Atomic Emission Spectrometry By: Alexa Kunch Chapter 10 Atomic Emission Spectrometry By: Alexa Kunch

Plasma Sources Total rate of Argon gas consumption Plasma: An electrically conducting gaseous mixture that contains a significant concentration of cations and electrons Overall Net charge due to the concentration of cations and electrons is zero Plasmas that use Argon ions can sustain temperatures as high as 10,000K Total rate of Argon gas consumption ranges from 5-20 L/min The sample is first nebulized, then it is introduced into the plasma

ICP Source Schematic of a typical ICP source similar to the one found on page 255 of the textbook

Applications of Plasma Sources Useful for both qualitative and quantitative elemental analysis because plasma sources produce spectra that are rich in characteristic emission lines High quality results due to: High stability Low noise Low background Freedom from interferences Plasma emission spectrometry allows the determination of all metallic elements

Number of Elements Detected at Concentrations of: Detection Limits Number of Elements Detected at Concentrations of: Method < 1 ppb 1-10 ppb 11-100 ppb 101-500 ppb > 500 ppb ICP Emission 9 32 14 6 Flame Atomic Emission 4 12 19 Flame Atomic Fluorescence 16 Flame Atomic Absorption 1 25 3 Table 10-3 Comparison of Detection Limits for Several Atomic Spectral Methods (page 269)

Chapter 13 An Introduction to Ultraviolet-Visible Molecular Absorption Spectrometry By Tim Cumming and Meg Dailey

Beer’s Law and Other Equations Transmittance: T=P/P0 Absorbance: A=log(P0/P) Beer’s Law: A=-logT A=logP0/P A=εbc

Beer’s Law “Few exceptions are found to the generalization that absorbance is linearly related to path length. On the other hand, deviations from the direct proportionality between the measured absorbance and concentration frequently occur when I> is constant.”

Sources of Instrumental Noise Case 1: Limited readout resolution or dark current and amplifier noise. Case 2: Photon detector shot noise Case 3: Cell positioning uncertainties and source flicker

Effect of Slit Width on Absorbance Measurements As the bandwidth increases, fine detail is lost Less peaks Peaks are more rounded As the bandwidth increases, peak height decreases Higher peaks with smaller bandwidth

Instrumentation Sources Wavelength Selectors Sample Containers Deuterium and Hydrogen lamps, Tungsten filament lamps, light-emitting diodes, and xenon arc lamps Wavelength Selectors Types are filters and monochromators Sample Containers Radiation Transducers Types include photon transducers and heat transducers Signal Processors and Readout Devices

Single-Beams vs. Double Beam Single-beam instrumentation includes of a lamp, a filter or monochromator, cells, a transducer, an amplifier, and a readout device Double-beam instruments includes a beamsplitter Double-beam instruments have more advantages Compensate for wide variations in source intensity with wavelength Continuous recording of transmittance and absorbance spectra

Single-Beam vs. Double-Beam

Typical Instruments Photometers Ultraviolet Absorption Photometers Visible photometers, probe-type photometers, filter selection Ultraviolet Absorption Photometers Spectrophotometers Instruments for the visible region, single-beam instruments for the ultraviolet-visible region, single-beam computerized spectrophotometers, double-beam instruments, double-dispersing instruments, and multichannel instruments