• Decrease font size
  • Return font size to normal
  • Increase font size
U.S. Department of Health and Human Services

Science & Research

  • Print
  • Share
  • E-mail

Volume IV - 5.4 Gas Chromatography, Selective Detectors

DFS Pyramid Logo

Orientation and Training

Food and Drug Administration

DOCUMENT NO.:

IV-05
VERSION NO.: 1.3

Section 5 - Pesticides Analysis

EFFECTIVE DATE: 10/01/2003REVISED: 02/14/2013

5.4.1  Electron-Capture Detector

A.  Objective

To train in proper instrument startup, and to introduce the fundamental principles, uses, and safe handling of the electron-capture detector (ECD).

B.  Assignment

Following trainer demonstration, start up a designated GC-ECD system and inject chlorinated pesticide standard mixture. 

C.  Reference

  1. U.S. Food & Drug Administration, Center for Food Safety and Applied Nutrition, Office of Plant, Dairy Foods and Beverages. Makovi, C. M. (Ed.), McMahon, B. M. (Ed. Emerita). (1994). Pesticides analytical manual-multiresidue methods (3rd ed., Vol. I, section 503 B-Detectors, updated October 1999). R.O.W. Sciences, Inc.

D.  Questions and Instructions

  1. Briefly describe the principles of the ECD.
  2. What are the advantages and disadvantages of the ECD?
  3. What is the maximum operating temperature for the 63Ni detector?
  4. What class of pesticides is generally determined using the ECD? What other types of chemicals respond to an ECD?
  5. Name at lest four factors that can affect detector response.

5.4.2  Nitrogen/Phosphorus Thermionic Detector

OPTIONAL training per laboratory discretion.

A.  Objective

To train in proper instrument operation, and to introduce the fundamental principles and uses of the nitrogen/phosphorus thermionic detector (N/P-TD).

B.  Assignment

The trainer will demonstrate the proper startup procedure for a gas chromatograph equipped with an N/P-TD. Inject an organonitrogen standard mixture.

C.  References

  1. U.S. Food & Drug Administration, Center for Food Safety and Applied Nutrition, Office of Plant, Dairy Foods and Beverages. Makovi, C. M. (Ed.), McMahon, B. M. (Ed. Emerita). (1994). Pesticides analytical manual-multiresidue methods (3rd ed., Vol. I, sections 503 E- Detectors, updated October 1999). R.O.W. Sciences, Inc.
  2. Kalb, B. and Beschoff, J. J.(1974). Chromatography Science, 12, 625-629.
  3. Laboratory Information Bulletin, LIB No. 1904.

D.  Questions

  1. Briefly describe the principles of the N/P-TD.
  2. What type of compound is detected by the N/P-TD under normal operating conditions?
  3. How does increasing H2 flow affect response of the N/P-TD?
  4. What hazards are associated with H2?
  5. Describe the modes of operation of the N/P-TD.
  6. What is the approximate difference in response between nitrogen and phosphorus with the N/P-TD?

5.4.3  Flame Photometric Detector

OPTIONAL training per laboratory discretion.

A.  Objectives

To train in proper instrument startup, and to introduce the fundamental principles and uses of the flame photometric detector (FPD).

B.  Assignment

The trainer will demonstrate the proper startup and shutdown procedures for FPD instrumentation. Inject an organophosphorus standard mixture.

C.  Reference

  1. U.S. Food & Drug Administration, Center for Food Safety and Applied Nutrition, Office of Plant, Dairy Foods and Beverages. Makovi, C. M. (Ed.), McMahon, B. M. (Ed. Emerita). (1994). Pesticide Analytical Manual-multiresidue methods (3rd ed., Vol. I, section 503 C-Detector, updated October 1999). R.O.W. Sciences, Inc.

D.  Questions and Instructions

  1. What are the differences between the FPD and the N/P-TD?
  2. Assuming optimum flame conditions, what FPD component is the next most likely to affect sensitivity?
  3. Which detector is placed first in a dual detection system containing an ECD and FPD in series? Why?
  4. Why is the ignition button depressed and hydrogen slowly introduced when igniting the FPD? 

