We demonstrate and describe how nanoporous liquid core waveguides can exclude scattering particles, making them an ideal integrated platform for analysis of turbid solutions. Milk with 0.5% fat showed an optical propagation loss of $0.05\mathrm{dB}/\mathrm{mm}$ at $633\mathrm{nm}$ in nanoporous waveguides compared to the $10.6\mathrm{dB}/\mathrm{mm}$ loss in standard cuvette measurements. To examine the nanofiltering effect, waveguides were infiltrated with solutions containing Rhodamine B molecules ( $1\mathrm{nm}$ ) and $22\mathrm{nm}$ red fluorescing polystyrene beads. With fluorescence spectroscopy we show that $22\mathrm{nm}$ beads are excluded, while Rhodamine B molecules penetrate the waveguides. This is further confirmed by fluorescence microscopy, also revealing a homogenous distribution of Rhodamine in the waveguide volume.