Standards standards

Resin type Standard Standard Standard Standard... 

Designation Standard Standard Standard Double drive... 

Standard /Standard /Standard enthalpy changej = I enthalpy content) — I endulpy conient) for reaction / of products / of reactants... 

Standardization—External standards, standard additions, and internal standards are a common feature of many quantitative analyses. Suggested experiments using these standardization methods are found in later chapters. A good project experiment for introducing external standardization, standard additions, and the importance of the sample s matrix is to explore the effect of pH on the quantitative analysis of an acid-base indicator. Using bromothymol blue as an example, external standards can be prepared in a pH 9 buffer and used to analyze samples buffered to different pHs in the range of 6-10. Results can be compared with those obtained using a standard addition. 

Primary Standard Standardization of Acidic Titrants Titration Reaction Comment... 

Quality Control. Because fine chemicals are sold according to specifications, adherence to constant and strict specifications, at risk because of the batchwise production and the use of the same equipment for different products ia multipurpose plants, is a necessity for fine chemical companies. For the majority of the fine chemicals, the degree of attention devoted to quahty control (qv) is not at the discretion of the iadividual company. This is particularly the case for fine chemicals used as active iagredients ia dmgs and foodstuffs (see Fine chemicals, standards). Standards for dmgs are pubHshed ia the United States Pharmacopeia (USP) ia the United States (6) and the European Pharmacopeia ia Europe (7). 

Standardization. Standardization is the process of adjusting the ratio of butterfat and soHds-not-fat (SNF) to meet legal or industry standards. Adding cream of high butterfat milk iato semm of low butterfat milk might result in a product with low SNF, thus careful control must be exercised. 

Construction. The parts, dimensions, and dimensional tolerances used in manufacturing of screw conveyors are highly standardized. Standards for dimensions and minimum service requirements are available (24—26). These are accepted by most of the industry. 

Federal standards Standards laid down by federal governments covering certain control aspects. 

When selecting and sizing compressors, care should be taken in determining which standard has been used to rate a compressor under consideration, particularly if the compressor has been produced abroad. All further discussions in this section will utilize only the API Mechanical Equipment Standards standard atmosphere. 

Figure 11.14 The main headings of the ISO 13485 2003 standard (Standard headings reproduced with permission of International Standards Organisation).

Functions of Standards. Fluorescent standards can be used for three basic functions calibration, standardization, and measurement method assessment. In calibration, the standard is used to check or calibrate Instrument characteristics and perturbations on true spectra. For standardization, standards are used to determine the function that relates chemical concentration to Instrument response. This latter use has been expanded from pure materials to quite complex standards that are carried through the total chemical measurement process (10). These more complex standards are now used to assess the precision and accuracy of measurement procedures. 

Requirements of Standards. Standards used In the calibration of mlcrospectrofluorometrlc Instrumentation must meet more stringent requirements than those used In macromeasurements. The effect of Increased excitation flux as well as spatial effects under magnification make many macromeasurement standards unsatisfactory for micromeasurements. Following are some of the requirements for fluorescence standards that are strongly Influenced by a change from the macro- to the micro-environment. 

Standardization. Standardization in analytical chemistry, in which standards are used to relate the instrument signal to compound concentration, is the critical function for determining the relative concentrations of species In a wide variety of matrices. Environmental Standard Reference Materials (SRM s) have been developed for various polynuclear aromatic hydrocarbons (PAH s). Information on SRM s can be obtained from the Office of Standard Reference Materials, National Bureau of Standards, Gaithersburg, MD 20899. Summarized in Table VII, these SRM s range from "pure compounds" in aqueous and organic solvents to "natural" matrices such as shale oil and urban and diesel particulate materials. 

The concentration of biodiesel (fetty acid methyl esters) and glycerides were analyzed by liquid chromatography (Shimadzu-lOA HPLC). An ODS-2 column (250x4.6mm) was used for the separation. The flow rate of the mobile phase (acetone acetonitrile=l l) was set to 1 ml/min. Peaks were identified by comparison with reference standards. Standards of methyl esters, monoglycerides, digjycerides and triglycerides were bought from Fluka. 

Cali JP, and Reed WP (1976) The role of the National Bureau of Standards standard reference materials in accurate trace analysis. In Lafleur PD, ed. Accuracy in Trace Analysis Sampling, Sample Handling, and Analysis, NBS Special Publication 422, Vol i pp 41-63. National Bureau of Standards, Washington, DC. 

Houben [256] has compared the determination of flame-retardant elements Br, P, S, K, Cl and F in polycarbonate using commercial (X40 and UniQuant ) software. For the X40 method, a calibration line for each element in PC or PC/ABS blends was mapped for the conversion of intensities to concentrations. With the universal UniQuant method, sensitivity factors (ks) were calibrated with pure standards. The X40 method turned out to be more reliable than UniQuant for the determination of FRs in PC and PC/ABS blends, even in the case of calibration of k values with PC standards. Standard errors of 5 % were achieved for Br, P, S and K, and 20% for Cl and F the latter element could not be determined by means of UniQuant (Table 8.44). GFR PC cannot be quantified with these two methods, because of the heterogeneous nature of the composites. Other difficult matrices for XRF analysis are PBT, PS and PP compounds containing both BFRs and Sb203 (10-30wt %) due to self-absorption of Sb and interelement effects. 

Identification of flavonoids Quantification of individual flavonoids depends heavily on the availability of standard references. Only a limited number of common flavonoids are commercially available as standards. Standard references for flavonoid glycosides are particularly difficult to find thus direct quantification of the native glycosides is nearly impossible. Analysis of the aglycones after acid or enzymatic hydrolysis is therefore common practice. When standard flavonoids are not available, or when unknown compounds are encountered in a particular fruit or vegetable, use of a DAD... 

ASTM Annual Book of Standards. Standard methods of building construction and materials. Method E 119-83. American Society for Testing and Materials Philadelphia, PA, 1985. 

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