Analysis of Copper (Cu) Levels from an Environmental
Scenario
UEL Analytical undertakes contract analysis for industry and local authority bodies. You are a scientist working within the analytical toxicology unit measuring toxin and heavy metal contaminants in soil and water samples. A Welsh farming community has reported an unusually large number of sheep and lamb deaths over the past few years. The Department for Environment, Food & Rural Affairs suspect flooding of a local mine several years ago may have resulted in copper leaching into water used in irrigation of pasture land contaminating the soil. Copper can be extremely toxic and chronic exposure to high levels can lead to a number of pathologies including death in both lambs and adult sheep.
You have been given experimental samples derived from soil on five farms in the affected area. You have also been given five control samples from an unaffected neighbouring community. Your colleague has processed the ten soil samples and extracted the copper into an aqueous solution, suitable for analysis.
Over two experiments you will:
1. Make a solution of copper sulphate which can be diluted to make standards
2. Dilute your standards, measure their absorbance and the absorbance of the environmental samples at 800nM to determine the copper concentrations
Record all data in your laboratory notebook.
You will then write a type written report of your results for your supervisor (tutor).
Health and Safety
Read and note the Hazard warnings on any chemicals. A risk and COSHH assessment has been performed to assess the hazards involved in this practical and is posted in the laboratory (and on Moodle)
You are to wear eye protection at all times during the practical work and gloves need to be worn when working with copper sulphate.
All spillages are to be reported to a demonstrator. Spillages on the bench are to be mopped up immediately. If chemicals are spilt on clothes or skin they are to be rinsed thoroughly with plenty of water. If chemicals are splashed in eyes, help must be sought immediately from a member of staff.
Practical 1. Preparing a standard solution of copper sulphate
Aim: To make up 25mL of a 0.1 Molar copper sulphate standard solution
Calculation: how to make 25mL of a stock solution of 0.1M cupric sulphate
1. Work out the molecular weight of cupric sulphate from the formula: CuSO4.5H2O, given the following relative atomic masses (Ar)
Cu = 63.57, S =32.06, O = 16 and H = 1.008
Record the calculation in your Practical Workbook and check your answer with a member of staff before proceeding. This is the mass of 1 mole of cupric sulphate.
2. How much cupric sulphate do you need to weigh out to make 25mL (0.025L) of a 0.1M solution? Check with your notes on concentrations and dilutions if necessary, record the mass in your workbook and confirm your answer with a member of staff.
Prepare a report on the Copper Toxicity Practicals
What you need to do:
You should already have written up the 2 practicals relating to the analysis of environmental copper samples in your laboratory workbook. This will be your source information for your final word processed report and the investigation.
The Results should describe the data you collected from these experiments. Graphs, tables and the results of any statistical analysis should be included in this section. We suggest you show
• A graph with your standard curve (including the line equation and R2 value).
• A table with the absorbance values of your soil samples with the corresponding calculated copper concentrations.
• A graph showing these results comparing the copper concentrations measured in the affected vs. control farms. If you perform a statistical analysis to support your interpretation of the data this should be included in this figure and also described in the results text.
The Discussion should present a short explanation of your results and what they mean in terms of the question that was being addressed. Do your results support the hypothesis that copper poisoning could be involved in the increased incidence of sheep and lamb death? Based on the results, what action would you recommend for the affected farms? Do further studies need to be performed? If there were any experimental problems that might make you question the validity of your results these should also be discussed. You can refer back to references used in the Introduction or add new ones to support statements made in the Discussion.
Attachment:- Results.pdf