ISO 9648:1988 pdf download – Sorghum一Determination of tannin content.
5.7 Spsctromster, eeth ce ii) mm thick. permirintj ,neesurennts at 525 nm
5,8 Pipstt.s.o1n.5niand20mlcspscey.
5.9 Graduated pIpette., of 5 ml and 10 ii capadty.
5.10 ‘lest tub… 140mm * 14mm.
5.11 VolumetrIc flasks, of 20 tol caoaaty.
6 Sampling
SerT1Cig shall be camed out in accordance with ISO fl.
Sorghum grains iitnd.d for det.rrnmstion of tIti tannin content mey be Conserved for sever momhs. protected from *twt light. and should preferably be dried.
7 Preparation of the teat sample
Remove eny estraneou. monet other then sorghum from the laboratory wvlo and crush tho sample In the mochenical crusher (5.11 so as to reduce it to particle. of. size 4ich wIl pass conipletaty lfwough the sIeve 15.2). MIx thoroughly.
The Lannw In Cned pmduitls nzidi7e rapiry and therefore it lb recommended to proceed Inmedlately Mth me analysis after crushing.
NOT! — The ciui.J product nay 1* con.emved er mo fOr e.eefb lpq protected frran the Ight. and thould pr.4.r.biy be ‘led,
8 Procedure
8.1 Water content of the test sample
Determrne the water content of the test sample In accordance with ISO 712.
8.2 Test portion
Introduce about 1 g of the tt sample lclau.e 71. welghed to tho noorcet I mg, into • centrifuge tube (5.4).
8.3 Determination
13.2 Remove 1 tel of the sup.matant liquid (8.3.1) using a ipefle (5.8) and introduce into a test tube (5.101. Successively add 6 ml of tester end I tel of dii arreviorWa solution (4.2) using a pipette, and then shako for a few aeconda using the shaker (6.1).
1.3.3 Remove 1 tel of the aupernatani liquId (8.3.11 watt a pipono 15.8) and miroduce It Into a test tube (5.10). Succasaivedy dd S nil of weter and 1 ml of th. larric citrate solution 14.4) using a pqette. shake for a few seconds using the shaker l5.6 then add 1 nil of the a……,…e solution (42) using a pipette and shake again for a few seconds uSing the shaker 15.61.
13.4 Transfer tit. solutions obtained m 8.3.2 and 8.3.3 eeto measuring cells and. 10mm ± 1mm alter the end of the operations camed out bI 83.2 and 8.3.3. measure the abeorbencee, et 525 nm, usWeg the spectrometer 15.7) ayaiinit a water blank.
The result Is the tfatence between th two absorbances.
8.4 Number of determinations
Carry out two doterminehone on test portion. taken from th seam test mpIe
8.5 Establishment of li• calibration curve
DeiteriTilne the calibration ceeve on the day of the determination ae sedicated in a) to ci.
a) Prepare x 20 red volumetric flasks 15.11) and, using a graduated pipette 15.91, add to them reepecttvely 0 ml, 1 ml. 2 ml, 3 ml, 4 nil and 5 ml of the tannic acid solution (41), Make tip to the merit sth the dimethylforemamid. solution (4.3). The caation scaie thus obtained Corresponds to tnnic acid contents of 0mg/nil, 0.2 mg/nil, 0.3 mg/mI. 0.4 mg/nil and 0.5 mg/mI respectively.
bi Pipette Into teal tubes 15.10) 7 red 01 ascIi of these sot. istione and add successively, using i pctte (5.8), 5 ml of water and 1 nil of the ferriç aminoniunn citrate solution (4.4), and shce for a few seconds uemg the shaker 15.61. Then add I nil of ammonia solution (4.21 and shake again tot a few seconds using th, shaker 15.6).
Transfer the solutions thus obtained into measuring cells end after 10 mire ± I miii measure the abeorbances, et 525 nm, uessg the spectrometer sg.nst a water btank
ci Plot the calibration curve, uhng the abeorbence values
— th, ordinate and the coeroepondhng concentrations of tannic aced on the calibration scab a)) as the ab, in iigransi per nsiftre,
The curve ihoeid not peas tivough the origin and shüll not be corrected tar the zero of the scale.
9 Expression of results
11 Test report
The test report shall specily the method usad, tha manufacturer and reference number of the tannic acid used, and the reult obtained. It shall also mention all operating details not
specified in this International Standard, or regarded a otional, together with details of any incidents which may have influenced the result.
The tost report shall include all information necessary for the complete identification of the sample.