Standardization of analytical methods

Finally, clinical chemistry of Lp(a) and apolipoprotein (a) is characterized by a variety of problems, caused by the structural complexity and heterogeneity of Lp(a), the homology of apo(a) with plasminogen, and the lack of standardization of analytical methods. 

Standards of analytical methods and requirements fix internal quality control... 

FIGURE 9 Hierarchy of, relationship between, and objectives and requirements for prevalidation [106], validation [62,63, 68], and standardization of analytical methods [62, 63, 67, 68,75,84] RSD = relative standard deviation, CV = coefficient of variation, SOP = standard operating procedure. 

The Reliability of Measurements. The Analysis of Data. The Application of Statistical Tests. Limits of Detection. Quality Control Charts. Standardization of Analytical Methods. 

Fig. 1 Exemplified overview and interconnectivity of standardization of analytical methods for food. CEN The European Committee for Standardization, ISO International Organization for Standardization, JSA Japanese Standardization Agency, AACC American Association of Cereal Chemists, AOAC Association of Official Analytical Chemists, CCMAS Codex Committee of Methods of Analysis and Sampling...

Several methods and procedures have been developed aiming at the detection of the same food derived from modern biotechnology. This has repeatedly caused problems in trade, as analytical results generated in different laboratories did not concur. It is of high importance to achieve a level of standardization of analytical methods, prevents any future trade disputes due to incompatibility of analytical methods. 

The reliability of measurements. The arrptysis of data. The application of statistical tests. Limits of detection. Quality control charts. Standardization of analytical methods. Chcmometrics. 

The opponents of fundamental studies with idealized electrocatalysts and reactions cannot deny the unique insight into surface molecular and electronic or energetic interactions that new surface and mechanistic techniques generate. A combination of surface spectrometries, isotopic reactions, and conventional electrode kinetics could help unravel some of the surface mysteries. The application of such methods in electrocatalysis is limited at present to hydrogen and oxygen reactants on simple catalytic surfaces. Extension to a variety of model and complex reactions should be attempted soon. The prospective explorer, however, should strive and attend with care the standardization of analytical methods for meaningful interpretations and comparisons. 

As a majority of the participants in the workshop were familiar with analytical work in the PAH field, this topic brought significant conclusions to the meeting. Some analytical problems were so demanding that a subcommittee on standardization of analytical methods and units was formed. 

The historical diversity and lack of standardization of analytical methods used prior to the 1980s means that the PAH data obtained from diverse environments by different workers prior to the 1980s are difficult to compare. In the 1980s, the availability of... 

Certified reference materials are intended primarily for calibration and in quality control of analytical techniques. A certified reference material is a reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure that establishes its traceability to an accurate realization of the unit in which the property values are expressed and for which each certified value is accompanied by an uncertainty at a stated level of confidence. They are used to test, validate, and optimize new analytical techniques as well as in quality control of routine laboratory work. Table 3 gives a list of environmental samples that provide certified values of PAH content. These are available from various bodies as certified reference materials. In measuring the concentration of a substance for certification purposes, more than two independent and reliable analytical methods are used. Certified reference materials when used for standardization of analytical methods will make comparisons between PAH data obtained by a variety of workers using... 

An early article by Gimther and Blinn (72) outlined the basic principles of pesticide residue analysis, including the possibilities for systematization and standardization of analytical methods. In many respects this thinking led to the evolution of today s methods, both single residue (SRM) and particularly integrated multi-residue methods (MRMs) that can include several hundred individual anal es, both parent compounds and significant breakdown products (13). 

Mahalingam,T. R.,Vijayalakshmi, S., Prabhu, R. K.,Thiruvengadasami, A., Mathews, C. K., and Shanmugasundaram, K. R. (1997). Studies on some trace and minor elements in blood A survey of the kalpakkam (India) population. Part I Standardization of analytical methods using ICP-MS and AAS. Bio. Trace Elem. Res. 57(3), 191. 

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. 

Analysis of Standards The analysis of a standard containing a known concentration of analyte also can be used to monitor a system s state of statistical control. Ideally, a standard reference material (SRM) should be used, provided that the matrix of the SRM is similar to that of the samples being analyzed. A variety of appropriate SRMs are available from the National Institute of Standards and Technology (NIST). If a suitable SRM is not available, then an independently prepared synthetic sample can be used if it is prepared from reagents of known purity. At a minimum, a standardization of the method is verified by periodically analyzing one of the calibration standards. In all cases, the analyte s experimentally determined concentration in the standard must fall within predetermined limits if the system is to be considered under statistical control. 

