Chemical Instrumentation & Calibration Flashcards
7 cards from real CPC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Chemical Instrumentation & Calibration flashcards as text
In ICP-OES, which type of interference occurs when an analyte emission line overlaps with a line from a matrix element?
Answer: Spectral interference
Spectral interference in ICP-OES occurs when emission lines of different elements overlap, causing inaccurate analyte signal readings.
What is the purpose of a Certified Reference Material (CRM) in analytical chemistry?
Answer: To establish traceability of measurements to SI units
CRMs provide metrological traceability by linking measurements to SI units through an unbroken chain of calibrations.
Which detector is most commonly used in modern gas chromatography for the detection of halogenated compounds at trace levels?
Answer: Electron capture detector (ECD)
The ECD is highly sensitive to electronegative halogenated compounds because they capture electrons from a radioactive source, reducing the standing current.
In UV-Vis spectrophotometry, what does the term 'stray light' refer to?
Answer: Radiation reaching the detector at wavelengths other than those selected by the monochromator
Stray light is any radiation outside the selected bandpass that reaches the detector, causing errors particularly at high absorbance values.
A pH meter is calibrated with buffers at pH 4.00 and 7.00. When measuring a sample at pH 10, what is the primary concern?
Answer: The calibration range does not bracket the sample pH, reducing accuracy
Measurements outside the calibrated range are extrapolations and less accurate; a three-point calibration including pH 10.00 buffer should be used for alkaline samples.
In atomic absorption spectroscopy (AAS), what is the role of the hollow cathode lamp?
Answer: To emit narrow-line radiation characteristic of the analyte element
The hollow cathode lamp emits element-specific narrow spectral lines that are absorbed by ground-state atoms of the same element in the atomizer.
Which calibration approach corrects for both instrument drift and matrix effects by adding a known amount of analyte directly to the sample?
Answer: Standard addition method
The standard addition method adds known analyte increments to the sample itself, so matrix effects and drift affect both analyte and spikes equally, allowing accurate quantitation.