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a means for preparing functionalized materials.28 An important
The 1.0 ꢀ 10ꢁ3 mol Lꢁ1 stock solution of Co2+, Cr3+, Pb2+ etc.
imidazole derivative is lophine (2,4,5-triphenylimidazole). It is were prepared by dissolving 11.9 mg of CoCl2$6H2O, 20.0 mg of
a well-known potential CL compound since 1877, and has been Cr(NO3)3$9H2O and 16.6 mg of Pb(NO3)2 etc. in 50 mL ultra-pure
used for analysis of some metal ions,29,30 and chlorinated water, respectively. And the working solution (1.0 ꢀ 10ꢁ7 mol Lꢁ1
)
compounds.31 Phenylimidazoles have been studied because of were prepared by diluting the stock solution with ultra-pure water.
their important laser properties.32 Further substitution by
Human serum samples were obtained from 4 patients in
phenyl groups has been studied for other signicant optical Qianwei Hospital of Jilin University. All experiments were per-
properties. Recently, a number of lophine derivatives were formed in compliance with the relevant laws and institutional
synthesized based on lophine skeleton substituted at the ortho- , guidelines, and the institutional committees have approved the
meta- and para-substituted in the 2-phenyl ring and para- experiments. The informed consent was obtained for any
substituted in the 4- and 5-aryl rings according to slightly experimentation with human subjects.
modied procedure of the Debus method.33,34 A variety of
lophine analogues having 2-pyridyl or 2-furyl group at both 4-
and 5-positions of heterocyclic imidazole derivatives have been
reported.35,36 Heterocyclic imidazole derivatives are a new type
of luminescent material with unique optical properties, and
have been studied with regard to their ultraviolet (UV), photo-
luminescence (PL) and CL properties.36,37
Synthesis and characterization of t-BDFI
The t-BDFI was synthesized according to the literature.40 The
synthesis route is shown in Fig. 1. First, furil was synthesized
from furfural by benzoic condensation and oxidation, and then
the t-BDFI was prepared by the condensation reaction of furil
with 4-tert-butylbenzaldehyde, ammonium acetate and acetic
acid. The absorption and uorescence spectra of the t-BDFI
were investigated, and the results are shown in Fig. 2. The rst
excitonic absorption peak of the t-BDFI is at around 316 nm,
corresponding with the uorescence peak of 427 nm.
Recently, we have synthesized a variety of imidazole deriva-
tives, and evaluated their CL properties with the aim of devel-
oping new CL reagents and reactions.38–40 In the present work, 2-
(4-tert-butylphenyl)-4,5-di(2-furyl) imidazole (t-BDFI) was
synthesized according to the reported method.40 The H2O2
could directly oxidize t-BDFI to produce CL emission in alkaline
medium. The addition of Co2+ into the t-BDFI/H2O2 CL system
could induce signicant enhancement of CL signal. The
possible enhancement mechanism of the CL reaction was also
further investigated. The effects of experimental conditions
were investigated. Under the optimal conditions, HSA could
induce inhibition of CL signal of the t-BDFI/H2O2/Co2+ system.
Based on the inhibition of CL for the t-BDFI/H2O2/Co2+ system
by HSA, a sensitive CL method has been developed for the
determination of HSA. The proposed method was applied to the
determination of HSA in human serum samples. The human
serum samples were prepared by the salting-out method with
saturated ammonium sulfate solution as precipitating
agent,20,41 and the obtained results were satisfactory.
The t-BDFI was characterized by melting point, IR, MS and
NMR. The obtained results by elemental analysis were in
conformity with the theoretical results. The results are described
as follows: mp 189–191 ꢂC. IR (KBr), n (cmꢁ1): 3122, 3068, 2962,
2860, 1602, 1528, 1491, 1436, 1364, 1268, 1201, 1080, 971, 886,
1
839, 732, 593. H NMR (300 MHz, CDCl3), d (ppm): 7.85 (d, J ¼
8.5 Hz, 2H), 7.49 (dd, J ¼ 1.8, 0.7 Hz, 2H), 7.46 (d, J ¼ 8.6 Hz, 2H),
7.00 (d, J ¼ 3.3 Hz, 2H), 6.52 (dd, J ¼ 3.4, 1.8 Hz, 2H), 1.34 (s, 9H)
ppm. 13C NMR (126 MHz, CDCl3), d (ppm): 152.89, 146.69,
126.81, 126.22, 125.67, 112.16, 107.91, 35.19, 31.62. MS (m/z): (M
+ H)+ 334.2 (calcd. 332.40). Calcd for C21H20N2O2: C, 75.88; H,
6.06; N, 8.43. The elemental analysis gave the molecular formula
of C21H20N2O2 (found: C, 75.91; H, 6.24; N, 8.67).
Apparatus
The CL analysis was conducted on a laboratory-built steady
injection CL system. The schematic diagram of the system is
shown in Fig. 3. The steady injection Analysis Processor FIA-
Experimental
Reagents and materials
All the reagents were of analytical reagent grade and all solu- 3100 (Beijing Wantuo Instruments Co., Ltd.) consists of two
tions were prepared with ultra-pure water. CoCl2$6H2O was peristaltic pumps, a sixteen-hole eight-way valve and a digital-
purchased from Shanghai Chemical Reagent Co. Ammonium system to control the time and pump pressure. The polytetra-
acetate, acetic acid, ammonium sulfate, NaOH, KCl, NaCl, uoroethylene (PTFE) tube (0.8 mm i.d.) was used as the
CaCl2, Ni(NO3)2$6H2O, BaCl2$2H2O, CdCl2, MnSO4$H2O, connection pipe in the steady system. The CL emission was
Cr(NO3)3$9H2O, Pb(NO3)2, FeCl2, FeCl3, ethanol and H2O2 detected by an ultra-weak luminescence analyzer (type BPCL
(30%) were purchased from Beijing Chemical Plant in China. manufactured at the Institute of Biophysics, Chinese Academy
HSA was purchased from Sigma. L-Asparagine, L-tryptophan, DL- of Sciences, Beijing, China).
b-phenylalanine and L-tyrosine were purchased from Beijing
The PL spectra were recorded on a RF-5301 spectrouorim-
Dingguo Biotechnology Co., Ltd. Furfural and 4-tert-butylben- eter (Shimadzu, Japan). The absorption spectra were recorded
zaldehyde were purchased from Tianjin Guangfu Fine Chemical on an Australian GBC Cintra 10e UV-vis spectrometer within the
Research Institute.
wavelength range from 200 to 800 nm. The CL spectrum was
The 1.0 ꢀ 10ꢁ3 mol Lꢁ1 stock solution of t-BDFI was obtained with a series of interference lters. The interference
prepared by dissolving 8.5 mg of t-BDFI in 25 mL ethanol, and lters were inserted between the sample cell and the photo-
the working solution (2.5 ꢀ 10ꢁ4 mol Lꢁ1) was prepared by multiplier tube (PMT). The spectral range detected with the
diluting the stock solution with ultra-pure water.
PMT is from 400 to 640 nm.
89570 | RSC Adv., 2015, 5, 89569–89576
This journal is © The Royal Society of Chemistry 2015