|Home||Profile||Market Place||Sweeteners||Lab Methods||Glossary||Search|
|Master Index||Environment||Application||Starch||Statistics||Tables||Write us|
International Starch Institute
Science Park Aarhus, Denmark
ISI 18-1e Determination of Hydroxyethyl Content in Starch
|1. Scope||The method is applicable to hydroxyethylated starch||LT 20.06.1966
|2. Principle||The hydroxyethyl ether is cleaved in boiling HJ-solution. The ethylene is
distilled and titrated.
|3. Apparatus||3.1 Analytical balance weighing to the nearest 0.1 mg.
3.2 Oil bath, thermostatic
3.3 Distilling apparatus with five collection flasks
|4. Reagents||4.1 Iodine hydrogen solution (HJ) for alkoxide determination; density
1.70; boiling point 126 -127 oC
4.2 Alcoholic silver nitrate solution: 15.0 g AgNO3 is dissolved in 28 ml distilled water. The solution is poured into 422 ml 95% ethanol. A few drops of concentrated nitric acid are added. 10.00 ml of the solution is titrated with (4.3) and with (4.4) as indicator (according to Vogel). Titre = A. Store solution in brown flask.
4.3 Ammonium thiocyanide 0.05N NH4SCN. Normality = N2
4.4 Ferric sulphate indicator: Nitric acid is added to a saturated solution until the brownish colour disappears.
4.5 Bromine-acetic acid solution: 600 ml conc. acetic acid is saturated with dry KBr (approx. 10 g). 2 ml bromine is added. 15.00 ml is titrated with (4.6). Titre = B. Keep dark and cool in brown tight flask. The solution is stable a couple of days after preparation.
4.6 Na-thiosulphate solution 0.05N Na2S2O3. Normality = N1
4.7 Potassium iodine solution, 10%: 10 g KJ ad 100 ml with distilled water.
4.8 Starch indicator, 1%: 1 g ad 100 ml with distilled water.
4.9 Cadmium sulphate, 5%: 5 g ad 100 ml with distilled water.
4.10 Red phosphorous, amorphous powder.
4.11 Carbon dioxide, dried gas
|5. Procedure||Weigh approximate 1 g (g) water free sample to the nearest mg into the distillation flask and add 40 ml (4.1).|
|Prepare distillation apparatus (3.3) and fill the flasks:
Washing flask no.1: 0.5 g (4.10) and add (4.9) to 3 cm above inlet tube.
Collection flask no. 2: 10.00 ml (4.2)
Collection flask no. 3. 15.00 ml (4.5)
Collection flask no. 4: 15.00 ml (4.7)
Flask no. 5: 10 ml (4.7) and 150 ml distilled water
|Flask and cooler is assembled immediately. Carbon dioxide (4.11) is added||one bobble/s|
|The distillation flask is heated on oil bath kept at 140 - 145 oC for one hour and heating is stopped.|
|1. Heat collector no 2 to 40 - 50 oC|
|2. Open valve no 5 slowly and close CO2 supply|
|3. Empty collector no 3 and 4 into a 500 ml flask.|
|4. Flush with distilled water and titrate immediately with (4.6) and 2 ml (4.8) as indicator. Titre = a.|
|5. Empty collector 2 into a 500 ml flask with 150 ml distilled water and flush. Heat to boiling and cool.|
|6. Titrate with (4.3) and 3-5 ml (4.4) as indicator. Titre = b.|
|7. Run a blank with 1 g native starch.||Blank on potato starch is approx. 0.2% C2H4O|
|6. Calculation||Calculate ethylene-oxide content of sample dry matter by averaging
results of two samples with two decimals.
C2H4O % = x + y - blank, where
x = 2.203 (A-a) N1 / g = C2H4O % distilled as C2H4
y = 4.405 (B-b) N2 / g = C2H4O % distilled as C2H5J
|Molecular weight of C2H4O = M = 44.05|
|7. Reference||H. J. Lortz; Anal. Chem. 28, 892 (1956)
| Top of Page | LabIndex |
Copyright© 1999. Read Disclaimer notice.
All rights reserved. International Starch Institute, Science Park Aarhus, Denmark.
Keywords: laboratory method determination hydroxyethyl hydroxyethylated starch