Like most people do, at the beginning of the new year I made a resolution to lose some weight and live a healthier lifestyle. I started to eat better; less processed food and exercising several days a week. But, one weak point that I have is soft drinks, I really enjoy the taste of a good cold soda with my lunch. So, again, like many I have decided to switch to diet sodas to cut out the calories, while not giving up the bubbly goodness that I enjoy.
This got me to thinking about what makes diet soda sweet if they don’t contain sugar. One of the earliest and most widely used artificial sweetener used is Aspartame.
Aspartame was first discovered by accident in 1965 by James Schlatter when he licked his fingers in the lab, something that should never be done, to lift a piece of paper, while doing synthesis work. The sweet tasting chemical was an intermediate step in a larger synthesis experiment he was conducting.
Not long after its discovery, aspartame started showing up in carbonated beverages as an zero calorie artificial sweetener. This is the sweetener found in all of the drinks that I tested.
The best way to look for the Aspartame is by HPLC-UV. The method used is below:
| Lucidity LC-UV Method | |
|---|---|
| Flow Rate | 2.0 mL/min |
| Column | Raptor C18 150 x 4.6 mm, 5 μm |
| Oven Temperature | 35 ºC |
| Sample injection | 20 μL |
| Wavelength | 210 ± 5 nm |
| Mobile Phase A | HPLC Grade Water |
| Mobile Phase B | Methanol |
| Gradient | |
| Time (min) | %B |
| 0.0 | 1 |
| 4.5 | 1 |
| 10.0 | 40 |
| 16.0 | 40 |
| 18.5 | 1 |
| 20.0 | 1 |
I went to the store and purchased three different soft drinks that have Aspartame as its sweetener. Sample preparation for these soft drinks were quite easy, the sodas were poured into a beaker, covered with film, and degassed for 30 minutes at 30 ºC. Once the samples were degassed, they were diluted 1:1 with HPLC grade water and vialed for analysis on the Lucidity LC-UV.
A new feature of the Lucidity LC-UV is the split-loop design of the autosampler. This allows for a more precise sampling of the sample into the loop and with the needle being part of the loop allows for mobile phase to clean the needle. There is no longer a need for a wash and waste vial on new Lucidity LC-UVs.
The batch was set up to run a blank, followed by five 100 μg/mL standards, a second blank, then the three samples with a blank in-between each of the samples with a blank at the end to clean out the LC-UV.
Overlay of 5 standards showing %RSD
The above chromatogram shows the 5 standards. As shown the area and retention time are quite similar with only a 0.69% RSD for the area and a 0.09% RSD for the retention time. The peak in the chromatogram was labeled as Aspartame in the method and compared to the chromatograms from the samples.
Chromatogram of sample A
Chromatogram of Sample B
Chromatogram of Sample C
Using the average area of the 100 μg/mL standard, the samples came out to 378 μg/mL for sample A, 254 μg/mL for sample B, and 171μg/mL for sample C.
Chromatogram of a blank water injection
The blank injection after all of the standards and samples was quite clean but not exactly free of carry over. The gradient flow only went to 40% methanol before returning to 1%, if I were to do this testing continuously, I would build in a section of the gradient to boost the methanol to about 75-90% to ensure that all of the aspartame was pushed off the column and the column was clean for the next run.
Over all this study was to run aspartame on the Lucidity LC-UV and to show off the new split loop autosampler design and its improvements to the LC-UV. Click the link below for more information or to request a demonstration of the Lucidity LC-UV!