GUNDUZ T., KILIC E., KOSEOGLU F., OZTAS S. G.
Analyst, cilt.113, sa.8, ss.1313-1316, 1988 (SCI-Expanded, Scopus)
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Yayın Türü:
Makale / Tam Makale
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Cilt numarası:
113
Sayı:
8
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Basım Tarihi:
1988
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Doi Numarası:
10.1039/an9881301313
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Dergi Adı:
Analyst
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Derginin Tarandığı İndeksler:
Science Citation Index Expanded (SCI-EXPANDED), Scopus
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Sayfa Sayıları:
ss.1313-1316
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Anahtar Kelimeler:
Conductimetric titration, Non-aqueous media, Potentiometric titration, α-Amino acids
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Ankara Üniversitesi Adresli:
Evet
Özet
Of the 22 α-amino acids studied, all but five (tyrosine, cystine, cysteine, glutamic acid and aspartic acid) have been titrated potentiometrically with perchloric acid in two solvents, glacial acetic acid and 90% acetonitrile - acetic acid. The half-neutralisation potentials and the pK′a values of the amino acids in these solvents have been calculated. The half-neutralisation potentials of the monoaminomonocarboxylic acids were ca. 390 mV in acetic acid and ca. 290 mV in 90% acetonitrile - acetic acid. The titrations of binary mixtures of histidine with monoaminomonocarboxylic α-amino acids have also been carried out in these solvents. The titration curves of binary mixtures of histidine with diaminomonocarboxylic acids showed only one stoicheiometric end-point, corresponding to the sum of the four amino groups. The data obtained from the titrations in glacial acetic acid suggested that this solvent has a strong levelling effect on the basicity of the amino groups of the α-amino acids. All the amino acids titrated potentiometrically could be determined with an error of less than ±3%. Seventeen of the 22 α-amino acids have also been titrated conductimetrically in acetic acid. All the α-amino acids gave one stoicheiometric end-point except for histidine and arginine which gave two. No reliable conductimetric titration curves or results could be obtained in 90% acetonitrile - acetic acid. In those conductimetric determinations of α-amino acids that were possible, the relative errors never exceeded ±3%. © 1988, the Royal Society of Chemistry. All rights reserved.