3348470
Description
Flashcards by Lydia Rossiter, updated more than 1 year ago
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Created by Lydia Rossiter
over 8 years ago
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| Question | Answer |
| What is the proper preservation technique for most samples? | cool to 4 degrees Celsius |
| What are the exceptions for sample preservation? | reduce pH under 2 = hardness metals ammonia test immediately = pH temperature chlorine |
| follow chain of custody | document chain of custody: sampler's name location of sample, date & time analysis required sampling conditions/storage info transportation date/time proof of lab acquisition |
| How can you improve quality control in the lab? | analyze reference-type samples split samples and compare results self-appraisal & evaluation |
| abnormal chlorine levels | max. disinfectant level/goal = 4.0 mg/L aiming for 0.5 mg/L right after chlorination aiming for 0.2 mg/L throughout distribution system |
| What are the steps for analyzing free residual chlorine using amperometric titration method? | 1. Place a 200 mL sample of water in titrator 2. start the agitator 3. add 1 mL of pH 7 buffer 4. titrate with 0.00564 N phenylarsene oxide solution 5. mL of phenylarsene =mg/L chlorine residual |
| chemicals that contribute to alkalinity (ability to neutralize acids) to water | bicarbonates/carbonates hydroxides of calcium, magnesium & sodium Affected by treatment chemicals: alum chlorine lime |
| pH scale | 0-14 negative log of the hydrogen ion activity |
| acids and bases | Acid = below 7 Base = above 7 |
| read a pH meter | 0-6.9 Acid 7 neutral 7.1-14 Base |
| temperature effects on pH | As the water temperature goes up, pH goes down (inverse) |
| calibrate a turbidimeter | Measure standard solutions (run at least one standard in each instrument range to be used) |
| chemicals that contribute hardness to water | calcium magnesium strontium iron manganese |
| abnormal hardness levels | Over 100 mg/L |
| abnormal levels of fluoride | 4.0 mg/L MCL < 1.7 recommended |
| chemicals that contribute taste and odor | Blue-green algae: geosmin & methylisoborneol (MIB) Chlorine Chloramines Aldehydes Phenols & Chlorophenols |
| abnormal taste and odors | Earthy: geosmin Musty: MIB Bleach: chlorine Swimming pool/bleach: chloramines Fruity: aldehyde Pharmaceutical/medicinal: phenols |
| bacteriological analysis methods | methods: Multiple tube fermentation Membrane filter Presence/Absence method |
| presence/absence test method | i 559+ one large test portion 100 mL broth with purple for pH inspect after 24 and 48 hours gas/acid produced turns yellow if coliforms are present will foam when shaken |
| multiple tube fermentation method | i 547+ untreated water = 15 tubes drinking water = 10 tubes different dilutions incubate 24/48 hours inspect for gas |
| Heterotrophic Plate Count (HPC) | ? |
| membrane filtration method | i 555+ large sample size for well/drinking smaller but more samples for lakes/rivers pour water through membrane filter place filter on pad with media (food) incubate in petri dish |
| bacteriological testing controls | I 544+? sodium thiosulfate to neutralize chlorine glassware washed and rinsed use distilled/demineralized water for prep of media, sterilized pipet avoid contamination from air, equipment, clothes or fingers |
| What is the difference between presumptive and confirmed results? | Presumptive: 24 hours, gas produced Confirmed: 48 hours, gas produced, coliform group confirmed, calculate confirmed MPN (most probable number) |
| What maximum holding times are IMMEDIATE? | pH Temperature Chlorine total residual Dissolved oxygen |
| What maximum holding time is 6 hours? | Odor |
| What maximum holding time is 6 months? | Hardness Metals - dissolved or suspended/total |
| What maximum holding times are 14 days? | Acidity Alkalinity Cyanide |
| What material should the sample container be made of? | polyethylene or glass glass only: odor polyethylene only: fluoride washed in detergent and hot water, rinsed in hot water, rinsed with distilled/deionized water |
| What volume is needed for a sample for ODOR? | 200 mL |
| What volume is needed for a sample for COLOR? | 500 mL |
| What volume is needed for a sample for HARDNESS? | 100 mL |
| What volume is needed for a sample for pH? | 25 mL |
| What volume is needed for a sample for TEMPERATURE? | 1,000 mL |
| What volume is needed for a sample for TURBIDITY? | 100 mL |
| What volume is needed for a sample for ALKALINITY? | 200 mL |
| What volume is needed for a sample for CHLORINE TOTAL RESIDUAL? | 500 mL |
| What volume is needed for a sample for FLUORIDE? | 300 mL |
| What are some causes of poor quality control in the lab? | sloppy technique deteriorated reagents and standards poorly operating instruments calculation mistakes |
| What are the keys to proper chemical storage? | ventilation well lighted segregate incompatible chemicals clean clearly label & date chemicals |
| What are the keys to safely moving chemicals? | use cradles or tilters for large vessels use a handtruck for cylinders clamp cylinders into place carry flammable liquids in safety cans |
| What are the keys to safely handling chemicals? | 1. Always flush the outside of acid bottles with water 2. Do not lay bottle stoppers on counter 3. Always pour acid into water 4. Secure small mercury spills and label them 5. Use a ventilated fume hood |
| analyze a water sample for free chlorine (DPD titrimetric method) | 1. Place 5 mL each of buffer reagent and DPD indicator in 250 mL flask and mix 2. Add 100 mL of sample and mix 3. Titrate rapidly with FAS titrant until red color disappears 4. Record amount of FAS used |
| analyze a water sample for total chlorine (DPD titrimetric method) | 1. Place 5 mL each of buffer reagent and DPD indicator in 250 mL flask and mix 2. Add 100 mL of sample and mix 3. Titrate rapidly with FAS titrant until red color disappears 4. Record amount of FAS used 5. Add one small crystal of KI and mix 6. Continue titrating until red color disappears 7. Record reading of FAS |
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