SSCK 1203 ANALYTICAL CHEMISTRY FOR ENGINEERING - Week 2 Lecture 4

Flashcards summarizing key concepts and techniques related to spectroscopic methods for inorganic analyte analysis, including Atomic Absorption Spectroscopy (AAS) and Atomic Emission Spectroscopy (AES).

Atomic Spectrometry Techniques

Spectroscopic-based methods used for determining the elemental composition of an analyte.

Decision criteria for choosing an atomic spectrometry technique

Cost, element range (single/multi-element), and detection limits are important.

FAAS (Flame Atomic Absorption Spectroscopy)

Technique that provides fast sequential multi-element analysis with ppb-ppm level detection limits.

ICP-MS (Inductively Coupled Plasma Mass Spectrometry)

Offers the best detection limits, covers almost all elements, and provides fast, multi-element analysis.

GFAAS (Graphite Furnace Atomic Absorption Spectroscopy)

Technique more expensive than FAAS, offers much better detection limits, but is slow and performs single-element analysis.

Difference between AAS and AES regarding light source

AAS requires an external light source, while AES does not because the sample itself can be the light source.

Advantage of AES over AAS

All atoms in a sample are excited and detected simultaneously in AES.

Common principles in AAS and AES

Nebulization, evaporation, atomization, and excitation or ionization.

External Light Sources used in AAS

Hollow Cathode Lamp (HCL) and Electrodeless Discharge Lamp (EDL).

Function of a Light Chopper in AAS

It is placed between the hollow cathode lamp and the flame, 'chopping' the light to allow the detector to differentiate between light emitted by the flame and the light from the lamp.

Common Oxidant-Fuel Combinations used in Flame AAS

Air-Acetylene and Nitrous Oxide-Acetylene.

Material used to construct burner heads for resistance to heat and corrosion

Titanium.

Why are burner heads constructed of titanium?

To provide extreme resistance to heat and corrosion.

Atomization

Converting a sample (solid or solution) into vapor particles, individual molecules, and individual gaseous atoms.

Components of an Atomic Absorption Spectrometer

Monochromator, hollow cathode lamp, burner-nebulizer, photomultiplier tube, and data recorder.

Level of Detection for Flame AAS (F-AAS)

Ppm.

How atomization is achieved in Graphite Furnace AAS (GF-AAS)

An electrically heated graphite tube replaces the flame, and the sample is dried, ashed, and vaporized within the tube.

Steps in a Graphite Furnace Program

Drying, pyrolysis (char), and atomization.

Purpose of using Argon gas in Graphite Furnace AAS (GF-AAS)

To avoid oxidation.

Purpose of Hydride Generation Atomic Absorption Spectrometer (HG-AAS)

To improve determination of metalloids by generating volatile covalent hydrides.

Cold Vapor Atomic Absorption Spectrometer (CV-AAS)

Used for mercury determination, reducing mercury using SnCl2 without needing external heating.

Components of a Monochromator

Consists of an entrance slit, collimating lens or mirror, dispersion element (prism or grating), focusing lens or mirror, and exit slit.

Function of a Photomultiplier Tube as a Detector

Detects one wavelength at a time based on the photoelectric effect.

Analytes determined by ASTM D5863 - 00a Standard Test Method

Nickel, Vanadium, Iron, and Sodium in Crude Oils and Residual Fuels.