# A Photonic Label-Free Biosensor to Detect _Salmonella_ spp. in Fresh Vegetables and Meat
## 3 Results and Discussion
### Sensor Selectivity and Efficiency
In the context of quantitative analysis, the working interval refers to a range of values for which the test method exhibits adequate precision, trueness, and linearity. Within this interval, the test method yields results with an acceptable level of uncertainty. Examination of the four curves suggested that the relationship between X and Y was linear. The correlation coefficient and the regression model were acceptable in all three cases, given that the correlation coefficient (r) approached 1.--Establishing the working interval for each calibration curve enabled estimation of several key parameters. In Figure 8, the lower limit, or approximate LoQ, was determined to be approximately 100 CFU/mL. This LoQ helped define the linear range of calibration. The LoD set the boundary of the working interval. It was approximately 10 CFU/mL. The upper limit of quantification (ULOQ) was influenced by the equipment and technique. It was inferred from the four curves. It set the upper boundary of the linear range. It was approximately 10\({}^{8}\) CFU/mL. Also, in Figure 8, the threshold spread (80) for the detection method was estimated by performing at least six detections (preferably 10) of samples at the breakpoint concentration. Quantifications of _Salmonella_ spp. in the enrichment cultures was read from Table 1. The unit of measurement for resonance was picometers (pm). These data were read from a laboratory setup reader after processing the contaminated samples, as detailed in Table 1. To calculate the LoD, the formula LoD = 3.3 \(\times\) s0 was applied. To calculate the LoQ, the formula LoQ = 10 \(\times\) s0 was used. The ULOQ was determined based on the specific requirements of the analysis. The results of previous studies [52; 53] suggest that foodborne pathogens in meat samples are detected more effectively when tests follow a two-step process involving a short enrichment step followed by a polymerase chain reaction (PCR) assay. This approach appears to be necessary for the successful detection of low concentrations of pathogenic bacteria in food samples. The results of the present research indicate that the method described in this study is equally effective in detecting _Salmonella_ spp. The immunosensor had comparable efficiency to that of the culture method and qPCR for the specific detection of _Salmonella_ spp., as reflected in Figure 8. This figure shows a positive correlation between the immunosensor and the culture method for both fresh vegetable and meat samples. In both cases, the correlation values were similar and close to 1, indicating a high level of agreement and correlation between the two methods. The immunosensor method offers several advantages over alternative methods, such as PCR. First, it eliminates the need for bacterial processing involving a lysis buffer and DNA purification kits, which is necessary for PCR analysis of _Salmonella_ spp. Second, usingspecific antibodies for detection removes the need for extensive preliminary work to assess primer specificity when developing qPCR protocols. This feature simplifies and streamlines the detection process.