Help for baseline drift removal/correction
Like I already mentioned in the comment, you might find MATLAB's detrend function useful. Generally it is useful for removal of linear (or piecewise linear) trend:

y = detrend(x);


Another solution, that should work in your case, is to use the polynomial fitting. This will remove the non-linear trend (providing you want that). A minimal code example:

% vectors t,x are given (time and the signal)
degree = 5; % to be adjusted
[p, S, mu] = polyfit(t, x, degree);
xp = polyval(p, t, [], mu);
y = x - xp;


Personally I do not recommend any Moving Average filtering, since it is introducing delay and can distort your signal.