What GCMS users Want ?

Detection Limit- Sensitivity

•          Depends on: Mass Analyzer, Vacuum Pump, Detector

Qualitative/Quantitative Study

•           Selection of Mass Analyzer

Mode of Analysis

•           SIM/Full Scan

•          Specific Applications

•          Budget

•          Training

•          Service Support

•          Application Support

Detection Limit: Normally mass analyzers plays important role or you can say heart of GC-MS.

There are analyzers who have sensitivity who have signal to noise ratio : 850:1

Best solution providers are Agilent Technologies, Perkin Elmer, Shimadzu.

Types of GCMS

        1. Time of Flight

        2. Quadrupole

        3. Ion-trap

        4. IRMS

        Each of these are applied in different fields

        Based on the requirements of analysis and conclusions to be drawn.

FLAME IONISATION DETECTOR IN GAS CHROMATOGRAPHY

• Mass sensitive detector.
• Operates by mixing hydrogen with carrier gas and burning it at a jet in a stream of air.
• A collector electrode is placed above the flame.
• P.D. is set up between the jet and the collector electrode.
• The jet is at -ve potential w.r.t. the collector.
• Organic compounds produce ions and electrons when burnt.                                                                     
• Electrical current is set up whose magnitude is proportional to the mass flow of the sample.

Detectors used in HPLC

•   MS – provides additional information of molecular weight and structure by fragmentation pattern
•  Photodiode Array (PDA) – Like a UV detector but gives UV traces for all wavelengths from 210 nm to 500 nm at the same time
•  Refractive Index – used for samples that don’t have any light absorbing characteristics, typically very insensitive
•  Electrochemical – detects oxidation/reduction of sample, extremely sensitive but difficult to use
•  Any detector can be added on at any time, modular.

How to choose a column ?

• Suitability for a specific application
• The column must do the job
• If already using a different column the new column should provide a benefit in performance or durability
• Reproducibility of the result from column to column and Lot to Lot
•  Reliable performance
• Stability & Life time of the column
• Less column changes will cause less instrument down time and therefore more sample can be run
• Compliance with official methods that might need to be followed
•  In case the customer needs to follow official methods like Pharmacopoeia, EPA, DIN or other local
• LC/MS suitability (for LC/MS user)
• Low Bleed of a column to reduce background signal/interference. This makes the identification in the MS easier.

Waters column