Henderson-Hasselbalch relationship

The ratio of HCOJ to H2CO3 at a physiological pH of 7.4 can be calculated by using the Henderson-Hasselbalch relationship ... 

Answer B. Back to Basic Principles and the Henderson-Hasselbalch relationship. From the table, pH - pKa = -2.2. For a weak base, a value of -2 represents 1% nonionized, so in the present case the percentage of the local anesthetic in the nonionized form is <1%. Local anesthetics usually have reduced activity when injected into tissue that is septic because only a small fraction of the molecules are in the form capable of crossing biomembranes. Remember that this is not the form that interacts with the Na ion channel—that s the ionized form of the local anesthetic. 

Sample Solution (a) Use the Henderson-Hasselbalch relationship to calculate the ratio of the concentration of the conjugate base (lactate) to the acid (lactic acid). 

Thus, on the basis of the principles we have diseussed earlier (Henderson-Hasselbalch relationship), it can be said that at a pH equal to the pKaOf the carbojqrl group (pKa,) the amino acid will exist as partly cation, partly zwitterion. Similarly, at pH equ to the pK<, of the amino group (pfQa) the amino acid will exist partly as anion and partly as zwitterion. In a solution in pure water the amino acid exists mostly as a zwitterion. Let us take the example of alanine. 

CO2 is indirectly measured by sensing of the pH of a bicarbonate buffer solution in equilibrium with the blood CO2, where the Henderson-Hasselbalch relationship (see Eq. 12.9) allows calculation of CO2 from the pH value [8]. Optical sensing methods for pH and CO2 are discussed in more detail in Chap. 12. 

This relationship is one form of the Henderson-Hasselbalch equation It is a useful relationship m chemistry and biochemistry One rarely needs to cal culate the pH of a solution—pH is more often mea sured than calculated It is much more common that one needs to know the degree of ionization of an acid at a particular pH and the Henderson-Hasselbalch equation gives that ratio... 

This relationship is known as the Henderson-Hasselbalch equation. Thus, the pH of a solution can be calculated, provided and the concentrations of the weak acid HA and its conjugate base A are known. Note particularly that when [HA] = [A ], pH = pAl,. For example, if equal volumes of 0.1 MHAc and 0.1 M sodium acetate are mixed, then... 

This chapter considered ionizable drug-like molecules. Absorption properties that are influenced by the pKj were explored. The impact of the pKj-absorption relationship on key physicochemical profiling underlying absorption (solubihty, per-meabihty and ionization) was examined in detail and several simpUfying equations were discussed. The various diff relationships considered in the chapter are systematized in Table 3.2. Table 3.3 summarizes the apparent pfQ shift method for detecting aggregates in solubility profiles, when the apparent pff value derived from Henderson-Hasselbalch analysis of log S pH profile does not agree with the... 

The Henderson-Hasselbalch equation is an equation expressing the relationship between pH, pK l, and the log of the ratio of the concentrations of the base to its conjugate acid or an acid to its conjugate base. It is derived from the K l or Kb expression. See Equations (5.26) to (5.30) in the text. They are each a form of this equation. 

The concentration of hydrogen ions liberated by the dissociation of an acid is related to the dissociation constant for that acid and this relationship can be expressed by the Henderson-Hasselbalch equation ... 

Another term frequently used in this discussion is the pKa. Its relationship to pH is described in the Henderson-Hasselbalch equation. Some modifications to this equation have been made to allow the calculation of many other physical/ chemical values, including the CMpH (Table 1.1). 

The Henderson-Hasselbalch equation describes the relationship between the pH, the pIQ, and the concentrations of the conjugate acid and base. 

Henderson-Hasselbalch equation An equation giving the relationship between the pH and the concentrations of base and acid in buffer solution. 

Ionization State of Amino Acids Each ionizable group of an amino acid can exist in one of two states, charged or neutral. The electric charge on the functional group is determined by the relationship between its pifa and the pH of the solution. This relationship is described by the Henderson-Hasselbalch equation. 

Amino acids in aqueous solution contain weakly acidic a-carboxyl groups and weakly basic a-amino groups. In addition, each of the acidic and basic amino acids contains an ionizable group in its side chain. Thus, both free amino acids and some amino acids combined in pep tide linkages can act as buffers. The quantitative relationship between the concentration of a weak acid (HA) and its conjugate base (A-) is described by the Henderson-Hasselbalch equation. 

The Henderson-Hasselbalch equation can be used to calculate the quantitative relationship between the concentration of a weak acid and its conjugate base. 

Apply the Henderson-Hasselbalch equation (see "Quantitative Relationships Involving Carboxylic Acids," the box accompanying Section 19.4) to calculate the CH3NH3+/CH3NH2 ratio in water buffered at pH 7. 

Equation 2.6 is the familiar Henderson-Hasselbalch equation, which defines the relationship between pH and the ratio of acid and conjugate base concentrations. The Henderson-Hasselbalch equation is of great value in buffer chemistry because it can be used to calculate the pH of a solution if the molar ratio of buffer ions ([A-]/[HA]) and the pKa of HA are known. Also, the molar ratio of HA to A- that is necessary to prepare a buffer solution at a specific pH can be calculated if the pKa is known. 

The Henderson-Hasselbalch equation thus gives the following relationships ... 

This equation essentially describes the relationship between pH and the degree of ionization of weak acids and bases. When applied to drugs, the equation tells us that when pH equals the apparent equilibrium dissociation constant of the drug (pKJ, 50 percent of the drug will be in the unionized form and 50 percent will be in the ionized form (i.e., log[base/acid] = 0 and antilog of 0 = 1, or unity). Application of the Henderson-Hasselbalch equation can, therefore, allow one to mathematically determine the exact proportion of ionized and nonionized species of a drug in a particular body compartment if the pKa of the drug and the pH of the local environment are known. 

Buffers stabilize a solution at a certain pH. This depends on the nature of the buffer and its concentration. For example, the carbonic acid-bicarbonate system has a pH of 6.37 when the two ingredients are at equimolar concentration. A change in the concentration of the carbonic acid relative to its conjugate base can shift the pH of the buffer. The Henderson-Hasselbalch equation below gives the relationship between pH and concentration. 

These are two forms of the Henderson-Hasselbalch equation. This useful relationship enables us to calculate the composition of buffers that have a specified pH. Note that if [HA] = [A-], then pH = p Ka. 

Above equilibrium is dependent on the mobile-phase pH and the relationship between ionic and nonionic form of the analyte is described by Henderson-Hasselbalch equation... 

This relationship is known as the Henderson-Hasselbalch equation and it shows that the pH will be equal to the when the ratio of conjugate base to acid is unity, since the final term will be zero. Consequently, the pAia of a buffer solution is an important factor in determining the buffer capacity at a particular pH. In practical terms, this means that a buffer solution will work most effectively at pH values about one unit either side of the pATa-... 

Rearranging Equation 2-9 into logarithmic form and. substituting the relationships expressed in Equations 2-3 and 2-4 yields the same Henderson-Hasselbalch equation (Eq. 

The relationship among pH, pK (the negative log of the dissociation constant), and the concentrations of an add and its conjugate base is described by the Henderson-Hasselbalch equation. 

This is the Henderson-Hasselbalch equation it indicates the relationship between pH and p/Ca. Notice that where the concentration of undissociated acid cHA and the concentration of its dissociated base cA" are equal then pH = pKa. Thus, the p/Ca value is the pH at which there is an equal proportion of dissociated and undissociated acid. 

---