determination of chlorine in human urine by detecting by luckboy

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									Chinese Chemical Letters Vol. 17, No. 5, pp 679-682, 2006 http://www.imm.ac.cn/journal/ccl.html

679

Determination of Chlorine in Human Urine by Detecting Backscattering Signals with a New Optical Assembly

Ke Jun TAN, Yuan Fang LI, Cheng Zhi HUANG∗, Xue Lian LIU
College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 Abstract: Detection of backscattering signals (BSS) generally suffers from the interference of reflected light, and it is hard to apply these signals for analytical purpose. Herein we provided an optical assembly, which effectively eliminated the interference of reflected light so that the scattering signals of analyte could be measured distinctly. With this assembly, chlorine in human urine could be detected with the limit of detection (LOD) of 2.0 ng/mL by measuring the enhanced BSS signals produced between the interactions of chlorine with silver nitrate. Keywords: Chlorine, urine, backscattering signals.

Resonance light scattering technique has been extensively applied in quantification of analyte, such as protein1, nucleic acid1, medicine1, and metallic ions2. Backscattering signals (BSS) has been generally applied in physics and biomedicine science3. However, for the interference of reflected light, BSS was not used for direct determination in terms of analytical chemistry. Herein we report a new optical-fiber setup based on measuring BSS for direct quantification of analyte in aqueous medium. We expect that this optical BSS assembly could be used for the determination of trace amounts of analyte. Figure 1 was a schematic diagram of our homemade optical fiber coupled BSS detection setup, which was selected based on our several designs. Optical probe 1 is a hard-glass cylinder, seting on its pedestal 2, a leaking orifice 3 for discarding the waste solution. Excited incident light beam from light source Xe lamp 7 transfers through optical fiber 6 and optical fiber entrance 4 to the solution. The BSS produced from the particles in the solution under the excitation of the incident light beam could be collected and reach to PMT 8 through the light transmission of the optical fiber 5. By adjusting the height of solution surface and the incident angle θ, the present BSS setup could effectively avoid the interference of reflected light, so that the scattering signals of analyte could be detected distinctly. Using optical fiber 5 and 6 to transfer the scattering signals and excited light could make it viable for on-line determination. The proposed BSS setup has a very simple structure and facilitates miniaturization.

∗

E-mail: chengzhi@swu.edu.cn

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Figure 1 Backscattering signals detection assembly
solution surface

7 H 6 8 light beam 5 4 2 a 3 1

1, optical probe; 2, pedestal; 3, leaking orifice; 4, optical fiber entrance; 5, optical fiber for BSS signals transmission; 6, optical fiber for excited light transmission; 7, Xe lamp; 8, PMT

The total measured intensity (It) of optical signals through PMT 8 is composed of the BSS (IBSS) intensity and the reflected light signal intensity (IRE), and it could be expressed as following equation: (1) I t = I BSS + I RE Wherein IBSS is the total BSS intensity consisted of all scattered particles and could be expressed as IBBS=NI. Wherein N is the number of scattering particles, and I is scattering intensity of a single particle. As the transmitted route of the reflected light shown in Figure 1, when the height of solution surface (H) was increased, the optical path of the reflected light was lengthened greatly and interference decreased markedly. In addition, it could be seen that the amounts of scattering particles could increase markedly when the scattering light path was lengthened. We defined the distance between optical fiber surface and sample cell as a, and the maximum length of scattering light path L, then L could be expressed as follows:
L= a cos θ

(2)

When light path is lower than L, the height of the solution surface could be derived:
H = a ⋅ tgθ

(3)

Therefore, IBSS makes the dominant contribution to the increase of It with increase of H. Since IRE decreased with increase of H, then decrease It was available when H ≥ a ⋅ tgθ . The value of IRE was very small and could be ignored in the total It-value, so when further increasing H, It could be considered to be constant. Figure 2 shows the effect of H on the scattering intensity It with the incident angle θ of 60o. It could be seen that each I-value of three standard formazin solutions increased with increase of H, when H was less than 17 mm. When H was higher than 40 mm, It was constant. The IRE is very small comparing with scattering intensity of distilled water and could be ignored.

