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Wei Zou

A comprehensive profiling of toxicological semivolatile compounds using GC-MS

Samples are extracted, cleaned, concentrated, and injected into GC-MS.

Standards and Reagents





The standards and reagents listed below are those in use at the time this procedure was written.  Alternate supplies may be used so long as they are of equivalent quality and all other calibration, quality control, and traceability requirements are met.  








Source Standards





“Source Standards” are those standards that are purchased from an outside vendor.  Obtain a Certificates of Analysis from the vendor of each source standard.  Label the certificate with the date received and file the certificate in the 3-ring binder.  Label the box or container the source standard arrived in with the date received.  





Source standards usually have an expiration date set by the manufacturer.  If no expiration date is listed, the expiration date is one year from date received.  Label the box or container the source standard arrived in with the expiration date if one is not listed.  Store the source standards as recommended by the manufacturer.  





Once a standard vial is opened, the holding time for any excess standard will be noted as one day for the gaseous standards and one week for the non-gaseous standards from the date the ampule is opened.  Label vials with the contents and expiration date.  Do not store standards in a refrigerator or freezer containing samples.  





DFTPP, Surrogate, and Internal Source Standards


Tuning Mixture:


GC/MS Tuning Mixture Restek #31615 1,000 ug/mL


DFTPP:


Decafluorotriphenylphosphine Supelco #4-8724 25,000 ug/mL


Surrogate:


Method 8270-Surrogate Standard Accustandard #M-8270-SS 4,000 ug/mL


8270 Surrogate Standard \(for ICV) Supelco #44649-U 


 2000 ug/mL for phenols, 1000 ug/mL for B/N


ISTD:


Internal Standard Mix Accustandard #Z-014J 4,000 ug/mL





8270 Calibration Source Standards


Method 8270 5 point curve w/o ISTD’s Accustandard #M-8270-CAL-SET


Consists of:


M-8270 Calibration Level 1 w/o ISTD M-8270-WL 20 ug/mL


M-8270 Calibration Level 2 w/o ISTD M-8270-WL-2.5X 50 ug/mL


M-8270 Calibration Level 3 w/o ISTD M-8270-WL-4X 80 ug/mL


M-8270 Calibration Level 4 w/o ISTD M-8270-WL-6X 120 ug/mL


M-8270 Calibration Level 5 w/o ISTD M-8270-WL-8X 160 ug/mL


Note: ISTD \(Accustandard #Z-014J) should be added to have a final concentration of 40 ug/mL no matter what the calibration level is.  


Note: Method 8270D recommends ICAL standards or a standard from the same manufacturer as the ICAL standards be used for spike standards.  However, NELAC 2003 Quality Systems Appendix D section 4.1.b.5 states the spiking standards must be from a different source than the ICAL standards.  In the same Appendix, section 1.1.2.1.C specifies that 16 compounds will be spiked and reported for lists greater than 20 compounds, rather than the 6 specified in the method.  





8270 Continuing Calibration Verification \(CCV) Source Standards


M-8270 Calibration Level 2 w/o ISTD M-8270-WL-2.5X-10ML 50 ug/mL


Note: ISTD \(Accustandard #Z-014J) should be added to have a final concentration of 40 ug/mL.  





8270 Target Compound Source Standards


SV Calibration Standards Kit \(for ICV) Supelco #48118


Consists of:


TCL Base-Neutrals Mix 1 Supelco #48900-U 2000 ug/mL


TCL Base-Neutrals Mix 2 Supelco #48120-U 2000 ug/mL


TCL Phenols Mix Supelco #48904 2000 ug/mL


TCL PAHs Mix Supelco #48905-U 2000 ug/mL


TCL Benzidines Mix Supelco #48906 2000 ug/mL


TCL Hazardous Substances Mix 1 Supelco #48907 2000 ug/mL


TCL Hazardous Substances Mix 2 Supelco #48908 2000 ug/mL








Reagents





Each reagent preparation must be documented in the standards preparation log book including calculation and dilutions.  Each prepared reagent must be assigned a unique ID, based on the manufacturer and the date prepared.  Each reagent received from an outside vendor should be labeled with the receipt date and expiration date.  Use or discard within 1 year, or sooner if problems are encountered.  





• Acetone, EM Science, Omni-Solv grade, VWR Catalog# TXEMAX01 161 CUT  


Store in a Flammables cabinet for no more than 3 months; after 3 months, aldol condensation products will start forming and interfering with the analysis.  





