Camping Burner-Based Flame Emission Spectrometer for Classroom Demonstrations

摘要

A flame emission spectrometer was built in-house for the purpose of introducing this analytical technique to students at the high school level. The aqueous sample is sprayed through a homemade nebulizer into the air inlet of a consumer-grade propane camping burner. The resulting flame is analyzed by a commercial array spectrometer for the visible spectrum in the range of 350-1000 nm. The cost of the instrument is mainly given by that of the spectrometer and computer/projector. The obtained emission spectrum is characteristic of each individual atom, such as sodium (589 nm) and potassium (766 nm), or molecule, such as calcium hydroxide (554 and 622 nm). The readout signal (either peak height or peak area) is shown to be proportional to the sample concentration. Both qualitative and quantitative analyses may be performed with this robust and low-cost device. Samples can be rapidly changed, giving a 95% response time of under 3 s. The analytical figures of merit were characterized for calcium, potassium, and sodium in different water samples, and the resulting precision (standard deviation) for a 1 s acquisition time was typically on the order of 2%. Observed calcium levels were lower than expected because of the presence of refractory compounds, such as calcium phosphate or sulfate, that are difficult to fully atomize with the simple flame used here. Lanthanum(III) chloride was successfully used to increase the calcium response. The lower limit of detection for sodium was approximately 3 ppb and comparable to that of conventional commercial emission spectrometers.