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Definition
| Suitable flowing mobile phase (m.p) or eluent is introduced to a mixture and components are separated by physiochemical interaction with the stationary phase (s.p) |
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| Development Chromatography |
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Definition
AKA TLC
solution of analyte is placed on a small spot on paper or plate then placed into a liquid mobile phase, which is drawn up by capillary action |
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Definition
AKA HPLC & GC
MP & SP are chosen so that diff compounds in sample have diff afinities for each (interactions will be determined by physiochemical properties) |
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Definition
| Electrical potential is applied and seperation is by movement of ionized species to the appropriate electrode |
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Term
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Definition
| • In development chromatography, distance moved by the analyte divided by the distance moved by the m.p. or eluent |
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Definition
| differences between distribution coefficients cs/cm |
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Definition
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Term
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Definition
| • In elution chromatography, time between sample injection and analyte peak reaching a detector at the end of a column |
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Definition
| Time taken for m.p. to pass through column |
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Term
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Definition
•Goal in elution chromatography for optimal sensitivity – sharp, symmetrical peaks; for development chromatography – small discrete spots or bands
•Analyte peaks or bands that move quickest tend to be sharper than those that elute later b/c there’s less time for zone broadening
•Extent of zone broadening determines efficiency of a column for a given analyte under the conditions used
•Efficiency can be expressed either as # of theoretical plates or plate number (N), or by the height equivalent of a theoretical plate (HETP) |
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Term
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Definition
| • Shape of a chromatographic peak is affected by rate of elution, but is also affected by the different paths available to solute molecules as they travel between particles of s.p. |
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Term
| Multiple Path and Eddy Diffusion |
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Definition
analyte molecules take different paths through the column at random; causes broadening of the solute band because different paths are of different lengths.
o spreading is proportional to particle size and is independent of m.p. velocity |
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Term
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Definition
| o For a band of analyte in a column, the concentration will be lower at the edges of the band than at the center because analyte diffuses out from center to edges |
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Term
| Resistance to Mass Transfer |
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Definition
o If eluent velocity is high and analyte has a strong affinity for the s.p., then the analyte in eluent will move ahead of analyte in the s.p., giving band broadening
oThe higher the eluent velocity, the larger the band broadening |
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Term
| •Extra-Column Contributions to Zone Broadening |
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Definition
| 3 factors to take into consideration: i) sample volume, ii) detector volume, and iii) the connecting tubing between the injection valve and the column, and the column and the detector |
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Term
| •Temperature Programming and Gradient Elution |
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Definition
required when the sample contains a large # of analytes of differing volatilities or polarities
the analytes are condensed in a tight band at the top of the column and only start to migrate when the temperature is high enough – some analytes are being separated while others remain stationary. The band broadening due to longitudinal diffusion is greatly reduced for later eluting peaks |
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Term
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Definition
| the # of peaks that can be represented on a chromatogram (used mainly in LC) |
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Term
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Definition
| very useful in temperature programming in GC and gradient programming in LC where conventional methods of column efficiency can’t be used. TZ represents the # of peaks that can be inserted between the peaks of two consecutive hydrocarbon homologues in a chromatogram |
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Term
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Definition
o Ideal chromatographic peak is a perfect Gaussian shape that reflects the additive combination of the random motions of the analyte in the system
o In practice, symmetrical peaks are not obtained; the peak asymmetry can be measured and compared to a true Gaussian peak |
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Term
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Definition
| • Retention index of a given analyte is calculated by difference from the retention indices of the normal alkanes eluting before and after the analyte |
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