How can I do a band pass filter over a interpolated time series?

I have a time series of density with a inconsistent sample interval, around 2-4 measurements per hour. I would like to select frequencies between 30 minutes(0.000555Hz) and 3 hour (0.0000926Hz), in order the identify alterations over the density data that occur only between these frequencies.

To archive this object a did a interpolation &nbsp yi = interp1(x,y,xi,'cubic') &nbsp and I am trying to apply the following band pass filter:

    fs=0.0167;
    fnyquist=0.0167/2;
    f1=0.0000926/fnyquist;
    f2=0.000555/fnyquist;
    [b,a]=butter(100,[0.0112 0.0669],'bandpass');
    y=filter(b,a,x);

This filter is not working, and I cant identify my error or how should I proceed to filter this kind of data that I have.

Thank you very much,

Gustavo