Mass-based

Molecular ion. An ion formed by the removal (positive ions) or addition (negative ions) of one or more electrons from a molecule without fragmentation of the molecular structure. The mass of this ion corresponds to the sum of the masses of the most abundant naturally occurring isotopes of the various atoms that make up the molecule (with a correction for the masses of the electrons lost or gained). For example, the mass of the molecular ion of the ethyl bromide CzHjBr will be 2 x 12 plus 5 x 1.0078246 plus 78.91839 minus the mass of the electron (m ). This is equal to 107.95751p -m, the unit of atomic mass based on the standard that the mass of the isotope = 12.000000 exactly. 

Potency of hGH preparations is quantitatively deterrnined, in terms of mass per vial, by one or more chromatographic procedures (50). Biopotency is calculated from the mass-based potency using a conversion factor, typically 3 lU/mg. Traditionally a bioactivity assay using hypophysectomized rats has been used to determine potency however, the imprecision of this assay has resulted in its use only as a semiquantitative indicator of bioactivity (1), sometimes referred to as a bioidentity test. 

All definitions of the mean given (eqs. 1—4) are based on the number of particles being measured. As opposed to number-based means, length, surface-area, and mass-based means have also been defined. The linear, or length mean (Lm) diameter,dj, is defined by the foUowiag equation ... 

Another tank car was punctured at Decatur (NTSB report 1975). TNT equivalencies of 4.3-10.2% and 47-111% were calculated on energy and mass bases, respectively. These equivalencies were calculated based upon a full tank car inventory (152,375 lb, 68,000 kg) of isobutane. 

Component Mass (mw) Protein Number Mass Size RNA Mass Bases... 

Each concentration measure is convenient for some types of calculations but inconvenient for others. Consequently, a chemist may need to convert a concentration from one measure to another. Example illustrates the conversion from a mass-based concentration, percent by mass, to a mole-based concentration, molality. Mole... 

Volume and mass-based expressions for the degree of crystallinity are easily derived from the experimentally measured density (p) of a semi-crystalline polymer. The method is based on an ideal crystalline and liquid-like two-phase model and assumes additivity of the volume corresponding to each phase... 

The enthalpic change from the solid to the liquid-like phase of a semi-crystalline polymer can be obtained from DSC [16]. The mass-based degree of crystallinity (XI)SC) is calculated as the ratio of the heat of fusion of the sample (AH) and the value per mole of purely crystalline polymer (AHc). 

Here, the densities of the gaseous and solid fuels are denoted by pg and ps respectively and their specific heats by cpg and cps. D and A are the dispersion coefficient and the effective heat conductivity of the bed, respectively. The gas velocity in the pores is indicated by ug. The reaction source term is indicated with R, the enthalpy of reaction with AH, and the mass based stoichiometric coefficient with u. In Ref. [12] an asymptotic solution is found for high activation energies. Since this approximation is not always valid we solved the equations numerically without further approximations. Tables 8.1 and 8.2 give details of the model. 

Fig. 11. Melt viscosity at 85 °C vs molar mass for hydroxy-functional hyperbranched aliphatic polyesters based on bismethylol propionic acid. Theoretical molar mass based on core bis-MPA ratio ( ) and Mn determined with SEC relative to linear polystyrene standards (O) [117]...

Shortly after the development of the early mass spectrometers, Li isotopes were identified by Francis Aston (1932). Although mass spectrometric techniques are those most commonly applied to the measurement of isotope ratios in geochemistry, attempts to quantify Li isotopes have been made using non-mass based emission methods (e.g., atomic absorption Zaidel and Korennoi 1961 various nuclear methods Kaplan and Wilzbach 1954 Brown et al. 1978 ... 

Note The calculation of relative molecular mass, Mr, of organic molecules exceeding 2000 u is significantly influenced by the basis it is performed on. Both the atomic weights of the constituent elements and the natural variations in isotopic abundance contribute to the differences between monoisotopic- and relative atomic mass-based values. In addition, they tend to characteristically differ between major classes of biomolecules. This is primarily because of molar carbon content, e.g., the difference between polypeptides and nucleic acids is about 4 u at Mr = 25,000 u. Considering terrestrial sources alone, variations in the isotopic abundance of carbon lead to differences of about 10-25 ppm in Mr which is significant with respect to mass measurement accuracy in the region up to several 10 u. [41]... 

