Volatile and Semivolatile Organics by Gas Chromatography/Mass Spectrometry (GC/MS): Capillary Column Technique
revised 10/23/95
1.0 Scope and Application
Analytical Method used for soil core samples from Hill AFB shipped in 40 ml vials with pH adjusted water and methylene chloride. Alterations to these core samples such as the use of surfactants may require changes to be made to this method.
2.0 Summary of Method
Upon receipt of samples the vials are stored at 4oC until ready for analyses. Samples are removed from the refrigerator allowed to equilibrate to room temperature and then sonicated for 15 minutes. After sonication the samples are centrifuged and an aliquot of the methylene chloride phase transferred to a 1.8 ml autosampler vial, internal standard and surrogates added, and is ready for GC/MS analyses.
3.0 Interferences
Raw GC/MS data from all blanks, samples, and spikes must be evaluated for interferences. If possible, these interferences must be eliminated or reported.
Contamination by carryover can occur whenever high-concentration and low-concentration samples are sequentially analyzed. To reduce carryover it is helpful to rinse the syringe used for injection into the GC/MS numerous times before and after injection. Whenever an unusually concentrated sample is encountered, it should be followed by the analysis of methylene chloride to check for cross contamination. Since these samples tend to have a highly concentrated background, blanks need to be analyzed as frequently as possible.
4.0 Apparatus and Materials
Gas Chromatograph- Hewlett Packard 5890 with capillary injection
Mass Spectrometer- Either a Hewlett Packard 5970 or 5972
Automatic Sampler- Hewlett Packard ALS 7673
Data Station- Hewlett Packard Chemstation
Column- J&W Scientific DB-1701, 30 meters, .25 mm I.D., .26 mm film thickness
Syringe- 10 ml
Balance- Analytical, 0.0001 g
Bottles- Glass with Teflon-lined screw caps or crimp tops
5.0 Reagents
Water- Millipore Corporation Milli-Q UV Plus
Methylene Chloride- Aldrich Cat. # 32,399-3 99.9+% PRA Grade
Organic Analytes- 97% pure or greater
Calibration Standards and Stocks- prepared according to MTU-EEL Procedure entitled Standard Preparation Procedure 5/19/92 DLP
Surrogates toluene d8 and 2-fluorobiphenyl
Internal Standard- Tetrachloroethene
MS Tuning Standard- Perfluorotributylamine
6.0 Sample Collection, Preservation, and Handling
This is to be performed by others, method unknown. Once samples are received at MTU-EEL they are stored at 4oC for not more than 14 days.
7.0 Procedure
7.1 Sample Preparation
In attempt to ensure complete extraction from the soil/water matrix into the methylene chloride, all samples are sonicated at room temperature, in a sonicator at 21 kilocycles per second for 15 minutes. After sonication the samples are centrifuged at 2300 revolutions per minutes for 15 minutes to separate the phases. After phase separation a 1.0 ml aliquot is removed from the vial and put into an HP autosampler vial with a Teflon lined septum and crimp cap.
7.2 Operating Conditions for the HP 5890 GC:
Injection port- 250oC
Oven Temp Initial Time- 3 minutes
Oven Temp Initial Value- 35oC
Oven Temp Program Rate- 6oC
Oven Temp Final Time- 0 minutes
Oven Temp Final Value- 137oC
Transfer Line Temp- 280oC
Column Head Pressure- 8.5 psi
Approximate Column Flow Rate- .9 ml/minute
Septum Purge Flow Rate- 8.0 ml/minute
Split Vent Flow Rate- 31.3 ml/minute
Splitless Time- .5 minutes
7.3 Operating Conditions of the HP ALS 7673:
Sample Wash- 3
Sample Pumps- 3
Sample Volume- 2 ml
Viscosity Delay- 2 seconds
Solvent A (methylene chloride) Wash- 3
Solvent B (methylene chloride) Wash- 3
7.4 Operation Conditions of the HP Mass Selective Detector:
Electron Multiplier Voltage (Relative to Autotune)- 200
Selective Ion Monitoring (SIM) Mode
Compound SIM Start Time Cycles/Sec
-----------------------------------------------------------------
1,1,1-trichloroethane 97.0 2.3 2.80
benzene 78.0 2.3 2.80
trichloroethene 130.0 2.3 2.80
toluene 91.0 4.0 7.63
Tetrachloroethene (I.S.) 166.0 5.0 4.10
ethylbenzene 91.0 5.0 4.10
o-xylene 91.0 5.0 4.10
decane 142.0 9.5 2.80
1,3,5-trimethylbenzene 105.0 9.5 2.80
undecane 156.0 11.5 2.80
dichlorobenzene 146.0 11.5 2.80
naphthalene 128.0 14.2 7.63
Average Pressure- 2.6 X 10-5
8.0 Calibration:
A seven point calibration curve must first be analyzed to verify proper operation of the GC/MS. After fitting the standards all analytes must meet acceptance criteria. This criteria includes:
1. percent relative standard deviations of less than 15 percent for the first seven compounds in section 8.1, 25 percent for naphthalene and o-dichlorobenzene, and 35 percent for undecane. This is used to determine if the GC/MS is exhibiting a deterioration of response (as determined in SW-846 Method 8270B section 7.3.4.1 page 13),
2. deviation of any single concentration point greater than;
35 percent for naphthalene and benzene,
20 percent for 1,3,5-trimethylbenzene, undecane, and ethylbenzene,
35 percent for the lowest standard of 1,1,1-trichloroethane, trichloroethene, toluene, o-xylene, and decane and 20 percent for the remainder of the concentrations of these compounds, from the predicted value of the calibration curve, see calibration curves in appendix 2.
