Laboratory Equipment Operation & Maintenance Flashcards

When a laboratory refrigerator temperature log shows a pattern of gradually rising temperatures over two weeks before exceeding the acceptable range, this pattern most likely indicates:

Answer: Compressor wear or refrigerant loss requiring preventive service

A gradual upward trend over two weeks is characteristic of a failing compressor or slow refrigerant leak, not acute events like a door left open which would show sharp, isolated excursions.

In flame atomic absorption spectrophotometry (AAS), the hollow cathode lamp must match the element being measured because:

Answer: Each lamp emits the specific resonance line wavelength for its element

Each hollow cathode lamp emits the precise resonance wavelength unique to its element, which is absorbed only by atoms of that element in the flame, providing element-specific detection.

A real-time PCR instrument's calibration curve has an efficiency value of 115%. This result indicates:

Answer: Possible PCR inhibitors or primer dimer formation in the reaction

PCR efficiency above 100–110% is typically caused by PCR inhibitors or artifacts like primer dimers that initially boost signal non-specifically, distorting the standard curve slope.

The purpose of daily use of a Levy-Jennings chart in QC monitoring is to:

Answer: Visually detect systematic and random error trends over time

Levy-Jennings charts display QC results plotted over time, allowing technologists to visually identify systematic shifts, trends, and random errors before they affect patient results.

When replacing a HEPA filter in a biological safety cabinet, the technologist must ensure:

Answer: All surfaces are decontaminated and the cabinet is off during replacement

Before HEPA filter replacement, all interior surfaces must be decontaminated (typically with formaldehyde gas or UV), and the cabinet must be turned off to protect the maintenance worker from aerosolized contaminants.

An osmometer used for serum osmolality freezes a sample and detects the freezing point depression. The osmolality reading is DIRECTLY determined by:

Answer: The degree of freezing point depression compared to pure water

Freezing point osmometers measure the depression of the freezing point below 0°C; each osmole of solute per kilogram of water lowers the freezing point by 1.86°C, allowing direct osmolality calculation.

During mass spectrometry (LC-MS/MS) operation in a toxicology lab, the internal standard is added to every sample primarily to:

Answer: Correct for variations in sample preparation and instrument response

Internal standards (structurally similar or isotopically labeled analogs) are added before extraction to correct for variability in sample preparation efficiency, extraction recovery, and instrument signal fluctuations.