Otto H. York Center for Environmental Engineering and Science

For most GC detectors, identification is based solely on retention times and is performed by comparing the retention time of the unknown peak to that of a standard. Since many compounds may possess the same retention time, there is always a doubt about the nature and purity of the compound in the separated peak. Among all detectors available in the lab, there is only one which provides additional qualitative (structural or elemental) information about the sample lacking in other GC detectors, and, therefore, is used directly for compound identification. This is Mass Selective Detector (MSD or MS).
 
Agilent 5977B  GC/MSD with 7693A Autoinjector. Agilent ChemStation for GC control and data handling. NIST Mass Spectral Library and NIST Chemical Structures Database.

5977B_data_sheet1785.pdf

Agilent 7890B GC/5977B MSD with 7693 Autoinjector. Agilent ChemStation for GC control and data handling. NIST Mass Spectral Library and NIST Chemical Structures Database.

The NIST 2017 Mass Spectral Library (267K compounds and 307K spectra) allows searching mass spectral database for the best spectral match of the analyte with the library and make mass spectrum interpretation easier.

Agilent 5973N Benchtop GC/MSD with HP Automatic Liquid Sampler. Agilent ChemStation for GC control and data handling. NIST Mass Spectral Library and NIST Chemical Structures Database.

The instrument is equipped with turbomolecular pumps and is operated in either electron impact or chemical ionization (positive and negative) modes. Among the most important advantages of 5973N mass selective detector, crucial for our applications are: high sensitivity (1 pg of octafluoronaphtalene with a signal to noise ratio of 10:1 with EI-SCAN mode) and a wide mass range from 1.6 to 800 amu for expanded compound identification. These features allow the detection and quantitative measurements of PCBs, dioxins, pesticides and other pollutants in a variety of environmental matrices and at very low concentrations. The HP MSD ChemStation provides complete automation of an integrated system (GC, MSD and automatic liquid sampler) and, therefore, improves productivity. MSD tuning, sample introduction, signal acquisition, data processing are automated by ChemStation methods. The system is equipped with the NIST 08 Mass Spectral Library (192K compounds and 220K spectra).