Determination of Chlorine in Human Urine

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Figure 2 Effect of solution surface height to total measured scattering intensity.
5000 5000 4000 4000
BSS

3000 3000 2000 2000
1000 1000
distilled water 40NTU 80NTU 120NTU

IBSS

0 0 0 0 20 20 40 40 60 60 80 100 120 80 100 120

HH (mm) /mm
θ =60o, a=10 mm, 40-NTU, 80-NTU, 120-NTU standard formazin solution. λ=371nm. Figure 3 Backward light scattering spectra
6 5 4 3 2 1
300 300 350 350 400 450 500 550 600 400 450 500 550 600

800 800 600 600
BSS

IBSS

400 400 200 200 0 0

Wavelength nm Wavelength //nm

Curves 1-6 represent 7.1, 0, 0.71, 1.42, 2.13 and 2.84 µg/mL of Cl-, respectively in the presence of 2.0×10-4 mol/L AgNO3, except curve 1 without any addition of AgNO3.

In order to identify the applications of the BSS assembly, we applied it to detect the chlorine in urine considering the importance of chlorine in clinical diagnosis and medicine study. Determination of chlorine in urine usually has been carried out using ion selective electrode and ion chromatography4,5. These methods, however, deal with complicated pretreatment, costly instrument and poor sensitivity. Figure 3 shows that both the BSS intensities of AgNO3 and KCl are weaker than those of AgCl at 300-600 nm wavelength ranges. It has found that IBSS at 371 nm was proportional to the concentration of Cl− over a range of 0.02-4.26 µg/mL, and the linear regression equation is ∆I=−1.67+279.5c (r=0.9971) with the limit of determination (LOD) 2 ng/mL(3σ/K)6, which lowered than that of right angle scattering assay for one order magnitude7. Common metal ions such as Na+, K+, Mg2+ could be allowed at the concentrations higher than 389 mg/L at the tolerance level of 5%, whereas other foreign substances, such as Zn2+, Pb2+, Cu2+, Cd2+, Br−, PO43-, I−, and Mn2+ could be allowed only at the concentration of lower than 0.08 mg/L. However, by diluted with water, all interferences in the determination of chlorine in human urine could be minimized.

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Two human urine samples from two healthy students of our university were determined by this method without any pretreatment, except 5000-fold dilution. Table 1 displays the determination results of the two urine samples according to the standard addition method procedure. It could be seen that the total contents of chlorine in human urine samples both were in the range of normal contents and the RSD values were lower than 2%8. In order to test our above design, we made contrast tests by optical fiber insert perpendicularly into the solution, which could not eliminate the interferences of reflected light from cell base or solution surface and could not be used to determine the chlorine in human urine samples directly. Therefore, this proposed BSS detection method is a simple and rapid based on very common precipitation reaction, and has a high sensitivity than those in right angle scattering determination.
Table 1 Sample
1 2

Total contents of chlorine in human urine samples Correlation Coefficient (r)
0.9999 0.9972

Linear regression equation (µg/mL)
∆I=277.8+247.0c ∆I=218.2+232.3c

Found (mg/mL, n=5)
5.60, 5.45, 5.69, 5.67, 5.65 4.78, 4.91, 4.81, 4.81, 4.68

RSD (n=5, %)
1.72 1.71

Concentration: AgNO3, 2.0×10-4 mol/L. λ=371 nm.

Acknowledgments
All authors herein thank the supports of the National Natural Science Foundation of China (No: 20425517) and Municipal Committee of Science and Technology of Chongqing, and Southwest University Foundation (SWNUF2005015).

References
C.Z. Huang, Y.F. Li, Anal. Chim. Acta, 2003, 500, 105. Y. K. Zhao, Q. E. Cao, Z. D. Hu, Q. H. Xu, Anal. Chim. Acta, 1999, 388(1-2), 45. V. Backman, M. B. Wallace, L. T. Perelman, et al., Nature, 2000, 406, 35. J. Sullivan, M. Douek, J. Chromatography A, 1998, 804(1-2), 113. T. Denis Rice, Talanta, 1988, 35(3), 173. J. D. Ingle Jr., S. R. Crouch, (H. Q. Zhang, F. D. Wang, W. Shi Version Edit.), Spectrochemical Analysis, Jilin Univ. Press, Changchun, 1996, 184. 7. S. W. Li, X. D. Su, X. H. Wang, J. Z. Pan, Y. He, Chem. Res. and Appl., 2004, 16(4), 535. 8. G. R. Jiang, N. L. Cui, The Handbook of Clinic Biochemical Test and Diagnosis, Henan Science & Technology Press, Zhengzhou, 1991, 342. 1. 2. 3. 4. 5. 6.

Received 23 November, 2005


								
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