Determination, quantitative

Many of the qualitative tests may be applied to the quantitative determination of sugars. The color developed in the presence of acids and phenols or the amount of metal or metallic oxide formed by the reduction of the salts of heavy metals by the sugars can be measured. Some of these methods can also be used on a micro-scale to determine quantitatively the sugar eluted from paper chromatograms. In some cases, difficultly soluble derivations such as the osazones or hydrazones can be weighed directly. Because of the absence of a stoichiometric relation for the methods, they are not completely satisfactory. Complete descriptions of many of the methods described will be found in the article by Bell 6). 

When sugars or their derivatives are reasonably pure, and in particular are free of optically active impurities, the measurement of the optical 

Usually the specific rotation varies somewhat with the concentration (c), and this effect must receive consideration. 

Mixtures of several sugars are more difficult to analyze by optical rotation methods, but sometimes the analysis is possible if the rotations of the components vary in a different manner when the solvent, the acidity, or the temperature is changed. The change in solvent may be brought about by the addition of salts (Chapter V) which markedly affect the rotations. If the specific rotations of the two components are known under two sets of conditions, the solution of two simultaneous equations will give the relative percentages of components x and y  

One of the most important sugar mixtures which can be analyzed by the optical rotatory method is the mixture of sucrose and its hydrolysis products, glucose and fructose. The process of hydrolysis of sucrose into glucose and fructose is known as inversion because of the change of the sign of rotation which takes place during the hydrolysis. Mixtures of this type are found in invert sirups, honey, etc. The polarimetric method for this purpose is based on the optical rotatory power of the original material and of the 

Investigations on the influence of the carbohydrates on soil properties, and attempts to determine the composition of soil organic matter, have prompted many workers to determine, quantitatively, the proportion of carbohydrates in soils. 

Attempts have been made to use colorimetric methods for the determination of the hexoses in soils. The reaction with an throne has been tried directly on the soil, but was found to give irreproducible results. However, this method works with soil hydrolyzates. In addition to what has been 

Hexoses of Delaware soils have also been determined, by quantitative paper-chromatography of soil hydrolyzates, as amounting to 1 to 2 % of the soil organic matter.  

Pentoses have frequently been determined in soils by the furfural-phloro-glucinol method.But phloroglucinol also gives precipitates with a variety of other aldehydes, such as 5-methyl-2-furaldehyde, 5-(hydroxymethyl)-2-furaldehyde, and formaldehyde. Orcinol and aniline acetate are much more specific reagents, and no aldehyde present in the hydrochloric acid distillate from soils has been found to interfere in the furfural determination by the orcinol method. The orcinol and aniline acetate methods give, for various Swiss and Norwegian soils, a pentose anhydride content of 0.5 to 8.5 % of the soil organic matter (see Table III) no corrections were made for the furfural derived from uronic acids. 

Pentoses have also been determined in the hydrolyzates of soils (IN sulfuric acid, 1 hour, 120°), after the removal of the uronic acids with anion exchanger, by Dial s orcinol method. They constituted 3 to 5 % of soil organic matter. 

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Carius method The quantitative determination of S and halogens in covalent (organic) compounds by complete oxidation of the compound with cone, nitric acid and subsequent estimation of precipitated AgX or BaS04. 

Quantitative determined visual recognition for usual inspections, indicate that for indications with lengths over about 1.5 mm tbe probability of recognition is about 100 %. This is also applied to the penetrant inspection. This does not include the so called "human factor" which means that it cannot be guaranted that the inspector detects all indications for instance not always observing the inspection surface with full concentration. 

Parikh A N and Allara D L 1992 Quantitative determination of moleoular struoture in multilayered thin films of... 

Aminothiazole present in urine or blood plasma forms a colored Schiff base when 5-nitrofurfural is added the colorimetric analysis of the Schiff base allows the quantitative determination of this thiazole (1571). The Schiff base may also be dosed by polarographic of spectro-photometric methods (1572). 

