• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Determination of pka of the given drug sample. The importance of pKa is that one can easily conclude how much drug is ionized and unionized. Unionized drug is better absorbed

Extracts from this document...

Introduction

Determination of pka of the given drug sample INTRODUCTION: Dissociation constant of a drug/compound is commonly refered to as pKa. It is a characteristic of drug. It is the estimation of ionized and unionized drug concentration at a particular pH. It is the pH at which 50% of drug is ionized and 50% is unionized. The dissociation constants of both acidic and basic drugs are expressed by pKa values. The importance of pKa is that one can easily conclude how much drug is ionized and unionized. Unionized drug is better absorbed. pKa can be calculated by following equation. pKa = pH +log(di -d/ d- dm) Where, di = absorbance of the ionized species. d = absorbance of solution tested. dm = absorbance of the unionized species. U.V. spectroscopy is widely used in pKa determination as we know lambda max is different for ionized and unionized drug or we can say that there is great difference between absorbance of ionized and unionized drug at a particular lambda. ...read more.

Middle

pH 6 : 5 ml of 0.2 M potassium hydrogen phthalate + 0.56 ml of 0.2 M Sodium hydroxide (6) pH 7 : 5 ml of 0.2 M potassium hydrogen phthalate + 2.9 ml of 0.2 M Sodium hydroxide (7) pH 8 : 5ml of 0.2 M boric acid + 5 ml of 0.2 M potassium chloride + 0.39 ml of 0.2 M Sodium hydroxide (8) pH 9 : 5ml of 0.2 M boric acid + 5 ml of 0.2 M potassium chloride + 2.08 ml of 0.2 M Sodium hydroxide (9) pH 10 : 5ml of 0.2 M boric acid + 5 ml of 0.2 M potassium chloride + 4.37 ml of 0.2 M Sodium hydroxide Preparation of primary stock: 10 mg of drug was accurately weighed and dissolved in 10 ml of 7:3 = methanol: water mixture as solvent to get concentration of 1 mg/ml. ...read more.

Conclusion

pH 296 nm 300 nm 303 nm Abs ?Abs/?pH Abs ?Abs/?pH Abs ?Abs/?pH 2 0.5229 - 0.5651 - 0.568 - 3 0.0215 0.5014 0.0571 0.508 0.1 0.468 4 0.01 0.0115 0.0158 0.0413 0.0437 0.0563 5 0.0436 0.0336 0.0448 0.029 0.1244 0.0807 6 0.2592 0.2156 0.5629 0.5181 0.5095 0.3851 7 0.436 0.1768 0.4736 0.0893 0.4318 0.0777 8 0.455 0.019 0.4683 0.0053 0.4541 0.0223 9 0.4824 0.0274 0.4909 0.0226 0.4707 0.0166 10 0.4788 0.0036 0.4708 0.0201 0.4399 0.0308 Plot of absorbance vs pH and its derivative graph (?Abs/?pH vs pH) were ploted at selected wavelengths as shown below. 296 nm: 300 nm: 303 nm : The peak in the derivative graph corresponds to the pKa of the drug since it is the point at which there is maximum change in absobance with a small change in pH. The average of three pka was calculated as: pka = (6 +6+6)/3 pka = 6 CONCLUSION : The pKa of the given drug was found to be 6. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Chemistry essays

  1. Marked by a teacher

    Method's of Drug Characterisation

    5 star(s)

    Take a few crystals of the unknown compound and dissolve it in 1ml of chloroform then spot the solution onto the chromatoplate using the 2 needles prepared. 4. Place the chromtoplate in the sealed tank. 5. Remove the plate once the solvent has travelled near to the top and

  2. Experiment 4 - Preparation and Reactions of Boric Acid, H3BO3

    and also in nuclear power plants to control the fission rate of uranium. It exists in colourless crystals form or white powder which dissolves in water. It has chemical formula of H3BO3 or B(OH)3. Boric acid is poorly soluble in cold water but dissolves readily hot water, alcohol and glycerine.

  1. Determining the concentration of copper(II) ions

    Also, since it was the first trial there could have been other sources of error such as in the cleaning of the electrodes after each solution was tested and also any contamination of the solutions while the electrodes were being cleaned.

  2. Spectrophotometric Determination of the Equilibrium Constant of a Reaction

    records and displays the value to the operator on an LCD screen. There are two general designs of spectrophotometers, single-beams and double-beams. When using any kind of spectrophotometer, one must perform auto-zero. The absorbance measured from the spectrophotometer can be related to the concentration of the analyte by the Beer-Lambert's

  1. Synthesis and Characterization by UV-Vis Spectroscopy, EPR, and HNMR of H2TPP and CuTPP Porphyrins

    was employed to ascertain the best solvent system that achieved separation of the subject compounds. In thin layer chromatography, an adsorbent-the so-called stationary phase-with particle sizes of ~40 µm, is affixed to a support such as glass, fiberglass, or plastic (Landgrebe, 2005).

  2. EXPERIMENTAL DESIGN: Measurement of Density and Determination of Partial Molar Volume, and the Effects ...

    This experiment used equipment and apparatus such as pycnometer, 250-mL beakers, 25-mL graduated cylinders, 10-mL pipet, 2-mL pipet, top-loading balance and aspirator. The pycnometer (see Appendix D, Figure 1) is a glass flask with a close-fitting ground glass stopper with a capillary hole through it.

  1. Forensic Chemistry - Ion Selective Electrode. The objective of experiment is to determine ...

    The measurement of slope factor gives an indication of the performance of the electrode system. If ion selective electrodes are not cleaned after use, and are subject to long term neglect, then the accuracy of the system is lost. This loss of performance can be monitored by a steady decrease in measured slope value during the calibration of a system.

  2. The aims of this experiment are to measure the heat of decomposition of hydrogen ...

    + Oâ(g) ÎHâ°=-94.64 2.2 Enthalpies of Physical and Chemical Change Physical Change: Almost every change in a system involves either a gain or loss of enthalpy. The change can be either physical, such as the melting of a solid to a liquid, or chemical, such as decomposition of hydrogen peroxide.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work