Analyte large ions

Mobile phases useful for suppressed conductivity detection of anions include sodium hydroxide, potassium hydroxide, and the sodium and potassium salts of weak acids such as boric acid. In nonsuppressed conductivity detection, the ionic components of the mobile phase are chosen so that their conductivities are as different from the conductivity of the analyte as possible. Large ions with poor mobility are often chosen, and borate-gluconate is popular. For cations, dilute solutions of a strong acid are often used for nonsuppressed conductivity detection. For more information on the application of electrochemical detection to inorganic analysis, see Ion Chromatography Principles and Applications by Haddad and Jackson,17 which provides a comprehensive listing of the sample types, analytes, sample pretreatments, columns, and mobile phases that have been used with electrochemical detection. 

Adding too much or too little IS can also limit the dynamic range of the assay, as the comparison of very large ion currents (detector saturation) with very small ion currents (poor ion statistics) will greatly increase the variance of the assay. A good guide is a threefold excess of the IS over the analyte but this may take a few trials to establish. 

MALDI-conditions [47] and also predicted by molecular modeling [40, 50], However, these model calculations also predicted that large clusters would have insufficient internal energy for a complete dissociation with evaporation of the neutrals. This result may also originate from insufficient simulation times and/or to too-hmited sizes of the simulation box [58], and does not necessarily reflect the situation for smaller to medium-sized clusters. While the initially charged matrix - analyte cluster ions never appear in the MALDI spectra with the typical solutes used, such as trifluoroacetic acid (TFA) or ammonium salts, they have been detected for extremely strong acids [60] their conjugate anions are extremely weak bases and thus stabiUze the formed ion pairs with protonated analyte sites. 

Analyte ions need to be transmitted with satisfactory efficiency so that they can arrive in the mass analyzer, and later in the detector. Small ionic species may likely diffuse right after ionization, while very large ions (formed from macromolecules) may not readily respond to electric field of ion guides and lenses. Geometry of ion guides next to the ion source may affect the efficiency of ion capture. 

Stem layer adsorption was involved in the discussion of the effect of ions on f potentials (Section V-6), electrocapillary behavior (Section V-7), and electrode potentials (Section V-8) and enters into the effect of electrolytes on charged monolayers (Section XV-6). More speciflcally, this type of behavior occurs in the adsorption of electrolytes by ionic crystals. A large amount of wotk of this type has been done, partly because of the importance of such effects on the purity of precipitates of analytical interest and partly because of the role of such adsorption in coagulation and other colloid chemical processes. Early studies include those by Weiser [157], by Paneth, Hahn, and Fajans [158], and by Kolthoff and co-workers [159], A recent calorimetric study of proton adsorption by Lyklema and co-workers [160] supports a new thermodynamic analysis of double-layer formation. A recent example of this is found in a study... 

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