Figure 2

Protocol for urine handling and analysis. Urine is firstly centrifuged and the supernatant is diluted with distilled water and a 5 μl sample is dried on to the ATR prism surface. After drying, a sample spectrum is recorded. The raw sample spectra are pre-processed by water vapor subtraction, normalization to the peak of urea and second derivative conversion. Features of interest are then quantitated by integration and statistical assessment (Origin Pro 9.1).