Synthesis of a novel host molecule of cross-linking-polymeric-β- cyclodextrin-o-vanillin furfuralhydrazone and spectrofluorimetric analysis of its identifying cadmium

Article abstract of DOI:10.1016/j.saa.2003.12.018

A novel host inclusion complex of cross-linking-polymeric-β- cyclodextrin-o-vanillin furfuralhydrazone (β-CDP-OVFH) was synthesized and characterized with IR and ¹H NMR spectra to confirm its structure. The coordination reaction of the host reagent with Cd²⁺ was studied and the optimum reacting conditions were observed carefully. A highly selective and sensitive spectrofluorimetric determination of trace amount of cadmium was proposed based on the reaction of Cd²⁺ with β-CDP-OVFH in ammonia water-ammonium acetate buffer medium of pH = 11.0. The molar ratio of β-CDP-OVFH to Cd²⁺ was 1:1. The maximum excitation and emission wavelengths were 393 and 494nm, respectively. The linear range of this method was from 3.0 to 500μgl^-1 with a detection limit of 0.80μgl ^-1. The effect of interferences in the determination of cadmium was investigated and the results showed that the host reagent had quite high capacity of identifying Cd²⁺. The proposed method was successfully applied to the determination of trace amount of Cd²⁺ in mussel and tea samples.

Full text of DOI:10.1016/j.saa.2003.12.018

Spectrochimica Acta Part A 60 (2004) 2425–2431
Synthesis of a novel host molecule of
cross-linking-polymeric-␤-cyclodextrin-o-vanillin furfuralhydrazone and
spectrofluorimetric analysis of its identifying cadmium
∗
Bo Tang , Li Zhang, Jie Zhang, Zhen-Zhen Chen, Yan Wang
College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, China
Received 27 October 2003; accepted 11 December 2003
Abstract
A novel host inclusion complex of cross-linking-polymeric-␤-cyclodextrin-o-vanillin furfuralhydrazone (␤-CDP-OVFH) was synthesized
1
2+
and characterized with IR and H NMR spectra to confirm its structure. The coordination reaction of the host reagent with Cd was studied
and the optimum reacting conditions were observed carefully. A highly selective and sensitive spectrofluorimetric determination of trace
2
+
amount of cadmium was proposed based on the reaction of Cd with ␤-CDP-OVFH in ammonia water–ammonium acetate buffer medium
2
+
of pH = 11.0. The molar ratio of ␤-CDP-OVFH to Cd was 1:1. The maximum excitation and emission wavelengths were 393 and 494 nm,
−
1
−1
respectively. The linear range of this method was from 3.0 to 500 ␮g l with a detection limit of 0.80 ␮g l . The effect of interferences in
2
+
the determination of cadmium was investigated and the results showed that the host reagent had quite high capacity of identifying Cd . The
proposed method was successfully applied to the determination of trace amount of Cd in mussel and tea samples.
2004 Elsevier B.V. All rights reserved.
2
+
©
Keywords: Synthesis of host inclusion complex; Cross-linking-polymeric-␤-cyclodextrin-o-vanillin furfuralhydrazone (␤-CDP-OVFH); Spectrofluorimetry;
Determination of cadmium
1
. Introduction
cent reagents to determine trace amount of cadmium. In
recent years, aroylhydrazones which contain the group of
–CONHN=CH– have played more and more important
Cadmium is one accumulative metal element and it
is harmful to most biology. The harm of cadmium con-
sists of disturbing the metabolism of copper, zinc, and
cobalt, inhibiting some systems of enzymes directly and
causing ostalgia and disturbance of nephridium. With the
aggravation of pollution, cadmium has caused more and
more harm on human health [1–3]. Therefore, it becomes
more important to find methods detecting trace amount of
cadmium in production and environmental protection. At
roles in determining metal ions as fluorescent reagents,
but their development is restricted because of their low
sensitivity and selectivity [12–16]. With the characteristic
structure [17,18], ␤-cyclodextrin (␤-CD) has received much
attention as a fine natural host reagent nowadays [19–23].
