Criteria for Drug Identification by Thin Layer Chromatography and Near Infrared Reflectance Spectroscopy
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Criteria for Drug Identification by Thin Layer Chromatography and Near Infrared Reflectance Spectroscopy Pervaise R. Khan A thesis submitted in partial fulfilment of the requirements of The University of London for the degree of Doctor of Philosophy in the Faculty of Medicine The School of Pharmacy, University of London October 2003 Supervisors: Prof A. 0. Moffat and Dr R. D.Jee ProQuest Number: 10104338 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10104338 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 Abstract A study was conducted of drug identification by thin layer chromatography using computer search techniques. This investigated the criteria for drug identification as used by pharmacopoeias, and various organisational bodies. The effect of varying standard control conditions, the use of standardising reference standards and running conditions were investigated. Computer based search methods incorporating fixed and moving windows, mean list length and discrepancy index were then used to identify drugs based upon Rf data. A probability of identification and the ability to rank drugs in order of likeliness of identification was produced from the Rf data. Achieving the current pharmacopoeial criteria and the feasibility of setting rigid criteria is discussed. Near Infrared (NIR) spectroscopy is a rapid non-destructive method of analysis which requires little or no sample preparation. The rapid, non-invasive identification of pure drug substances and tablets from a database of over 300 drugs by NIR is described, making use of simple chemometrics. An investigation of sample presentation and physical effects upon NIR spectra is presented. Novel drug profiling studies are described that differentiate between different tablet manufacturers demonstrate identification based upon NIR data. Methods include the analysis of pure drugs and tablets by NIR, the setting up and validation of the database and identification of unknowns against the database. The data were analysed and the methods optimised using a number of chemometric procedures such as second derivatives, correlation spectral matching, wavelength distances, polar co-ordinates, centres of gravity and scanning probability windows. Identification by NIR spectroscopy is demonstrated for unknown pure drugs and tablets with varied success for the type of substance, tablet and chemometric method used. A low number of mis-identifications were reported. A ranking method of identification based upon spectral match is incorporated with optimisation and criteria to be used in the general method. Table of Contents Abstract.....................................................................................................................2 Acknowledgement ..................................................................................................14 Chapter 1 Introduction ......................................................................................15 1.1 Thesis layout ...........................................................................................15 1.2 Background to the thesis topics ............................................................ 16 1.3 Aims and Objectives...............................................................................17 1.4 Background to thin layer chromatography ............................................ 20 1.4.1 Theory ...............................................................................................22 1.5 Background to NIR spectroscopy .......................................................... 23 1.6 Fundamentals of NIR spectroscopy ...................................................... 25 1.6.1 Molecular vibrations ........................................................................ 27 1.7 Diffuse reflectance in the NIR region ....................................................34 1.7.1 Kubelka - Munk theory .................................................................... 34 1.7.2 Lambert Cosine law ........................................................................ 36 1.7.3 Mie Scattering ................................................................................. 37 1.8 NIR applications ...................................................................................... 38 1.8.1 Regulatory work .............................................................................. 39 1.8.2 Pharmaceutical applications .......................................................... 42 1.8.2.1 Raw material and pure drug identification and qualification. 42 1.8.2.2 Identification of dosage forms ...................................................46 1.9 Instrumentation ....................................................................................... 52 1.9.1 The spectrophotometer ...................................................................54 1.9.1.1 The source ................................................................................55 1.9.1.2 The monochromator ................................................................56 1.9.1.3 Detectors ....................................................................................56 1.9.1.4 Software .....................................................................................57 1.10 Chemometrics ......................................................................................... 58 1.10.1 Derivatives....................................................................................... 58 1.10.2 Correlation spectral match ............................................................. 63 1.10.3 Maximum wavelength distance match .......................................... 64 1.10.4 Principal Components Analysis ...................................................... 65 1.10.5 Polar Qualification System (PQS) ..................................................67 1.11 Sample presentation .............................................................................. 74 1.11.1 Factors ............................................................................................. 76 1.11.2 Instrument scans..............................................................................78 1.11.3 Sample packing and presentation ..................................................78 1.11.4 The effect of grinding and particle size .......................................... 79 1.11.5 Vial types and base diameter sizes.................................................80 Chapter 2 Experimental .................................................................................... 82 2.1 Thin layer chromatography (Chapter 3 ) ................................................82 2.1.1.1 Locating Agents ........................................................................ 86 2.1.2 Computer based searches ..............................................................87 2.2 NIR spectroscopy - general sampling regimen ..................................... 88 2.2.1 Powdered samples ........................................................................... 88 2.2.2 Setting up a spectral database ............................... 89 2.2.3 Tablet Samples................................................................................89 2.3 Sample presentation (Chapter 4 ) ...........................................................90 2.3.1 Instrument scans...............................................................................90 2.3.1.1 Sample packing and presentation ...........................................91 2.3.2 The effect of grinding samples ....................................................... 91 2.3.3 Investigation of vial types and base diameter sizes .......................92 2.3.4 Particle size........................................................................................93 2.4 Drug Identification (Chapter 5 ) ................................................................ 94 2.4.1 Part 1 - initial study...........................................................................94 2.4.2 Part 2 - Large number of compounds ............................................ 95 2.5 The identification of actives in whole tablets (Chapter 7 ) .................... 96 Chapter 3 Identification by thin layer chromatography ....................................98 3.1 Summary of aim s ..................................................................................... 98 3.2 Method ...................................................................................................... 98 3.3 Results and Discussion ............................................................................99 3.3.1 Statistical Analysis of the Data .........................................................99 3.3.2 Run distance....................................................................................100 3.3.3 Temperature ....................................................................................105 3.3.4 Spot mass ........................................................................................108 3.3.5