The fragment resulting from the loss of a single methyl group (M − 15) is often absent, and other fragments are often spaced by intervals of fourteen mass units, corresponding to sequential loss of CH2 groups.
ðə fɹˈæɡmənt ɹɪzˈʌltɪŋ fɹʌmðə lˈɔs əvə sˈɪŋɡəl mˈɛθəl ɡɹˈuːp ˈɛm mˈaɪnəs fˈɪftiːn ɪz ˈɔfən ˈæbsənt, ænd ˈʌðɚ fɹˈæɡmənts ɑːɹ ˈɔfən spˈeɪst baɪ ˈɪntɚvəlz ʌv fˈoːɹtiːn mˈæs jˈuːnɪts, kˌɔːɹɪspˈɑːndɪŋ tə siːkwˈɛnʃəl lˈɔs ʌv sˌiːˈeɪtʃ tˈuː ɡɹˈuːps.