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Analytical chem315 > 9(18)-10 > Flashcards

9(18)-10 Flashcards

1
Q

MS could provide _______ and _______ information if coupled with liquid chromatography (LC). But there is a problem: LC creates a huge volume of ______ (as solvent evaporizes), which need to be removed before introduction into MS. Because MS only works in ________!

A

qualitative; quantitative; gas; Vacuum;

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2
Q

___________ (ESI) solving water problem which is very huge because now protein can be analyzed. ______ is supplied, and _____ charged sample droplets are generated. The droplets gets smaller and smaller till only ______.

A

electrospray ionization; high-voltage;positive;ions;

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3
Q

Strong ________ at nebulizer outlet combined with coaxial flow of ____ gas creates a fine _______of ______ particles. There is little _____.

A

electric filed; N2 (drying gas); aerosol; charged

fragementation;

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4
Q

Atmospheric pressure chemical ionization (APCI) contains _______ between the nebulizer and the MS

A

heater (~500 degree)

*fine mist heats up to ~125 C

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5
Q

extraction is useful for 3 reasons: _____, ______, ______.

A

isolating analyte; remove of the bad matrix; concentrate the sample;

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6
Q

solvent extraction: solvent with lower density (lighter) goes on ____ of aqueous phase.

A

top;

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7
Q

If partition coefficient is large in case of [S]2/[S]1 where 2 is the organic phase, then the solute would move into the _____.

A

organic phase;

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8
Q

If solute is acid or base, molecular form and charge may change with ____.
Charged species are _____ soluble in aqueous solution, and neutral and hydrophobic ones are _____ soluble in organic solvent.

A

pH;
more;
more;

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9
Q

Setting pH as pKa of the anaylte would cause 50% _____ of analyte.
Solution can be _____ pH and make the species _____ charged.
Therefore the species would stay in the _______ phase.

A

lose;
increase; neutral
organic;

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10
Q

Metal chelator separate _____ ions from each other where it _______ complex one ion with an ______ ligand and extract the complex into an organic solvent.
The metal ion become _____ charged.

A

metal; selectively; organic;

neutral;

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11
Q

Chelator are ______ .

A

weak acid;

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12
Q

Dithizone (green) + lead (colorless) -> metal complex (red)
Formation of _____ makes the complex extreme hydrophobic and _____ charged.
Then the addition of ______ solvent can extract the complex in to the organic solvent.

A

benzene rings;
neutral;
organic;

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13
Q

Frequently used chelators are 8-hydroxyquinoline (oxine) and Cupferron.

A

metal binds to N and Os in these chelators

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14
Q

The selectivity of the chelator can be achieved by controlling the _____.
The selected pH is where K (_______) is large for one metal and small for others.

A

pH; partition coefficient;

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15
Q

At pH ____ Cu2+ is completely extracted while Pb2+ and Zn2+ remain in the aqueous phase.

A

5

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16
Q

isolated form of plant pigments easily dissolved in petroleum ether (ligroin), but not from plant leaves.
Because there is a force between the molecules we call _____.

A

adsorption

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17
Q

In other words, the dissolving power of ligroin for the pigments is ______ than the adsorption force of the plant tissue.

A

lower

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18
Q

selected ______ (made of cellulose like plant leaves).
_______ are the solvent that pass through it.
_______ can overcome the adsorption force between the plant tissue.
Adsorption is observed by _______ of column effluent

A

filter paper;
adsorbent (*such as ethanol and ligorin);
ethanol;
color change;

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19
Q

1901, best separation of plant pigments mixture on a starch like inulin column (and CaCO3/Al2O3) using 10 % ______ in ligroin

A

ethanol;

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20
Q

The plant experiment discovered the presence of ____ pigments, chlorophyllin alpha and beta.
It is an example of ________(TLC)

A

two;

thin layer chromatography;

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21
Q

Partition chromatography separate similar substance by repeated _______ by two _______ liquids.

A

extraction; immiscible;

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22
Q

Chromatography operates on same principle as extraction, but one phase _____ in place while other ______ .

A

held in place; moves past it

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23
Q

The solute with greater affinity stays in the column ____ than others, which means it will elute _____.

A

longer; later

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24
Q

process of passing _____/___ through a chromatography column is _____.