The cross-linking-polymeric-␤-CD (␤-CDP) has advan-
tage over ␤-CD on including and identifying capacity and
has a wide application foreground in the field of molecule
identification [24–26]. In this paper, we synthesized the
cross-linking-polymeric-␤-cyclodextrin-o-vanillin furfural-
hydrazone (␤-CDP-OVFH), characterized its structure with
present, determination of Cd2 by atomic absorption spec-
trometry [4,5], spectrophotometry [6], and ICP-MS [7–9]
have been often used while spectrofluorimetry [10,11] has
been used scarcely. Compared with these methods, spec-
trofluorimetry has advantages such as higher sensitivity,
better selectivity, less samples, simpler, and faster. So it
is very important to quest sensitive and selective fluores-
+
1
IR and H NMR spectra and studied the coordination re-
action of ␤-CDP-OVFH with Cd2 . The ␤-CD cavities in
␤-CDP-OVFH protected the single-excited state molecule
of the fluorescent complex from being quenched by water
and soluble oxygen which improved the quanta yield, so
the sensitivity was improved greatly. The steric effect of
+
∗
Corresponding author. Tel.: +86-531-6180010;
␤
-CDP-OVFH made it difficult to include big molecules,
fax: +86-531-6180017.
E-mail address: tangb@sdnu.edu.cn (B. Tang).
so the selectivity was improved. In the determination of
1
386-1425/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2003.12.018

2
426
B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
cadmium with ␤-CDP-OVFH, the linear range was from
2.3.2. Synthesis of OVFH
−
1
−1
3
.0 to 500 ␮g l with a detection limit of 0.80 ␮g l . The
1.26 g (0.010 mol) of formacylhydrazine were added into
40.0 ml of 95% ethanol and the mixture was heated to dis-
solve completely. 1.52 g (0.010 mol) of o-vanillin was added
into 20.0 ml of 95% ethanol and the mixture was heated
to dissolve. The solution of o-vanillin was added into the
formacylhydrazine solution dropwise, then the mixture was
refluxed for 2 h in a water bath of 90–100 C, cooled and
pumped out. The precipitate was recrystallized from ethanol
and washed with 10.0 ml of 95% ethanol three times then
effect of interferences in the determination of cadmium was
investigated and the results showed that the host reagent
2
+
had quite high capacity of identifying Cd . The deter-
mination of small guest ion—Cd2 with the host reagent
has advantages such as high sensitivity, good selectivity,
stability, and so on. To our knowledge, no papers reported
dealing with the inclusion complex, so search of new pat-
tern host molecule reagents using ␤-CDP as matrix has a
better application foreground.
+
◦
2.10 g of yellowish powder was obtained with a yield of
◦
81%. The melting point of the powder was 147–148 C. Ele-
mental analysis gave a composition of: C 59.92%, H 4.61%,
and N 10.81%, which was in good agreement with the the-
oretical composition of OVFH: C 59.97%, H 4.65%, and N
10.77%.
2
. Experimental
2
.1. Apparatus
All fluorescence measurements were carried out on a
2.3.3. Synthesis of β-CDP
Perkin-Elmer (Norwalk, CT, USA) LS-50 spectrofluorime-
ter equipped with a xenon lamp and 1.0 cm quartz cells.
The slit of excitation and emission were 5 and 4 nm, re-
spectively. All pH measurements were made with a pH-3C
digital pH-meter (Shanghai Lei Ci Device Works Shanghai,
China) with a combined glass–calomel electrode. The IR
spectra were recorded on a PE-983 IR spectrometer (KBr
10.5 g of ␤-CD was dissolved in 25.0 ml of NaOH (35%)
and 8.50 ml of epichlorohydrin was added dropwise. The
reaction mixture was kept at 90 C for 5 min with stirring.
◦
After the solution was cooled to room temperature and neu-
−
1
tralized with 6.0 mol l of HCl, it turned into a transparent
yellowish solution. This solution was dialyzed with a dialysis
bag (molecular weight less than 3500) in order to eliminate
NaCl and remnant material. The solution was concen-
trated to 50.0 ml. 25.0 ml of the concentrated solution was
freeze-dried under low pressure, then 4.30 g of ␤-CDP was
−
1
discs (cm ), Perkin-Elmer, Norwalk, CT, USA). Elemen-
tal analysis measurements were performed with a PE-240
CHN elementary analytical meter (Perkin-Elmer, Norwalk,
1
◦
CT, USA). The H NMR spectra were recorded on a FX-90Q
obtained. The product decomposed at 240 C. The average
Nuclear Magnetic Resonance Spectrometer (DMSO as sol-
vent, JEOL, Japan).
molecular weight of the complex was 5300, which was mea-
sured by gelatin chromatogram. It could be concluded that
there were four ␤-CD units in one complex molecule [27].
