Photometric apparatus with a flow cell coated with an amorphous fluoropolymer

A flow cell for housing a liquid sample and for exposing a liquid sample to light which comprises

• a conduit having a smooth inner wall formed of an amorphous fluoropolymer having a refractive index less than the refractive index of water,
• said amorphous fluoropolymer having a thickness at least as great as the wavelength of light such that when said conduit is filled with water, visible light and ultra-violet light can be transmitted along the axis of said conduit by total internal reflection, substantially without loss.