Final answer:
A mass spectrometer can analyze multiple gases simultaneously by ionizing and separating molecules, making it not restricted to any specific portion of the electromagnetic spectrum.
Step-by-step explanation:
To analyze multiple gases simultaneously, the most effective instrument would be a mass spectrometer. This device can be used in conjunction with gas chromatography to separate and identify different compounds. A mass spectrometer does this by breaking down substances and separating the resulting ionized molecules. These capabilities are imperative in various applications such as identifying unknown substances, illegal drugs, or explosives, and are not limited to analyzing spectra in any particular portion of the electromagnetic spectrum.