Milk powder is supplemented by a vital antioxidant, Vitamin C. With the help of 2,6-dichlorophenolindophenol (DPIP) as the titrant, the double Au-ring electrode gives an excellent titration curve, and easy to clean.
Using a bi-voltametric titration with the OMNIS system, a quick and reliable determination method of Vitamin C in milk powder is established.
Samples
Milk powder (with 709 mg/kg ascorbic acid)
Sample Preparation
16.4 grams of milk powder is weighed using the balance, and taken in a 1 L volumetric flask. It is then dissolved in around 500 mL of deionized water. The quantity of deionized water sufficient to fill the flask up to the mark is then added.
Analysis
50 mL of milk powder solution is taken in the titration vessel using a pipette. Titration is then carried out using DPIP with 0.25 g/L concentration until after the equivalence point is achieved.
Configuration
| . |
. |
| Main module Pick&Place S |
2.1010.0010 |
| Pick&Place module |
2.1014.0010 |
| "Peristaltic" (2-channel) pump module |
2.1016.0010 |
| Gripper fingers 42.8 - 65 mm |
6.02601.010 |
| Dummy panel for module plate |
6.02600.000 |
| OMNIS Rod Stirrer "Sample Robot" |
2.1006.0010 |
| Stirring propeller 30 mm ETFE |
6.01900.010 |
| Titration head 3xNS14 / 4x6.4 mm (P&P) |
6.01403.030 |
| OMNIS Advanced Titrator |
2.1001.0210 |
| OMNIS 20 mL cylinder unit (titrant) |
6.03001.220 |
| Analog measuring module |
6.02101.010 |
| Electrode cable plug-in head G (pol.) / plug P, 1.5 m |
6.02104.050 |
| OMNIS Stand-alone license (including one instrument license) |
6.06003.010 |
| OMNIS instrument license, 1x |
6.06002.010 |
| Double Au-ring electrode |
6.00353.100 |
Solutions
| . |
. |
| Titrant |
β(DPIP) = 0.25 g/L |
Parameters
| . |
. |
| Mode |
MET Ipol |
| I(pol) |
1.0 μA |
| Pause |
30 seconds |
| Stirring rate |
8 |
| Volume increment |
50 μL |
| Signal drift |
30 mV/min |
| Max. waiting time |
32 seconds |
| Min. waiting time |
0 seconds |
| Dosing rate |
Maximum |
| Stop volume |
20 mL |
| Stop EP |
1 |
| Volume after EP |
1.0 mL |
| EP criterion |
30 mV |
| EP recognition |
Greatest |
Results
| . |
. |
. |
| Sample |
Ascorbic acid |
S(rel) / % |
| Milk powder |
0.086% (n = 5) |
0.89 |
About Metrohm
At Metrohm is one of the world’s most trusted manufacturers of high-precision instruments for chemical analysis. Metrohm was founded in 1943 by engineer Bertold Suhner in Herisau, Switzerland. Today, Metrohm is represented in 120 countries by subsidiaries and exclusive distributors. The global Metrohm Group also includes the Dutch companies Metrohm Applikon and Metrohm Autolab, manufacturers of online analyzers and instruments for electrochemical research, respectively. Recently, the Metrohm Group was joined by Metrohm Raman, a leading manufacturer of handheld Raman spectrometers.
Metrohm is the global market leader in analytical instruments for titration. Instruments for ion chromatography, voltammetry, conductivity, and stability measurement make the Metrohm portfolio for ion analysis complete. Instruments for Near-infrared and Raman spectroscopy are another, strongly growing segment of the Metrohm portfolio.
Metrohm is a problem solver, both in the laboratory and within the industrial process. To this end, the company offers their customers complete solutions, including dedicated analytical instrumentation as well as comprehensive application know-how. More than 30% of the company’s employees at the Metrohm international headquarters in Herisau work in R&D.
Metrohm has been owned 100% by the non-profit Metrohm Foundation since 1982. The Metrohm Foundation, which does not exert any influence on the company’s business operations, sponsors gifted students in the natural sciences, supports charitable and philanthropic purposes and, above all, ensures the independence of the company.
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