Applied Chemistry,
Vol. 15, No. 1, May 2011, 29-32
29
Salicylic Acid 정량을 위한 Europium-Salicylic Acid 복합체의 계면활성제
증감 형광법에 관한 연구
MD R-Mahmnur Alam⋅Mohammad Kamruzzaman⋅김소연⋅조해진⋅이상학†⋅김영호*,†⋅서정기**
경북대학교 화학과, *경북대학교 차세대에너지기술연구소, **한국표준과학연구원 삶의질측정표준본부
Study of Surfactant Sensitized Fluorescence of Europium-Salicylic
Acid Complex for the Determination of Salicylic Acid
MD R-Mahmnur Alam⋅Mohammad Kamruzzaman⋅So Yeon Kim⋅Hae Jin Jo⋅Sang Hak Lee†⋅
Young Ho Kim*,†⋅Jung Kee Suh**
Department of Chemistry, Kyungpook National University, Daegu 702-701, Korea,
*Research Institute of Advanced Energy Technology, Kyungpook National University, Daegu 702-701, Korea,
**Health Metrology Group, Korea Research Institute of Standards and Science, Daejeon 305-600, Korea
Abstract
Surfactant enhanced fluorescence (FL) of europium-salicylic acid (SA) complex has been
studied. It was observed that weak FL of Eu(III) at the wavelength of 589 nm and 612 nm
was found to be enhanced after addition of salicylic acid and cetyltrimethylammonium
bromide (CTAB) surfactant upon excitation at 395 nm. Under optimized condition, FL
intensity of Eu(III) at 612 nm responded linearly with the concentration of SA in the range
of 5.5×10-9
to 1.5×10-6
M of SA. The detection limit was calculated from the calibration
curve(3Sb/m) as 9.27×10-9
M.
Keywords: Fluorescence, Europium, Salicylic Acid, Cetyltrimethylammonium Bromide
1. Introduction
The salicylic acid (SA) and its salts-salicylates are naturally available in many plants such
as willow bark and oil of wintergreen[1]. It is the main metabolite of acetylsalicylic acid
(ASA) which is the most widely used drug as a painkiller and anti-inflammatory[2]. ASA is
hydrolyzed to salicylate in the stomach and as soon as it enters in blood circulation[3].
Spectrofluorometric method is widely used in different fields of the chemical analysis owing
to its high sensitivity and selectivity and simple instrumentation. Several fluorimetric
methods have been reported for the determination of SA[4-6]. It is reported that lanthanide
ions have an important role as a fluorescence (FL) probe in bioanalytical applications
because of their high sensitivity and selectivity[7]. Lanthanide sensitized FL provide large
Stokes shift, narrow emission bands, and long FL lifetimes[8]. In this study, cetyltrimethy-
lammonium bromide (CTAB) enhanced fluorescence of Eu(III) - SA complex has been
proposed for the determination. The influence of the solutions on the FL intensity was
investigated.
30 MD R-Mahmnur Alam⋅Mohammad Kamruzzaman⋅김소연⋅조해진⋅이상학⋅김영호⋅서정기
2. Experimental
2.1. Reagents and Standard Solutions
Deionized water (DI) was used throughout the experiments. SA (Sigma-Aldrich) stock
solution of 1×10-3
M and Eu(III)(Sigma-Aldrich) solution of 1×10-2
M was prepared by
dissolving the appropriate amount in DI water. A stock solution of 1×10-2
M CTAB was
prepared by dissolving the required amount in warm DI water. Tris-HCl buffer was prepared
by dissolving appropriate amount of tris(hydroxymethyl)aminomethane in DI water and pH
was adjusted using 0.1 M HCl. Other reagents used for this study were of analytical grade
purity from a standard supplier.
2.2. Apparatus and Procedure
FL measurements were conducted with a spectrofluorimeter (F-4500, Hitachi, Japan)
equipped with a 150 W xenon lamp and photomultiplier tube (Model R 928, Hamamatsu,
Japan). A pH meter (Orion, 520A, USA) was used for pH adjustment. The following
procedure was adopted for FL measurements in this study. A certain volume of Eu(III)
solution, 1.0 ml of buffer (pH, 8.5), appropriate volume of CTAB solution and finally SA
were added to a 10 mL volumetric flask. Next, the FL spectra of the system were measured
in a 1 cm quartz cell with the excitation and emission wavelengths of 395 nm and 612 nm
respectively.
