ENVR 1401 LAB EXERCISE Lab : Toxicity Testing and Determining the LC 50

Transcription

1 SAFETY CONCERNS: ENVR 1401 LAB EXERCISE Lab : Toxicity Testing and Determining the LC 50 Chemical splash goggles must be worn by everyone in the lab while chemicals are out and in use. Goggles and a sterilizing cabinet have been provided in the lab classroom. Safety glasses are not permitted as a substitute. Chemicals being used in this exercise should be handled with care. DO NOT MIX these chemicals under any circumstance. Care should be taken to not cross-contaminate when using dropper bottles or mechanical pipettes. Instructor should be immediately notified if any substance is spilled. Students are NOT to clean up any spills. Instructor should be immediately notified if any glassware is broken or damaged. Students are NOT to clean up any broken glass. Use the buddy system and keep a watchful eye on your lab partners. If any student begins to feel light-headed or dizzy or has any other adverse reaction to the chemicals, notify the Instructor immediately! Any student with asthma or other serious respiratory condition should notify the Instructor so that appropriate care can be exercised. LAB CLEAN-UP: Materials: Properly dispose of all waste materials ONLY as directed by the Instructor. DO NOT MIX CHEMICALS!!! All lab equipment should be cleaned and returned to the cart; Petri dishes should be thoroughly rinsed and dried before returning them to the cart. Lab table tops should be wiped down and cleaned before you leave the lab. Petri dishes (4 per group) can be washed and reused Brine shrimp Brine solution (3.5 % w/v NaCl and water) need 600 ml per class Vinegar need about 50 ml in small dropper bottle (1 per group) Ammonia need about 50 ml in small dropper bottle (1 per group) Bleach need about 50 ml in small dropper bottle (1 per group) 3 Pipettes (1 ml) each labeled for the respective contaminants Pipette pumps Grease pencils Beakers (5 or 10 ml) Graduated cylinders (25 ml) Magnifiers or hand lens (minimum 2 per group) NAME: Lab Section: Revised: September 22,

2 Beakers (Extra large) for waste one each labeled for Vinegar, Bleach and Ammonia Beaker (Extra large) for tested Brine Shrimp PROCEDURE: 1. Use four (4) petri dishes one for control and one for each of the three substances to be tested. Label them as C for Control, Amm for Ammonia, B for Bleach and Vin for Vinegar. 2. Obtain a minimum of 12 brine shrimp in a 25 ml cylinder. Add brine to bring the level to a total of 20 ml. Repeat this step for each of the 4 Petri dishes. 3. Cover the Petri dishes. Wait and observe the brine shrimp for 5 minutes. Record the number of live brine shrimp in each of the four Petri dishes. NOTE: Be sure to count and record the number of LIVE brine shrimp remaining after each time interval this is critical as the brine shrimp may exhibit cannibalistic behavior!! 4. What is your hypothesis (i.e., what is your prediction ranking the toxicity of these three contaminants): Most Toxic: Intermediate Toxicity: Least Toxic: 5. Using the mechanical pipette, add 0.5 ml of the respective contaminant to the appropriate Petri dish. Quickly replace the cover, use a GENTLE swirling motion to uniformly distribute the contaminant in the Petri dish. Wait 5 minutes and then count the number of live brine shrimp. NOTE: Be sure to keep the contaminant dropper bottles closed unless removing aliquots. This will minimize the amount of vapors released and reduce inhalation exposure. 6. Add another 0.5 ml of respective contaminant to the appropriate Petri dish, observe for 5 minutes and record the results. 7. Add 1 ml of the respective contaminant to the appropriate Petri dish, observe for 5 minutes and record the results. REPEAT this step until a total of five 1-ml aliquots have been added and the data recorded for each interval. NOTE: If you have not achieved at least 80% mortality, then add the respective contaminant in 2 ml incremental amounts to the appropriate Petri dish until a minimum of 80% mortality has been reached. 8. Use the number of live brine shrimp remaining after each timed interval to calculate the number that died. Calculate the cumulative percent mortality at each concentration level and record. Concentration-Response Curves Construct a single graph which shows the dose-response curves for all three substances tested. This graph must be constructed with Excel or similar database/graphing software and must include all three curves on the same graph (see example on following page). o Be sure to double click on Vertical Axis Values and change the Axis Options to maximum = fixed = 100, since mortality can not exceed 100 %. Revised: September 22,

3 Formal Laboratory Report Prepare a formal laboratory report following all guidelines in the Background provided in Lab 4 on the Scientific Method. Append your Laboratory Report to this assignment. Remember to: Type the report (1 margins, 1 ½ line spacing, 10 or 12 point Times New Roman font). Develop and use appropriate headings for all sections of your report. Be sure to include and properly reference your data tables in your Results. Append and properly reference your dose-response graph in your Discussion. Remember this is a collaborative effort in the lab, but your formal laboratory report should reflect your own thoughts and effort. Spelling, good grammar, punctuation, sentence and paragraph structure will count for 5 points of your lab report grade Final result (data table and graph) should look similar to this though obviously your dose-response curves will reflect your actual data. Revised: September 22,

4 Table 1. Toxicity Testing: Brine Shrimp Raw Data NaCl Brine CONTAMINANT Number of LIVE Brine Shrimp (ml) (ml) Amount (ml) % Concentration Control Ammonia Bleach Vinegar Revised: September 22,

5 Table 2. Toxicity Testing: Percent Mortality of Brine Shrimp Concentration (%) Vinegar Bleach Ammonia Revised: September 22,