Quiz4 Flashcards
The coupling of LC with MS is much more difficult than GC-MS, but higher desirable as this would allow one to separate/detect proteins. Solving this problem was accomplished by applying a ____ between the LC column capillary and the inlet to the MS which results in the formation of a mist of ____ sample droplets, which eventually change into gas phase ions. This technique is called ____.
high voltage
positively charged
electrospray ionization MS
The analysis of complex biological samples (blood plasma, urine) is challenging, but useful: if we can separate all contained molecules we can identify those which distinguish healthy people from people that have a disease. Such molecules are called ____.
biomarkers
M. Tswett made the observation that pure plant pigments (eg. chlorophyll alpha + beta) can be ____ in petrolether (PE), but that the same pigments cannot be “extracted” from mushed up plant leaves by petrolether because of a force which he called ____. This force can be overcome by using solvents which have a larger ____ than PE.
dissolved
adsorption
dissolving power
If we want to quantitatively extract a hydrophobic pesticide that is a weak acid (pKa=4.0) from groundwater to chloroform, we should adjust the pH to ____ to make sure the analyte molecules have ____.
A mixture is chromatographically separated based on the different ____ of the analytes between the ____ and the ____ phase.
partitioning
mobile
stationary
True/ False: The retention factor k of a peak corresponds to the time the analyte spends in the stationary phase divided by the time the analyte spends in the mobile phase
True
The flux of molecules from a region of high concentration to a region of low concentration can be expressed by ____.
mol/m^2*s
One measure of the column efficiency is the ____, which is a term that is related to the theory of distillation. It refers to the theoretical distance which is required for one ____ of the analyte between the mobile and the stationary phase. If we want to improve the separation we should strive to ____ this value as this would ____ per column length.
plate height H
equilibration
reduce
increase number of plates
The optimal flow rate to operate a chromatographic system can be experimentally determined by finding the ____ on the ____ curve.
minimum
VanDeemter
Size exclusion chromatography can separate molecules based on their size. Large molecules elute first, whereas small molecules elute later. In contrast to all other types of chromatography, there is no ____ between the analytes and the stationary phase.
interaction
If we want to isolate a specific protein out of a mixture of hundreds of proteins (eg. from a cell lysate) it would be most appropriate to use ____ as this type of chromatography employs specific interactions between an analyte molecule (eg. a protein) and a second one (eg. antibody).
affinity chromatography
Short answer
121BB neither
