J. Kuijt et al., Detection of nonderivatized peptides in capillary electrophoresis using quenched phosphorescence, ANALYT CHEM, 73(21), 2001, pp. 5026-5029
A capillary electrophoresis detection technique for (small) peptides is pre
sented, i.e. quenched phosphorescence, a method that is generally applicabl
e and does not require chemical derivatization. For this purpose, a novel p
hosphorophore, 1-bromo-4-naphthalenesuffonic acid (BrNS), was synthesized.
BrNS has sufficient water solubility and provides strong phosphorescence at
room temperature over a wide pH range. the detection is based on the dynam
ic quenching of the BrNS phosphorescence background signal by electron tran
sfer from the amino group of the peptides at pH 9.5-10. For the di- and tri
peptides Val-Tyr-Val, Val-Gly-Gly, Ala-Ser, Gly-Asn, Gly-Ala, and Gly-Tyr,
detection limits in the range of 5-20 mug/L were obtained. The novel techni
que is even a good alternative for the (limited) group of peptides containi
ng tyrosine and, thus, exhibiting native fluorescence as well as strong UV
absorption: using Gly-Tyr, Val-Tyr-Val, methionine enkephalin, and human an
giotensin II as test compounds, quenched phosphorescence detection was foun
d to compare favorably with absorption detection at 190- and 266-nm laser-i
nduced fluorescence detection, as performed with a recently developed, smal
l-size, quadrupled Nd-YAG laser.