2
.2. Reagents
-Cyclodextrin was purified by recrystallization, the
2.3.4. Synthesis of host molecule (β-CDP-OVFH)
␤
0.200 g of o-vanillin furfuralhydrazone was dissolved in
−
1
0
.10 mg ml of standard stock solution of cadmium was
5.00 ml of methanol and 6.00 ml of concentrated ␤-CDP
solution was added. The color of solution changed from
yellowish to brown and precipitation was observed simul-
diluted to work solution, a buffer solution (pH = 11.0,
−
1
0
.20 mol l ) of ammonia water–ammonium acetate was
−
4
−1
◦
prepared, ␤-CDP-OVFH (5.0 × 10 mol l ) and OVFH
taneously. The mixture solution was kept at 50 C with
−
3
−1
(
1.0 × 10 mol l ) solution was prepared in 100 ml of
stirring for 30 min, cooled and filtered under reduced pres-
sure, then the precipitation was recrystallized from ethanol
and washed with 10 ml of doubly distilled water for three
times. After dried, 0.290 g of brown crystal was obtained
ethanol. All chemicals used were of analytical reagent or
higher grade and doubly distilled water was used through-
out.
◦
with a yield of 13%. The melting point was 181–182 C.
2
2
.3. Synthesis of host molecule reagent
.3.1. Synthesis of formacylhydrazine
2.4. Spectrofluorimetric determination of cadmium
2.70 ml of methyl-furoate (about 0.025 mol) and 3.00 ml
Into a 10 ml color comparison tube were added 1.50 ml
of 85% hydrationhydrazine (about 0.025 mol) were added
into a 50 ml of flask then 25.0 ml of 95% ethanol was added.
The mixture was refluxed for 5 h in a water bath of 80–90 C
of NH3·H2O–NH4Ac buffer solution (pH
=
11.0,
−1
0.20 mol l ), certain amount of 5.0 ␮g ml cadmium
−
1
◦
standard solution, 2.50 ml of ethanol and 0.30 ml of
−
4
−1
−3
−3
−1
−1
then distilled by decompression to eliminate ethanol and
residual hydrationhydrazine. The red-brown and ropy liquid
was obtained and cooled in ice-water, then the white and
wax solid was obtained with a yield of 75%. The melting
5.0 × 10 mol l ␤-CDP-OVFH (or 1.0 × 10 mol l
−
4
−1
OVFH, or 5.0×10 mol l ␤-CDP and 1.0×10 mol l
OVFH), then it was diluted to volume. The solution was
mixed thoroughly and equilibrated for 10 min at room tem-
perature, then the fluorescence intensity was measured at λ
◦
point of the solid was 75–76 C.

B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
2427
(
ex/em) = 393/494 nm against a reagent blank. A calibra-
Table 2
The 1H NMR spectra of OVFH and ␤-CDP-OVFH (δ (ppm))
tion graph was prepared under the same conditions for the
determination of cadmium. The excitation and emission slit
both set to 5 nm.
Compound
Function group
Ar–OH
N–H
Phenyl
Ar–OCH3
CH=N
and furan
2
.5. Sample treatment
.2500 g of tea sample (GBW08505) was put into a 100 ml
δOVFH
12.00
11.98
−0.02
10.80 6.40–7.95
10.79 6.32–7.92
−0.01 −0.03 to
3.83
3.82
−0.01
8.65
8.64
−0.01
δ
␤
δ
- aC DP-OVFH
ꢀ
0
−0.08
of beaker and 2.50 ml of nitric acid was added, the solution
was marinated for one night, then 0.25 ml of perchloricacid
was added. The mixture was heated slowly until copious
white fumes disappeared. After being cooled, 20 ml doubly
distilled water was used to wash the precipitation for three
times. The solution was adjusted to neutrality with NaOH
and transferred to a 100 ml of measuring flask and fixed to
volume.
a
ꢀ
δ = δ␤-CDP-OVFH − δOVFH.