Quantitative determination is also possible by ultraviolet spectroscopy with the intense absorption at 320 nm (94). They may also be characterized electrochemically with a mercury electrode (95),... 

A quantitative determination using a single external standard was described at the beginning of this section, with k given by equation 5.3. Once standardized, the concentration of analyte, Ca, is given as... 

A spectrophotometric method for the quantitative determination of Pb + levels in blood yields an Sjtand of 0.474 for a standard whose concentration of lead is 1.75 ppb. How many parts per billion of Pb + occur in a sample of blood if Ssamp is 0.361 ... 

A second spectrophotometric method for the quantitative determination of Pb + levels in blood gives a linear normal calibration curve for which... 

A third spectrophotometric method for the quantitative determination of the concentration of in blood yields an Sjamp of 0.193 for a 1.00-mL sample of blood that has been diluted to 5.00 mb. A second 1.00-mL sample is spiked with 1.00 )J,L of a 1560-ppb Pb + standard and diluted to 5.00 mb, yielding an Sspike of 0.419. Determine the concentration of Pb + in the original sample of blood. 

A fifth spectrophotometric method for the quantitative determination of the concentration of Pb + in blood uses a multiple-point standard addition based on equation 5.6. The original blood sample has a volume of 1.00 mb, and the standard used for spiking the sample has a concentration of 1560 ppb Pb +. All samples were diluted to 5.00 mb before measuring the signal. A calibration curve of Sjpike versus Vj is described by... 

A sixth spectrophotometric method for the quantitative determination of Pb + levels in blood uses CQ+ as an internal standard. A standard containing 1.75 ppb Pb + and 2.25 ppb CQ+ yields a ratio of Sa/Sis of 2.37. A sample of blood is spiked with the same concentration of Cu +, giving a signal ratio of 1.80. Determine the concentration of Pb + in the sample of blood. 

Yang, M. J. Orton, M. L. Pawliszyn, J. Quantitative Determination of Caffeine in Beverages Using a Combined SPME-GC/MS Method, /. Chem. Educ. 1997, 74,... 

Powell, J. R. Tucker, S. A. Acree, Jr., et al. A Student-Designed Potentiometric Titration Quantitative Determination oflron(ll) by Caro s Acid Titration, ... 

An acidimetric quantitative determination is based on treatment of the hydantoia with silver nitrate and pyridine ia aqueous solution. Complexation of the silver ion at N-3 Hberates a proton, and the pyridinium ions thus formed are titrated usiag phenolphthaleia as an iadicator. In a different approach, the acidity of N-3—H is direcdy determined by neutralization with tetrabutylammonium hydroxide or sodium methoxide ia dimethylformarnide. 

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

In solution, lignin is most conveniendy analyzed quaUtatively and quantitatively by uv spectroscopy. Typical absorptivity values, D, at 280 nm for milled wood (MW) lignins and other types of lignins are Hsted ia Table 4. These values are used for quantitative determination of the lignins ia suitable solvents. 

X-Ray Methods. In x-ray fluorescence the sample containing mercury is exposed to a high iatensity x-ray beam which causes the mercury and other elements ia the sample to emit characteristic x-rays. The iatensity of the emitted beam is directly proportional to the elemental concentration ia the sample (22). Mercury content below 1 ppm can be detected by this method. X-ray diffraction analysis is ordinarily used for the quaUtative but not the quantitative determination of mercury. 

Ion-specific electrodes can be used for the quantitative determination of perchlorates in the parts per million (ppm) range (109) (see Electro ANALYTICAL techniques). This method is linear over small ranges of concentration, and is best appHed in analyzing solutions where interferences from other ionic species do not occur. 

Because few scatter events are recorded, attenuation compensation is relatively easier for PET using an external positron emitting source. As a result, the technology for quantitative determinations of radioactivity distributions is significantly more advanced in PET imaging. Technology development for SPECT, however, is improving this parameter. 

