*4.6. Data Analysis and Statistics*

All determinations, except for the real time recordings in direct sensor titration experiments (Figure 3), were performed at least in triplicates, and error bars on the graphs represent the standard deviation (SD) of the replicates for each datum point. SDs were calculated as the square root of variance of the deviation of each datum point relative to the mean. Sigmoid calibration curves were obtained by logistic mathematical fitting using the Rodbard equation [82], which were also used for determination of the IC<sup>50</sup> values. LOD values were defined as an analyte concentration corresponding to a signal that differs from the background level by 3 SDs of the background.

**Author Contributions:** Conceptualisation, I.S. (Inna Székács), N.A. and A.S.; methodology, I.S. (Inna Székács) and N.A.; software, I.S. (István Szend˝o); validation, I.S. (Inna Székács) and N.A.; formal analysis, N.A. and A.S.; investigation, I.S. (Inna Székács); resources, I.S. (István Szend˝o); data curation, I.S. (Inna Székács); writing—original draft preparation, I.S. (Inna Székács); writing review and editing, N.A., I.S. (István Szend˝o) and A.S.; visualisation, A.S.; supervision, A.S.; project administration, A.S.; funding acquisition, N.A. and A.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Hungarian National Research, Development and Innovation Office, project NVKP\_16-1-2016-0049 "In situ, complex water quality monitoring by using direct or immunofluorimetry and plasma spectroscopy".

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of Research on Animals of the Food Science Research Institute, National Agricultural Research and Innovation Centre, Budapest, Hungary (protocol code PE/EA/45-6/2020, last date of approval 21 February 2020).

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy reasons.

**Conflicts of Interest:** The authors declare no conflict of interest.
