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NBS buffers: commercially obtained low ionic strength solutions at pH 4.00, 700, and 10.00 (stable indefinitely; store in the chem lab refrigerator when not in use).
Tris buffer: tris(hydroxymethyl)amino methane or 2-amino-2-(hydroxymethyl)-1,3-propanediol
Bis buffer: bis(hydroxymethyl)methylamino methane or 2-amino-2-methyl-1,3-propanediol (not commercially available because of its highly hygroscopic nature; prepare as follows):
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1.
- Heat reagent water in a glass beaker while adding Bis and stirring.
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2.
- When precipitation is observed (saturation), add HCl until pH = 7 as tested with pH paper.
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3.
- Cool solution (a gel forms in the beaker), then decant the water and place in a warm oven until dry.
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4.
- Scrape dry remains from the bottom of the beaker and place in a vacuum desiccator to cool.
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5.
- Take first weight quickly upon removal from desiccator when making up the buffer. See ODP Tech Note 15 for complete instructions on making up the powdered buffer
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- Redry in oven and cool in desiccator each time prior to weighing
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- Make new Bis buffer at the beginning of each expedition.
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