1
3.1.2. The H NMR spectra of OVFH and β-CDP-OVFH
In order to confirm if OVFH entered into the ␤-CDP
1
cavities, the H NMR spectra of OVFH and ␤-CDP-OVFH
were obtained. The results were listed in Table 2. It was
easy to see that the chemical shifts (δ) of all hydrogen atoms
moved to higher field to different extents. The changes of
Ar–OH, N–H, CH=N, and Ar–OCH3 were not obvious
while the changes of phenyl and furan were prominent. The
results showed that the phenyl and furan rings of OVFH
entered into the ␤-CD cavities. The rich electron ␤-CD
cavities improved the electron cloud density of the hydro-
gen included, so the shield effect was increased. This made
the chemical shifts of hydrogen atoms included move to
higher field. Because Ar–OH, N–H, CH=N, and Ar–OCH3
0
.2000 g of dry mussel sample (GBW08571) was inciner-
ated in porcelain crucible after cleaned, then it was charred
at 550 C in a muffle for 2 h. After being cooled, 4.00 ml of
◦
HNO3 and 0.50 ml of HClO4 were added. The mixture was
heated slowly until copious white fumes disappeared. Af-
ter being cooled, 20 ml doubly distilled water was used to
wash the precipitation for three times. The solution was ad-
justed to neutrality with NaOH and transferred to a 100 ml
of measuring flask and fixed to volume.
1
0.00 ml of the two above solutions was put into
were located outside the cavities, their changes were not
obvious.
1
00 ml of separating funnel, respectively, then 2.00 ml of
−
1
H2SO4 (1 + 1), 2.00 ml of KBr solution (2.5 mol l ) and
6
.00 ml of water were added in turn. The equilibrized
3.1.3. The IR spectra of OVFH and β-CDP-OVFH
mixture was extracted twice with 10.00 and 5.00 ml of
diantipyrylmethane–chloroform (DAM–CHCl3) solution
The peak shape of OVFH did not change after included
by ␤-CDP, but the wave locations of hydroxybenzene–OH,
C=O, Ar–O and C=N all shifted to different extents. The
IR spectra showed that the wave locations of the function
(2.5%), respectively. The aqueous layer was discarded and
the extract was washed with 20.00 ml of H2SO4–KBr lotion.
The organic phase was combined, then Cd2 was extracted
with 10.00 ml of NH3·H2O (2 + 98). The aqueous phase
was collected and diluted 10-fold, then determined by the
method developed.
+
−1
−1
−1
group increased 30 cm (–OH), 19 cm (–OH), 5 cm
−1 −1 −1
(
C=O), 5 cm (Ar–O), 5 cm (Ar–O) and 3 cm (C=N),
respectively (Table 3). Because hydroxybenzene–OH and
Ar–O jointed with benzene ring, C=O jointed with furfuran
ring directly and benzene and furfuran rings entered into
the cavities, the rich-electron cavities of ␤-CDP increased
the density of electron cloud and led to the increment of
frequency. Although C=N did not joint with benzene or
furfuran directly, they formed a conjugated system with
benzene and furfuran rings, which led to the increment of
the density of electron cloud but not too much. The re-
sults of IR spectra showed that the new host reagent had
formed.
3
3
3
. Results and discussion
.1. Confirmation of host molecule
.1.1. Physical properties
The physical properties such as melting point, crystal
shape, and color of OVFH and ␤-CDP-OVFH were listed in
Table 1, which indicated a new reagent had formed.
Table 3
The IR spectra of OVFH and ␤-CDP-OVFH (cm 1)
−
Table 1
Changes of physical properties
Compound
Band and group
–OH
Compound
Melting point
Crystal shape
Color
C=O
1660
1665
+5
Ar–O
1250, 1305
1255, 1310
+5, +5
C=N
1612
1615
+3
◦
OVFH
147–148 C
Pine needle shape Yellowish
OVBH
␤-CDP-OVFH
3420, 3250
3450, 3269
+30, +19
◦
␤-CDP
Decomposed at 240 C Powder
White
◦
␤
-CDP-OVFH 181–182 C
Stick shape
Brown
ꢀ

2
428
B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
Fig. 1. The structure of ␤-CDP-OVFH.
