By Anonymous on Monday, June 21, 2004 - 08:32 pm:

Hi
If anyone can help me understand
*Generally what is a standard stock solution and how is it prepared?
**How are calibration standards prepared using the stock solution?

Regards

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By Anonymous on Tuesday, June 22, 2004 - 08:07 am:

A stock solution is generally a higher concentration solution of an analyte(s) in a solvent. For example 10,000 ppm w/v (1%w/v or 1g per 100 mL volume)

If you know the density of this 1% solution then you can weigh amounts of several of them into another volumetric solution and know the precise w/v amount of each. Making up different amounts per volumetric solutions gives you calibration stds at different concentrations.

If it a stock solution prepared by volume not weight, the dilution is done my volume not weight. However, using weight not volume is more accurate. Most commercial stds are prepared by weight, even gas standards!

Each calibration std (each dilution, in other works) is made from the same stock solution to improve accuracy