Atomic Absorption Spectroscopy Questions and Answers

Answer: A

Dissolved solids build up on the burner slot, narrowing it and disturbing the flame, which reduces the number of atoms in the beam. A warming lamp would drift upward if anything, and detector and flame changes are not systematic in this way. Aspirating water between samples and cleaning the slot are the routine remedies, and the drift's direction is what identifies it as a fouling problem rather than an electronic one. Checking the units of each quantity catches a wrong formula before the arithmetic begins.

Answer: B

At nanogram levels a trace of analyte on a tip, in the argon line or left in the tube from a previous sample is comparable with the amount being measured. Wavelength, lamp current and chopper frequency would produce systematic rather than erratic behaviour. When a measurement approaches the amount of analyte present in ordinary laboratory dust, contamination becomes the dominant source of scatter and cleanliness becomes the dominant skill. Framing the question as which quantity the change acts upon makes the answer follow without calculation.

Answer: C

The first two are correct and the third is the reverse: a continuum source would have almost all its transmitted light unabsorbed, because the atomic line is far narrower than any monochromator band. That is precisely why the line source exists. A statement inverting the reason for a technique's defining design choice is worth doubting before any detail is checked. Framing the question as which quantity the change acts upon makes the answer follow without calculation. Most errors here come from carrying a result across from a neighbouring case where it does not hold. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Most errors here come from carrying a result across from a neighbouring case where it does not hold. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: D

The first and third are correct and the second is backwards: a hotter flame increases ionisation, which is why an ionisation suppressant so often accompanies the nitrous oxide flame. The hotter flame is used to overcome chemical interference from refractory oxides, and it creates an ionisation problem in exchange. That each remedy introduces its own difficulty is the recurring shape of this topic.

Answer: A

Both are true and the second is the reason: a population already close to a hundred per cent barely changes with temperature, while the tiny excited fraction that emission depends on changes by a large factor. Measuring a quantity that is already near its maximum makes a method robust against the variable that determines it, which is a design principle worth recognising well beyond this technique.

Answer: B

The reason is true but the assertion is false: high current produces a dense cloud of ground-state atoms in front of the cathode which absorb the centre of the line, broadening it and reducing sensitivity. Lamp life suffers as well. Whenever a source and an absorber are the same element, the source's own vapour is a hazard, and the optimum current is a compromise rather than a maximum.

Answer: C

The pairing is A-P, B-Q, C-R. Four kinds of interference each with its own remedy is what makes an unexpected result diagnosable rather than merely disappointing, and identifying which kind is present is the whole of the diagnosis. Standard additions happens to address the last two and the chemical one as well, which is why it is reached for so often.

Answer: D

The first three are correct and the fourth is not, so three match. Silicon forms a refractory oxide that an air-acetylene flame cannot break, so it requires the hotter nitrous oxide flame. Matching an element to an atomiser means asking how stable its oxide is and how readily it ionises, and those two questions between them settle nearly every case.

Answer: A

This is a hollow cathode lamp, so called because the cup shape confines the sputtered atoms where the discharge can excite them. Sputtering is what happens inside it rather than its name, a continuum lamp is the opposite kind of source, and heating is not how it works. The name describes the geometry that makes the arrangement efficient, and reading it literally explains why the cathode is shaped as it is. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: B

Higher throughput is a flame advantage - a furnace takes a couple of minutes per determination against a few seconds. The other three are its genuine strengths. Trading speed for sensitivity is the choice between the two atomisers, and a laboratory with many straightforward samples will make it the other way from one with few difficult ones.