Mass spectrometry methods are generally used for analysis of environmental contaminant monitoring, particularly in aquatic environments (though they can be applied in non-aquatic environments, such as with screening pesticides on plant matter), paired with chromatography for separation. For target screening, this means using gas chromatography–mass spectrometry (GC-MS) or liquid chromatography–mass spectrometry (LC-MS) methods "that use single reaction monitoring (SIM) or selected reaction monitoring (SRM) modes." However, for suspect and non-target screening, these methods are inadequate due to recording only a limited number of compounds and insufficient useful information can be determined about unknown compounds, particularly given the dearth of LC-MS comparison libraries. For those non-targeted screening approaches, high-resolution mass spectrometry and high mass accuracy chromatography techniques are required. Combinations of quadrupole, time-of-flight, ion trap, and orbitrap mass spectrometry analyzers have emerged, along with high-performance liquid chromatography (and ultra-high-performance liquid chromatography), to more rapidly and effectively tackle suspect and non-target screening.