CWEA | 1
CWEA LABORATORY ANALYST GRADE 2
CERTIFICATION EXAM | STUDY GUIDE | LATEST
UPDATE 2026/2027 | PRACTICE QUESTIONS AND
ANSWERS | EXAM REVIEW MOST RECENT.
Table of Contents
1. Quality Assurance and Quality Control
2. Sample Collection, Preservation, and Holding Times
3. Laboratory Instrumentation and Equipment
4. Analytical Methods and Techniques
5. Microbiology and Biological Testing
6. Laboratory Safety and Chemical Handling
7. Data Analysis, Calculations, and Reporting
8. Chain of Custody and Documentation
9. Regulatory Compliance and Standards
10. Wastewater Treatment and Environmental Chemistry
, CWEA | 2
Question 1: Which of the following is the primary purpose of a quality assurance program in
a wastewater laboratory?
A) To increase sample throughput
B) To ensure that analytical results are accurate, precise, and defensible
C) To reduce the cost of laboratory supplies
D) To replace the need for calibration
Correct Answer: B) To ensure that analytical results are accurate, precise, and
defensible
A quality assurance program establishes policies, procedures, and practices that ensure
laboratory results are reliable and legally defensible. It encompasses all activities that
contribute to the generation of accurate and precise data.
Question 2: What is the primary purpose of a method blank in analytical chemistry?
A) To measure the sample's true concentration
B) To check for contamination or interference in reagents and the analytical process
C) To calibrate volumetric pipettes
D) To measure dissolved oxygen
Correct Answer: B) To check for contamination or interference in reagents and the
analytical process
A method blank contains all reagents and undergoes the same analytical procedure as
samples, but without the analyte. It helps identify contamination or interference that could
affect sample results.
Question 3: A laboratory quality control chart is used to:
A) Track employee attendance
B) Monitor analytical performance over time
C) Record sample receipt dates
D) Document instrument maintenance
Correct Answer: B) Monitor analytical performance over time
, CWEA | 3
Quality control charts plot QC sample results over time, helping analysts identify trends,
shifts, or out-of-control conditions in analytical performance. They are a fundamental tool for
statistical process control.
Question 4: What is the purpose of a spike recovery test?
A) To determine the boiling point of a sample
B) To evaluate the accuracy of an analytical method and detect matrix interferences
C) To measure the pH of a sample
D) To calibrate a spectrophotometer
Correct Answer: B) To evaluate the accuracy of an analytical method and detect matrix
interferences
Spike recovery involves adding a known amount of analyte to a sample and measuring the
percentage recovered. It assesses method accuracy and identifies matrix effects that may
suppress or enhance recovery.
Question 5: Which of the following is the primary purpose of a calibration curve in
instrumental analysis?
A) To establish the relationship between instrument response and analyte concentration
B) To clean the instrument between samples
C) To determine the sample's pH
D) To measure sample turbidity
Correct Answer: A) To establish the relationship between instrument response and
analyte concentration
A calibration curve is constructed by measuring the instrument response to known standards
at various concentrations. The resulting curve is used to determine the concentration of
unknown samples based on their instrument response.
Question 6: What is the recommended preservation method for a nitrate-nitrogen sample
before analysis?
A) Refrigeration at 4°C
B) Addition of hydrochloric acid
C) Freezing at −20°C
D) Storage at room temperature
, CWEA | 4
Correct Answer: A) Refrigeration at 4°C
Nitrate samples are generally stable under refrigeration at 4°C. Freezing is unnecessary,
strong acids are not required, and room temperature storage can lead to chemical changes or
microbial activity affecting nitrate levels.
Question 7: What is the maximum holding time for a BOD sample?
A) 6 hours
B) 24 hours
C) 48 hours
D) 14 days
Correct Answer: C) 48 hours
The maximum holding time for BOD samples is generally 48 hours when preserved at 4°C.
Samples should be analyzed as soon as possible to prevent changes in organic content.
Question 8: Which type of sample container is typically used for microbiological testing of
potable water?
A) Glass container with metal cap
B) Sterile plastic or glass container with sodium thiosulfate
C) Amber glass container with Teflon-lined cap
D) Plastic container with nitric acid preservative
Correct Answer: B) Sterile plastic or glass container with sodium thiosulfate
Microbiological samples require sterile containers. Sodium thiosulfate is added to neutralize
any residual chlorine that could inhibit bacterial growth. Amber glass is used for light-
sensitive analytes, and nitric acid is used for metals.
Question 9: What is the purpose of sodium thiosulfate in a microbiological sample container?