The fire assay, the antecedents of which date to ancient Egypt, remains the most rehable method for the accurate quantitative determination of precious metals ia any mixture for concentrations from 5 ppm to 100%. A sample is folded iato silver-free lead foil cones, which are placed ia bone-ash cupels (cups) and heated to between 1000 and 1200°C to oxidize the noimoble metals. The oxides are then absorbed iato a bone-ash cupel (ca 99%) and a shiny, uniformly metaUic-colored bead remains. The bead is bmshed clean, roUed fiat, and treated with CP grade nitric acid to dissolve the silver. The presence of trace metals ia that solution is then determined by iastmmental techniques and the purity of the silver determined by difference. 

The alkah metals are commonly separated from all other elements except chlorine before gravimetric determination. In the absence of other alkaUes, sodium maybe weighed as the chloride or converted to the sulfate and weighed. WeU-known gravimetric procedures employ precipitation as the uranyl acetate of sodium—2inc or sodium—magnesium. Quantitative determination of sodium without separation is frequently possible by emission or atomic-absorption spectrometric techniques. 

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

Using any of the carrier proteins available in highly purified form, eg, TBG or TBPA, a convenient and accurate quantitative determination of and is possible by displacement of radioiodinated or T. This procedure enables their quick determination at low concentrations even in the presence of coundess other substances that occur in body duids (31). In a similar fashion, intact cell nuclei or solubilized proteins from rat fiver cell nuclei, which display high affinities for thyroid hormones, especially T, have been used to establish relative binding affinities of many thyromimetic compounds (7). 

There should be sufficientiy large numbers of animals to allow a quantitative determination of the average response and the range of responses, including the demonstration of hypersensitive populations. When objective procedures are undertaken, these should be sufficient to allow vaUd statistical comparison to be made between treated and control groups. 

However, in order to precisely define the nature of a neurotoxic process, its mechanism of production, and the quantitative determinants for the... 

Standardization and Testing". The final vaccine is tested for safety, potency, and residual chemicals. Safety includes testing for endotoxin and stetihty. Potency is evaluated by quantitative determination of the amount of hemagglutinin in the vaccine. Antibody to this glycoprotein is associated with protection. The single radial immunodiffusion (SKID) technique is used to standardi2e the mass of this protein in comparison to a reference preparation. 

The yellow form (11) on acidification is converted to the more stable thiol form (12). On oxidation, typically with alkaline ferhcyanide, yellow form (11) is irreversibly converted to thiochrome [299-35-4] (14), a yellow crystalline compound found naturally in yeast but with no thiamine activity. In solution, thiochrome exhibits an intense blue fluorescence, a property used for the quantitative determination of thiamine. 

Dichlorine monoxide can be quantitatively determined alone or in admixture with CI2, by iodometry the acid consumed is a direct measure of CI2O (65). The reactions involved are... 

Polymerization-grade chloroprene is typically at least 99.5% pure, excluding inert solvents that may be present. It must be substantially free of peroxides, polymer [9010-98-4], and inhibitors. A low, controlled concentration of inhibitor is sometimes specified. It must also be free of impurities that are acidic or that will generate additional acidity during emulsion polymerization. Typical impurities are 1-chlorobutadiene [627-22-5] and traces of chlorobutenes (from dehydrochlorination of dichlorobutanes produced from butenes in butadiene [106-99-0]), 3,4-dichlorobutene [760-23-6], and dimers of both chloroprene and butadiene. Gas chromatography is used for analysis of volatile impurities. Dissolved polymer can be detected by turbidity after precipitation with alcohol or determined gravimetrically. Inhibitors and dimers can interfere with quantitative determination of polymer either by precipitation or evaporation if significant amounts are present. 

An unknown commercial detergent may contain some combination of anionic, nonionic, cationic, and possibly amphoteric surfactants, inorganic builders and fillers as weU as some minor additives. In general, the analytical scheme iacludes separation of nonsurfactant and inorganic components from the total mixture, classification of the surfactants, separation of iadividual surfactants, and quantitative determination (131). 

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