kjˈɛldɑːl mˈɛθəd ɪz nˌɑːt ɐplˈɪkəbəl tə kˈɑːmpaʊndz kəntˈeɪnɪŋ nˈaɪtɹədʒən ɪn nˈaɪtɹoʊ ænd ˈɑːzoʊ ɡɹˈuːps ænd nˈaɪtɹədʒən pɹˈɛzənt ɪn ɹˈɪŋz ˈiː.dʒˈiː. pˈɪɹɪdˌiːn, kwˈɪnəlˌiːn, ˈaɪsəkwˌɪnəlˌiːn æz nˈaɪtɹədʒən ʌv ðiːz kˈɑːmpaʊndz dʌznˌɑːt kənvˈɜːt tʊ æmˈoʊniəm sˈʌlfeɪt ˌʌndɚ ðə kəndˈɪʃənz ʌv ðɪs mˈɛθəd.
Kjeldahl method is not applicable to compounds containing nitrogen in nitro and azo groups and nitrogen present in rings (e.g. pyridine, quinoline, isoquinoline) as nitrogen of these compounds does not convert to ammonium sulfate under the conditions of this method.