Hybrid ions

In the magnetic-sector/TOP hybrid, ions produced in an ion source pass through the magnetic sector first and then might enter the TOF section, depending on how the hybrid is operated. The hybrid can be used as two separate instruments or as two instruments in conjunction with each other. 

Zwistigkeit, /. difference, dispute, discord. Zwitter, m. hermaphrodite hybrid bastard mongrel (Petrog.) zwitter. -ion, n. hybrid ion, amphoteric ion. 

In neutralizing a resonance hybrid ion it is always the stronger, more highly dissociated, of two possible acids that is formed the more rapidly. This accounts for the difference in product of the neutralization under equilibrium as compared with rate-controlled conditions. In the scheme shown below, the acid A H is the product if the ion is neutralized with a strong acid and the mixture worked up immediately, while the weaker and more stable acid, AH, is the product if the mixture is neutralized with a weak acid (which allows an appreciable concentration) or worked up only after a delay. An example is the isolation of... 

There are numerous other reports that illustrate the potential use of MALDI-TOF-MS for the rapid identification of various strains of B. anthracis. For instance, by using a new hybrid ion-trap MALDI-TOF instrument, in situ proteolytic digestion of... 

There are many more types of cluster ion sources than there are neutral cluster sources, in part because of the wide variety of ion-forming techniques available and in part because cluster ion sources are often hybrids of established neutral cluster sources and ion-forming environments. Some non-hybrid ion sources which can generate cluster ions include ion sputter, flow tube. Penning... 

When an amino acid is dissolved in water, it exists in solution as the dipolar ion, or zwitterion (German for hybrid ion ), shown in Figure 3-9. A zwitterion can act as either an acid (proton donor) ... 

Symmetrical placement of the ion-selective membrane is typical for the conventional ISE. It helped us to define the operating principles of these sensors and most important, to highlight the importance of the interfaces. Although such electrodes are fundamentally sound and proven to be useful in practice, the future belongs to the miniaturized ion sensors. The reason for this is basic there is neither surface area nor size restriction implied in the Nernst or in the Nikolskij-Eisenman equations. Moreover, multivariate analysis (Chapter 10) enhances the information content in chemical sensing. It is predicated by the miniaturization of individual sensors. The miniaturization has led to the development of potentiometric sensors with solid internal contact. They include Coated Wire Electrodes (CWE), hybrid ion sensors, and ion-sensitive field-effect transistors. The internal contact can be a conductor, semiconductor, or even an insulator. The price to be paid for the convenience of these sensors is in the more restrictive design parameters. These must be followed in order to obtain sensors with performance comparable to the conventional symmetrical ion-selective electrodes. 

The contact problems are mitigated in the hybrid ion sensor by making the internal conductor shorter and shorter until it is more natural to talk about its thickness rather than its length. The material of this internal contact has not changed during this transition and neither has the electrochemistry at the interface. Thus, the only difference between the coated wire and the hybrid sensor is the length (or thickness) of the contact. We therefore skip it and go directly to the solid-state ISFET, in which the thickness of the internal contact is zero. In other words, the ion-selective membrane is placed directly at the input dielectric of the field-effect transistor (Fig. 6.20). 

Homing, S. R., Fange, O., Wieghaus, A., Malek, R., and Senko, M. W. (2004). Simultaneous acquisition of two ion signals using two detectors in a hybrid ion trap/fourier transform ICR mass spectrometer. In Proceedings of the 52nd ASMS Conference on Mass Spectrometry and Allied Topics, Nashville, TN. 

Zwitter ions — Ions that have opposite charges at different sites of the molecule, e.g., amino acids in the zwit-terionic form +H3N-CH(R)-COO . Zwitter means in German hermaphrodite. Zwitter ions do not move in an electric field and thus conductometric measurements do not allow detecting their hermaphroditic character. - Kolthoff and - Furman [i] used the term hybrid ion however, that term is now obsolete. 

In some cases (dyes, etc.) the adsorption of solute in the surface may be so great that a solid film may be formed. The surface tensions of solutions containing hybrid ions may be greater or less than that of water.3 The change of surface tension of a solution with time was found by McBain, Ford, and Mills to be very slow, many days being needed to attain the niaximum effect,... 

In the second step of addition, a negative ion or basic molecule attaches itself either to the carbonyl carbon or to the jS-carbon of the hybrid ion I. 

These contain hybrid ions intermediate between the pyrophosphate ion and the infinite iinear metaphosphate ion, in which the terminal PO4 groups share one 0 and the intermediate groups two 0 atoms. The normal sodium triphosphate. 

It has usually been assumed in the literature that the formation of hybrid ions takes place only to a small degree. As regards the hybrid ions of the amino acids, Michaelis actually states, Their concentrations are undoubtedly always vanishingly small. N. Bjerrum has advanced considerably our knowledge of the behavior of amino acids by assuming that these ampholytes are present in aqueous solutions for the most part... 

In order to illustrate the hybrid ion theory, we shall compare ammonium acetate with an amino acid of which the acid and basic dissociation constants are respectively the same as those of acetic acid and ammonium hydroxide. We know that in 0.1 molar solution, ammonium acetate is 0.5% hydrolyzed and the salt is 99.5% ionized. If we employ the same equation (40 in Chapter One) to calculate the degree of hydrolysis of the amino acid, we find that it too is 0.5% hydrolyzed. Thus it appears logical to assume that the remainder of the ampholyte is present in the ionogenic form. 

If we let A denote the amino acid NH2RCOOH, +A" the hybrid ion, A+ the cation, and A the anion, then according to the older view... 

The radical difference between the classical and modern views is readily seen from equations (17) and (18). The basic character, as defined by the older theory, actually is determined by the true acidic dissociation constant based on the hybrid ion conception. Conversely, the acidic nature is governed by the true basic dissociation constant. 

A complete analogy exists between the behavior of an amino acid towards acids and bases and that of a salt of the ammonium acetate type, with the restriction that hybrid ions do not conduct an electric current. The ammonium and acetate ions, of course, do conduct because of their free charge. 

The fact that Walbltjm found a large temperature coefficient for the Ka of glycine supports the hybrid ion theory. The dissociation constants of carboxylic acids and of ammonia show small temperature coefficients. If Walblum s data are recalculated to yield the true basic dissociation constant, we find only a twofold increase in this constant between 10° and 70°. 

The equilibrium between amino acids and hybrid ions. 

The solution of an amino acid contains hybrid ions and the residual amino acid. This equilibrium may be described by ... 

The value of n can be determined only approximately. For dimethylglycine, glycine, and phenylalanine, n = 10 and for glycylglycine, n equals 10. It is safe to assume that the undissociated portion of these amino acids is present as the hybrid ion. 

The strong acid form II appears to be a hybrid ion (cf. also methyl orange and methyl red, page 146). It is possible that in the presence of large amounts of mineral acid, the dissociation of the sulfonic acid group is repressed so that the indicator exists as a cation (form III). 

The investigations of A. Thiel and coworkers, and of I. M. Kolthoff indicate that the free acid form of methyl orange is a hybrid ion (cf. Chapter Two) ... 

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