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17 Cards in this Set
- Front
- Back
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MP in HPLC is... |
Liquid |
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Bonded stationary Phase |
-liquid SP bonded to particle packing material -Reacting the silica particles with an organochlorosilane -The R group prevents partial solubility of the SP with MP |
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Modes of HPLC |
-Normal phase -Reversed phase |
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Normal phase |
-non-polar mobile phase -Polar stationary phase -used to separate polar compounds |
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Reversed phase |
-polar mobile phase -non-polar stationary phase -Eluent strength is increased by adding less polar solvents -Used to separate non-polar compounds |
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Modes of Elutions |
-Isocratic elution -Gradient elution |
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Gradient elution vs. Isocratic elution |
-if ^t/tg > 0.25 use gradient elution -if ^t/tg , 0.25 use isocratic elution where ^t= difference between the retention times of the first and last peak tg= time over which the solvent composition is changes |
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Order of elution in LC |
-Governed by the mobile phase polarity - in reverse phase the most polar solutes elute first -in normal phase the most non-polar elute first |
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Columns |
-Pre-column (guard column) -Analytical coulumn |
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Optiming resolution on a given column |
-ionic or ionisable solutes adjust the pH of the MP -For other solutes change the composition of the MP |
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in a reverse phase separation changing from a more polar solvent to a less polar solvent... |
Decreases the capacity factor in reversed phase |
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In a normal phases separation changing from a less polar to a more polar solvent... |
decreases the capacity factor in a normal phase |
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van Deemter equation |
-optimum flow rate is lower than GC -reduce band broadening keep particle size small and uniform to increase plate numbers -Thin film of SP -Columns packed tightly |
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Types of detectors for HPLC |
-Spectrophotometric detectors -electrochemical detectors -other |
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Spectrophotometric detectors are... |
-UV-VIS -Photo diode array -Fourier transform infared -Fluorescene |
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Electrochemical detectors... |
Measure current flowing through a pair of electrodes |
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Other detectors are... |
-Refractive index -Mass spectrometry |