3. Results and Discussion
3.1. Characteristics of FL Spectra
Excitation and emission spectra of Eu(III), Eu(III)-CTAB and Eu(III)-CTAB-SA were
recorded. The results indicated that FL of Eu(III) has very weak intensity to be observed
(Fig. 1a). After incorporation of CTAB in Eu(III) solution in presence of buffer solution,
characteristic FL intensity of Eu(III) is found to be enhanced at the wavelength of 595 nm
and 612 nm (Fig. 1b), corresponding to 5D0-
7F1 and
5D0-
7F2 transition of Eu(III). It was
interesting to observe that addition of SA solution into the mixture of Eu(III)-CTAB caused
the enhancement of FL intensity of the system several times (Fig. 1c). This speculation was
the basis of the proposed method for the determination of SA in trace amount.
3.2. Influence of pH
The FL intensity was examined over the pH range from 7 to 10 to observe the influence
of pH. The intensity is significantly enhanced by increasing the pH of the tris buffer solution
from 8 to 9. Fluorescence intensity was maximized at pH 8.5. Thus pH 8.5 was chosen for
this study.
3.3. Influence of Concentration Eu(III) Solution
The influence of the concentration in the range of 9.0×10-3
to 5.5×10-4
M of Eu(III) was
31Salicylic Acid 정량을 위한 Europium-Salicylic Acid 복합체의 계면활성제 증감 형광법에 관한 연구
investigated as shown in Fig. 2. Results showed that FL intensity reaches maximum when 5
×10-3
M Eu(III) solution has been used. Therefore, 5×10-3
M Eu(III) was used in following
experiments as optimum concentration.
Fig. 1. Emission Spectra (a) Eu(III), (b) Eu
(III)-CTAB and (c) Eu(III)-CTAB-SA.
Conditions: [Eu(III)], 5×10-3
M; [CTAB],
3.5×10-6
M; [SA] 3.5×10-6
M; pH 8.5.
Fig. 2. Influence of Concentration of Eu(III).
Conditions: [CTAB], 3.5×10-6
M; [SA],
3.5×10-6
, M ; pH 8.5.
3.4. Influence of Concentration of Surfactant
Several kinds of surfactant such as SDS, CTAB, SDBS, and Triton-X 100 were examined
on the FL intensity of the system. The best result was achieved using CTAB. Next, the
system intensity was verified by changing the concentration of CTAB from 9.0×10-5
M to
1.0×10-8
M. The strongest intensity was obtained from 3.5×10-4
M of CTAB. Thus this
concentration was considered as optimum value for this study.
Fig. 3. Calibration curve for the determination of SA. Conditions: [Eu(III)], 5×10-3 M; [CTAB],
3.5×10-6
M; [SA], 5.5×10-9
to 1.5×10-6
M; pH 8.5.
3.5. Calibration Curve and Detection Limit
Under aforementioned optimal condition FL intensity against the concentration of SA was
linear (Fig. 3) in the range of 5.5×10-9
to 1.5×10-6
M with regression equation of
32 MD R-Mahmnur Alam⋅Mohammad Kamruzzaman⋅김소연⋅조해진⋅이상학⋅김영호⋅서정기
Y=223+2.75×108CSA (R=0.9997) where CSA is the concentration of SA in M and Y is the FL
intensity. The limit of detection as defined by IUPAC, CLOD=3 Sb/m (where Sb is the
standard deviation of the blank signals and m is the slope of the calibration curve) was
calculated to be 9.27×10-9
M. The relative standard deviation (RSD) was 1.27%.
4. Conclusion
The determination of SA by surfactant enhanced fluorescence of Eu(III) has been
proposed. In presence of buffer solution, Eu(III), CTAB and SA produce fluorescence
complex. The obtained limit of detection was at nano molar level.
Acknowledgement
This Research was supported by Kyungpook National University Research Fund, 2009.
References
1. V. Dumitrescu, M. Surmeian, C. Doneanu, S. Stanescu, Anal. Chim. Acta. 333, 181, (1996).
2. G. J. Roth, D. C. Calverley, Blood, 83, 885, (1994).
3. T. M. Brody, T. M. Brody, J. Larner, K. P. Minneman (Eds.), Human Pharmacology-Molecular to
Clinical, 3, 414, (1998).
4. M. M. Karim, . H. S. Lee, Y. S. Kim, H. S. Bae, S.H. Lee, Anal. Chim. Acta, 576, 136, (2006).
5. A. M. De la peña, M. D. Moreno, I. D. Merñs, F. Salinas, Talanta, 43, 1349, (1996).
6. R. Medina, M. L. F. Córdova, P. O. Barrales, A. M. Díaz, Int. J. Pharm. 216, 95, (2001).
7. S. Nie, R. N. Zare, Annu. Rev. Biophys. Biomol. Struct, 26, 567, (1997).
8. J. Georges, Analyst, 118, 1481, (1993).
Top Related