5.4.4  Hall Electrolytic Conductivity Detector

OPTIONAL training per laboratory discretion.

A. Objectives

To train in proper instrument startup, and to introduce the fundamental principles and uses for the Hall electrolytic conductivity detector (HECD).

B.  Assignment

Under the direction of the trainer, inject a known standard solution using the proper operation mode.

C.  References

  1. U.S. Food & Drug Administration, Center for Food Safety and Applied Nutrition, Office of Plant, Dairy Foods and Beverages. Makovi, C. M. (Ed.), McMahon, B. M. (Ed. Emerita). (1994). Pesticide analytical manual-multiresidue methods (3rd ed., Vol.I, section 503 D-Detector, updated October 1999). R.O.W. Sciences, Inc.
  2. Laboratory Information Bulletin, LIB No. 2473, and LIB No. 2473A. 

D.  Questions

  1. Briefly describe the principles of the HECD in the halogen mode.
  2. What are two major advantages of the HECD over an ECD?
  3. Are there any advantages of the HECD (sulfur mode) over the FPD?
  4. Explain the steps to prepare the HECD for operation in the halogen mode.

5.4.5 Mass Selective Detector 

A. Objectives

To demonstrate the proper instrument setup, vacuum system operation, leak detection, tuning, and operation of the Mass Selective Detector and use of the Chemstation software

B.  Assignment

  1. The trainer will demonstrate the following:
  2. Starting up and shutting down the MSD including the pump down and venting procedures.
  3. Vacuum integrity using the Air and Water Check procedure.
  4. Tuning the MSD using the manual and autotune procedures.
  5. Operating the MSD in the full Scan Mode.
  6. Identifying compounds using the Library Search routines.
  7. Operating in the Selected Ion Monitoring ( SIM) mode, including selection of ions to be monitored, dwell times and retention time windows.
  8. Preparing a GC/MSD analytical sequence for a SIM Method.
  9. Analyzing data generated by a SIM analytical run, including verifying the identification of compounds, and quantization of detected compounds. 

C.  References

  1. Laboratory Information Bulletin Number, No. 4304. 
  2. Laboratory Information Bulletin Number, No. 4308. 

D.  Questions

  1. Why should a MSD with a diffusion pump be cooled below 100º C before venting?
  2. What can we learn from the ratio of air to water ions in the Air and Water Check?
  3. What is the highest electron multiplier voltage setting?
  4. In the full scan mode, what is the mass to charge range available?
  5. Describe the libraries available using the data system.
  6. What are the trade offs between the following: dwell time, number of ions monitored in a SIM Method and the shape of the chromatographic peak?
  7. Why is the start operation of the MSD delayed? (i.e. a few minutes after the sample is injected).

5.4.6  Halogen Specific Detector

A. Objectives 

To train in proper instrument startup, and to introduce the fundamental principles and  use for the Halogen Specific Detector (XSD).

B.  Assignments

After the trainer’s demonstration the trainee will inject a known organochloride standard solution using the proper instrument setup.  The chromatographic results obtained will be discussed thoroughly.   

C.  References

  1. Model 5360 Halogen Specific Detector (XSD TM) Operator’s manual. Revision 2.0, May 1995, from O.I Analytical Corp, 151 Graham Road, P.O. Box 9010, College Station, Texas 77842-9010.

D.  Questions

  1. What gases are necessary for the operation of the Halogen specific detector (XSD)? Explain the purpose of each gas.
  2. What classes of compounds can be determined using the Halogen specific detector (XSD)?
  3. Why is the Halogen specific detector (XSD) operated at elevated temperatures? 
  4. What are the advantages of the Halogen Specific detector (XSD) over other halogen selective detectors?
  5. Describe briefly the Principle of Operation of the Halogen Specific Detector (XSD).