Reference standards purity

Fig. 2. An SPC control chart of the purity analysis of a reference standard where (—) represents the average value and UCL and LCL are the upper and...

Schirmer has succinctly summarized the strengths and limitations of phase solubility analysis [40]. The principal advantages are that (1) a reference standard known purity is not required, (2) the number and types of impurities in the sample need not be known, (3) all required solubility information is obtained from the analysis, (4) the technique can be applied to the analysis of any solute that can be dissolved in some solvent, (5) the deduced results are both precise and... 

Primary standard A specially manufactured analytical reagent of exceptional purity for standardizing solutions and preparing reference standards. 

Chiral or achiral assay and purity determinations are done according to an external calibration calculation procedure, either with or without internal standardization. The calibration is performed against a 10% w/w (compared to the nominal concentration of the sample solution at 100% w/w) reference standard solution. The sample solution for the purity determination remains at the 100% w/w level, while that of the assay determination is diluted 10 times. The reason for the difference in concentration levels is similar to the purity method. A suggested sample injection sequence can be... 

Chemicals that are used as reference standards are also commonly described in move 1. As with other chemicals, the name, purity, and vendor should be included. Moreover, the final concentration of any stock standard solution should be mentioned (in addition to any other dilute solutions prepared from the stock solution). Do not explain how a stock solution (or any solution) was prepared simply state the final concentration and solvent (e.g., 100 pg/L in ethanol), as illustrated below and in excerpt 3E. 

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. 

The purity of the reference standard used to prepare spiked samples can affect the study data. For this reason, an analytical reference standard of known identity and purity should be used to prepare solutions of known concentrations. If possible, the reference standard should be identical to the analyte. When this is not possible, an established chemical form (free base or acid, salt, or ester) of known purity can be used. Three types of reference standards are generally used ... 

The source and lot number, expiration date, certificates of analyses when available, and/or internally or externally generated evidence of identity and purity should be furnished for each reference standard. 

The quantitative analysis is only as good as the reference material allows. The reference standard is used as the primary standard against which all determinations are made. Reference standard characteristics should be appropriately determined and documented for each batch. Copies of this documentation must be included with study records and must be available for inspection. The reference standard should be (1) of the highest purity obtainable, (2) independently characterized to establish identity, strength or potency, and purity, (3) in the most stable form, and (4) stored under suitable conditions. 

To reduce the source of bias, it is important to have an authentic reliable reference standard, a properly maintained and calibrated balance, knowledge of the purity and form of the standard, calibrated glassware, calibrated pipettes, analyte-free matrix, and pooled and individual lots. Poor calibration, incorrectly or poorly prepared standards, interaction between analytes and container, and incomplete reactions will lead to bias. Some further precautions can be taken to minimize the possibility of errors, such as preparing QC samples in bulk (pools) and separately from the calibrators, which are prepared fresh everyday. 

Satisfactory results for a method can only be obtained with well-performing equipment. Therefore, before an instrument is used to validate a method, its performance should be verified using universal standards (47). Special attention should be paid to the equipment specifications that are critical for the performance of the method. For example, if detection limit is critical for a specific method, the detector specifications for baseline noise and the response to the specified compounds should be checked. Furthermore, any reagent or reference standard used to determine critical validation parameters should be double-checked for accurate composition and purity. 

Tightening of acceptance criteria for existing reference standards to provide greater assurance of product purity and potency. 

Chemical analyses by INAA were conducted at the Archaeometry Laboratory at the Missouri University Research Reactor Center (MURR). Aliquots of sample were oven-dried at 100 °C for 24 h. Amounts of approximately 150 mg were weighed into small polyvials used for short irradiations. At the same time, 200 mg of each sample was weighed into high-purity quartz vials used for long irradiations. Along with the majolica samples, reference standards of SRM-I633a (coal fly ash) and SRM-688 (basalt rock) were similarly prepared, as well as quality control samples of SRM-278 (obsidian rock) and Ohio Red Clay (standards treated as unknowns). 

All chemicals, reagents, mobile phases, reference standards, quality control samples with purity, grade, their source, or detailed instructions on their preparation. 

Authenticity evaluation has recently received increased attention in a number of industries. The complex mixtures involved often require very high resolution analyses and, in the case of determining the authenticity of natural products, very accurate determination of enantiomeric purity. Juchelka et al. have described a method for the authenticity determination of natural products which uses a combination of enantioselective multidimensional gas chromatography with isotope ratio mass spectrometry (28). In isotope ratio mass spectrometry, combustion analysis is combined with mass spectrometry, and the 13C/12C ratio of the analyte is measured versus a C02 reference standard. A special interface, employing the necessary oxidation and reduction reaction chambers and a water separator, was used employed. For standards of 5-nonanone, menthol and (R)-y-decalactone, they were able to determine the correct 12C/13C ratios, with relatively little sample preparation. The technical details of multidimensional GC-isotope ratio MS have been described fully by Nitz et al. (29). A MDGC-IRMS separation of a natural ds-3-hexen-l-ol fraction is... 

Reference standards must be characterized as to purity, batch or lot nuntoer, source, storage requirements, and traceability, and... 

The material from an appropriate bulk supply of the matrix material is weighed into a suitable container and homogenised. Where appropriate, portions of the matrix material are tested for the analytes of interest and for possible interferences. Pesticide and environmental test samples are usually prepared by spiking known amounts of substances of specified chemical purity into the bulk sample matrix. The spiking process is witnessed and cross-checked by a second scientist and full records of the process and of reference standard solutions used are maintained so that they can be verified if required. 

Uncertainties associated with qualitative analysis and with purity assessment, especially at the reference standards characterization, are subjects of increasing attention of the metrological and the analytical communities [18, 19, 20, 21, 22, 23]. 

A listing of reference standards, system suitability standards, impurities, and degradants, where applicable. List the purity and source, allowing for equivalency where applicable. 

Refined and bleached rapeseed oil were obtained from Onbio Co. Ltd. (Pucheon-Si, Korea). Table 1 presents the fatty acid composition and characteristics of rapeseed oil. Reference standards of FAMES such as palmitic, stearic, linolenic, linoleic, and oleic methyl ester of >99% purity were purchased from Sigma (St. Louis, MO). Methanol and catalysts such as KOH, NaOH, and sodium methoxide were analytical-grade chemicals. 

Purity of Reference Standards and the Targeted Calibration Range... 

In other words, the purity of analyte and IS reference standards determines the maximum possible concentration span. Sometimes, it is impossible to simultaneously satisfy both (1) and (2), i.e C >C In this case, either calibration range needs to be adjusted (narrowed) or analyte or internal standard reference standards of higher purity must be used. 

As with small molecules, the key analytical parameters to be addressed for therapeutic proteins on a lot-to-lot basis are identity, purity, and potency. In addition, a rigorous proof of structure is required for the reference standard lot to be used for routine analysis of production batches. 

Henderson, T.J., Quantitative NMR spectroscopy using coaxial inserts containing a reference standard purity determinations for military nerve agents, Anal. Chem., 74, 191-198 (2002). 

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. 

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