Master standards

One unit of bacitracin USP is defined as the activity given by 26 micrograms of the dried FDA master standard. The USP requirement for commercial bacitracin is a potency of at least 40 units per milligram in a bioassay with Micrococcusflavus or Sarcina lutea. Pure bacitracin A has a potency of about 100 units per milligram. Standards for animal feed grades of bacitracin are available (71,81,82) as are analytical methods (67). 

The current official FDA Chlortetracycline Working Standard is chlortetracycline hydrochloride, Lot //501-632B-95-1 (9/29/53), obtained from Lederle, which markets the antibiotic under the proprietary name Aureomycin. The current working standard has an assigned potency of 1000 yg/mg (the term yg applied to chlortetracycline means the chlortetracycline activity (potency) contained in 1 yg of the FDA Chlortetracycline Master Standard (Lot 990-107-141-1), which is also chlortetracycline hydrochloride). 

Calibrated periodically or prior to use to master standards traceable to the NIST (National Institute for Standards and Technology)... 

Preparation of Standards. Standards for ash analysis were prepared from commercially available pure salts in aqueous solution with appropriate acids addition where necessary to match acid concentrations in the samples as well as to hold materials in solution. Master standard solutions were prepared so that serial dilutions for the construction of working curves were possible. A constant amount of silicon and aluminum (equivalent to 20% Si-5% Al) interference solution was added to each set of standards along with lithium tetraborate to carefully match... 

A standard is prepared by weighing 100 mg benzene into a 10-cm3 volumetric flask. This is diluted to the mark with benzene-free toluene. This can be used as a master standard. Each cubic centimeter of solution contains 10 mg benzene. The master standard is then used to prepare several additional standards as follows ... 

There are several advantages of the double standard preparation as used above. Significant amounts of toluene are conserved and the standards are prepared by single volume measurements (except for the one weight measurement). Also, other components can be added to the second set of standards at the time of preparation from other master standards. These components can then be varied independently of each other. 

In practice, a master standard of component A and one of component C are prepared on a weight to volume basis in a solvent. Mixing known volumes of each of these two standards can provide a variety weight ratios of the two materials for the initial linearity check. The standard of component A can also be used to add a known amount of A to a known weight of sample. 

Calibration standards in the chosen solvent may be prepared by subsequent dilution of the above standard. As an alternative to lubricating oil, solvents such as MIBK, xylene or white spirit may be used directly to prepare the master standard. It is not always necessary to follow rigidly the above procedure as many of the organometallics dissolve easily in a range of... 

Natamycin is included in the United States Pharmacopeia [3], in the Code of Federal Regulations as drug substance [4] as well as food additive [5], and in the Minimum Requirements for Antibiotic Products of Japan [6]. The microbiological activity of natamycin is expressed in fig anhydrate per mg. The FDA master standard has an assigned potency of 922 fig of anhydrous natamycin per milligram. This standard is identical to Gist-brocades natamycin trihydrate reference standard lot 711-EN-78-1. 

Standard solutions are the fundamental basis for the accuracy of assays. In preparing standards, it is usually necessary to make a number of assumptions, related to the purity and behavior of the standards. Standards and samples are assumed to react with assay reagents in the same way, and matrix effects are assumed absent. Standard solutions should be dilutions of a stock solution of highly purified material. Often, in the case of a hormone or other complex molecule, the standard is assigned a concentration or unit value based on a comparison with a master standard curve prepared from an international standard. 

Master standards calibrated by reference to primary standards and usnally in the form of porcelain or opaque glass panels, ceramic tiles, acrylic painted chips, etc. These are maintained with extreme care, nsually at the standards institutes, and are used only to calibrate other secondary standards. Working standards used as a reference for a group of laboratory iirstrumetrt standards. These are usually ceramic or porcelain tiles. 

It can be seen that, in all except the last two cases, the colour values of the standards are traceable, via the working and master standards, back to the primary standard. 

Sample panels are produced and the total population of standards are evaluated, eliminating those standards with scratches, dirt, too much color variation or not close enough to the desired target color. What remains is a sample set of the best color standard panels. Quantify at this point can vary depending on how many were originally produced. This sample set may or may not represent the mean of the total standards population, however it will have its own color variation within the subset. To find what that actual variation may be requires measurements be taken. These standards panels are further categorized into subsets with terms like reference standard, master standard and working standard. 

In conformity with principles laid down by the Conference of the States Parties, with due regard to the Programme of Work and Budget and the OPCW Financial Regulations and Rules, and taking into consideration the master standards of job classification as developed by the International Civil Service Commission (hereinafter the ICSC ), the Director-General shall prepare and submit to the Executive Council for its consideration and approval, proposals for the classification of posts according to the nature of the duties and responsibilities required. 

The standard is generic , i.e. it provides a generalized approach to the management and design of functional safety systems that can be applicable to any type of industry. It is intended for direct use in any project but it is also intended to be the basis for industry sector standards. Hence, more specific industry sector standards will be expected to follow with alignment of their principles to the master standard . 

Names of supplieis in the United Kingdom can be obtained From the Institute of Petroleum. Two master standards aie held by the IP For icFerence. 

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