Preservative Analysis in Wet Wipes and Cosmetic Products

HPLC Analysis of Preservatives in Wet Wipes and Cosmetic Products HPLC analysis of preservatives in wet wipes and cosmetic products, and the effects of using monolithic columns instead of standard C18 columns that become unusable in a short time under high pressure on analysis performance and cost.

Objective of the Study

Standard C18 columns used in the analysis of wet wipes and cosmetic products become clogged quickly, become unusable in a short time under high pressure, and the shortening of column lifespan is reflected in analysis costs. To address this situation, the goal is to extend column lifespan by using monolithic silica columns instead of standard C18 columns, and to achieve more effective and efficient analysis through savings in acetonitrile quantity and time. Monolithic silica technology enables ultra-fast and robust separations with standard HPLC systems. Monolithic columns can be used not only with standard HPLC systems but also with systems such as UHPLC and LCMSMS. Unlike conventional particle-packed columns (5 μm, 3 μm, 2 μm, etc.), monolithic columns consist of a rod-shaped, single-piece polymeric silica gel packing. Mesopores with pore sizes of 13-15 nm on the polymeric silica gel provide low column back pressure at high flow rates, while macropores with pore sizes of 1.15-2 μm increase column selectivity. Particularly in viscous products such as creams, ointments and syrups, and in food samples with complex matrices, monolithic columns are frequently preferred because they are much longer-lived (approximately 3 times) compared to conventional particle-packed columns. This method can be applied to products such as creams, eyeliner, mascara, blush and lipstick.

Methods and Materials

Our study was conducted using Shimadzu LC-2030C Plus 3D model HPLC. Analyses were carried out using Merck Chromolith® column.     1. HPLC 2. Detector (Photodiode array - PDA) 3. HPLC Column 4. Analytical balance (0.001 g precision) 5. Ultra-pure water system 6. Syringe tip filter (0.45 μm) 7. Mobile phase filtration apparatus 8. Automatic pipette (0-1 mL) 9. Laboratory glassware Mixer 10. Vial Standards 11. Acetonitrile (ACN) 12. Sodium acetate (CH3COONa) 13. pH meter

1. Benzoic Acid, Phenoxyethanol, Dehydroacetic Acid

Preparation of Samples and Solutions • Standard stock solution of 2 ppm benzoic acid, 15 ppm phenoxyethanol, 3 ppm dehydroacetic acid is prepared. • Internal standard is added and diluted to desired concentrations, filtered through 0.45 μm filter and the filtrate is placed in vials. • In the sample preparation section; liquid squeezed from wet wipes is transferred to a beaker. 1 mL sample and internal standard are diluted with 50% ACN/water, filtered through 0.45 μm filter and the filtrate is placed in vials.

Analytical Conditions

Device: Shimadzu HPLC Model: LC-2030C Plus 3D Column: Merck Chromolith® Performance (100 mm x 4.6 mm) Detector: PDA Detector Wavelength: 254 nm Column Oven Temperature: 40 °C Injection Volume: 10 μL Flow Rate: 2 mL/min Duration: 4 min Mobile Phase: 20 mM CH3COONa pH 4.2 ACN (75/15) [caption id="attachment_153974" align="aligncenter"] Figure 1. Benzoic acid, Phenoxyethanol, Dehydroacetic acid[/caption]

2. Sodium Benzoate, Potassium Sorbate Sample and Solution Preparation

• Standard stock solution of 3.6 ppm sodium benzoate and 3.6 ppm potassium sorbate is prepared and diluted to desired concentrations with 50% ACN/water, filtered through 0.45 μm filter and the filtrate is placed in vials. • In the sample preparation section; wet wipes are squeezed and the liquid is emptied into a beaker. 1 mL sample and internal standard are diluted with 50% ACN/water, filtered through 0.45 μm filter and the filtrate is placed in vials.

Analytical Conditions

Device: Shimadzu HPLC Model: LC-2030C Plus 3D Column: Merck Chromolith® Performance (100 mm x 4.6 mm) Detector: UV detector Wavelength: 254 nm Column Oven Temperature: 40°C Injection Volume: 10 μL Flow Rate: 2 mL/min Duration: 4 min Mobile Phase: 20 mM CH3COONa pH 4.2 ACN (75/15)   As a result of the analyses performed with Merck Chromolith® column and Shimadzu LC-2030C Plus 3D HPLC, 50% savings in acetonitrile consumption were achieved compared to standard C18 column, and analysis times were cut in half. However, in user feedback, it was noted that when using new C18 columns, they started analysis at 110 bar column pressure and found that the respective columns quickly deformed by rising to high pressures; conversely, the Merck Chromolith® column with its 25 bar pressure was observed to be more resistant to clogging and longer-lived.

Reference

Ant Teknik Application Note-KMY016 HPLC Analysis of Preservatives in Wet Wipes and Cosmetic Products

Ömer Halit Turmuş Chemist Application Team Leader Ant Teknik