• Dichloromethane, EM Science, Omni-Solv grade, VWR Cat# TXDX0837-39CUT  


Store at room temperature for up to 1 year.  





• Hexane, JT Baker, Ultra Resi-Analyzed grade, VWR Catalog# JT9262-3  


Store at room temperature in a Flammables cabinet for up to 1 year.  





• Acetone/Hexane, 1:1, v/v  


Prepare by carefully decanting approximately 1 L of acetone into a brown solvent jug containing approximately 1 L hexane.  Label the bottle with the reagent ID.  Store in a Flammables cabinet under the fume hoods for no more than 3 months.  





• Ottawa sand, 20-30 mesh, Fisher Catalog # S23-3  


Wash with dichloromethane several times. Kiln bake at 400°C for 4 hours then cool in a dessicator. Store at room temperature for up to 1 year.  








Working Standards





“Working standards” are those standards that are prepared by the analyst.  Document the preparation of all working standards in the standards preparation log book.  The log book entry should include the prep date, source standard information \(concentration and volume of standards used, lot number of standard), solvent name, solvent volume, solvent lot#, final volume and concentration of working standard, expiration date of working standard, and preparation chemist’s initials.  





Prepare working standards using gas-tight Class-A syringes and volumectric flasks.  Working standards expire either 60 days from the date prepared, or on the earliest expiration date of the source standards used to make the working standard, whichever comes first.  The expiration date of a working standard cannot exceed the expiration date of the source standard\(s) used to prepare it.  





• PEM \(50 ug/mL)


Add 50 uL of GC/MS tuning mixture source standard \(Restek #31615) into a 1-mL volumetric flask, top to the marker with dichloromethane.  





• DFTPP \(50 ug/mL)


Add 20 uL of DFTPP source standard \(Supelco #4-8724) into a 10-mL volumetric flask, top to the marker with dichloromethane.  





• ICV \(50 ug/mL of targets and B/N, 100 ug/mL of A, 40 g/mL of ISTD)


Add into a 10-mL volumetric flask the following: 


1. 250 uL of each TCL Mix in the SV Calibration Standards Kit \(Supelco #48118);  
  2. 500 uL of 8270 SV Surrogate Spike Mix \(Supelco #44649-U);  
  3. 100 uL of Internal Standard Mix \(Accustandard #Z-014J)  
  Then, top to the marker with dichloromethane.  


Aliquot 10 mL WS into 1-mL amber-color crimp-cap GC vials with 300 uL insert, wrap with PTFE tape and store at 4°C.  





• Surrogate Mixtures \(200 ug/mL Acid and 100 ug/mL B/N)


1. Add 1mL of each Acid \(Restek #31063) and B/N \(Restek #31062) source standard into a 50mL volumetric flask, top to the marker with dichloromethane.  Cap and invert to mix.  
  2. Aliquot 10 mL WS into 10-mL amber-color screw-thread Teflon-lined cap vials \(Scientific Specialties Service Inc.), wrap with PTFE tape and store at 4°C – enough for 20 samples. When use, transfer to V-Vials with Mininert screw cap valves – 10 mL vials and 15 mm screw cap thread.  
  3. Use 500uL per sample.  
  


• Spike Mixture \(100 ug/mL of target compounds)


1. Add 1mL of each SV Calibration Standards \(Supelco #48118) into 20mL volumetric flask, top to the marker with dichloromethane. Cap and invert to mix.  
  2. Aliquot ~3 mL WS into 4-mL amber-color screw-thread Teflon-lined cap vials \(Scientific Specialties Service Inc.), wrap with PTFE tape and store at 4°C – enough for 20 samples. When use, transfer to V-Vials with Mininert screw cap valves – 5 mL vials and 15 mm screw cap thread.  
  3. Use 500 μL per sample.  
  


• Direct Inject Standard \(Surrogates: 100 for Acid & 50 for B/N ug/mL, Targets: 50 ug/mL, ISTD: 40 ug/mL)


Add into an amber-color crimp-cap GC vial the following: 


1. 500 uL of surrogate working standard;  
  2. 500 uL of spike working standard;  
  3. 10 uL of Internal Standard Mix \(Accustandard #Z-014J).

• Balance, analytical  - top loading capable of weighing to 0.01 g  


• Glass VOA vials \(collection tubes) – 60mL volume with PTFE-lined septa


• Spatula, stainless steel  


• Syringes – 10μL, 250μL, 500μL


• Graduated cylinders – 10mL, 25mL


• Shaker table – adjustable to allow thorough mixing of matrix and solvent.


