Quadrupole Q

For any given set of rf and dc voltages on the opposing pairs of rods, only ions of one m/z ratio display a stable oscillation enabling them to reach the detector. Unstable ions hit the initial part of the analyzer, often a pre-filter, are discharged and lost. 

The pre-filter, which is connected electrically to the analyzer, is not essential but can be removed conveniently for cleaning. 

Quadrupole analyzers have unit resolution throughout their mass range i.e one mass is discriminated from the next, be that 28 from 29 or 2,000 from 2,001. This classifies quadrupoles as low-resolution instruments which are poorly suited to obtain accurate mass data. A consequence of the poor resolution is that two ions with the same nominal mass but with different empirical formulae, and therefore different exact masses (isobaric ions), will not be separated, but instead, their masses will be averaged into the mJz observed value. Furthermore, the peaks are broad (-1 mIz wide), and thus it is difficult to obtain precise measurements of the centroids. The mass range of quadrupoles extends to 4 kDa for singly charged ions. These analyzers are compatible with all ionization methods except MALDI (because of the mass range limitation). 

Additional benefits of Q analyzers include ease of use, small footprint, and lower cost. Disadvantages include the low duty cycle (per m/z) and the lack of accurate mass capabitity. 

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The electric quadrupole Q 2co) involves both the gradient of the electromagnetic incident electric field E u)) and the gradient of the electric quadrupole susceptibility tensor Xq 2o), CO, co). This problem is nonetheless solved by the mere addition of supplementary terms in the surface susceptibility tensor. As a result, the surface susceptibility tensor becomes an effective tensor instead of a purely surface specific one [27,38] ... 

Notes HR = High Resolution HR-ICPMS, Q = Quadrupole Q-ICPMS, 1 = First generation MC-ICPMS, 2" = Second generation MC-ICPMS. 

Pyrolysis Field ionisation (FI) Quadrupole (Q) Daly detector... 

The spin interactions, dipole-dipole (D), nuclear electric quadrupole (Q) and chemical shielding (C.S), may be formally written in terms of irreducible tensors of rank l34 in Hz ... 

The coupling of a mass spectrometer to CE and CEC provides a powerful system for the analysis of pharmaceuticals and complex biological mixtures. This can replace or complement other conventional detection methods such as UV, electrochemical, or LIE that provide less structural information. The use of mass spectrometer as a detector enhances the usefulness of the CE and CEC and allows an efficient separation and identification of complex mixtures, obtaining structure and/or molecular mass information. The choice of mass analyzers used in CE/CEC-MS depends on factors such as sensitivity, mass resolution, requirement for structural elucidation, and the type of application (Table 5). The analyzers that have been used in CEC analysis include time-of-flight (TOE), quadrupole (Q), ion-trap (IT), fourier... 

Type 2 Nuclei with I = V2. These nuclei have a non-zero magnetie moment and are NMR visible and have no nuclear eleetrie quadrupole (Q). The two most important nuclei for NMR speetroseopy belong to this eategory H (ordinary hydrogen) and (a non-radioaetive isotope of earbon occurring to the extent of 1.06% at natural abundanee). Also, two other commonly observed nuclei and P have I = V2. Together, NMR data for H and C account for well over 90% of all NMR observations in the literature and the discussion and examples in this book all refer to these two nuelei. However, the spectra of all nuclei with I = V2 can be understood easily on the basis of common theory. 

The quantities A and B are usually called the constants of the magnetic dipole and electric quadrupole interactions. The nuclear matrix elements in (22.27) for k = 1 and 2 are proportional to the magnetic dipole p and electric quadrupole Q nuclear momenta, respectively ... 

Figure 12 Ne Is nondipole photoelectron angular asymmetry parameter y A(a>) for the Ne C605 anion along with the dipole D and quadrupole Q amplitudes and cos A (A = 2 — ti) [28].

Brandao et al. also applied the bottom-up approach to compare seed-protein profiles of herbicide-tolerant soybean and its near-isogenic line (60). Some 2-DGE parameters such as the loaded mass of the proteins, the pH separation range, and manual/automatic image editing were optimized prior to the evaluation (Figure 2). Of the 10 proteins with at least 90% variation found to be differentially expressed between the GM soybean and its counterpart, 8 proteins were successfully identified by MALDI coupled to a quadrupole (Q)-TOF MS. 

Inductively coupled plasma mass spectrometry (ICP-MS) is one of the most significant analytical advances to occur in the last 20 years as it allows multielement analysis of solutions and solids to be performed at subnanogram concentrations. Instrumental advances have occurred such that Quadrupole (Q) ICP-MS units are now in routine use in many laboratories. In this chapter, the use of Q-ICP-MS and high performance liquid chromatography (HPLC)-ICP-MS is discussed as regards the quantification of total As and As species in seafood. To highlight the strengths and weaknesses of the use of ICP-MS, data are used that were mainly produced in the laboratories of the authors of this chapter. 

Some mass spectrometers combine several types of analysers. The most common ones include two or more of the following analysers electromagnetic with configurations EB or BE, quadrupoles (Q), ion traps (ITs) with Paul ion traps or linear ion traps (LITs), time-of-flight (TOF), ion cyclotron resonance (ICR) or orbitrap (OT). These are named hybrid instruments. The aim of a hybrid instrument is to combine the strengths of each analyser while avoiding the combination of their weaknesses. Thus, better performances are obtained with a hybrid instrument than with isolated analysers. Hybrids are symbolized by combinations of the abbreviations indicated in the order that the ions travel through the analysers. 

Common combinations of electric (E) and magnetic (B) sectors, quadrupoles (Q) and collision cells (C). The lowercase q indicates a focusing quadrupole. 

The idea of correlating momentary multipoles stands behind the customary modeling of dispersion interaction in the form of a multipole expansion, including dipole-dipole (D-D), dipole-quadrupole (D-Q), quadrupole-quadrupole (Q-Q), and so on, terms. We owe the earliest variational treatments of this problem not only to Slater and Kirkwood [34], but also to Pauling and Beach [35], However, when the distance R decreases and reaches the Van der Waals minimum separation, the assumption that electrons of A and B never cross their trajectories in space becomes too crude. The calculation of the intermonomer electron... 

Analyzer/parameter Quadrupole (Q) Ion trap (IT) Time-of-flight (TOP)... 

Table 5. Coulomb interaction Clergies between two (transition) dipoles (p—p). dipole — linear quadrupole ( i—(J) and two linear quadrupoles (Q—Q)...

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