3
.1.4. The structure of β-CDP-OVFH
The reaction molar ratio of ␤-CDP and OVFH was tested
depressed, which reduced the mutual collision of molecules
and the non-radiative transition. The complexometric ef-
fect of Cd2 with OVFH made the rigidity and plane of
␤-CDP-OVFH improved. Furthermore, the ␤-CD cavity
could also protect the fluorescent single state molecule
+
as 1:1, 1:2, 1:4, 2:1, and 4:1, respectively. The results
showed that when the ratio was 1:2, both yield and crystal
shape were the best, so we presumed that each molecule of
of ␤-CDP-OVFH–Cd2 from the quenching of water and
+
␤
-CDP-OVFH consisted one ␤-CDP and two OVFH. This
conclusion was agreement with the structure of Fig. 1.
soluble oxygen.
If we simply added the same dosage of ␤-CDP and OVFH
into the reaction system rather than ␤-CDP-OVFH, ␤-CDP
could still offer a feasible microenvironment of weaker po-
larity and stronger rigidity, so the quenching effect of water
and soluble oxygen on the fluorescent single state molecule
3
.2. Excitation and emission spectra
Under the selected conditions, the maximum excita-
tion and emission wavelengths were 393 and 494 nm,
respectively (Fig. 2). We found that the complex of
␤
of OVFH–Cd2 was reduced and the fluorescence inten-
+
-CDP-OVFH–Cd2 had very strong fluorescence intensity
+
sity was improved, compared to the system without ␤-CDP.
2
+
However, the steric effect of ␤-CDP restrained OVFH–Cd
from entering into the cavities of ␤-CDP, so the rigidity
while the reagent blank had low signal, which indicated
that ␤-CDP-OVFH had a higher signal-to-noise than OVFH
in the determination of cadmium. With the driving force of
hydrophobic interaction, van der Waals force and hydrogen
bond, the OVFH molecule entered into the ␤-CDP cavities
and formed a supermolecule host reagent–␤-CDP-OVFH.
Two ␤-CD units of the ␤-CDP cooperated to include phenyl
and furan rings of OVFH, which improved the rigidity
of the host reagent. The ␤-CD cavities in ␤-CDP-OVFH
offered a non-polar microenvironment, the movement free-
dom of the formed fluorescent complex molecule and the
relaxation effect of the water molecule were both greatly
and plane of OVFH–Cd2 could not be improved further. In
+
␤
-CDP-OVFH, the steric effect made it easy to include with
2
+
appropriate guest (for example Cd ) [28], so the selectivity
was improved greatly.
3.3. Effect of pH
The pH of the medium could change the existent con-
formation of reagent and metal ion, which affected di-
rectly the formation and stability of the complex. So it
ꢀ
2+
ꢀ
Fig. 2. Excitation (a) and emission spectra (b). 1 and 1 were the fluorescent spectra of ␤-CDP-OVFH–Cd and blank, respectively; 2 and 2 were the
2
+
ꢀ
2+
fluorescent spectra of OVFH–Cd and blank, respectively; 3 and 3 were the fluorescent spectra of ␤-CDP + OVFH + Cd and blank, respectively. The
concentration of reagents were: 5.0 × 10− mol l of ␤-CDP-OVFH; 1.0 × 10 mol l of OVFH; 5.0 × 10 mol l of ␤-CDP; 500 ␮g l of Cd
5
−1
−4
−1
−5
−1
−1
2+
.

B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
2429
and 3.00 ml of ethanol. Therefore, 2.50 ml of ethanol was
selected.
3.6. Effect of amount of β-CDP-OVFH
The influence of the amount of ␤-CDP-OVFH on the flu-
orescence intensity of the complex was studied under the
conditions established above. The fluorescence intensity in-
creased with the amount of ␤-CDP-OVFH up to 0.20 ml,
remained constant between 0.20 and 0.40 ml and decreased
slowly thereafter. A suitable amount of ␤-CDP-OVFH was
advantageous to form fluorescent complex, while superflu-
ous ␤-CDP-OVFH could decrease the fluorescence intensity
Fig. 3. Effect of pH on the relative fluorescent intensity of the
2
+
−5
−1
2+
2+
␤
-CDP-OVFH–Cd C (␤-CDP-OVFH): 5.0 × 10 mol l ; C (Cd ):
of ␤-CDP-OVFH–Cd . Thus, 0.30 ml of ␤-CDP-OVFH
was selected throughout the experiment.
