Gas Chromatography Principles Quiz

A separation technique where a gaseous sample is transported through a column by a carrier gas. The stationary phase is usually a non-volatile liquid or a solid, and the analytes are gases or volatile liquids.

A type of GC where the stationary phase is a non-volatile liquid coated on the inside of the column or on a fine solid support. The analyte is partitioned between the mobile phase and the stationary phase.

A type of GC where the analyte is adsorbed directly onto the solid particles of the stationary phase.

A type of injection in GC where a small portion of the sample is injected into the carrier gas stream. The sample is mixed with the carrier gas and then enters the column.

A type of injection in GC where the entire sample is injected into the carrier gas stream. The sample is vaporized and then enters the column.

A type of injection in GC where the sample is injected directly onto the column. The sample is vaporized and then enters the column.

A type of detector used in GC that detects the presence of organic compounds. It uses a flame to ionize the organic compounds, which then produces a signal.

A technique used in GC and SFC where the temperature or pressure of the column is increased over time. This allows for the separation of a wider range of compounds.

A technique used in GC where the temperature of the column is gradually increased during the separation process. This allows for the separation of compounds with different boiling points.

A technique used in GC where the pressure of the carrier gas is gradually increased during the separation process. It is less common than temperature gradient and is used for compounds that cannot withstand high temperatures.

A technique used to avoid band broadening in splitless injection. The initial column temperature is set lower than the solvent's boiling point, causing the solvent to condense at the beginning of the column. As the solutes catch up, they are concentrated in the solvent, forming a narrow band.

The ratio of the sample that reaches the column in a split injection. It is not always reproducible between runs, which can lead to inaccuracies in quantitative analysis.

Quantitative analysis can be inaccurate in GC when the split ratio is not reproducible between runs.

The smaller the diameter of an open tubular column (OTC), the higher the resolution. This is because molecules have less space to diffuse, leading to sharper peaks. However, this also requires higher pressures to push the sample through the column.

The stationary phase can degrade due to high temperatures, causing the silanol groups to become exposed, leading to tailing in the chromatogram (peaks become wider and less defined). The stationary phase can also leak from the column, causing "ghost peaks" in the chromatogram.

Decreasing the thickness of the stationary phase in gas chromatography (GC) reduces the retention time of analytes. Because there is less material to interact with, the analytes move through the column faster.

Decreasing the thickness of the stationary phase in GC leads to a decrease in the amount of sample that can be loaded onto the column. This is because there is less material to hold the sample.

By decreasing the thickness of the stationary phase in GC, the resolution is increased. This is because there is less diffusion of the analytes as they move through the column.

The capacity factor (K') is calculated by dividing the difference between the retention time of an analyte (tR) and the dead time (tM) by the dead time. It provides a measure of the interaction between the analyte and the stationary phase.

Hydrogen (H2) is often used as a carrier gas in GC because it provides better resolution compared to nitrogen (N2). This is due to the faster diffusion of solutes through lighter carrier gases.

Helium (He) is a common carrier gas in GC because it is compatible with all detectors and is relatively inert. However, it can be more expensive than nitrogen (N2).

A technique in gas chromatography (GC) where the temperature of the column is increased over time, allowing for the separation of a wider range of compounds by eluting them at different temperatures.

A technique in supercritical fluid chromatography (SFC) where the pressure of the column is increased over time, allowing for the separation of a wider range of compounds by eluting them at different pressures.

A type of chromatography that uses a supercritical fluid as the mobile phase. Supercritical fluids are substances above their critical temperature and pressure, exhibiting properties of both liquids and gases.

The point at which a substance can exist in both liquid and gaseous states simultaneously. It's defined by the critical temperature and pressure of the substance.

The property of a substance to increase in density as the pressure is increased. This plays a key role in SFC, as increased density affects how the analyte interacts with the stationary phase.

The process of comparing the retention time of an unknown compound to a known standard. It helps to identify compounds by verifying if the unknown compound matches the standard.

A technique that uses a mass spectrometer to determine the molecular weights of analytes and/or their fragments.

A fluid at a temperature and pressure above its critical point, exhibiting properties between those of a gas and a liquid.

The height equivalent to a theoretical plate (HETP) is a measure of the efficiency of a chromatography column. A smaller HETP indicates a more efficient column, resulting in sharper peaks and better separation.

In SFC, the flow rate is adjusted to optimize separation efficiency. A higher flow rate leads to a shorter analysis time but might reduce separation quality. Finding the sweet spot is key.

A gradual change in the composition of the mobile phase during chromatography. In SFC, this is achieved by manipulating the pressure.

A separation technique that uses an electric field to separate charged molecules based on their mobility. It has widespread application in biotechnology.

The use of CE in biotechnology involves studying and manipulating biological molecules like proteins, DNA, and RNA.

Carbon dioxide is a commonly used supercritical fluid in SFC. It has a low critical temperature, is non-toxic, compatible with common detectors, and considered environmentally friendly.