| 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 03-1e Determination of Sulphated Ash in Starch at 525 oC
| 1. Scope | The method is applicable to native, modified and hydrolysed starch.
|
LT 12. Dec. 1966 Rev. LT 21. Nov. 1997 |
| 2. Principle | Incineration of starch sample at 525 oC in the presence of
sulphuric acid
|
|
| 3. Reagents | 3.1 Sulphuric acid solution Add 100 ml of concentrated sulphuric acid to 300 ml of distilled water. |
Pour and mix carefully - use eye protection |
| 3.2 Hydrochloric acid solution Add 100 ml of concentrated hydrochloric acid to 500 ml distilled water
|
Pour and mix carefully - use eye protection | |
| 4. Apparatus | 4.1 Analytical balance weighing to the nearest 0.1 mg. 4.2 Ashing dish of platinum or quarts 4.3 Electrically heated furnace. 4.4 Desiccator with dry drying agent 4.5 Bunsen burner 4.5 Water bath
|
|
| 5. Procedure | Careful clean the ashing dish (4.2) and calcinate it 1/2 hour in furnace (4.3) at 525 oC. | |
| Cool dish in desiccator (4.4) to room temperature and weigh on balance (4.1) to nearest 0.1 mg. Weight = w0 | Clean always new dish in boiling HCl (3.2) and rinse in water | |
| A sample of starch syrup may conveniently be dissolved in distilled water on a water bath (4.5) by 60 - 70 oC. The solution is allowed to cool to room temperature. An aliquot is used as test portion in stead of the sample itself. | ||
| Place 10 g of sample or an aliquot portion of a dissolved sample in ashing dish. Weigh on balance (4.1) to nearest 1 mg. Weight = w1 | Take 2 g if ash >10% and 5 g if ash > 5% | |
| Mix sample with 5 ml sulphuric acid solution (3.1). Rinse stirring rod with little water. Collect rinsing in ashing dish. | ||
| Incinerate the sample on a Bunsen burner (4.5) or equivalent until completely carbonised. | Possibly pre-evaporate on hot plate or equivalent | |
| Finish incineration in the furnace (4.3) at 525 oC until
residual carbon has disappeared. Cool. Moisten ash with several drops of sulphuric acid solution (3.1). Evaporate and incinerate again for 1/2 hour. |
Incinerate 2 hours | |
| Cool in desiccator to room temperature. Weigh immediately after removal
from desiccator to nearest 0.1 mg. Weight=w2
|
||
| 6. Calculation | Sulphated ash in percent of sample as is (average two results to the
second decimal) = Ash % = 100 x (w2 - w0) / (w1 - w0)
|
Correct eventually to dry basis |
| 7 Notes | Sulphuric acid facilitates ashing (wet combustion) and convert volatile chlorides into non-volatile sulphates. | |
| Consider ash determination in hydrolysates by conductivity; ref: G. Tegge
& G. Richter, Starch, 38 (1986) no. 4, 137-142)
|
||
| 8. Reference | International standard: ISO 5809 |
| Top of Page | LabIndex |
Copyright© 1999. Read Disclaimer notice.
All rights reserved. International Starch Institute, Science Park Aarhus, Denmark.
Keywords: laboratory,method,determination,sulphated,ash,starch