Hello Johnpaul,

This is an old method that was used to determine Free Alpha Amino Nitrogen in barley worts in our laboratory, although I have very little direct experience with it myself. It may be useful as a starting point?

1 Colour Reagent

Dissolve 100 g disodium hydrogen phosphate dodecahydrate (Na2HP04. 12H20)

60 g anhydrous potassium dihydrogen phosphate (KH2P04)

5 g ninhydrin AR

3 g fructose

and make up to 1 litre in distilled water. This solution will keep for 2 weeks if stored in an amber bottle.

(Do NOT substitute the dodecahydrate form of the disodium hydrogen phosphate with a calculated amount of the anhydrous salt.)

2 Diluting solution

Dissolve 2 g potassium iodate (KI03) in 600 mL distilled water, then add 400 mL 96% ethanol.

3 Glycine standard 200 mg / L

Dissolve 0. 1072 g glycine AR. in distilled water and dilute to 100 mL. Store solution in refrigerator. For use dilute 1 mL with distilled water to give a working standard solution containing 2 mg alpha-nitrogen per litre.

1 Dilute 1 mL FHWE wort to 100 mL with distilled water.

2 Pipette 2 mL of diluted sample into a capped glass test tube. Include a blank (distilled water) and 3 diluted glycine standards per batch.

3 Add 1 mL colour reagent and loosely cover with lid.

4 Place into a boiling water bath for exactly 16 minutes then cool in a 20C bath for 20 minutes.

5 Add 5 mL diluting solution and mix.

6 Read absorbance at 570 nm against distilled water, within 30 min of the diluting solution being added.

Free alpha - amino nitrogen mg/L = ((Abs570nm test sample - Abs570nm blank)/mean Abs standards) x 2 x 100

Care should be taken not to introduce traces of amino acids by contamination with saliva or skin. It is recommended that automatic pipettes and dispensers be used whenever possible. Glassware must be very carefully washed and then handled only by the external surfaces.

Regards,

Denise.