## 2 Materials and Methods
### Determination of Model Cosmetics Containing Achillea millefolium Extract  
#### 2.10.1 Preparation of the Cosmetic Cream  
The creams were prepared using the following raw materials: Capric/Caprylic Triglycerides (trade name: Crodamol GTCC, supplier: Croda Inc., Yorkshire, UK); Cetaeryl Alcohol (trade name: Sabowax AO, supplier: SABO S.p.A, Rome, Italy); Cetaerth-20 (trade name: Eumulgin B2, supplier: BASF Personal Care); Glyceryl Stearate (trade name: Cithrol GMS 0402, supplier: Croda Inc.,Yorkshire, UK); Butyrospernum Parkii Butter (Seatons Refined Shea Nut Butter, supplier: Croda Inc., Yorkshire, UK); Isopropyl Palmitate (trade name: Crodamol IPP, supplier: Croda Inc., Yorkshire, UK); Glycerin (trade name Glycerine, supplier: Brenntag, Warsaw, Poland); Sodium Benzoate and Potassium Sorbate (supplier: Akema Fine Chemicals, Rome, Italy); and distilled water.  
Four cosmetic creams were prepared, differing in their composition only in extract content. The base cream without extract is designated as E0. creams E1, E5, and E10 contain extract in concentrations of 1%, 5%, and 10%, respectively. The exact composition of the samples is provided in Table 1.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Ingredients (INCI)**} & \multicolumn{4}{c}{**Composition [\%av/v]**} \\ \cline{2-5}  & **E0** & **E1** & **E5** & **E10** \\ \hline \multicolumn{5}{c}{Oil phase} \\ \hline Capric/Caprylic Triglycerides & 8.0 & 8.0 & 8.0 & 8.0 \\ \hline Cetaeryl Alcohol & 7.0 & 7.0 & 7.0 & 7.0 \\ \hline Cetaerth-20 & 3.0 & 3.0 & 3.0 & 3.0 \\ \hline Glyceryl Stearate & 2.0 & 2.0 & 2.0 & 2.0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Formulation of cosmetic creams with yarrow extract.  
Cream samples (Figure 2) were obtained using the classic hot emulsification method. The method consists of heating the oil and aqueous phases separately and combining both phases at high temperatures. Then, the entire system is simultaneously mixed and cooled. Both phases of the prepared creams (oil, containing Capric/Caprylic Triglycerides, Cetaaryl Alcohol, Ceteareth-20, Glyceryl Stearate, Butyrospermum Parkii Butter and Isopropyl Palmitate, and aqueous, containing water and Glycerin) were heated to 70 \({}^{\circ}\)C. Then, the oil phase was poured into the water phase and mixed until complete homogenisation. After lowering the cream temperature to 40 \({}^{\circ}\)C, the preservative (as an aqueous solution) and _Achillea millefolium_ extract were added.  
The samples were stored for 2 months after production to observe their stability. No signs of instability were observed during storage. The pH values measured at that time (using the multifunctional field-laboratory meter CX-401 Elmetron, Poland) of the creams were in the range of 5.6-5.9. No significant differences were noted between the pH values of the samples differing in extract content.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Ingredients (INCI)** & \multicolumn{4}{c}{**Composition [\%/\(w\)]**} \\ \cline{2-5}  & **E0** & **E1** & **E5** & **E10** \\ \hline \multicolumn{5}{c}{Oil phase} \\ \hline Butyrospermum Parkii Butter & 1.0 & 1.0 & 1.0 & 1.0 \\ Isopropyl Palmitate & 1.0 & 1.0 & 1.0 & 1.0 \\ \hline \multicolumn{5}{c}{Aqueous phase} \\ \hline Glycerin & 2.0 & 2.0 & 2.0 & 2.0 \\ \hline Sodium Benzoate & 0.5 & 0.5 & 0.5 & 0.5 \\ \hline Potassium Sorbate & 0.5 & 0.5 & 0.5 & 0.5 \\ \hline _A. millefolium_ extract & - & 1.0 & 5.0 & 10.0 \\ \hline Aqua & up to 100 & up to 100 & up to 100 & up to 100 \\ \hline \hline \end{tabular}
\begin{tabular}{c} INCI, International Nomenclature of Cosme Ingredients; E0, the base cream; E1, cream with extract in concentrations of 1%; E5, cream with extract in concentrations of 5%; E10, cream with extract in concentrations of 10%.  
\end{table}
Table 1: _Cont._  
Figure 2: The prepared cosmetic creams; from the left: E0, the base cream; E1, cream with extract in concentrations of 1%; E5, cream with extract in concentrations of 5%; E10, cream with extract in concentrations of 10%.