It puts the lotion in the LC
One of the issues that manufacturers of lotions must over come is the growth of bacteria, yeasts and molds. These microbials cause the products to go to waste and need to be controlled to extend the shelf life of the product. One of these preservatives is phenoxyethanol, which is effective against gram-negative and gram-positive bacteria.
The concentration of phenoxyethanol allowed in skincare products is 1% or less, and is considered save at these levels.
For the testing I made a standard solution of phenoxyethanol and decided to test two products that I use regularly. One is an SPF 50 sunscreen and a face lotion. Both samples were weighed into a centrifuge tube, and about 1 gram of each was used. Then, to put these samples into solution I used the SimplePrep system using the method shown below:
| Lucidity SimplePrep Method | |
|---|---|
| Solution | 90:10 Ethanol:Water |
| Volume | 35 mL |
| Temperature | 60 ℃ |
| Agitation | On |
| Time | 5 Minutes |
| Filtering | Off |
Once the samples were finished in the SimplePrep, they were capped and placed in the refrigerator to cool. Once cooled the samples were filtered using a 0.45 μm syringe filter into an LC vial for analysis.
While the samples cooled I made a 0.02% solution of phenoxyethanol in the same 90:10 ethanol:water solution used for the samples. Then, everything was run using the Lucidity LC-UV using the method below:
| Lucidity LC-UV Method | |
|---|---|
| Flow Rate | 1.5 mL/min |
| Column | Raptor C18 150 x 4.6 mm, 5.0 μm |
| Injection volume | 20 μL |
| Oven Temperature | Ambient |
| Wavelength | 270 nm |
| Flow | Isocratic – 10 minutes |
| Mobile Phase | Methanol:Water (65:35) |
The standard was run first to establish a retention time for the phenoxyethanol peak, then a blank, followed by the samples with a blank separating them, followed by one last blank to clean the LC.
Chromatogram of the phenoxyethanol standard
The phenoxyethanol peak was clean with a great response from the UV detector.
Chromatogram of the lotion sample
The lotion only showed one peak that the software identified as phenoxyethanol.
Chromatogram of the sunscreen sample
The sunscreen shows several peaks but there is a clear peak at the same retention time as the phenoxyethanol. Both chromatograms are very clean with a steady base line.
The samples were easily put into solution by the Lucidity SimplePrep and the phenoxyethanol was detected by the Lucidity LC-UV. This wasn’t a quantification, but merely an identification and a qualitative attempt. Using the masses of the samples, and a calibration curve the exact concentration of phenoxyethanol can be determined using the Lucidity LC-UV.
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