Reference standard availability

In case there is a need to perform wavelength accuracy and photometric accuracy measurements for the far-UV region below 240 nm, there are new certified reference standards available from Stama Cell [18]. The wavelength standard is a solution of rare earth oxides solvated in dilute sulfuric acid. The standard exhibits well-characterized absorption bands at 210, 211, 222, 240, and 253 nm (Figure 10.13). The photometric accuracy standard consists of a series... 

The establishment of reference standards is adopted at the suggestion of the related panels after due consideration of the opinion of the NIHS, which is directly responsible for establishing those reference standards in cooperation with the Society of Japanese Pharmacopoeia. The Society of Japanese Pharmacopeia (Shibuya 2-12-19, Shibuya, Tokyo 150-0002, Japan) is a non-profit private organization that carries out activities in support of MHW administration and regulation of pharmaceuticals. The Society plays several roles and, in particular, makes reference standards available including a part of the pharmacopeial reference standards. It also distributes Pharmacopeia and related informative documents, such as the JP Forum, and convenes public meetings and symposia. 

The expiration date is also an important consideration in terms of source and availability of the reference substance. Based on the study design, expiration date and amount of reference standard available, the analyst must determine if a new lot of reference standard will be required at some future date to support on-going stndy sample analyis. If it appears that the standard will be consumed or will expire prior to the completion of the study, the client should be contacted immediately to discuss the need to identify a source for additional material. In some instances, a new... 

Compound 4 was suspended in poly(methyl methacrylate) (PMA) and then cast into a thin film. The "polymer solution" of 4 was then subjected to corona poling at elevated temperature. The poling process afforded a polymer film which exhibited significant SHG (Scheme III). Using a primary frequency of 1064 nm the SHG band at 532 nm i.e. green light) was visible to the naked eye. At this time there were no reference standards available for quantification of the data. After standing for several days the film showed little, if any SHG activity. 

Reference Standards. Many of the identification tests and assays require the use of reference standards. These standards are available for purchase from the USPC. 

Rhinitis is characterized by nasal stuffiness with partial or full obstmction, and itching of the nose, eyes, palate, or pharynx, sneezing, and rhinorrhoea. If left untreated it can lead to more serious respiratory diseases such as sinusitis or asthma. Although several types of dmgs are available for treatment, nasal spray topical corticosteroids are widely regarded as the reference standard in rhinitis therapy (250). 

Table 10.3 presents for each country, for the period 1994-97, the number of drug samples submitted for testing, samples tested and the failure rate in those tests. Data are available from all 10 countries on the total number of samples submitted and the number of samples tested, and these show that seven countries— Australia, Cypms, Estonia, Malaysia, the Netherlands, Venezuela and Zimbabwe — have been able to meet the demand for testing (92-100%). Uganda has a relatively low test rate of 56% for the submitted samples, followed by Cuba and Tunisia at 72% and 88%, respectively. The lack of certain equipment and materials, such as reference standards and reagents, constrains analysis in Cuba, Cyprus, Uganda and Zimbabwe. 

Optical microscope asbestos reference standards for use in identifying and quantifying asbestos types are available both from NIST and the Institute of Occupational Medicine flOM) in Edinburgh, Scotland. The lOM materials consists of various asbestos materials actinolite, amosite, anthophyUite, chrysotile (both from Cassiar, Canada and Zimbabwe), crocidolite and tremoUte. 

The BERM symposia have served further to clarify understanding of the basic attributes of a good reference standard that is indispensable for establishing new frontiers in the science of measurements, and to highlight the invaluable infrastructure and proven record of metrological excellence available at the National Measurement Institutes to accomplish such tasks. 

At present, there is no reference method available. There is tremendous need to develop a purified reference material to standardize the assays. 

In order to measure the exact amount of a specific protein (analyte) by IHC signal intensity, a critical requirement is the availability of a standard reference material (present in a known amount by weight) that can be used to calibrate the assay (IHC stain). It is then possible to determine the amount of test analyte (protein) by a translation process from the intensity of IHC signals. In this respect it is helpful to consider the IHC stain as a tissue based ELISA assay (Enzyme Linked ImmunoSorbent Assay), noting that ELISA is used in the clinical laboratory as a standard quantitative method for measuring protein by weight in fluids, by reference to a calibrating reference standard. 

Fig. 13 Correction curve generated with silicon powder. The silicon powder is a Standard Reference Material available from the National Institute of Standards and Technology, Gaithersburg, Md. (Reproduced with permission of the National Institute of Standards and Technology, from Ref. 71.)...

Estimating the amount of a metabolite when an authentic reference standard is not available is still a challenge. Yu et al.191 described a procedure that uses the results of an in vitro metabolite identification based on a test compound that produces 14C-labelled metabolites essentially the 14C-labelled metabolites are used to provide a correction factor for the MS response when assaying samples that contain the same metabolite in a study that did not use the 14C-labelled test compound. Flop192 described another novel approach for metabolite quantitation based on the observation that the MS responses for most compounds are very similar to responses from nanospray ESI. Valaskovic et al.193 also reported equimolar MS responses for multiple compounds when the flow rate to the nanospray ESI source was set to about 10 nl/min. It is too soon to know whether these intriguing findings can be readily applied to discovery metabolite identification studies. 

Figure 2.2 shows the total ion current trace and a number of appropriate mass chromatograms obtained from the pyrolysis gas chromatography-mass spectrometry analysis of the polluted soil sample. The upper trace represents a part of the total ion current magnified eight times. The peak numbers correspond with the numbers mentioned in Table 2.1 and refer to the identified compounds. The identification was based on manual comparison of mass spectra and relative gas chromatographic retention times with literature data [34, 35] and with data of standards available. In some cases unknown compounds were tentatively identified on the basis of a priori interpretation of their mass spectra (labelled tentative in Table 2.1). 

A wide range of high quality, non-certified carotenoid and chlorophyll chemical standards are commercially available (e.g., Sigma-Aldrich, DHI, and Roth). The availability of a mixed pigment reference standard and biological matrix reference materials would improve analytical performance in individual laboratories, facilitate method and laboratory in-... 

Table 9.1 A selection from the Table of Light Stable Isotope Standard Reference Materials avail-...

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