# Development and Optimization of a SPME-GC-FID Method for Ethanol Detection
## 3 Results
### Results Validation
Linearity refers to the ability to generate results linearly proportional to the concentration of the target analyte. \[y=Sx+b \tag{5}\]  
The results indicate that a temperature of 30 \({}^{\circ}\)C, a time of extraction of 20 min, and the addition of 30% salt resulted in the best conditions for ethanol detection. The limit of quantification and limit of detection found indicate the lowest concentration of ethanol that can be accurately detected by the method, while the Pearson coefficient of 0.998 indicates a highly positive correlation between the measured variables. Furthermore, calibration curves for PBS, from now on called Matrix B, and artificial sweat, from now on called Matric C, were also prepared, as shown in Figure 8.  
A method's precision is how consistently it generates the same results when applied to the same sample or samples. A CV of less than 10% is a regularly used criterion for acceptable accuracy in analytical chemistry. As indicated in Table 3, the accuracy of a method optimized under specified circumstances (30 \({}^{\circ}\)C, 20 min, 30% NaCl) was tested both inter-day and intra-day. The variance in findings achieved when the procedure is applied to the same samples on various days is referred to as inter-day precision. The variance in findings achieved when the procedure is applied to the same samples on the same day but at various times is referred to as intra-day precision. These experiments yielded useful information on the repeatability and consistency of the improved approach. If the approach has good inter- and intra-day accuracy, it can be regarded as dependable for regular laboratory analysis. If the findings vary significantly, more optimization or tweaks may be required to increase the method's precision. The intra-day precision for aqueous samples was 3.8%, while the inter-day precision was 5.1%, according to the data. The intra-day precision for PBS samples was 6.4%, and the inter-day precision was 14.5%. The intra-day precision for sweat samples was 3.8%, and the inter-day precision was 15.2%. These findings suggest that the improved approach is more exact for watery samples, with decreased variability in measurements within and across days. The PBS and sweat samples, on the other hand, have less accuracy and increased variability in readings. This might be due to the complex matrix of biological samples, which can interfere with analyte extraction and detection. Overall, the precision of findings indicates that the refined approach may be suitable for the precise and reliable detection of ethanol in aqueous samples, but additional tuning may be required for the analysis of biological fluids such as PBS and sweat. Furthermore, the improved method's limit of quantification (LOQ) was evaluated under particular circumstances for aqueous, PBS, and sweat samples. The LOQ is the lowest concentration of analyte that the technique can consistently quantify. The improved approach yielded LOQ values of 0.68 mg/L for aqueous samples, 0.96 mg/L for PBS samples, and 1.29 mg/L for sweat samples. These LOQ values demonstrate that the approach can detect and quantify ethanol in aqueous samples at lower concentrations than PBS and sweat samples. This might be because the matrix composition and complexity of the different sample forms vary. The LOQ values obtained for all sample types were within acceptable limits for ethanol detection, showing that the refined approach is sensitive enough to be employed in a variety of applications. Figure 8: Calibration curves for different matrices in the optimized conditions (ethanol concentration: 10 mg/L; NaCl addition: 30%; extraction time: 20 min; extraction temperature: 30 \({}^{\circ}\)C. A—ultrapure water; B—PBS; C—sewat.