Standard Methods for the

Method, There are two standard methods for the estimation of urea, (i) the hypobromite method, (ii) the urease method (p. 519). The chief merit of the hypobromite method is the rapidity of the analysis the results obtained are considered sufficiently accurate for most medical requirements, e.g., for the estimation of urea in urine. For accurate metabolic work, however, the urease method should be employed. 

A standard method for the preparation of an a ammo acid uses a bromo carboxylic acids as the substrate and aqueous ammonia as the nucleophile... 

Acyl transfer from an acid an hydride to an alcohol is a standard method for the prep aration of esters The reaction IS subject to catalysis by either acids (H2SO4) or bases (pyri dine)... 

Nucleophilic substitution by ammonia on a halo acids (Section 19 16) The a halo acids obtained by halogenation of car boxylic acids under conditions of the Hell-Volhard-Zelinsky reaction are reac tive substrates in nucleophilic substitu tion processes A standard method for the preparation of a ammo acids is dis placement of halide from a halo acids by nucleophilic substitution using excess aqueous ammonia... 

The reaction of an aryl diazonium salt with potassium iodide is the standard method for the preparation of aryl iodides The diazonium salt is prepared from a primary aro matic amine m the usual way a solution of potassium iodide is then added and the reac tion mixture is brought to room temperature or heated to accelerate the reaction... 

Reduction of aryl nitro compounds (Sec tion 22 9) The standard method for the preparation of an arylamine is by nitra tion of an aromatic ring followed by reduction of the nitro group Typical re ducing agents include iron or tin in hydro chloric acid or catalytic hydro genation... 

Normality is an older unit of concentration that, although once commonly used, is frequently ignored in today s laboratories. Normality is still used in some handbooks of analytical methods, and, for this reason, it is helpful to understand its meaning. For example, normality is the concentration unit used in Standard Methods for the Examination of Water and Wastewaterf a commonly used source of analytical methods for environmental laboratories. 

American Public Health Association. Standard Methods for the... 

Examine a procedure from Standard Methods for the Analysis of Waters and Wastewaters (or another manual of standard analytical methods), and identify the steps taken to compensate for interferences, to calibrate equipment and instruments, to standardize the method, and to acquire a representative sample. 

Marecek and colleagues developed a new electrochemical method for the rapid quantitative analysis of the antibiotic monensin in the fermentation vats used during its production. The standard method for the analysis, which is based on a test for microbiological activity, is both difficult and time-consuming. As part of the study, samples taken at different times from a fermentation production vat were analyzed for the concentration of monensin using both the electrochemical and microbiological procedures. The results, in parts per thousand (ppt), are reported in the following table. 

Precipitation gravimetry continues to be listed as a standard method for the analysis of Mg + and S04 in water and wastewater analysis. A description of the procedure for Mg + was discussed earlier in Method 8.1. Sulfate is analyzed by precipitating BaS04, using BaCb as the precipitant. Precipitation is carried out in an... 

Several standard methods for the quantitative analysis of food samples are based on measuring the sample s mass following a selective solvent extraction. For example, the crude fat content in chocolate can be determined by extracting with ether for 16 h in a Soxhlet extractor. After the extraction is complete, the ether is allowed to evaporate, and the residue is weighed after drying at 100 °C. This analysis has also been accomplished indirectly by weighing a sample before and after extracting with supercritical GO2. 

Method 3500-Mg D as published in Standard Methods for the Examination of Water and Wasteveater, 18th ed. American Public Health Association Washington, DC, 1992, pp. 3-73 to 3-74. 

Inorganic Analysis Acid-base titrimetry is a standard method for the quantitative analysis of many inorganic acids and bases. Standard solutions of NaOH can be used in the analysis of inorganic acids such as H3PO4 or H3ASO4, whereas standard solutions of HCl can be used for the analysis of inorganic bases such as Na2C03. 

Inorganic Analysis Complexation titrimetry continues to be listed as a standard method for the determination of hardness, Ca +, CN , and Ch in water and waste-water analysis. The evaluation of hardness was described earlier in Method 9.2. The determination of Ca + is complicated by the presence of Mg +, which also reacts with EDTA. To prevent an interference from Mg +, the pH is adjusted to 12-13, precipitating any Mg + as Mg(OH)2. Titrating with EDTA using murexide or Eri-ochrome Blue Black R as a visual indicator gives the concentration of Ca +. 

Method 417B in Standard Methods for the Analysis of Water and Wastewater, American Public Health Association Washington, D.C. 15 ed., 1981, pp. 356-360. 

British Standard Methods for the Determination of Particle Sis e Powders, Part I, Subdivision of Gross Sample Down to 0.2 Milliliters, BS3406 Part I, British Standards, London, 1961. 

Quality Control. The spectrometer is the most suitable instmment for determining most low level residual impurities. ASTM E414 is the standard method for the measurement of impurities in copper by the briquette dc-arc technique (65). In this method, the sample in the form of chips, drillings, or powder is briquetted and excited in a d-c arc opposite a high purity copper rod. Impurities in the ranges noted can be measured ... 

Currently, there is continuing work on an iadustry standard method for the direct determination of monomer, dimer, and trimer acids. Urea adduction (of the methyl esters) has been suggested as a means of determining monomer ia distilled dimer (74). The method is tedious and the nonadductiag branched-chain monomer is recovered with the polymeric fraction. A micro sublimation procedure was developed as an improvement on urea adduction for estimation of the polymer fraction. Incomplete removal of monomer esters or loss of dimer duriag distillation can lead to error (75). 

H2NOH-HC1, Pyr, 60°. This is the standard method for the preparation of oximes. Ethanol or methanol can be used as cosolvents. 

Since 17a-ethynyl-17 -hydroxy steroids are so readily prepared, they represent attractive starting materials for conversion to 20-ketopregnanes. Standard methods for the hydration of aliphatic acetylenes (e.g, mercuric salts alone, with aniline, or with BF3) give variable results, and sometimes no product at all, due to D-homo rearrangement. 233,235,265-7 mercury... 

Phillips, H. 1987. A Comparison of Standard Methods for the Determination of Maximum Experimental Safe Gap (MESG). Proc. International Symposium on the Explosion Hazard Classification of Vapors, Gases, and Dusts, pp. 83-108. Publication NMAB-447. National Materials Advisory Board, Washington, DC. 

In 1911, Ame Pictet and Theodor Spengler reported that P-arylethyl amines condensed with aldehydes in the presence of acid to give tetrahydroisoquinolines. Phenethylamine 6 was combined with dimethoxymethane 7 and HCl at elevated temperatures to give tetrahydroisoquinoline 8. Soon after, the Pictet-Spengler reaction became the standard method for the formation of tetrahydroisoquinolines. 

A variant, the 1,6-Hofmann elimination, has become a standard method for the synthesis of [2.2]paracyclophanes 17 although it often gives low yields. 

If there is any doubt as to the purity of the reagents used, they should be tested by standard methods for the impurities that might cause errors in the determinations. It may be mentioned that not all chemicals employed in quantitative analysis are available in the form of analytical reagents the purest commercially available products should, if necessary, be purified by known methods see below. The exact mode of drying, if required, will vary with the reagent details are given for specific reagents in the text. 

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