AOAC 2019 First Action Methods

(n) (o) (p)

L-cystine (Sigma Aldrich C7602) or equivalent L-glutamic acid (Sigma Aldrich G8415) or equivalent Glycine (Sigma Aldrich G7403) or equivalent

(q) L-histidine monohydrochloride monohydrate (Sigma Aldrich H8125) or equivalent (r) L-isoleucine (Sigma Aldrich I2752) or equivalent (s) L-leucine (Sigma Aldrich L8912) or equivalent (t) L-lysine monohydrochloride (Sigma Aldrich L5626) or equivalent (u) L-methionine (Sigma Aldrich M5308) or equivalent (v) L-phenylalanine (Sigma Aldrich P5482) or equivalent (w) L-proline (Sigma Aldrich P5607) or equivalent (x) L-serine (Sigma Aldrich S4311) or equivalent (y) L-threonine (Sigma Aldrich T8441) or equivalent (z) L-tyrosine (Sigma Aldrich T8566) or equivalent (aa) L-valine (Sigma Aldrich V0513) or equivalent (bb) Taurine (Sigma Aldrich T0625) or equivalent (cc) L-norvaline (Sigma Aldrich N7627) or equivalent (dd) Citrulline (Sigma Aldrich C7629) or equivalent (ee) L-hydroxyproline (Merck 1.04506.0010) or equivalent C. Reagents (a) 0.1% Phenol in 12MHCl: Weigh 0.10 g of phenol, dissolve in 100 mL 37% HCl (12MHCl) in a Schott bottle. (b) 6M Sodium Hydroxide: In a 100 mL Schott bottle weigh 24 g sodium hydroxide pellets, dissolve andmake up to 100 mL with water. (c) 1M Sodium Hydroxide: In a 1 L Schott bottle weigh 40 g sodium hydroxide pellets dissolve and make up to 1 L with water. (d) 0.2M Sodium Hydroxide: Take a 20 mL aliquot of 1M Sodium hydroxide into a 100mL volumetric flask and make up to volume with water. (e) 1M Hydrochloric Acid: In a 1 L Schott bottle add ~500 mL water. To this add 83.3 mL of 37% HCl, mix and make up to volume with water. (f) 0.2M Hydrochloric Acid: Take 20 mL aliquot of 1M HCl into a 100 mL volumetric flask and make up to volume with water. (g) 0.1M Hydrochloric Acid: Take 10 mL aliquot of 1M HCl into a 100 mL volumetric flask and make up to volume with water. (h) 1% DTDPA in 0.2M NaOH (%m/v): Weigh 1.0 + 0.02 g of 3,3’-dithiodipropionic acid into a 100 mL volumetric flask, dissolve and make up to volume with 0.2M NaOH. Make fresh for each run. (i) 5% Disodium tetraborate in water (%w/v) (borate buffer): Weigh 5 + 0.2 g of disodium tetraborate decahydrate into a 100 mL volumetric flask, dissolve and make up to volume with water. Filter using 0.45 µm filter. Prepare fresh daily.