A) To neutralize residual chlorine
B) To preserve the sample for metals analysis
C) To adjust the pH of the sample
D) To prevent algal growth
Correct Answer: A) To neutralize residual chlorine
CWEA LABORATORY ANALYST GRADE 2
CERTIFICATION EXAM | STUDY GUIDE | LATEST
UPDATE 2026/2027 | PRACTICE QUESTIONS AND
ANSWERS | EXAM REVIEW MOST RECENT.
Table of Contents
1. Quality Assurance and Quality Control
2. Sample Collection, Preservation, and Holding Times
3. Laboratory Instrumentation and Equipment
4. Analytical Methods and Techniques
5. Microbiology and Biological Testing
6. Laboratory Safety and Chemical Handling
7. Data Analysis, Calculations, and Reporting
8. Chain of Custody and Documentation
9. Regulatory Compliance and Standards
10. Wastewater Treatment and Environmental Chemistry
, CWEA | 2
Question 1: Which of the following is the primary purpose of a quality assurance program in
a wastewater laboratory?
A) To increase sample throughput
B) To ensure that analytical results are accurate, precise, and defensible
C) To reduce the cost of laboratory supplies
D) To replace the need for calibration
Correct Answer: B) To ensure that analytical results are accurate, precise, and
defensible
A quality assurance program establishes policies, procedures, and practices that ensure
laboratory results are reliable and legally defensible. It encompasses all activities that
contribute to the generation of accurate and precise data.
Question 2: What is the primary purpose of a method blank in analytical chemistry?
A) To measure the sample's true concentration
B) To check for contamination or interference in reagents and the analytical process
C) To calibrate volumetric pipettes
D) To measure dissolved oxygen
Correct Answer: B) To check for contamination or interference in reagents and the
analytical process
A method blank contains all reagents and undergoes the same analytical procedure as
samples, but without the analyte. It helps identify contamination or interference that could
affect sample results.
Question 3: A laboratory quality control chart is used to:
A) Track employee attendance
B) Monitor analytical performance over time
C) Record sample receipt dates
D) Document instrument maintenance
Correct Answer: B) Monitor analytical performance over time
, CWEA | 3
Quality control charts plot QC sample results over time, helping analysts identify trends,
shifts, or out-of-control conditions in analytical performance. They are a fundamental tool for
statistical process control.
Question 4: What is the purpose of a spike recovery test?
A) To determine the boiling point of a sample
B) To evaluate the accuracy of an analytical method and detect matrix interferences
C) To measure the pH of a sample
D) To calibrate a spectrophotometer
Correct Answer: B) To evaluate the accuracy of an analytical method and detect matrix
interferences
Spike recovery involves adding a known amount of analyte to a sample and measuring the
percentage recovered. It assesses method accuracy and identifies matrix effects that may
suppress or enhance recovery.
Question 5: Which of the following is the primary purpose of a calibration curve in
instrumental analysis?
A) To establish the relationship between instrument response and analyte concentration
B) To clean the instrument between samples
C) To determine the sample's pH
D) To measure sample turbidity
Correct Answer: A) To establish the relationship between instrument response and
analyte concentration
A calibration curve is constructed by measuring the instrument response to known standards
at various concentrations. The resulting curve is used to determine the concentration of
unknown samples based on their instrument response.
Question 6: What is the recommended preservation method for a nitrate-nitrogen sample
before analysis?
A) Refrigeration at 4°C
B) Addition of hydrochloric acid
C) Freezing at −20°C
D) Storage at room temperature
, CWEA | 4
Correct Answer: A) Refrigeration at 4°C
Nitrate samples are generally stable under refrigeration at 4°C. Freezing is unnecessary,
strong acids are not required, and room temperature storage can lead to chemical changes or
microbial activity affecting nitrate levels.
Question 7: What is the maximum holding time for a BOD sample?
A) 6 hours
B) 24 hours
C) 48 hours
D) 14 days
Correct Answer: C) 48 hours
The maximum holding time for BOD samples is generally 48 hours when preserved at 4°C.
Samples should be analyzed as soon as possible to prevent changes in organic content.
Question 8: Which type of sample container is typically used for microbiological testing of
potable water?
A) Glass container with metal cap
B) Sterile plastic or glass container with sodium thiosulfate
C) Amber glass container with Teflon-lined cap
D) Plastic container with nitric acid preservative
Correct Answer: B) Sterile plastic or glass container with sodium thiosulfate
Microbiological samples require sterile containers. Sodium thiosulfate is added to neutralize
any residual chlorine that could inhibit bacterial growth. Amber glass is used for light-
sensitive analytes, and nitric acid is used for metals.
Question 9: What is the purpose of sodium thiosulfate in a microbiological sample container?
A) To neutralize residual chlorine
B) To preserve the sample for metals analysis
C) To adjust the pH of the sample
D) To prevent algal growth
Correct Answer: A) To neutralize residual chlorine