A

liquid/gas; elution

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25
Q

separated a mixture into its components based on ______ of compounds.

A

partitioning

*partitioned between the stationary and mobile phase

26
Q

________ chromatography (Tswett) is where solute adsorbed on surface of solid particles, the stronger the solute molecules adsorbed, the slower it travels.

A

adsorption;

  • think about the lab did in organic chem
  • functional group attached to the adsorbent (P124 check)
27
Q 
\_\_\_\_\_\_ chromatography (martin and synge) is liquid stationary phase bonded to solid surface (SiO2) 
solute partitions between stationary (liquid) and mobile phase (a gas in gas chromatography)
A

partition

28
Q 
\_\_\_\_\_\_ chromatography (adams and holmes) is anions (SO3-) or cations (N(CH3)3+) covalently attached to stationary phase (polymer resin).
The mobile phase is the liquid
A

ion-exchange

29
Q

mobile anions held near ______ that are covalently attached to stationary phase.
Anion-exchange resin is where only _____ can be attracted to it.

A

cations;
anion;

*difference between cation and anion exchange resin is important

30
Q

_____ chromatography (porath) separates molecules according to their size, larger ones elute first followed by smaller ones.

A

size exclusion;

*good for baseline separation between proteins

31
Q

______ chromatography is the most _____ kind, it employs specific interactions between one kind of solute molecule and a second one that is covalently attached (immobilized) to stationary phase.

A

affinity; selective;

32
Q

example of affinity chromatography is the binding of ______. The technique is useful if only interested in ____ protein.

A

antigen (antibody) to the particles; one;

33
Q

The speed of mobile phase passing through chromatography column is determined by two things.

A

1) volume flow rate (volume solvent/unit time; ml/min)

2) linear flow rate ( distance of solvent travelled/unit time)

34
Q

There are two factors that determine how well compounds separated.

A

1) the farther apart the better their separation

2) the wider the peaks the poorer their separation

35
Q

How to measure the efficiency of a separation?

A

by resolution!

- solute moving through column and spreads into a gaussian shape (bell shape)

36
Q

The _____ solute resides in column the ______ the band/peak

A

longer; broader

37
Q

For quantitative analysis resolution _____ is highly desirable

A

> 1.5

38
Q

_______ causes longer time in column which leads to broader peak.
It is net transport of solute from region of high concentration to low concentration by random movement of molecules.

______ peak in short time vs _____ peak in longer time.

A

diffusion; sharper and higher; shorter and wider;

39
Q

Brownian motion

bead bouncing around

A

the bead is pushed by water molecules moving with random directions and speeds.
change in the x and y coordinates of the bead in successive intervals follow a Gaussian distribution.

40
Q

_________ measures rate at which molecules move from region with high concentration to one with low concentration

A

diffusion coefficient

41
Q

____ (J) = mol per m^2 per second (mol/m^2 * s) of molecules diffusing across a plane of unit area is proportional to _________ gradient and diffusion coefficient.
J = - D (dc/dx)

A

flux; concentration;

42
Q

Diffusion in liquids ____ times slower than in gases.

Macro-molecules diffuse _____times slower than small molecules.

A

10^4;10-100

43
Q

plate height (=2D/Ux=variance/x) is the measure of ________ . It is the length of column required for one ______. It is named from theory of ________.

The _____ plate height = ______ band width. Prefer the band width to be as small as possible.

A

column efficiency; equilibration; distillation
smaller; narrower; * GC 0.1 -1.0 mm, HPLC 10Um, CE<1Um

*If solute travelled a distance x at linear flow rate Ux (m/s), time on column t=x/Ux (distance divide by flow rate)

44
Q

The ability of column to separate components is improved by _____ plate height, where more number of theoratical plates=N

Number of plates in entire column: N = _______ if plate height is small enough.

A

decreasing; dimensionless

*more number of plates, more thinner slices and shorter bands, equilibration established more often

45
Q

Different solutes passing through the same column result in different plate heights because they each have different D (_______)

A

diffusion coefficient

46
Q

Why does bands spread?
band of solute spreads as it travels through column and emerges at detector with standard deviation of sigma.
each individual mechanism that contributes to broadening produces a standard deviation of sigma*

A

*standard deviation itself is not added.