A number of analytical methods have been developed for the determination of chlorotoluene mixtures by gas chromatography. These are used for determinations in environments such as air near industry (62) and soil (63). Liquid crystal stationary columns are more effective in separating m- and chlorotoluene than conventional columns (64). Prepacked columns are commercially available. ZeoHtes have been examined extensively as a means to separate chlorotoluene mixtures (see Molecularsieves). For example, a Y-type 2eohte containing sodium and copper has been used to separate y -chlorotoluene from its isomers by selective absorption (65). The presence of ben2ylic impurities in chlorotoluenes is determined by standard methods for hydroly2able chlorine. Proton (66) and carbon-13 chemical shifts, characteristic in absorption bands, and principal mass spectral peaks are available along with sources of reference spectra (67). 

Vapor-phase decomposition and collection (Figs 4.16 to 4.18) is a standardized method of silicon wafer surface analysis [4.11]. The native oxide on wafer surfaces readily reacts with isothermally distilled HF vapor and forms small droplets on the hydrophobic wafer surface at room temperature [4.66]. These small droplets can be collected with a scanning droplet. The scanned, accumulated droplets finally contain all dissolved contamination in the scanning droplet. It must be dried on a concentrated spot (diameter approximately 150 pm) and measured against the blank droplet residue of the scanning solution [4.67-4.69]. VPD-TXRF has been carefully evaluated against standardized surface analytical methods. The user is advised to use reliable reference materials [4.70-4.72]. 

X sensitivity of analytical method (mg) suitable hygiene standard (mg/m )... 

Saturated solutions of some reagents (T) 829 Schoniger oxygen flask see Oxygen flask Schwarzenbach classification 53 Screened indicators 268 Sebacic acid 469 Secondary pH standards 831 Selective ion meters 567 Selectivity coefficient, 559 in EDTA titrations, 312 in fluorimetry, 733 of analytical methods, 12 Selenium, D. of as element, (g) 465 Semi-log graph paper 572 Sensitivity (fl) 834, (fu) 732 Separation coefficient 163, 196 Separations by chromatographic methods, 13, 208. 233, 249... 

This chapter has shown, however, that errors can be investigated and evaluated with more assurance in x-ray emission spectrography than in the general run of analytical methods. The standard counting error (10.3) can serve as a satisfactory criterion of operating conditions and as a standard of reference to which the other errors are conveniently -compared. But it is manifestly unwise to assume without proof, as has often been done, that the standard counting error gives the precision of the analytical result. 

The purpose of this chapter is to describe the analytical methods that are available for detecting, measuring, and/or monitoring methyl parathion, its metabolites, and other biomarkers of exposure and effect to methyl parathion. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used for environmental samples are the methods approved by federal agencies and organizations such as EPA and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by groups such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that modify previously used methods to obtain lower detection limits and/or to improve accuracy and precision. 

Radioisotope-labeled nitrosamines have proven valuable in development of analytical methods and for demonstrating efficiency of recovery of nitrosamines from tobacco products and smoke (37-39). The very high specific activity required for low part-per-billion determinations has discouraged most analysts from using this approach. Unless a radiochromatographic detector with adequate sensitivity is available, samples must be counted independently of the final chromatographic determination, and one of the advantages of internal standardization, correction for variation in volume injected, is lost. 

The Pharmacopoeial Forum fulfills a vital role in promoting industry-wide communication between those involved with quality assurance, the development of standards and analytical methods. It contains an up to date list of official USP Reference Substances, with current and recently changed lot numbers. Reference Substances not yet available and those under development are also described. The publication acts as an international open forum in which scientists are invited to express their views, suggestions, ideas and comments regarding new drug standard development and revisions to existing monographs. Pharmacopoeial Forum is published, on a subscription basis, six times a year, back issues are available for USP website see Table 84. 

The BBA publishes reviews of analytical methods for existing a.i. References and a table of a.i. which can be determined using the standard multi-method S19 or its new modular version are presented on the World Wide Web. ... 

A standard format for the presentation of analytical methods is not obligatory. However, each study should contain such information normally present in complete method descriptions. The list of key points presented in the SANCO Guidance Document d may serve as a guide ... 

The integration of analytical methods in European standards requires their acceptance by several national experts within special working groups and in a final weighted vote of National Standards Bodies. Therefore, there needs to be very high confidence in the performance of methods. Consequently, methods should be tested in inter-laboratory method validation studies, with the exception of those multiresidue methods which are widely used throughout Europe. In the case of CEN methods there is no doubt about residue definition but detailed requirements about the number of matrices and concentration levels in validation experiments do not exist. Eor this reason it may be that CEN methods are validated for important crops only. 

---