• Digital Sonifier, Model S-450D with ½” tapped horn


• Centrifuge – table top, swing bucket with adapters for VOA vials


• Disposal pipets, Pasteur


• Glass funnels, long stem


• Weighing dish, Aluminum, low form, fluted, 1 3/8 fl. oz.


• Tweezer, stainless steel


• TurboVap LV, Zymark


• Concentrator tubes – 40mL with graduated 1mL tapered tip  


• Autosampler vials - 2mL with caps of PTFE-lined septa and 200μL  glass inserts with feet





GC-MS  Maintenance





    1.1. Gas Management  


• Gas purifiers: Every 6 to12 months.  Replacement schedule is based on capacity and grade of gases.  In general, replace non-indicating traps every 6 to 12 months or when detector gas indicating traps start to change color.  Replace indicating traps when indicating material is spent.  


• Split vent trap: Every 6 months.  





     1.2. Sample Introduction and Inlets  


• Syringes: Every 3 months.  Replace syringe if dirt is noticeable in the syringe.  Replace the needle if septa wear is abnormal or the needle becomes clogged.  


• Inlet liner and liner O-ring: Weekly.  Check often.  Replace when dirt is visible in the liner or if chromatography is degraded or if CCV fails.  


• Inlet septum: Daily.  Check often.  Replace when signs of deterioration are visible \(gaping holes, fragments in inlet liner, poor chromatography, low column pressure, etc.).  


• Inlet gold or stainless steel seal: Monthly.  Check for scratches, corrosion, or build-up of non-volatile sample components and replace if dirty, or if CCV fails after changing liner and septa.  





     1.3. Columns  


• Front-end maintenance: Weekly – monthly.  Remove 1⁄2 to 1 loop from the front of the column when experiencing chromatographic problems \(peak tailing, decreased sensitivity, retention time changes, etc.).  Replace inlet liner, septum and clean inlet as necessary.  Guard column may be useful for increasing column lifetime.  


• Replacement: As needed.  Replace when trimming and/or solvent rinsing no longer return chromatographic performance or early eluting compounds lost in solvent peak.  


• Ferrules: As needed.  Replace when changing columns and inlet/detector parts.  





     1.4. Mass Selective Detectors


• Tune MSD: As needed.  Keep plenty of PFTBA \(part number 05971-60571) on hand.  


• Check the calibration vial: Every 6 months.  Vial can be refilled without venting the system.  


• Replace the foreline pump oil: Every 6 months.  Check the fluid weekly.  Change when the fluid becomes discolored or every 6 months.  


• Replace the diffusion pump fluid: Every year or as needed.  Check the fluid weekly.  Too little fluid will cause the pump to run at a higher temperature, resulting in degradation and loss of high vacuum.  Change when the fluid is discolored or contains particulates.  


• Clean the ion source: As needed.  Clean when performance deteriorates to remove contamination and restore the electrostatic properties of the ion lensing system.  Replace scratched parts to maintain optimal performance.  This may be done when column is replaced.

3 working days for a batch of 24 samples.

8.1. Agilent Environmental GC/MSD Instrument and ChemStation Operation Volume 1 & 2, Course Number H4050A, Student Manual.  


8.2. ISO/IEC 17025:2005 General requirements for the competence of testing and calibration laboratories, 2005.  


8.3. 2003 NELAC Standards.  


http://www.nelac-institute.org/docs/2003nelacstandard.pdf.  


8.4. EPA Method 8000C, Determinative Chromatographic Separations.  


http://www.epa.gov/osw/hazard/testmethods/pdfs/8000c_v3.pdf.  


8.5. EPA Method 8270D, Semivolatile Organic Compounds By Gas Chromatography / Mass Spectrometry \(GC/MS), Revision 4, February 2007.  


http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/8270d.pdf.

CC BY-NC 3.0

Solid samples are prepared by shake extraction method or sonication.  Aqueous samples are extracted by separatory liquid-liquid extraction method.  The semi-volatile compounds are introduced into the GC/MS capillary column that is temperature-programmed to separate the analytes, which are detected with a mass spectrometer \(MS) interfaced to a gas chromatograph \(GC).

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Method Article

Wei Zou

Wei Zou

Zou's lab, California State Government

Corresponding Author

DOI:

10.1038/protex.2013.003

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SVOC, GC-MS, profiling

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Wei Zou

Wei Zou

Zou's lab, California State Government

Corresponding Author

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CURRENT STATUS: Posted

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DOI:

10.1038/protex.2013.003

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