STP Laboratory Practice 4

Question 1

What is the appropriate response when a laboratory worker discovers an unlabeled container of unknown liquid?

Accepted Answer

Treat it as hazardous, label it 'Unknown,' isolate it, and report it to the safety officer

Answer

Unknown chemicals must be treated as hazardous, properly quarantined, and reported so they can be characterized safely before any further handling or disposal.

Question 2

In the context of laboratory quality systems, what does 'traceability' mean for a measurement result?

Accepted Answer

The property of a measurement result that can be related to a stated reference through an unbroken chain of calibrations

Answer

Metrological traceability links a measurement result to a national or international standard through an unbroken documented calibration chain.

Question 3

Which of the following best describes the purpose of a blank sample in an analytical run?

Accepted Answer

To detect background signal, contamination, or matrix interference in the absence of the analyte

Answer

A blank contains all components of the assay except the analyte, so any signal detected indicates background noise or contamination.

Question 4

When working with a biological safety cabinet (BSC), which action will DISRUPT the protective airflow and should be avoided?

Accepted Answer

Rapidly moving arms in and out of the cabinet

Answer

Rapid arm movements across the cabinet opening create turbulence that disrupts the air curtain, allowing potential cross-contamination or exposure.

Question 5

A pipette is calibrated to deliver 1000 µL. During a gravimetric check using water at 20°C, it consistently delivers an average of 985 µL. This is an example of:

Accepted Answer

Systematic error (bias) with acceptable precision

Answer

A consistent offset in the same direction from the true value represents systematic error (bias), which can often be corrected through recalibration.

(STP) Scientist Training Programme Practice Test

(STP) Scientist Training Programme Practice Test

STP Laboratory Practice 4