1 university of massachusetts at amherst department of chemistry project 3: silver nitrate detection...

1University of Massachusetts at Amherst Department of Chemistry

Project 3: Silver Nitrate Detection of the Arsine Gas produced from the Gutzeit Reaction

Goal: To improve the limits of detection for the standard Gutzeit reaction by using silver nitrate as a reagent.

Measurement Method: digital image analysis of the reaction products on the surface of the strip.

Objectives: Design an appropriate strip and optimize the silver nitrate solution used on test strips.

2University of Massachusetts at Amherst Department of Chemistry

Materials and Methods: Strip Preparation

1. Solution: 0.2% AgNO3 (m/v) in 1% HNO3.

2. Strip Preparation: 10 μL to 1 cm x 1.2 cm piece of #3 filter paper.

3. Drying Procedure: oven dry at 700 C for 30 minutes.

4. Strip Support: Dried strips were applied to the same plastic backing used by Hach strips using double-sided tape and are stored in an opaque container with desiccant packet.

3University of Massachusetts at Amherst Department of Chemistry

Experimental Design

Goals: to test a wider concentration range 0-100 µg L-1 (ppb), use different software for analysis, and collect large sample sizes for each concentration for statistical analysis.

Targeted concentrations: 0, 2.5, 5, 10, 20, 40,

50, 60, 80, 100 µg L-1 (ppb).

Analysis: again by computer software.

4University of Massachusetts at Amherst Department of Chemistry

Plot of blue pixel value versus concentration of arsenic in water in µg L-1 with the measurement of arsine gas with silver nitrate as a reagent.

Images of 2.5, 5, 10, 20 and 50 µg L-1 test results in increasing order for comparison.

5University of Massachusetts at Amherst Department of Chemistry

Results and Statistical Evaluation

T-test: to see if there is a statistically significant difference between the component values as the concentration increases.

Using 95% confidence ( = 0.05), the difference between the average blue pixel value, values from 0, 2.5, 5, 10 and 20 µg L-1 (ppb) are considered statistically significant.

6University of Massachusetts at Amherst Department of Chemistry

Conclusion for the Silver Nitrate Determination of As(III)

This strip: offers much more visibly clear results at low arsenic concentrations (<20 µg L-1 [ppb]) in comparison to the Hach kit.

Advantages:• Eliminates the use of mercury• Could be engineered to have a greater linear working range than

mercuric bromide.• Improved color formation over a wider range of concentrations.

Factors such as reaction time and AgNO3 concentration should

be studied. Portable scanners could be used.

7University of Massachusetts at Amherst Department of Chemistry

Project 4: Determination of Arsenic using Mol-Blue and Cameras

Goal: To develop a field portable technique for measurement of As (V) using Molybdenum Blue.

Measurement Method: digital camera.

Quantification technique: Color analyzing software.

8University of Massachusetts at Amherst Department of Chemistry

Project 5: Determination of Arsenic by Flow Injection

R1

R2

Detector895nm

waste

Injection valve

Reaction coil

2

2

mL/min

R1: Acidic molybdate solution R2: Ascorbic AcidRetention time ~5 minutes

Frenzel, W., Titzenthaler F., Elbel,S. Talanta, 1994, 41, 1965-1971.

9University of Massachusetts at Amherst Department of Chemistry

Project 6: Determination of the Stoichiometry of the Molybdenum Blue Polymer

Goal: To Determine the Ratios of Mo, P, and As in the molybdenum blue polymer.

Measurement Method: ICP-OES

Gouzerh, P.; Proust, A. Main-group element, organic, and organometallic derivatives of polyoxometalates. Chem. Rev. 1998, 98, 77.

10University of Massachusetts at Amherst Department of Chemistry

Project 7: Study of Single Nucleotide Polymorphisms in the Promoter Regions of Cytokine Genes of Arsenic Exposed Population in West Bengal, India

The study was conducted on 20 arsenic-exposed individuals with skin lesions (symptomatic) and 20 arsenic-exposed individuals without skin lesions (asymptomatics) in Murshidabad, a highly affected district where arsenic content in drinking water ranges from 50-1200 g L-1. Medical histories were taken and smokers were eliminated from the sample population.

Marshal Science SNP Web Site, http://www.science.marshall.edu/murraye/341/snps/Human%20Genetics%20MTHFR%20SNP%20Page.html, (accessed August, 2010)

11University of Massachusetts at Amherst Department of Chemistry

Publication Plans and Conclusion

Digital Image Analysis of Gutzeit Method to Improve Precision, a document in process; targeted publication is Royal Society of Chemistry journal Analytical Methods.

Determination of Arsenic in Soils with Gutzeit Chemistry. The Use of Silver Nitrate as a Reagent for the Measurement of Arsenic.

Single Nucleotide Polymorphisms in the Promoter Regions of Cytokine Genes of Arsenic Exposed Populations in West Bengal, India. Potential Targets: Journal of Clinical Immunology, Carcinogenesis, and Mutation Research.

12University of Massachusetts at Amherst Department of Chemistry

Thank You and Questions

• Dr. Julian F. Tyson

• Members of the Committee

• Members of the Tyson Research Group • The undergraduate researchers

• The Rise Fellowship

• The National Science Foundation

• Staff of the University of Massachusetts Chemistry Program