Laboratory methods Analysis of all regulatory organic and

Fluorescence was measured in a 10 mm pathlength quartz cuvette (Starna Scientific Ltd), on both the prototype portable instrument and a bench top instrument. Emission scans were taken on the bench top device at the same peak T (280 nm) and peak C (335 nm) excitation wavelengths as the portable device, with the emitted fluorescence detected in 2 nm steps between 290–400 nm and 345–450 nm, respectively, and excitation and emission slit widths both set to 5 nm. Sets of three repeat analyses were made for each sample on both devices, with each repeat being subjected to three technical repeats. Results presented Lithocholic Acid therefore an average of nine readings. Between each test, the cuvette was thoroughly rinsed with distilled water. To maintain consistency of measurement conditions, blank scans using a sealed cell containing deionised water were run systematically to measure the intensity of the Raman line of water at 348 nm excitation wavelength. The mean Raman value during the study period was 412 intensity units. Before and after each set of tests a reading was taken on the portable and bench top device with distilled water in a sealed cuvette to check machine stability. All tests were conducted in temperature controlled laboratories at 20 °C. All fluorescence data are presented as the ratio of measured fluorescence to Raman intensity and are referred to as Raman-normalised fluorescence intensity.