measured in the author s laboratory. In quadrupole ICP-MS with and without a hexapole coUision cell, an abundance sensitivity of 6 x 10 and 6 x 10 , respectively, for determination in the presence of abundant with high ion intensity was determined by Boulyga et al. ° A significant improvement in abundance sensitivity for the determination of the isotope ratio has been obtained by multi-collector ICP-MS (Nu Plasma... 

E Bailey, PB Farmer, JH Lamb. The enantiomer as internal standard for the quantitation of the alkylated amino acid S-methyl-cysteine in haemoglobin by GC-CI-MS with single ion detection. J Chromatogr 200 145—152, 1980. 

Fujii, T. The Determination of Traces of Organohalogen Compounds in Aqueous Solution by Direct Injection Gas Chromatography-Mass Spectrometry and Single Ion Detection, Analytica Chimica Acta 92, 117 (1977)... 

Simultaneous Estimation of Testosterone, Progesterone, and Androstene-dione by Gas Chromatography-Mass Spectrometry with a Single Ion Detection Correlation with Radioimmunoassay... 

The Quantification of Mepyramine Using an Homologous Internal Standard Plus a Deuterated Carrier with a Gas Chromatographic-Mass Spectro-metric System Operating in Single Ion Detection Mode Adv. Mass Spectrom. 7B 1551-1554 (1978) CA 89 99525x... 

Mass filter Min/Max Count Rates (cps) Single ion detection Dynamic Range Spatial Recognition... 

As the MS detection method the MS/MS mode was chosen. The single ion detection (SIM/SIS) of the ion trap analyser has been compared using matrix samples and did not deliver the required compound selectivity for trace level quantitation in matrix, see Figure 4.80. 

The described method provides a general approach for the accurate and effective determination of 48 fragrance allergens in toy samples. The MS/MS acquisition mode instead of single ion detection allows the identification and quantitation of the fragrance allergens at levels compliant with the current EU regulations in the complex matrix of the toy samples. 

Langenbeck, U., Hoinowski, A., Mantel, K. and Mohrung, H.-U. (1977a), Quantitative gas chromatography and single ion detection of aliphatic a-keto acids from urine as their 0-trimethylsilylquinoxalinol derivatives. J. Chromatogr.y 143,39. 

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