Spectral high mass resolution with sector field

Fig. 3.2. High-resolution double-focusing mass analyser with Nier-Johnson geometry. The electrostatic sector filters ions according to kinetic energy before magnetic sorting according to m/z. The combination of electric and magnet fields produces narrow peaks and high spectral resolution.

However, sulfur measurement by ICP-MS is hampered by the low ionization efficiency. Because sulfur has a relatively high first ionization potential, the ionization of sulfur in the argon plasma is only 10%. ° In addition, serious polyatomic ions, such as 0 0-", N 0+ and 0 0, 0 0H+, interfere with the main isotopes, S and " S, respectively. These spectral interferences at m/z 32 and 34 can be overcome by a sector field ICP-MS (ICP-SF MS) with a mass resolution of about ml Am = 4000. ... 

High-resolution sector-field ICP-MS (SF-ICP-MS), be it double or single focusing, offers superior detection limits, and more precise quantitative and isotope ratio results when measurements are performed in low-resolution mode due to the flat-top spectral peaks. Use of higher mass resolution (up to 10000) results in sharper spectral peaks and resolves polyatomic interferences from the target element signals. The result is improved detection capability for certain elements compared to quadrupole ICP-MS. Prominent examples of elements where measurements with SF-ICP-MS are beneficial are Fe, V, Cr, As and Se. ... 

Among various types of mass analysers (including magnetic-sector instruments, quadru-poles, ion traps), time-of-flight (ToF) systems have gained a prominent place in the field of polymer MS. ToF systems are eminently compatible with MALDI. MALDI produces ions in pulses, while ToF accept ions in pulses. As a result, ToF provides a very high sensitivity for the ions produced with MALDI. ToF systems also offer a high spectral resolution and accuracy and ToF systems are relatively simple and, lately, relatively affordable (Table 7.4). 

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