A secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS) system and a portable membrane inlet mass spectrometer (MIMS) have been used for the first time to detect and monitor insect sex pheromones, both qualitatively and quantitatively. Monitoring insect sex pheromones in the field is important because mating disruption works only when pheromone concentrations remain sufficiently high and spatially uniform. Measuring pheromone levels enables quick identification of coverage gaps, helping prevent pest resurgence and optimizing reapplication to reduce unnecessary costs and inputs. Compounds tested include: (Z)-11-Hexadecenal, (Z)-11-Hexadecen-1-yl acetate, and (Z)-11-Hexadecen-1-ol. Gas-phase experiments were performed at concentrations ranging from low ppt to low ppm. For both methods, the results obtained showed excellent linearity within the examined concentration range, ppt limits of detection (LOD) for the SESI-HRMS system, and ppb limits of detection for the MIMS, low limits of quantification (LOQ) for both methods, and fast response (rise and fall) times. In addition, SESI-HRMS was tested for the direct analysis of real-life Plutella xylostella VOC samples, detecting the three key female pheromone components in female, but not male, headspace samples.