Instrumental Analysis Flashcards
What is instrument analysis in chemistry?
Instrument analysis involves using specialized instruments to qualitatively and quantitatively analyze the composition and structure of substances.
Name three common instruments used for chemical analysis.
UV-Visible spectrophotometers, gas or liquid chromatographs (GC/LC), and mass spectrometers.
What is spectrophotometry?
Spectrophotometry measures the intensity of light absorbed by a sample at a specific wavelength to determine its concentration.
How does a UV-Vis spectrophotometer work?
It passes ultraviolet or visible light through a sample and measures the absorbance, which is related to the concentration of absorbing species via the Beer-Lambert Law.
State the Beer-Lambert Law and its formula.
A = εlc, where A is absorbance, ε is the molar absorptivity, l is the path length, and c is the concentration.
What is chromatography?
Chromatography is a technique used to separate mixtures based on differences in the distribution of compounds between a stationary phase and a mobile phase.
Differentiate between gas chromatography (GC) and liquid chromatography (LC).
GC separates volatile compounds in the gas phase, whereas LC separates compounds dissolved in a liquid mobile phase.
What is High Performance Liquid Chromatography (HPLC)?
HPLC is an advanced form of liquid chromatography that uses high pressure to push solvents through a column, allowing for faster and more efficient separation.
What is Mass Spectrometry (MS)?
Mass spectrometry measures the masses and relative concentrations of ions, providing molecular weight and structural information about a compound.
How does Nuclear Magnetic Resonance (NMR) spectroscopy work?
NMR spectroscopy exploits the magnetic properties of certain nuclei; when placed in a magnetic field and exposed to radiofrequency radiation, nuclei resonate at characteristic frequencies that reveal molecular structure.
What information does Infrared (IR) spectroscopy provide?
IR spectroscopy identifies functional groups and molecular bonds based on the absorption of infrared light at characteristic frequencies.
How is a sample typically prepared for chromatographic analysis?
Samples are usually dissolved in a suitable solvent, filtered, and sometimes derivatized to enhance volatility or detectability before injection into the chromatograph.
What is the role of a detector in instrument analysis?
Detectors convert physical or chemical changes in the sample into measurable signals, allowing for qualitative and quantitative analysis.
Explain the principle of flame photometry.
Flame photometry measures the emission of light by certain metal ions when excited in a flame, with the intensity of the emitted light used to determine concentration.
What is an electrochemical sensor?
An electrochemical sensor detects chemical species by measuring the electrical signals generated by their oxidation or reduction at an electrode surface.
How does thermal analysis (e.g., Thermogravimetric Analysis, TGA) work?
Thermal analysis measures changes in a material’s properties as a function of temperature, such as weight loss in TGA when a sample decomposes or loses volatile components.
What are the advantages of instrumental methods over classical methods in chemical analysis?
Instrumental methods offer higher sensitivity, accuracy, speed, and the ability to analyze complex mixtures and trace components.
How is calibration performed in instrument analysis?
Calibration involves analyzing standards with known concentrations to create a calibration curve, which is then used to determine the concentration of unknown samples.
Define the terms ‘limit of detection’ (LOD) and ‘limit of quantification’ (LOQ).
LOD is the lowest concentration of an analyte that can be reliably detected, while LOQ is the lowest concentration that can be quantitatively measured with acceptable precision.
What factors influence the sensitivity and selectivity of an analytical instrument?
Factors include the instrument’s design, the choice of detector, sample preparation techniques, and the properties of the analyte and matrix.
How does resolution affect the quality of analysis in techniques like chromatography or spectroscopy?
Higher resolution allows for the separation or distinction of compounds with similar properties, leading to more accurate identification and quantification.
What safety considerations are important when using analytical instruments?
Proper training, use of personal protective equipment (PPE), adherence to instrument operating procedures, and knowledge of the hazards associated with chemicals and equipment.
Describe one application of instrument analysis in environmental chemistry.
Chromatography and mass spectrometry are used to detect and quantify pollutants in water, soil, and air samples.
How do advances in instrument analysis impact the field of chemistry?
Technological advancements enable more precise, faster, and lower-cost analyses, driving innovation in research, quality control, and environmental monitoring.
Why is instrument analysis critical for modern chemical research and industry?
It provides detailed, reliable, and rapid information on chemical composition and structure, which is essential for product development, regulatory compliance, and scientific discovery.
