Semiquantitative

The simplest molecular orbital method to use, and the one involving the most drastic approximations and assumptions, is the Huckel method. One str ength of the Huckel method is that it provides a semiquantitative theoretical treatment of ground-state energies, bond orders, electron densities, and free valences that appeals to the pictorial sense of molecular structure and reactive affinity that most chemists use in their everyday work. Although one rarely sees Huckel calculations in the resear ch literature anymore, they introduce the reader to many of the concepts and much of the nomenclature used in more rigorous molecular orbital calculations. 

Deviation includes, in fact, the summation of steric and electronic effects, and basicity is somewhat a useful predictor for properties of complex dyes (solvent sensitivity, isomeric forms of trinuclear dyes) and gives also semiquantitative data for color structure relation (atomic)... 

An approach to copolymerization has been advanced by Price and Alfrey which attempts to both combine resonance and polarity considerations and accomplish the data reduction strategy of the last paragraph. It should be conceded at the outset that the Price-Alfrey method is only semiquantitative in its success. Its greatest usefulness is probably in providing some orientation to a new system before launching an experimental investigation. 

Equation 6 shows that the adsorption of component 1 at a partial pressureis reduced in the presence of component 2 as a result of competition for the available surface sites. There ate only a few systems for which this expression (with 5 1 = q 2 = 5 ) provides an accurate quantitative representation, but it provides useful quaUtative or semiquantitative guidance for many systems. In particular, it has the correct asymptotic behavior and provides expHcit recognition of the effect of competitive adsorption. For example, if component 2 is either strongly adsorbed or present at much higher concentration than component 1, the isotherm for component 1 is reduced to a simple linear form in which the apparent Henry s law constant depends onp. ... 

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. 

Immunodiffusion and immunoprecipitation, developed ia the 1940s as a means to identify and semiquantitate specific proteias, were the direct precursors to the development ia 1953 of Immunoelectrophoresis, a method used ia many clinical laboratories (5). Single- and double-gel immunodiffusion and immunoelectrophoresis were, ia effect, the first standardized and routinely used immunoassay methods (see Electroseparations, electrophoresis). 

Latex agglutination immunoassays are easily formatted into simple kits which can provide yes/no and semiquantitative estimates of antigen (or antibody) in a sample. The first such assay was developed in 1957 for rheumatoid factor (15) and assays are on the market for the deterrnination of many species of bacteria, fungi. Mycoplasma, parasites, ckettsia, and vimses, as well as for the deterrnination of autoimmune disease, hormones (qv), dmgs (see Pharmaceuticals), and blood proteins (16). Latex agglutination is also the basis of many home pregnancy tests. 

Flame Resistance. Traditionally, small-scale laboratory flammabiUty tests have been used to initially characterize foams (38). However, these do not reflect the performance of such materials in bulk form. Fire characteristics of thermal insulations for building appHcations are generally reported in the form of quaHtative or semiquantitative results from ASTM E84 or similar tunnel tests (39). Similar larger scale tests are used for aircraft and marine appHcations. 

Elame-spread and smoke-density values, and the less often reported fuel-contributed semiquantitive results of the ASTM E84 test and the limited oxygen index (LOI) laboratory test, are more often used to compare fire performance of ceUular plastics. AH building codes requite that ceUular plastics be protected by inner or outer sheathings or be housed in systems aH with a specified minimum total fire resistance. Absolute incombustibHity cannot be attained in practice and often is not requited. The system approach to protecting the more combustible materials affords adequate safety in the buildings by aHowing the occupant sufficient time to evacuate before combustion of the protected ceUular plastic. 

The total phosphoms content of the sample is determined by method AOCS Ja 5-55. Analysis of phosphoUpid in lecithin concentrates (AOCS Ja 7-86) is performed by fractionation with two-dimensional thin-layer chromatography (tic) followed by acid digestion and reaction with molybdate to measure total phosphorous for each fraction at 310 nm. It is a semiquantitative method for PC, PE, PI, PA, LPC, and LPE. Method AOCS Ja 7b-91 is for the direct deterrnination of single phosphoHpids PE, PA, PI, PC in lecithin by high performance Hquid chromatography (hplc). The method is appHcable to oil-containing lecithins, deoiled lecithins, lecithin fractions, but not appHcable to lyso-PC and lyso-PE. 

