Tutorial 9: buffer capacity Flashcards
give different names buffer capacity goes by
buffer efficiency, buffer value, buffer index
T or F:
pharmaceutical solutions are buffered to a low capacity
truey wuey
T or F:
pharmaceutical solutions are buffered to a high capacity
falsy
low capacity
scientific term:
the magnitude of the resistance of a buffer to pH changes
buffer capacity (β)
T or F:
boric acid is suitable for eye preparations but not for IV injections
truey wuey
T or F:
boric acid is suitable for IV injections but not for eye preparations
falsy
the opposite
_____ and _____ buffers are incompatible with any compounds including the salts of silver, iron, magnesium and zinc
borate and phosphate
borate and phosphate buffers are incompatible with any compounds including the salts of__,___,___ and ___
silver, iron, magnesium and zinc
which salts are borate and phosphate buffers incompatible with?
zinc, silver, magnesium and iron salts
____ buffers form complexes with excipients like glycerol and carbohydrates
borate
borate buffers form complexes with excipients like ___ and ____
glycerol, carbohydrates
T or F:
borate buffers are compatible with excipients like glycerol and carbohydrates
falsy
they form complexes with them, not compatible
how is blood pH maintained as 7.4?
with the help of primary buffers in blood plasma and secondary buffers (hemoglobin) in erythrocytes
what are the two buffer systems in blood plasma?
carbonic acid/bicarbonate and phosphoric acid/sodium phosphate
what are the two buffer systems in erythrocytes?
hemoglobin/oxyhemoglobin and phosphoric acid/sodium phosphate
T or F:
lachrymal fluid has great buffer capacity
truey
T or F:
β is proportional to the concentration of buffer components added to the solution
truey
T or F:
β doesn’t necessarily depend on the ratio of its components
falsy
it is proportional to the conc of its components
T or F:
β depends on the pKa of weak acid or base
truey
what does β depend on?
pKa of acid or base
conc of its components
volume of medium
T or F:
β is a fixed value
falsy
the ___ the change in pH change in a solution after adding base/acid, the greater the buffer capacity
lower/smaller
T or F:
β will increase with external addition of acid or base
falsy
it will decrease because the added acid/base will consume buffer therefore lower the β
T or F:
β will decrease with external addition of acid or base
truey because the added acid/salt will consume more buffer
T or F:
the final pH of the buffer is more important than the capacity
falsy
β and the volume used in relation to the medium’s volume aremore important
how can β be expressed in terms of amount of stronk acid or base added to change the pH?
β equals the amount of stronk acid or base in moles of H+ or OH- per liter, to bring pH down by one unit
when will a buffer have maximum capacity
when pKa of weak acid or base is closed to the desired pH
or the ratio of (salt)/acid equals 1
when log (ratio) equals 0
T or F:
all buffers work best at the same pH
falsy
each buffer works best at a certain pH
the higher the difference between the pH of the solution and pKa, the ___ the capacity
lower
T or F:
the higher the difference between the pH of the solution and pKa, the higher the capacity
falsy
the lower
T or F:
he lower the difference between the pH of the solution and pKa, the higher the capacity
truey weuy
how many times can you dilute lachrymal fluid before an alteration in pH is noticed?
15 times
T or F:
how much a solution can be diluted until pH changes is known as buffer capacity or buffer value
falsy
that’s dilution value
scientific term:
how much a solution can be diluted until pH changes
dilution value
__ in the air makes makes conjunctival fluid more acidic
CO2
for eye drops, irritation and discomfort and flow of tears will occur if the pH drops below ___ or above ___
6.6, 9
T or F:
for eye drops, irritation and discomfort and flow of tears will occur if the pH drops below 6.9 or above 7.8
falsy
6.6, 9.
phosphate buffer - boric acid soltuion
which one causes discomfort in the eyes?
phosphate buffer
which buffer is most suitable for the eyes and what is its pH?
boric acid solution. pH of 5
T or F:
boric acid causes irritation in the eyes because its pH is 5
falsy
it causes no discomfort
T or F:
phosphate buffer causes irritation in the eyes
truey
why is boric acid more suitable for the eyes than phosphate buffer?
- boric acid has a lower buffer capacity
- the physiological response to various ion species
T or F:
Ophthalmic solutions are usually not buffered or buffered to a low capacity
falsy
this applies on parenteral solutions
why are parenteral solutions not buffered or buffered to a low capacity?
becuase blood buffers will do their job and bring them within the stable pH range
what is the normal urine pH for an adult?
6
what is the range of urine pH?
4.8-7.8
what does the kidney do when pH of urine is below normal values?
retain hydrogen ions
what does the kidney do when pH of urine is above normal values?
it will excrete hydrogen ions to bring the pH to its normal range
T or F:
When the urine pH is below normal values, the kidney will excrete hydrogen ions to bring pH back to normal
falsy
kidney does this when pH of urine is higher than normal
T or F:
hydrogen ions are retained by the kidneys and when the urine pH is above 7.4
truey
T or F:
hydrogen ions are retained by the kidneys and when the urine pH is below 4.8
falsy
it will retain H+ when pH is above 7.4
T or F:
some food and drinks can alter urine pH
truey
why are strong acids and bases able to act as buffers?
because of their high conc of H+ and OH- ions
why is KCL added to HCL buffers even though they don’t participate in the buffering?
they are added to adjust ionic strength
T or F:
potassium chloride is added to HCL buffers to help in buffering
no it doesn’t help in buffering but it adjusts ionic strength
the pH of the stomach ranges from __ to __ depending on the presence of food in it
1, 4
the pH of the stomach ranges from 1to 4 depending on ___
whether or not there is food in it
what does the gastric (digestive) fluid made of?
HCL, KCL and NaCl
what does the acidic environment of the stomach aid in?
digestion + prevention of infection
T or F:
the higher the capacity the higher the irritation
truey
T or F:
the lower the capacity the higher the irritation
falsy
the lower the irritation
what happens if we use a low capacity buffer on the eyes but add a large volume?
irritation, because the higher the volume of pharmaceutical solution used the higher the irritation
to avoid irritation, the volume of pharmaceutical solution must be low and has a high capacity
falsy
should have low volume and low capacity
to avoid irritation, the volume of pharmaceutical solution must be low and has a low capacity
Truey
T or F:
to avoid irritation, the volume of pharmaceutical solution must be low and has a low capacity whereas physiological fluid should have high volume and high capacity
SO TRUEY
to avoid irritation, what should be the relationship between capacity and volume of pharmaceutical solution (a) and physiological fluid (b)?
(a) must have low V low capacity
(b) must have high V high capacity
T or F;
ionized forms of drugs can easily penetrate biological membranes
falsy
unionized
T or F:
ionized forms of drugs tend to stay in the aqueous environment in the body
truey
T or F:
unionized forms of drugs can easily penetrate biological membranes
truey
why can unionized forms of drugs penetrate biological membranes?
because BM are lipid, unionized drugs are more lipid soluble while unionized forms are water soluble
T or F:
it is important that the drug will be in ionized form in the part of the body where it is placed to be absorbed.
falsy
must be unionized
it is important that the drug will be in ___ form in the part of the body where it is placed to be absorbed.
unionized
