Characterization methods reference standards

Phase-solubility analysis17 (sometimes referred to as phase equilibrium purification) is the quantitative determination of the purity of a substance through the application of precise solubility measurements. At a given temperature, a definite amount of a pure substance is soluble in a definite quantity of solvent. The resulting solution is saturated with respect to the particular substance, but the solution remains unsaturated with respect to other substances even though such substances may be closely related in chemical structure and physical properties to the particular substance being tested. There are examples of the use of this technique in HPLC methods development18 and in the characterization of reference standards,19 but the... 

The predorninant method for the analysis of alurninum-base alloys is spark source emission spectroscopy. SoHd metal samples are sparked direcdy, simultaneously eroding the metal surface, vaporizing the metal, and exciting the atomic vapor to emit light ia proportion to the amount of material present. Standard spark emission analytical techniques are described in ASTM ElOl, E607, E1251 and E716 (36). A wide variety of weU-characterized soHd reference materials are available from major aluminum producers for instmment caUbration. 

Elaboration of the method for the identification of colour compounds by RPLC MS should comprise four steps (1) spectral characterization of reference materials (standards) and subsequent optimization of detection parameters, as well as those of their chromatographic separation (2) analysis of natural dyestuffs used as colouring materials in historical objects (3) analysis of model samples (dyed fibres, paintings) prepared according to old recipes (4) application of the acquired knowledge to identification of colourants present in historical objects. 

There are different reasons for interlaboratory tests. One is method validation, e.g. prior to the standardization of characterization of reference materials, which have to be certified. The third and most important for quahty assurance is proficiency testing of laboratories. There are different requirements for each type of interlaboratory test. 

Authentic sample a purified and characterized sample of a related substance. Unlike reference standards, authentic samples may not be of high purity. However, the purity of an authentic sample has to be determined before use. Authentic samples are used in method development to identify related substances in the analysis. In addition, they are used extensively to prepare the spiked samples in method validation. 

Reference Standard. One of the limitations of the external standard method is that a well-characterized reference standard is essential. In addition, each analysis requires accurate weighings of small quantities (e.g., 10 mg) of reference standard. Therefore, weighing error can affect method precision and accuracy. 

To establish safety and to ensure consistency, the complete chemical composition should be provided for every material used in the manufacture of a packaging component. Test results from appropriate qualification and characterization tests should be provided. Adequate information regarding the tests, methods, acceptance criteria, reference standards, and validation information should be also provided. 

Before an analytical method can be validated, it is necessary to qualify those materials that will serve as reference standards. To allow for expeditious validation, it is important to source and/or synthesize and characterize... 

A bioassay is an analytical procedure that uses a responsive biological system (biological function) to measure the biological potency of a product (Mire-Sluis et al., 1996). The most appropriate method to determine it is by comparing the biological activity of a sample with a well-characterized reference standard. 

Reference materials give an indication of bias and precision for your method. They can be purchased from a number of vendors (e.g., NIST, Environment Canada) and should be analyzed on a monthly basis. When reference materials are not available, a reference standard can be used. A reference standard is a highly purified compound that is well characterized. 

A description and the results of all the analytical testing performed on the manufacturer s reference standard lot and qualifying lots to characterize the drug substance should be included. The section should provide information from specific tests regarding the identity, purity, stability, and consistency of manufacture of the drug substance. All test methods should be fully described and the results provided. 

The development and standardization of reliable test procedures requires an ample supply of well-characterized reference materials. These samples are used for round-robin tests by participating laboratories in the method development. A reliable set of reference materials are available from the National Bureau of Standards. These special reference materials are described by Haines in this symposium series. The Bureau has packaged the materials in an appropriate size and secure container. Producer and user laboratories have these reference materials available to cross-check results and resolve differences in specification analyses. These reference standards are available at a reasonable cost. 

Two areas of research, psychophysics and sensory evaluation, have made recent contributions to the understanding of oral sensations of heat derived from peppers. Psychophysical studies have characterized observer s responses to heat from spice-derived compounds, focussing on such aspects as time-intensity functions, areas of oral stimulation, correlation with evoked salivary flow, interactions with basic tastes, and effects of sequential stimulation. Sensory evaluation of the heat level of ground red pepper has recently been advanced by the validation of a new method which solves many of the problems inherent in the previous Scoville procedure. The new method is based on anchored graphic rating by panels Who are trained with physical reference standards. The procedure has shown excellent reliability, fine discriminations among samples, and high correlations with instrumental determinations of capsaicinoid content of pepper samples. 

Obviously, the universal goal of any measurement technique is to obtain reproducible results regardless whether the samples come from different sources with different matrix effects, are run by different operators, in different laboratories, on different occasions and using different lots of reagents. This is usually accomplished by characterization of the newly developed assay in terms of sensitivity, selectivity, robustness and correctness (i.e., accuracy and precision). Evaluation of sensitivity and precision does not normally constitute a problem for a newly developed immunoassay, and accuracy can be attained by comparison with the results obtained by a reference ( standard ) method. However, the evolution of assay standardization from this point on is much more difflcult. The following section deals with application-specific problems related to validation and standardization of immimoassay. 

The desirability of characterization methods which are not comparative (i.e. dependent upon the availability of a previously designated reference standard of the same drug substance)... 

Any discussion of the method development/validation process should consider obtaining a sufficient quantity of a qualified reference standard and appropriate samples to support the development and validation campaign. In most cases, the limit of the accuracy of the analytical test will be related to the correctness of the standard s assay. There is little consensus on the common requirements of reference standards as outlined by the regulatory authority typical practice favors an approach of thorough analytical characterization of the standard supported by adequate documentation. 

Description or reference to test methods used in characterization of the standard... 

Physical-chemical characterization Reference standard characterization Specifications and analytical methods Certificates of analysis... 

Only one lot of well-characterized product or reference standard should be used in the validation. Product lot or batch is not a factor in method validation. Factors that are typically assessed are instrument or machine, analyst or operator, day, and other factors external to the method itself that come into play in the typical running of an assay. 

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