Initial lead discovery Start with prefer 10-100 hits Limited by massive installed base of other methods. Current paradigm requires only singlepoint estimate of activity, because low-potency hits are expected (therefore, power of MS-based systems may overmatch the task). Mass-based recognition of compounds may be thwarted by isobaric compounds or impurities. 

Fig. 16.26 Water dissolution of DNAPL mixture, (a) theoretical dissolution curve for a DNAPL mixture consisting of 10% TCM, 40% TCE, and 50% PCE (v/v) (b) ratios of TCE and TCM, PCE and TCM, and PCE and TCE as a function of source depletion. Reprinted with permission from Broholm K, Eeenstra S, Cherry JA (2005) Solvent release into sandy aquifer. 2. Estimation of DNAPL mass based on multiple-component theory. Environ Sci Technol 39 317-324. Copyright 2005 American Chemical Society...

The density of the elements is also an important parameter with regard to obtaining a high heat of combustion in a reactor of limited volume. The volumetric heat of combustion (kj m" ) shows differences compared to the mass-based heat of combustion (kj kg" ). For example, the volumetric heat of combustion of Zr is the highest of the fuel elements and that of Ti is the next highest when oxidized by oxygen gas. 

Usually, this also results in a smaller mass based average size (L50m) (1). 

The process inputs are defined as the heat input, the product flow rate and the fines flow rate. The steady state operating point is Pj =120 kW, Q =.215 1/s and Q =.8 1/s. The process outputs are defined as the thlrd moment m (t), the (mass based) mean crystal size L Q(tK relative volume of crystals vr (t) in the size range (r.-lO m. In determining the responses of the nonlinear model the method of lines is chosen to transform the partial differential equation in a set of (nonlinear) ordinary differential equations. The time responses are then obtained by using a standard numerical integration technique for sets of coupled ordinary differential equations. It was found that discretization of the population balance with 1001 grid points in the size range 0. to 5 10 m results in very accurate solutions of the crystallizer model. 

S is the analyte property-based selectivity [3] (i.e., mass-based or diameter-based) of the system, as explained in the text below... 

Alkaloids may be classified as relatively low molecular mass bases containing one or more nitrogen atoms, often present in a ring system. They are found mainly in plants (from which over 6000 different alkaloids have been extracted). They are especially abundant in flowering plants, particularly lupins, poppies, tobacco and potatoes. They also are synthesized by some animals, insects, marine organisms and microorganisms. Most producers simultaneously synthesize several distinct alkaloids. 

Relative Humidity ratio of the vapor pressure of water in air compared to the saturated vapor pressure of pure water at the same temperature, measure of the amount of water vapor in an air mass expressed as percent of how much water vapor that air mass can hold Relative Mass mass measured with respect to a standard, atomic masses based on C-12 standard... 

The Pt alloy monolayer nanoparticle catalysts (e.g., Pt-Re layer on Pd cores) showed a clearly improved specific (Pt surface normalized) ORR activity their Pt mass-based electrocatalytic activity, however, exceeded that of pure Pt catalysts by an impressive factor of 18 x— 20 x. Their noble metal (Pt, Re, and Pd) mass-based activity improvement was still about a factor 4x. The Tafel slope in the 800-950 mV/RHE range suggested that the surface accumulation of Pt-OH species is delayed on the Pt monolayer catalyst. The enormous increase in Pt mass-based activity is obviously due to the small amount of Pt metal inside the Pt monolayer. 

With permission from J.H. Beynon, Mass Spectrometry and its Application to Organic Chemistry, Amsterdam, 1960. The columns headed FM contain the formula masses based on the exact mass of the most abundant isotope of each element these masses are based on the most abundant isotope of carbon having a mass of 12.0000. Note that the table includes only C, H, N, and O. 

Some of the most prominent spectral interferences can be resolved with a resolution from 4000 up to 10000, depending on the analytical problem. It can be tempting to calculate the resolution necessary to resolve two masses based only on their exact masses and the specified resolving power of the instrument. However, the resolution required will depend on the relative magnitude of the spectral overlap and analyte ion signals. For example, to resolve the overlap of Cl" and H Ar", a resolution of 3900 would be sufficient when considering the exact masses alone. However, as can be seen in Figure 1.10, a resolution of 10000 is needed to provide baseline resolution of the two peaks (because the H Ar ion is much more intense). 

---