Electrochemical Sensor for monitoring Endocrine Disrupting Chemicals - - PowerPoint PPT Presentation

Electrochemical Sensor for monitoring Endocrine Disrupting Chemicals in Foods and Water

Samuel N. Kikandi , Hillery Barb, Omowunmi A. Sadik, Department of Chemistry, State University of New York-Binghamton, Binghamton, NY 13902-6000. 1st Annual Finger Lakes Research Conference October 8, 2005. Finger Lakes Institute at Hobart and William Smith Colleges 601 S. Main Street, Geneva, NY 14456 1:45 – 2:00 pm

Outline

• Background information
• EDCs screening methods/techniques
• Objective
• Our technical approach
• Preliminary results
• Conclusion
• On-going /future work
• Acknowledgement

Backgound information

• Endocrine disrupting chemicals(EDCs) are

chemicals commonly called environmental hormones that mimic or block the natural estrogen activities in the body by binding to the estrogen receptor

• There is increasing concern worldwide over the

adverse effects of endocrine disrupting chemicals (EDCs) on human health .

• Has created a need for screening systems to detect

the diverse group of environmental chemicals that mimic estrogenic actions and are hypothesized to decrease male fertility

Compound Commercial products

• Synergistic combination of quercetin

and vitamin C

• Promotes healthy immune and

respiratory system function Figure 1:Quercetin and commercial products

Resveratrol.

• Powerful antioxidant for anti-aging

benefits

• Promotes a healthy lipid balance
• Supports the immune and cardiovascular

systems

Compound Commercial product

Figure 2:Resveratrol and commercial products

Genistein, an isoflavone phytonutrient derived from soybeans, has been the focus of scientific research since 1966 Genistein(GEN)

Compound Commercial product

Other available category: Menopause and prostrate Figure 3: Genistein and commercial products

Screening Analytical methods/Techniques(1)

• LC/MS to supplant GC/MS methods that require

derivatizations has also been reported[Pure Appl.

Chem., Vol. 75, Nos. 11–12, pp. 1843–1857, 2003]

• Screening systems to detect environmental

estrogen reported in our lab(Sadik O. A., Witt D .Environmental Science

& Technology – Feature Article, 33(17): A368-75, 1999)

• Fluorescence immunoassays, which are capable
• f detecting endocrine disrupting compounds in

wastewater have been reported(Yan F., Sadik O. A.Analytical

Chemistry, 2001, 73, 5272-5280)

• Amperometric tyrosinase-based biosensor (Tyr-

CPE) reported for the detection of some EDCs in

• ur lab[Silvanna A and Sadik O.A Anal. Chem. 2004, 76, 552-560]

Screening Analytical methods/Techniques(2)

However, real time stepwise electrochemical mechanisms or mode of action are unknown !

• Electrochemical detection mechanism has been

proposed in our lab[Ngundi M. Sadik O.A., Suye S., Takashi Y

.Electrochemistry communications 5 (1): 61-67 Jan 2003]

Objectives

• To determine the real time mode of action action/

mechanism

• Develop a real time electrochemical sensor for both

quantitative and qualitative analysis of EDCs real samples(water, foods,fruits and so on)

Technical approach

Specifically:

• Improve EDCs to a better detection limit than

currently reported to facilitate Electrochemical and GC-MS determination

• Follow up electrochemical processes for real

samples at real time.

• Design electrochemical sensor that is less

complex, more robust and has good sensitivity, reliability, reproducibility and low detection limit.

Table : Theoretically Predicted free and derivatized quercetin m/z values with derivatization

Retention, Rt,min. 14.98 15.21 26.56 27.16 nTMS (predicted) +2TMS

• 6CH3

+3TMS

• 6CH3

4TMS

• CH3

5TMS

• CH3

m/z Predicted Observed 356 355,357 429 428 575 575 647 647

Experiment progression

Preliminary results on Quercetin

500000 1000000 1500000 2000000 2500000 3000000 3500000 10 20 30 40 Time(min) A bundance 27.14 19.1 14.9 quercetin BPA

O O O O O O O Si Si Si Si Si

Figure 4:Total ionic chromatogram(TIC)

• f derivatized quercetin

Quercetin (polar) Derivatized Quercetin (less polar)

Results: GC-MS (1)

50000 100000 150000 200000 250000 300000 350000 400000 450000 200 400 600 800

m/z A bunda nc e 357 372 73 207

• 5000

5000 10000 15000 20000 25000 200 400 600 800 M/z Abundance 429 355 73 503

+2TMS

• 6CH3

+3TMS

• 6CH3

Figure5 : Quercetin m/z values observed for (a) addition of 2 TMS (b) addition of 3 TMS

Results : GC-MS (2)

10000 20000 30000 40000 50000 60000 70000 80000 200 400 600 800 m/z abundance 575 487 207 73 100000 200000 300000 400000 500000 600000 700000 800000 200 400 600 800 m/z Abundance 647 575 73

Figure 5: Derivatized quercetin m/z values observed for(c) addition of 4 TMS (d) addition of 5 TMS

At Rt=26.55 min +4 TMS

• 1 CH3

At Rt=27.16 +5TMS

• 1CH3

Results: GC-MS (3)

• Electrochemical data supports the GC-MS results
• Suggests a stepwise oxidation mechanism for quercetin

Results(4): Electrochemistry

• 12
• 10
• 8
• 6
• 4
• 2

2 250 450 650 850 1050

Potential(E vs Ag /Ag+ 0.1M) V Current(µA) 1 hr 2 hr 16.5 hr

0.5 hr

Figure 6 :Cyclic voltammetry of quercetin in

• rganic solvent

Bulk electrolysis Stepwise

• xidation of quercetin

• 0.2
• 0.1

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 190 290 390 490 590

tb t0( 0hrs) t2(1.08 hr) t3(1.67 hr) t4(2.08 hr) t5(2.5 hr ) t6(3 hr) t7(3.5 hr) t8(17 hrs)

Results (5) :UV-VIS

Figure 7:Results showing the changes in the UV/VIS spectra of Quercetin Wavelength(nm)=432 nm

Summary/Conclusions

• GC-MS:Stepwise derivatization of quercetin –OH groups

has been observed

• Electrochemistry:Quercetin oxidation appears to follow a step

by step electrochemical mechanism

• UV-VIS:New compound(s)/intermediate forms
• GC-MS, electrochemistry and UV-VIS data agree.
• Electrochemical sensor development is feasible for Quercetin and
• ther EDCs
• We can determine the real time levels and nature of EDCs in

water, drinks, foods and fruits which is a good indicator of the level of quality for health and environment purposes

On-going and Future work

• Determine using real time levels and nature
• f EDCs in water, foods, drinks and fruits
• This work was supported by the National

Science Foundation and the NYS Center for Advanced Technology. Acknowledgement

• Follow up the quercetin real time electrochemical
• xidations coupled with improved GC-MS detection limit
• f detection.