## 2 Results and Discussion
### Evaluation of Factors  
Due to variation of factors, these were coded as temperature (\({}^{\circ}\)C) (A); equilibration time (min) (B); extraction time (min) (C); magnetic stirrer speed (rpm) (D); sample volume (mL) (E); water: honey (\(v/w\)) (F). The temperature showed a significant effect on volatile recovery. Setting 60 \({}^{\circ}\)C as an upper limit diminished the probability of losing compounds due to thermal desorption from fiber and avoiding at the same time the formation of by-products. As it is seen in Table 2 the dominant volatile compounds of thyme honey present high boiling points in most as a measure of their volatility. Characteristically, the isolation of 3-hydroxy-4-phenyl-2-butanone, and (\(Z\))-3-hydroxy-4-phenylbut-3-en-2-one increased exponentially with temperature as shown in Figure 2.  
Equilibration time does not influence significantly the volatile isolation. However, this factor ensures the repeatability of volatiles qualitative and quantitative determination [21] so it should be taken into account. The above remark agrees with the results of this study based on the determination of the coefficient (\(p<0.05\)). The extraction time was a significant parameter with a positive influence on most of the volatile compounds. The obtained results indicate that extraction time under 30 min didn't achieve a state of equilibrium while over 30 min saturation of the fiber occurred leading to reduced adsorption of volatiles. Also, at 60 min extraction time lower isolation efficiency of compounds with high volatility was observed. As previously remarked by [PERSON] et al., [21], compounds with short equilibration time can be displaced gradually from the fiber and counterbalanced by compounds with lower volatility. Therefore, depending on the nature of the honey and the purpose of the study the extraction time can be varied. The magnetic stirrer speed is one factor that has not been evaluated so far. Stirring accelerates mass transfer between phases and the establishing phase equilibrium allowing better isolation of compounds with lower volatility. Predictive models were created to evaluate the magnetic stirrer speed and the correlation with other factors. The obtained results indicate that the investigated range of magnetic stirrer speed, for dominant volatile compounds, presented a state of relative impact by comparing the factor coefficients. So, it was seen that benzaldehyde presented positive effect by D, BD, CD, DF, D\({}^{2}\), 2-phenylacetaldehyde by BD, DF, undecane by AD, BD, CD, DF, nonanal by D, AD, 2-phenylethan-1-ol by BD, 2-phenylacetonitrile by BD, D\({}^{2}\), 1-phenylbutane-2,3-dione by D,  
Figure 2: Temperature effect in the isolation of 3-hydroxy-4-phenyl-2-butanone, and (\(Z\))-3-hydroxy-4-phenylbut-3-en-2-one. AD, BD, D\({}^{2}\), methyl nonanoate by D, AD, CD, DE, 3-hydroxy-4-phenyl-2-butanone by DE, D\({}^{2}\), and (Z)-3-hydroxy-4-phenylbut-3-en-2-one by D\({}^{2}\). However, these terms are predictive and they cannot be used for modeling future responses but can be used to re-create the results of this experiment. In each case, the speed of the magnetic stirrer should be taken into account. In some cases, while increasing the sample volume, in a stable vial, the SPME fiber adsorbed more volatile compounds and then remaining relatively constant [31]. Equilibrium is attained more rapidly in the headspace of the vial and volatiles can diffuse more quickly and efficiently to the coating on the fiber [32]. However, in this study, increasing the sample volume did not confirmed the above case. This factor didn't have a significant impact on the isolation of volatiles except for undecane and methyl nonanoate (\(p<0.05\)). Another study also reported that the efficiency of isolation is the same for all volumes examined [21]. The ratio of water: honey (\(v/w\)) was considered as important as the temperature for all responses. Dilution of the honey sample with water in specific proportions in contrast with undiluted honey increased the isolation of the major volatile compounds.