H. W. Fishbum, Jr., and W. E. DiU, Jr., "A Method for the Semiquantitative Analysis and Identification of Mixed Phases of Manganese Dioxide," paper presented at the Power Sources Conference, Atlantic City, N.J., May 10, 1961. 

The compositional distribution of ethylene copolymers represents relative contributions of macromolecules with different comonomer contents to a given resin. Compositional distributions of PE resins, however, are measured either by temperature-rising elution fractionation (tref) or, semiquantitatively, by differential scanning calorimetry (dsc). Table 2 shows some correlations between the commercially used PE characterization parameters and the stmctural properties of ethylene polymers used in polymer chemistry. 

Pulsed spark sources, in which the material to be analyzed is part of one electrode, are used for semiquantitative analyses. The numerous and complex processes involved in spark discharges have been studied in detail by time- and space-resolved spectroscopy (94). The temperature of d-c arcs, into which the analyte is introduced as an aerosol in a flowing carrier gas, eg, argon, is approximately 10,000 K. Numerous experimental and theoretical studies of stabilized plasma arcs are available (79,95). 

Cubic equations, although simple and able to provide semiquantitative descriptions of real fluid behavior, are not generally useful for accurate representation of volumetric data over wide ranges of T and P. For such appHcations, more comprehensive expressions with large numbers of adjustable parameters are needed. 7h.e simplest of these are the extended virial equations, exemplified by the eight-constant Benedict-Webb-Rubin (BWR) equation of state (13) ... 

Wavelength dispersive x-ray fluorescence spectrometric (xrf) methods using the titanium line at 0.2570 nm may be employed for the determination of significant levels of titanium only by carefiil matrix-matching. However, xrf methods can also be used for semiquantitative determination of titanium in a variety of products, eg, plastics. Xrf is also widely used for the determination of minor components, such as those present in the surface coating, in titanium dioxide pigments. 

Zinc smelters use x-ray fluorescence spectrometry to analyze for zinc and many other metals in concentrates, calcines, residues, and trace elements precipitated from solution, such as arsenic, antimony, selenium, tellurium, and tin. X-ray analysis is also used for quaUtative and semiquantitative analysis. Electrolytic smelters rely heavily on AAS and polarography for solutions, residues, and environmental samples. 

Mica [12001 -26-2]—Cl Pigment White 20, Cl No. 77019. A white powder obtained from the naturally occurring mineral muscovite mica, consisting predominantly of a potassium aluminum siHcate, [1327-44-2] H2KAl2(Si0 2- Mica may be identified and semiquantitatively determined by its characteristic x-ray diffraction pattern and by its optical properties. 

This equation is a reasonable model of electrokinetic behavior, although for theoretical studies many possible corrections must be considered. Correction must always be made for electrokinetic effects at the wall of the cell, since this wall also carries a double layer. There are corrections for the motion of solvated ions through the medium, surface and bulk conductivity of the particles, nonspherical shape of the particles, etc. The parameter zeta, determined by measuring the particle velocity and substituting in the above equation, is a measure of the potential at the so-called surface of shear, ie, the surface dividing the moving particle and its adherent layer of solution from the stationary bulk of the solution. This surface of shear ties at an indeterrninate distance from the tme particle surface. Thus, the measured zeta potential can be related only semiquantitatively to the curves of Figure 3. 

For semiquantitative or quantitative analyses, the separated dyes can be measured with a reflectance densitometer or they can be extracted from the plate or paper and measured by transmittance spectrophotometry. 

So, extractive and photometric determination of 2,4-D with CV and also the test-scale for its semiquantitative determination with separation from instmmental basis are proposed. 

Yes, semiquantitative without standards quantitative with standards. Not a trace element method. 

Photoluminescence finds its greatest strengths as a qualitative and semiquantitative probe. Quantification based on absolute or relative intensities is difficult, although it is useful in applications where the sample and optical configurations may be carefully controlled. The necessary conditions are most easily met for analytical applica-... 

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