Characterization to Estimate the Size of Gold Nanoparticles Deposited in Pregnancy Tests Using Diffuse Reflectance Spectroscopy

When using a pregnancy test, a urine sample is deposited in one side of the nitrocellulose strip, which moves by capillary action to the other side of the test, where there are immobilized particles or biomarkers that indicate a positive or negative test result. Based on the manufacturer’s data sheet, these are usually colloidal gold nanoparticles. This paper describes the results of a characterization study using diffuse reflectance spectroscopy on qualitative pregnancy tests. The importance of this study resides in the possibility of finding invalid tests or false negatives in the results, at the same time, the approximate size of the nanoparticles can be determined indirectly by analysing the spectra obtained experimentally.