Exam 2: Assuring Good Measurements

An analyst performs and external standard calibration for fentanyl and obtains the following data points (concentration in ppb, area counts): 20.0, 9599 50.0, 21456 100.0, 45326 250.0, 102391 500.0, 210561 Using the resulting calibration curve, calculate the concentration of fentanyl (ppb) in a sample that generates area counts of 48722 (4 digits).

A laboratory validates a method for weighing solid dose drug powders on a single balance used by 4 analysts. They establish the figures of merit shown in the portion of the uncertainty budget shown below. What is the combined standard uncertainty for this balance in grams rounded to the same number of digits as the balance displays?

A laboratory receives a seizure of 1000 tablets. They decide to test 10% of these. These tests show that all tablets contain methamphetamine. This is an example of

An analyst performs and external standard calibration for fentanyl and obtains the following data points (concentration in ppb, area counts): 20.0, 9599 50.0, 21456 100.0, 45326 250.0, 102391 500.0, 210561 What is the slope and the intercept of the resulting linear equation (to one decimal place)?

Quality control is defined here as

A laboratory receives a seizure of 592 kilogram "bricks" of white powder. All appear to be similar based on physical characteristics. The legal threshold that divides charges between possession (less severe potential punishment) from distribution (more severe potential punishment) is 10 kilograms. Assuming all weigh close to a kilogram, what is the minimum number of bricks that must be shown to contain a controlled substance?

What is the difference between bias and trueness as used in forensic chemistry?

The primary purpose of a calibration curve is to

A laboratory validates a method for weighing solid dose drug powders on a single balance used by 4 analysts. They establish the figures of merit shown in the portion of the uncertainty budget shown below. A case sample is weighed on this balance with a result of 28.35 grams. What is the estimated uncertainty of this weight with a coverage factor of 2 (~95%) in grams?

Measurement uncertainty expresses

Which type of calibration curve uses ratios of concentrations and responses?

The international body the coordinates standards of metrology and definitions is

An analyst decides to calculate the %error as a measure of bias. A certified reference material (CRM) contains a drug metabolite at a concentration of 12.8 micromolar 0.03 micromolar. The analyst tests this sample and obtains a result of 12.1 micromolar 0.1 micromolar. What is the %error (to one decimal place)?

Which of the following is false regarding an internal standard compound

You are tasked with developing a critical assay to detect a poison in biological fluids. Quantitation has to be as exact as possible. Your best choice when purchasing a chemical standard is a

A laboratory receives a seizure of 592 kilogram "bricks" of white powder. All appear to be similar based on physical characteristics. The laboratory has tested many such seizures in the past months and all have been shown to be cocaine. Use the ENFSI spreadsheet to determine how many samples must be initially tested to show that 99% of the seizure contains cocaine with 99% confidence.

The correlation coefficient (R2) is a measure of

The warning limit of a control chart are typically +/-

Which type of calibration provides the best matrix match?

Which organization provides the detailed analytical procedures that all forensic laboratories must use?