BS ISO 6732:2010 pdf download

BS ISO 6732:2010 pdf download.Milk and milk products –  Determination of iron content – Spectrometric method (Reference method).
4.9 Sodium acetate, saturated solution.
Dissolve 232.59 & anhydrous sodium acetate (CH3COONa) in 500 ml of water (4.1).
If the sodium acetate available Is not ron-free, purify it as follows.
Dissolve 232,5 g of sodium acetate in 500 ml of water. Filter through a filter paper. Add 3 ml of the hydroxylarnmonium chloride solution (4.10). Extract the solution with 10 ml of the bathophenanthroline solution (4,12). Remove the upper layer. Repeat these two operations until the upper layer remains colourless.
4.10 Hydroxylammonlum chloride, solution.
Dissolve 209 of hydroxylaminonium chloride (HONH3CI) in water (4.1) and make up to 100 ml, Filter through a filter paper. Extract the solution with 5 ml of the bathophenanthroline solution (4.12). Allow the layers to separate properly. Remove the upper layer. Repeat these two operations until the upper layer remains colourless
NOTE Generally, live exirections are suftic2ent,
If the solution was prepared more than 24 h before use, it is advisable to repeat the extraction with the bathophenanthroline.
Instead of the hydroxylemmonium chloride solution, a freshly prepared solution of ascorbic acid can be used as a reducing agent. The ascorbic acid solution can be made by dissolving 109 of ascorbic acid in 100 ml of water. The solution should be extracted with the bathophenanthroline solution in exacity the same way as described for the hydroxytammoniurn chloride solution. It should be stored in a refrigerator. Instead of 3 ml of the hydroxylammonium chloride solution, 3 ml of this ascorbic acid solution can be used in 4.7, 49 and 6.2.1.4.
4.11 lsoamyl alcohol (3-methyl-i -butanot).
Distil, if necessary, in an iron-free distillation unit.
4.12 Bathophenanthrolln., solution.
Dissolve 83,1 mg of bathophenanthroline [4,7-diphenyl-1 ,1 0-plienanthroline (C24H16N2)J in 100 ml of the isoamyl alcohol (4.11).
4.13 PotassIum permanganate solution.
Dissolve 100 mg of potassium permanganate (KMnO4) in 50 ml of water (4.1).
4.14 Iron. standard solution corresponding to 1 000 mgof iron per litre.
Dissolve 7,0229 of arnmonium iron(II) sulfate hexahydrate [(NH4)2Fe(S04)2 6H20J in 250 ml of water (4.1). Add 8 ml of sulfuric acid (4.6) and cool to room tern perature. Make up to 1 000 ml with water.
A volume of 1 ml of this standard solution contains 1 mg of iron.
NOTE Convnercially available prepai-ations idi contain 1 000mg of iron can be used instead of the ainmonium iron(ll) sulfate hexahydrate.
4.15 Iron. standard solution corresponding to 1 mg of iron per litre.
On the day of use, pipette (5.11) 1 ml of the standard won solution (4.14) into 250 ml of water (4.1), Add I ml of sulfunc add (4.6) and make up to 1 000 ml with water.
A volume of 1 ml of thés standard solution contains 1 pg of iron.
5 Apparatus
IMPORTANT — Maintain glassware and equipment, as well as the laboratory environment as clean as possible in order to avoid contamination by rust. Each laboratory should check and identify its own sources of contamination.
Store clean glassware, Including the glass beads (5.8), In 10 % mass fraction nltflc acid solution. Rinse three times before use with distilled water and then three times with double-distilled water. If necessary, dry by successively nnsing with ethanol (4.2) and diethyl ether (4.3).
Usual laboratory equipment and in particular the following.
5.1 AnalytIcal balance.
5.2 CentrIfuge, capable of producing a radial acceleration of 2 500g. with tubes of capacity at least 150 ml.
5.3 Grinding device, appropriate to the nature of the sample.
5.4 Sieve, nominal size of openings 500 pm, ISO 565111, made of iron-free material.
5.5 Water baths
5.6 MIcro-burners or electric heaters, which do no( emit iron-containing particles.
5.7 DIgestion flasks (Kjeldahl). capacity approximately 70 ml. with ground-glass stoppers, calibrated on the lower part of the neck at 50 ml.
5.8 Glass beads, preferably made of quartz, which do not release ion during the digestion procedure (see 8.2.1).
5J Measuring cylinders, capacities 5 ml, 10 ml and 25 ml. ISO 4788(61.
5.10 Graduated pipettes, capacities I nil, 2 ml and 5 ml, graduated in divisions of 0.1 ml, ISO 835141.
5.11 One-mark pipettes, capacities I ml. 2 ml, 3 ml, 4 ml, 5 ml, 10 ml and 25 ml, ISO 646(21 class A.
5.12 Spectrometer, suitable for measunng absorbance at 533 nm, equipped with cells of optical pathlength.