−
1
5
00 ␮g l
.
made a great effect on the fluorescence intensity of the
␤
3.7. Effect of temperature and reaction time
-CDP-OVFH–Cd2 complex. According to the experi-
+
mental method, 1.50 ml of different pH value buffer solu-
tion was added and fluorescence intensity was determined.
The experimental results showed that the relative fluores-
cence intensity reached the highest value and remained
constant between 10.6 and 11.3 (Fig. 3), so the opti-
mum pH of 11.0 for the complex formation was selected.
Among Tris–HCl, Na2B4O7–NaOH, KH2PO4–K2HPO4
and NH3·H2O–NH4Ac buffer solution systems, it was more
sensitive for the reaction system in NH3·H2O–NH4Ac
The influence of temperature was tested. The experimen-
tal results showed that high temperature increased the colli-
sion of molecules, which made the collision probability of
excited molecules and solvent molecules increase and re-
sulted in the declination of fluorescence intensity. So the
room temperature was selected. The relative fluorescence
intensity reached a maximum after 10 min and remained
constant for at least 1 h, then decreased slowly. Therefore,
all coordination reactions were kept for 10 min at the room
temperature.
−
1
buffer solution (0.20 mol l ).
3
.4. Effect of amount of buffer solution
3.8. Stoichiometry of the complex
The influence of the amount of buffer solution on the
relative fluorescence intensity of the solution containing
The stoichiometry of the complex was studied un-
der the established experimental conditions by the molar
ratio and continuous variation methods. Both methods
showed that the composition of the complex was 1:1
−
1
2+
−5
−1
5
00 ␮g l of Cd and 1.0×10 mol l of ␤-CDP-OVFH
was studied. The fluorescence intensity remained constant
between 1.00 and 2.00 ml and decreased slowly thereafter.
Thus, 1.50 ml was selected throughout the experimental
work.
2
+
(Cd :␤-CDP-OVFH). For the ␤-CD cavity was hydropho-
bic, it would reduce the stability of the complex if the guest
had a greater polarity or electric charge, so the neutral
host molecule was the best matching to the ␤-CD cavity
[29]. As described above, there were four ␤-CD units in
one ␤-CDP molecule, so there were two OVFH molecules
in one host reagent molecule. It was easy to see that the
complex was neutral and suitable for the composition of the
3
.5. Effect of organic solvent
The effect of organic solvent on the fluorescence intensity
of the ␤-CDP-OVFH–Cd2 complex was studied. Table 4
showed that the complex has higher fluorescence intensity in
ethanol than in any other organic solvents. The fluorescence
intensity of the complex remained constant between 2.00
+
complex, which was 1:1 (Cd2 :␤-CDP-OVFH). So we pre-
sume the model structure of the complex was as shown in
Fig. 4.
+
Table 4
2
+
Effect of organic solvent on fluorescence intensity (F) of the ␤-CDP-OVFH–Cd complex and the reagent blank
F
Organic solventa
Methanol
Ethanol
Isopropanol
Acetonitrile
Ether
Acetone
N,N-Dimethylformamide
Blank
Complex
24
82.5
22
96
32.3
77.1
35.7
92.4
15.1
75.5
47.8
102.7
59.9
113
a
The amount of every organic solvent was 2.50 ml.

2
430
B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
Table 5
Characteristics of fluorimetric methods for cadmium
Reagent
Linear range
Detection
−1
limit (␮g l )
Major interference
Ref.
−
1
(␮g l
)
+
2+
3+
2+
2+
2+
2+
3+
2+
8
-Hydroxyquinoline-5-sulfonic acid and bromo-cetyltrimethylamine
5–100
20–1000
10–60
4–20
3.0–500
4.2
10
4.5
0.88
0.80
Fe3 , Cu , Co , Ni
[10]
[11]
[31]
[32]
2
+
Luminol-8-hydroxyquinoline-5-sulfonic acid-H2O2
9
Rhodamine S-polyrinylalcohol-124
␤
Zn , Al
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
+
2+
2+
2+
-(1 ,4 ,7 ,10 ,13 -Pentaazacyclo-pentadecyl)methylanthracene
Cu , Cu , Hg , Cr
3
+
Bi , Pd , Hg
3
+
3+
-CDP-OVFH
Al , Fe , Zn , Ni
This work
3
.9. Effect of interferences
Table 6
Determination of cadmium in mussel and tea samples (P = 0.95).
