Analytical Reagents

Pharm Calibration Standards

Pharmacopoeia Calibration Standards / Colour Reference Solutions according to Pharmacopoeias

Colour reference solutions are used to control the degree of coloration of red, yellow, green, blue and brown liquids. This examination is described in various pharmacopoeias, e.g. Ph. Eur., USP (United States Pharmakopoeia) or federal institutes, e.g. ASTM (American Society of Testing and Materials).

Sigma-Aldrich has been innovative in this product line and since early 2002 the most commonly used colour reference solutions according to Ph. Eur., USP or APHA (American Public Health Association) are available. Using these solution it is possible to compare international and standardized colouring of liquids. You can choose between two package sizes, 2 or 10 ml, and every solution is sealed in airtight ampoules. Every set has an expiry date, prescribed by the appropriate Pharmakopoeias and a certificate of analysis.

The Ph.Eur. solutions are available as a complete set of 37 solutions, divided into the five colour series, red (R1-R7), greenish-yellow (GY1-GY7), yellow (Y1-Y7), brownish-yellow (BY1-BY7) and brown (B1-B9). Each colour series can also be obtained separately.

The US Pharmakopoeia prescribes twenty different colour solutions, marked A - T, covering the range red, yellow, green, blue and purple. These solutions are available as one set.

The ASTM issues as well a standard method for the visual measurement of the colour of essentially light coloured liquids, using the platinum-cobalt scale. This test method is referred to by many as APHA colour. The preparation of these platinum-cobalt standards was originally described by A. Hazen. Subsequently the term "Hazen Colour" often occurs in combination with this test. The complete APHA set comprises 20 standard solutions, marked with different colour standard numbers (5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 100, 150, 200, 250, 300, 350, 400, 450, 500).

The perception of colour and colour matches is dependent on conditions of viewing and illumination. Determinations should be made using diffuse, uniform illumination under conditions that reduce shadows and nonspectral reflectance to a minimum. Liquids should be compared in matched colour-comparison tubes, against a white background. Colours of standards should be as close as possible to those of test specimens for quantifying colour differences.

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