lab quiz 1-2 Flashcards
sorption
2 processes. Adsorption and absorption.
absorption
molecules cross the membrane interface to enter the interior of the cell
important physiological process
adsorption
when the molecules (adsorbate) attach to a solid surface (adsorbent/interface).
adsorbate
is a liquid solute in a solution or gas which is being adsorbed
solid surface in adsorption (adsorbent)
called interface
physical adsorption (physisorption)
is a physical process where the adsorbate is held to the surface of the solid by WEAK VAN DER WAALS forces. this adsorbate-adsorbent interaction can easily be broken by changes in temp and pH and adsorbent easily regenerated (process or regeneration is called desorption).
at equilbruim adsorption and desorption are at constant rate
so concentration of the adsorbate is constant
chemical adsorption
is a chemical process where a chemical bond (ionic/covalent) is formed between adsorbent and adsorbate. Stronger adsorbate and adsorbent interactions more challenging to make desorption
Adsorbents are typically classified into three types
adsorbents- used for decoloring and refining food for pharmacological effects.
- hydrophilic and polar oxygen containing compounds, like silica gel
- non-polar carbon containing compounds, such as activated carbon and graphite
- porous polymer matrix with non-polar and polar f-groups
activated charoal
common adsorbent used in pharmacy and medicine. it can adsorb wide range of adsorbates, it is used to treat toxicity due to oral drug indigestion.
the drug gets absorbed by charcoal and this reduces the systemic absorption into GI tract
the amount of absorbate adsorbed is
dependent on the adsorbent qt size, and grade (particle size and quality )
the MOLES of adsorbate adsorbed by A GRAM of adsorbent
is used to express the effectiveness of adsorbent for specific adsorbate.
factors that influence adsorption
temperature
layer
type of adsorption
concentration of adsorbate
quantity of adsorbent
as temperature increases
adsorption will DECREASE (TEMP AND ADSORPTION INVERSALLY PROPORTIONAL)
EXTENT OF adsorption depends on 3 factors
- capacity- SA of adsorbent and receptor sites on adsorbate
2.affinity- properties of adsorbent and adsorbate
- equilibrium conditions (temp and conc of the adsorbate)
quantity of adsorbate
by unit weight of adsorbent
at equilibrium conc
x
x/m and m
C
as we increase the conc the x/m will increase linearly and increase adsorption
y=mx +c
x/m =kC
freundlich empirical eq
(i) for adsorption of gases (as a mono layer) to solids. Log values are used to linearize the equation
(ii) log values, the equation of the curve is modified to an equation of a straight line
At low pressure, the extent of adsorption (x/m)
varies linearly with the gas pressure
At moderate pressure, (x/m)
varies exponentially to gas pressure
At high pressure, (x/m)
is independent of gas pressure
Langmuir isotherm is based on several assumptions.
- Adsorption is a second order reaction (dependent on adsorbent and adsorbate concentration.
- The surface of the adsorbent is uniform and has a fixed number of active (adsorbent) sites.
3.Adsorbate is adsorbed at the surface as a single monolayer. molecules of adsorbate do not deposit on each other
- One adsorbate molecule is adsorbed to only one single active site.
- The adsorption is random and non-specific physio-adsorption via weak forces (van der Waals).
- equilibrium, the fraction of the active sites θ is occupied by adsorbed molecules fraction of free active sites is 1-θ. This value remains constant for the specific temperature and concentration.
- Adsorbed molecules do not interact with each other or with other molecules in the system.
SPECIFIC AREA OF ADSORBENT
S = (N) x(Csa)/b
S = (Avogadro’s number x molecular cross-section of the adsorbate)/Langmuir constant
Greater the value better the adsorption capacity of the adsorbent.
Adsorption is useful in treating oral drug overdose.
true
Alkaloid drugs and theophylline absorption in the GI tract are reduced by oral administration of
activated charcoal adsorbent. the drug is adsorbed to the charcoal and excreted in the feces.
Citric acid is a triprotic acid (i.e. contains three ionizable hydrogen [H+} or 3 Eq/mole)
Sodium hydroxide is a monobasic base (has one [OH-} or 1 Eq neutralizes one ionizable hydrogen [H+} ).
Hence 3 moles (3 Eq) of sodium hydroxide neutralize 1 mole (3 Eq) of citric acid.
Phenolpthalein (pKa 9.3) is used as pH indicator (color change: colorless to pink color) is used to detect the endpoint of the neutralization.
Phenolpthalein (pKa 9.3) is used as pH indicator (color change: colorless to pink color) is used to detect the endpoint of the neutralization.
Regression Analysis: Before performing the statistical analysis for goodness-of-fit, the experimental data should be evaluated for errors (calculations, techniques).
R-squared is a statistical measure of how close the data are to the fitted regression line. Linear regression calculates an equation that minimizes the distance between the fitted line and all of the data points. In general, the higher the R-squared, the better the model fits your data. R-squared is a useful measure that indicates how well the linear model fits a set of observations.
Antacid
alkalizing formulations are prescribed when stomach acid to help increase pH (basic) and reduce acidity.
suspensions
LIQUID FORMULATION, we have drug insoluble in a vehicle. 2 phase-solid and aq. Phase. Heterogeneous solution.
We would prepare different forms
because of ppl would be children or who cannot swallow. The drug is insoluble; you can only use suspension, if the drug is not very stable. Over time the drug would settle. If the drug has small particle size then if it settles then this can cause interlocating and form a cake at the bottom, and the drug when shaken cannot disperse equally.
Suspending agents
helps increase the viscosity of the soln, if you have a dilute soln the drug settles quickly. Viscosity agent helps increase the pore-ability AND redispersibility of the drug
Titration
helps to understand the neutralization capacity of the suspension
1 ml of preserve is 100 ml of suspension, so 60ml (formulation) is X= 0.6ml of preservative
50x = 1mL of preservative can preserve 50 ml, so if we prepare 60ml of formulation we need to add 1.2ml
fine powders
defluoccation
decrease in wet-ability or caking
higher surface energy and SA
