AC Arc
Definition and meaning of AC Arc in chemistry.
An AC arc is an alternating-current electrical discharge used as an excitation source in atomic emission spectroscopy. It vaporizes and excites a solid sample so that it emits light characteristic of the elements it contains.
In more detail
Because the current alternates, the arc extinguishes and reignites during each cycle, which spreads the discharge more evenly over the sample and gives better reproducibility than a direct-current arc, though usually with lower sensitivity. AC arcs were once common for qualitative and semi-quantitative elemental analysis but have largely been replaced by the inductively coupled plasma (ICP).
Key facts
| Type | Alternating-current discharge |
|---|---|
| Use | Excitation source in emission spectroscopy |
| Compared with | DC arc (more sensitive, less reproducible) |
| Field | Analytical instrumentation |
An AC arc struck between two graphite electrodes packed with a powdered sample produces light that a spectrometer separates into the emission lines of each element present.
Frequently asked questions
What is an AC arc used for?
It is used to excite solid samples in atomic emission spectroscopy so the elements present emit their characteristic wavelengths of light for analysis.