Question

In atomic absorption spectroscopy, back ground correction performed using a single hollow cathode lamp pulsed first with a low current and then with a high current is called:

• A. Smith Hieftje background correction
• B. Continuous source background correction
• C. Zeeman effect background correction
• D. Hollow cathode background correction

Answer 1

The Correct Option is A

In atomic absorption spectroscopy, background correction is essential to accurately measure the concentration of elements in a sample by compensating for any absorbance due to the matrix or other interfering components. Among the various methods used for background correction, the Smith Hieftje method is one of the most effective techniques.

Smith Hieftje Background Correction Method: This technique involves the use of a single hollow cathode lamp pulsed at two different currents: a low current and a high current. Here's how it works:

1. Low Current Pulse: The lamp is run at a low current, which produces a narrow atomic line emission corresponding to the element of interest. This portion of the emission is absorbed by the element in the sample as well as any background interference.
2. High Current Pulse: The lamp is pulsed at a higher current. At this high current, self-absorption broadens the emission line. The broadened line is not absorbed by the analyte atoms (because they absorb only the narrow line) but is absorbed by the background interferences.

By comparing the signals obtained from the low and high current pulses, the Smith Hieftje method effectively corrects for the background interference. The corrected signal is obtained by subtracting the absorbance at high current from the absorbance at low current.

Conclusion: Therefore, the correct answer to the question regarding the type of background correction using a single hollow cathode lamp pulsed with a low and high current is Smith Hieftje background correction.

Why Other Options Are Incorrect:

• Continuous Source Background Correction: Involves the use of a continuous light source, not appropriate for pulsing with a single hollow cathode lamp.
• Zeeman Effect Background Correction: Uses magnetic fields to distinguish between analyte and background absorption, not related to pulsing current.
• Hollow Cathode Background Correction: This term is more general and doesn't specify the pulsing method used in Smith Hieftje.