AOAC Methods in Codex STAN 234 (Preliminary Methods Review)

606

JounNAL OF 1'H!E A.O.A.c. (Vol. 43, Nc1. 3 1 I

n~ent, ethylcnedio.mine t,etrnacetic acid, diso– c.limn salt (EDTA). Bi and Te also give colored carba.mate!\ at pH 8.5 but are decom– posed to colorfoss compounds with IN Na.OH. Cu ,,omplcx is stable. Range of color de,•elop– mcut. is 0-50 mmg. Bh\nk is about l mmg Cu. />recautioris Clean glnsswarc with hot HN0 3 • Use white petrolatum to lubricate stopc<>cks of separators nnd do not use brass chains. Pm·ify H.,0 and IIN0, 1 by dist,ilhtion in Pyrex. • Reagents (a) Sod-iiim diethylclithiocarbamate ( carba– mate solution) .-Dissolve 1 g of the salt in H,O, dilute to 100 ml, and filter. Store in re– frigC?rntor and prepare weekly. (b) Citrnte-EDT,-1 solution.-Dissolve 20 g dihasic NH. 1 citrate and 5 g ethyleneJiamine te\,r:i:.ect.ic acid ,fo;odium salt (Eastman) in H,O and dilute f,o 100 ml. Remove traces of Cu by 11.dding 0.1 ml ci1rbnmate solut,ion and ext.ract.ing wil,h 10 ml CCl 4 • Repeat extraction until CCl 1 extract is colorles.'!. (c) Cuppt!1' st1md(1.rd solution.-1 mg/ml. Pin.re 0.2000 g Cu wire or foil into 125 ml <'rlcnmcy~1r. Adtl 15 ml HNO 3 (1+4), cover flask with wateh glass, and let Cu dis or as many 1111 H~SO., ns g dry sample, but at least 5 ml. Digci;t ns in 24.3. '\Vhcn sample contains large amount of fat, make pm-tial digestion with IINO. until only fot. is undisi;olved. Cool, filter free ·of solid fat, wnsh rctiiduc with 11 2 0, add H 2 SO 4 to .filtrate, un

ent, filte1· th-rough acid-w11shcd ii!ter \-•:I rinse paper 'll•it.h H,,O, :md dilutr: to lDJJ ML Determine bla.uk- on all reagent, u~I! method. Isolation and lJc1ermintJti-o:ri of Cu Pipet 25 ml _snmplc solution imto !DO ll" :!lit ml shori-sl-cm seJ)ar:ttor amd add :w lJtl <:i1 EDTA rongimt. Add 2 Jrops thy:mol bhJr• l cator, 34.91 (1k), m1d 6N NH~OH dropwise til color turns .grefm 01· blue ,green. Cool; 1, 1 1 ml car.bamnte solution UD third sep1m1tOl!j Again wash CCI~ extro.ct with 10 ml IY NaOH. Detrffmine nbso1

Codex Trial Method Review