Spectrophotometry is a tool regularly used in chemical, pharmaceutical and microbiological laboratories, for a quantitative analysis of the concentration of a substance dispersed in a liquid. In a standard architecture, the light beam is generated by a coherent source or a monochromator, and the intensity is measured by a photomultiplier tube or a photodiode before and after the test sample is inserted. Using a simple geometrical-optics approach, we demonstrate that it is possible to achieve accurate measurements of absorbance, refractive index and turbidity also using a low-cost LED-based spectrophotometer.
Microscopy direct bacteria live/dead cell counting
Bacterial identification and enumeration is an essential procedure for antibiotic and toxicology tests, as well as for the evaluation of drug and food safety. Microbiological analysis relies on the accurate evaluation of the number of microbial cells on a glass slide, using an epifluorescence microscope; on the other hand, microbial viability is determined measuring the membrane permeability to fluorescent dyes. We propose an accurate automated image processing for bacterial direct cell counting.