47
Q

Plate height is proportional to _______ of chromatographic band (H=sigma^2/x)

A

variance

48
Q

3 band-broadening mechanisms that are: (the van deemter equation, Ux =flow rate)

1) proportional to flow rate
2) inversely proportional to flow rate
3) independent of flow rate

A

1) C; 2) B ; 3) A constants

*they are constants for a given column and stationary phase.
thus changing the column and stationary phase changes A,B,C.

49
Q

increase flow rate will ______ diffusion

A

decrease

50
Q

Longitudinal diffusion is (____)

zone of solute after longer time on column.

A

B/Ux;

it is much faster in gas than in liquid thus the optimum linear flow rate in gas C is higher than in LC.

51
Q

A term arise from multiple effects for which theory murky
______ .
(Eddy diffusion)

A

multiple flow path;

some flow path are longer than others, molecules entering the column at the same time on the left are eluted at different times on the right.

52
Q

finite equilibration time between phases
_____ comes from finite time required for solute to equilibrate between mobile and stationary phase.
The slower the linear flow, more complete equlibiration and less broadening.

A

C-term;

P556

53
Q 
Electrospray ionization (ion spray) 
   For positive  ion mass spectrometry, the nebulizer is held at \_\_ V and the spray chamber is held at \_\_\_\_ V. It is reversed for negative.
   It requires \_\_\_\_ buffer concentration so the ions in buffer do not overwhelm analyte ions in the MS. 
   For protein, it is common to find \_\_\_\_\_\_ ions such as [M +nH] n+ and sometimes, [M +nNa]n+ or [M +nNH4]n+.
  There is \_\_\_\_\_ fragmentation. It can be intentially increased by \_\_\_\_\_\_\_\_\_. Adjusting the skimmer cone \_\_\_\_\_\_ controls the degree of fragmentation; Where N2 molecules is collided with positive ions under low pressure.
A

0, -3500;
low; multiply charged; little; collisionally activated dissociation (collision-induced dissociation) occurs between capillary and skimmer; voltage (large -> fragmentation)

*water is involved.

54
Q

Atmospheric pressure chemical ionization
____ and coaxial flow of ____ convert eluate into a fine mist from which solvent and analyte _____.
The distinct feature is _____ is applied to a metal needle in the path of the aerosol. electric _____ needle creates electric discharge under ATM pressure.
Analyte must be capable of forming the _____ MH+.
It produce ______ charged ions and is ______ for macromolecules such as proteins.

A

heat; N2; evaporates;
High voltage; corona (a plasma containing charged particles);
protonated ion;
single; unsuitable;

*fragmentation is little but can be adjusted with skimmer cone voltage difference.

55
Q

LC creates a huge volume of _____ when solvent vaporizes at the ______ between the column and the mass spectrometer.
Most of these gas must be ______ before ion separation.

A

gas; interface; removed

56
Q

MS requires high vacuum to prevent _____ during ion separation.
Chromatography is a ______ technique.
The problem of combining the two together is to _______ the huge _____ of _____ between the chromatograph and the spectrometer.
Some buffer additives that are ______ must be avoided for MS. There are other compatible ones.

A

molecular collisions; high pressure;
remove; excess; matter (in context to LC and MS is gas);
nonvolatile ( such as phosphate buffer);

*avoid additive concentration >20 mM and detergent concentration >10Um

57
Q

There is no attractive interaction between the stationary phase and the solute in the _______ chromatography.

A

molecular exclusion

58
Q

The linear flow rate corresponds to 0.30mL/min which is _____.
1 cm of column length contains 0.0565mL of mobile phase, 0.30mL would occupy 5.3 cm of column length.

A

0.30mL/min(volume flow rate) ; 5.3 cm/min

59
Q

The ______ phase or an unretained solute travels through the column in the ______ possible time (tm)

A

mobile; minimum;

60
Q

The van deemter equation tells how the ______ and _____ affect plate height.

A

column; flow rate

61
Q

Advantage of open tubular columns than the packed columns are:

A

higher resolution, shorter analysis time, increased sensitivity and lower sample capacity.

Allows increased linear flow rate or a longer column or both;
decreased plate height, thus higher resolution.

Analytical chem315 (5 decks)

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