Specifically, we show that the singular value decomposition of the Jacobian matrix of the mapping from gas composition vectors to sensor response vectors is key to determining unresponsive directions and responsive directions, ranked by sensitivity, in composition space. In particular, unresponsive directions follow from the null space of the Jacobian. We illustrate this under the context of quantitative sensing for diluents and higher-hydrocarbons in natural gas (N 2 , CO 2 , and C 2 H 6 in CH 4 ) using gravimetric, MOF-based sensors comprised of HKUST-1 and Co-MOF-74. We use experimental gas adsorption data and ideal adsorbed solution theory to model the mass of adsorbed gas in each MOF in response to different gas compositions. Under several case studies, we visualize the unresponsive and ranked responsive directions together with the underlying mixed gas adsorption model.