Raj APPI Modern pharmaceutical analysis techniques

To knowledge about the pharmaceutical analysis techniques in used, techniques.

1. Atmospheric Pressure Photo Ionization(APPI ) Rajratn Thorat M.Pharm 2nd year, Nanded pharmacy collage nanded .

2. Introduction Atmospheric pressure photoionization ionization (APPI) is a soft ionization technique for liquid chromatography-mass spectrometry (LC-MS) that uses photochemical action to ionize samples in the gas phase. The APPI facilitates the analytical detection of weakly polar and non-polar compounds by mass spectrometry.

3. Principle of APPI The APPI light source can be derived from  an argon lamp, a xenon lamp, a xenon lamp, or the like . Among them, xenon lamps are used most frequently, and the red light energy emitted by xenon lamps is between common solvents and most compounds.

4. APPI Mechanisms Direct APPI: M + h ν → M+. + e Analyte molecule M is ionized to molecular ion M+. – If analyte ionization potential is below Kr lamp photon energy Subsequently: M+. + SH → [M+H]+ + S • Molecular ion M+. may abstract a hydrogen to form [M+H]+ ie a CI process

5. Dopant APPI: D + h ν → D+. + e- • Photoionizable dopant D is in excess & yields many D+. ions D+. + M → → [M+H] + + D • Analyte M ionized by proton transfer from dopant or solvent D+. + M → M+. + D • D+. ionizes analyte M by electron transfer ie charge transfer

6. Energetics for Photoionization Energetics for Photoionization PhotoMate ™ lamp (Krypton 10.0 eV , 10.6 eV ) Ionization Potentials (IP) ( Anthracene 7.4 eV Fluoranthene 7.8 eV Caffeine 8.0 eV 4-Nitrotoluene 9.5 eV 2,4,6-Trinitrotoluene 10.59 eV ) Dopant Ionization Potentials (Toluene 8.82 eV Acetone 9.70 eV ) Solvent Ionization Potentials (Methanol 10.85 eV Acetonitrile 12.19 eV Water 12.61 eV )

7. • The photons from the Kr lamp can only photoionize compounds of lower IP • Common HPLC solvents like H 2O, CH 3OH and CH 3CN are NOT ionized and therefore cannot aid ion formation • In this circumstance, only direct photoionization of the analyte can yield characteristic ions such as M+. (not very efficient) – Subsequent ion/molecule reactions can form [M+H] + • Dopants are used that will be ionized by the Kr lamp

8. Application of APPI The application of APPI with LC/MS is commonly used for  analysis of petroleum compounds, pesticides, steroids, and drug metabolites lacking polar functional groups  and is being extensively deployed for ambient ionization particularly for explosives detection in security applications.