CPC Chemical Instrumentation & Calibration 2

Question 1

In ICP-OES, which type of interference occurs when an analyte emission line overlaps with a line from a matrix element?

Accepted Answer

Spectral interference

Answer

Spectral interference in ICP-OES occurs when emission lines of different elements overlap, causing inaccurate analyte signal readings.

Question 2

What is the purpose of a Certified Reference Material (CRM) in analytical chemistry?

Accepted Answer

To establish traceability of measurements to SI units

Answer

CRMs provide metrological traceability by linking measurements to SI units through an unbroken chain of calibrations.

Question 3

Which detector is most commonly used in modern gas chromatography for the detection of halogenated compounds at trace levels?

Accepted Answer

Electron capture detector (ECD)

Answer

The ECD is highly sensitive to electronegative halogenated compounds because they capture electrons from a radioactive source, reducing the standing current.

Question 4

In UV-Vis spectrophotometry, what does the term 'stray light' refer to?

Accepted Answer

Radiation reaching the detector at wavelengths other than those selected by the monochromator

Answer

Stray light is any radiation outside the selected bandpass that reaches the detector, causing errors particularly at high absorbance values.

Question 5

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?

Accepted Answer

The calibration range does not bracket the sample pH, reducing accuracy

Answer

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.

(CPC) Certified Professional Chemist Practice Test

(CPC) Certified Professional Chemist Practice Test

CPC Chemical Instrumentation & Calibration 2