A systematic study of the interferences in the determi-
Sample
Standard
value (␮g g
Measured value
R.S.D. (%)
−
1
−1
(␮g g−1) (n = 6)
)
nation of cadmium (100 ␮g l ) was carried out under the
conditions established above. The criterion for interference
was defined as an tolerable error not exceeding ± 5.0% in
the determination. No interference was encountered from
Mussel
Tea
4.5 ± 0.3
0.032 ± 0.005
4.43 ± 0.09
2.4
5.6
0.030 ± 0.001
+
−
−
−
−
(
(
tolerance ratio in mass): NH4 , I , NO3 , NO2 , Br
2
−
−
−
2−
3−
over 1000); CO3 , CH3COO , F , SO4 (500); PO4
,
ods and very wide linear range as well, which composed
the distinctive merits of it.
2
−
2−
SO3 , C2O4
(300); tartaric acid (200); Mo(VI) (150);
2
+
3+
2+
3+
2+
2+
Ba (100); citric acid (80); B (50); Ca (10); Cu
,
,
2
+
2+
2+
2−
2+
3+
Co , Mn , Pb , Cr2O7 , Be (5); Al , Fe , Zn
Ni (1). From the results, we could see that the host reagent
3.11. Determination of cadmium in tea and mussel samples
2
+
(
␤-CDP-OVFH) had a better selectivity and finer identifying
The determination results were shown in Table 6. The
2
+
.
capacity on the small guest—Cd
measured value was in good agreement with the standard
value, which indicated that the proposed method was reliable
to determine trace amount of cadmium.
3
.10. Analytical characteristics
Under the optimum experimental conditions, there was
a linear relationship between the relative fluorescence in-
2
+
4. Conclusion
tensity and the concentration of Cd
in the range of
.0–500 ␮g l with a correlation coefficient (r) of 0.9996.
The regression equation was ꢀF = 0.643 + 13.11C
␮g/10 ml). The detection limit, as defined by IUPAC [30],
−
1
3
We consider the reaction of host and guest is the dual iden-
tifying action through the studies. At first, ␤-CDP has a spe-
cial identifying action and the driving force is hydrophobic,
hydrogen bond interaction and the release of high-energy
water. Secondly, ␤-CDP-OVFH also has identifying action
with the driving force of electrostatic interaction. Because
the fluorescent structure of plane, rigidity and large conju-
gation of ␲ bond are formed and the fluidness of electron
is improved due to the rich-electron cavities of ␤-CDP in-
creasing the density of electron cloud of the complex. At the
same time, the coordinated action of poly cavities makes the
plane and rigidity improved further, which leads to higher
quanta efficiency and sensitivity.
(
−
1
was determined to be 0.80 ␮g l . The relative standard
deviation (R.S.D.) was 2.2% obtained from a series of
−
1
2+
1
1 standards each containing 250 ␮g l
of Cd . The
proposed method was compared with other common fluori-
metric procedures (Table 5). As we could see, the proposed
method had higher sensitivity than other fluorimetric meth-
In this paper, we applied ␤-CDP-OVFH as a host molecule
to determine Cd2 successfully, presented dual identifica-
tion theory, and provide a wonderful host reagent for analy-
sis of trace amount cadmium. The use of ␤-CDP-OVFH as
a host molecule to determine small guest has the advantage
of high sensitivity, good selectivity, and stability. In addi-
tion, the novel host molecule is excellent fluorescent reagent,
which can be applied to the identification and determina-
tion of cadmium. Therefore, the search of new pattern of
host molecule reagent using ␤-CDP as matrix has a widely
applying foreground.
+
Fig. 4. Model structure of the complex.

B. Tang et al. / Spectrochimica Acta Part A 60 (2004) 2425–2431
2431
Acknowledgements
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(
[
[
Financial supports from the Important Project of the Na-
tional Natural Science Foundation of China (No. 20335030)
and the Main Nature Science Foundation of Shandong
Province in China (No. Z2003B01) are gratefully acknowl-
edged.
(
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