3. Reproducibility will be monitored with the use of a range table or shewart plot as described in "Handbook for Analytical Quality Control in Water and Wastewater Laboratories" USEPA, June 1972. Range tables for this analysis are not completely statistically defined yet as the defining population for determination is not yet large enough. However; range tables have been provided with this method to illustrate the technique and to provide preliminary data for measuring the methods ability to provide reproducible data, see appendix 1. In the tables in appendix 1 you will also find the reproducibility data for the samples already analyzed by this method. These control limits will be modified as more data is generated.
In general, the higher concentration standards should exhibit lower errors than the lower concentrations and the errors should be randomly distributed and the fit be approximately linear.
As standards are prepared by using the actual analytes verification of operation and calibration can be easily determined. To help correct for errors due to injection all analytes are divided by the internal standard, 1-bromo-4-fluorobenzene, and plotted as area ratios. After initial verification at least three standards should be analyzed after every 10 samples at or near the quantitation limit, a mid range standard, and a standard at or near the highest concentration of the calibration curve. This is performed to ensure that the calibration does not drift as a function of time. If these, "Calibration Check Compounds", as called by SW-846 Method 8270B section 7.4.4. page 15 differ less than or equal to 20 percent the initial calibration is assumed to be valid. If the criterion is not met for any one Calibration Check Compounds corrective action must be taken.
Since the standards are prepared in house and of good quality reagents we considered these to be the "true value" and matrix spikes and surrogates will be used to determine the percent recovery or accuracy. Since the samples are sent to us pre-extracted, the spike is performed by injecting 5 ml of methylene chloride containing the target analytes to yield a final concentration of approximately 5 mg/l, this concentration is accurately determined at the time. A separate injection of 5 ml for surrogates is added to the extractant to yield a concentration of approximately 1 mg/l of each target analyte, accurately determined at the time. It should be noted that the matrix spike only accounts for matrix interferences in the methylene chloride extractant.
The control limits for the surrogates are not yet determined. They will be determined after analyzing 30 samples and will be set at +/- 3 standard deviations and should be compared to those set in SW-846, method 8270B table 8 to see if they are reasonable. The surrogates for this method are toluene d8 and 2-fluorobiphenyl.
Ten percent of the samples are analyzed in duplicate and 20 percent of the samples should be blanks.
8.1 Quantitation Limits:
Compound Quantitation Limit mg/l
1,1,1-trichloroethane 56
benzene 76
trichloroethene 61
toluene 57
toluene d8 57
ethylbenzene 54
o-xylene 58
m-xylene 58
decane 84
1,3,5-trimethylbenzene 192
undecane 206
o-dichlorobenzene 207
naphthalene 192
2-fluorobiphenyl 100
9.0 GC/MS Analysis:
Once the standard or sample is in the autosampler vial a 5 ml injection of 1-bromo-4-fluorobenzene in methylene chloride is added to act as an internal standard to yield a concentration of approximately 500 mg/l, this concentration is accurately determined at the time. Samples that required dilution are diluted volumetrically. Direct injection of 2 ml of the methylene chloride phase is made into the injection port via a splitless injection on the GC/MS where separation and detection occur based on the conditions stated in sections 7.2 to 7.4. A sample chromatogram is given in appendix 3.
10.0 Data Interpretation:
10.1 Qualitative Analyses:
The qualitative identification of compounds determined by the method is based on retention time, and on comparison of the sample mass spectrum. In order to obtain the greatest sensitivity for these samples typically only one characteristic ion has been chosen for identification purposes. The relative retention time of the sample component should not exceed +/- 0.06 retention units for the respective check standard.
10.2 Quantitative Analyses:
When a compound has been identified, the quantitation of that compound will be based on the integrated abundance of that characteristic ion.
The calibration curve is expressed by the following equation
y = Parameter 1 * Area Ratio + Parameter 2.
The linear regression is performed on the natural log of the area ratio versus the natural log of the concentration. The inverse of the natural log is then taken of y to yield the concentration of the target analyte in the methylene chloride phase. This is the number that will be reported. The format for reporting is yet to be determined.
11.0 Quality Control:
The requirements for this project are:
1. Before processing any samples, the analyst should demonstrate through the analysis of a method blank, that interferences from the analytical system, glassware, and reagents are under control. Since samples are being supplied with no reagent, trip, field etc. blanks it is impossible to assure that interferences from the glassware and reagents are under control.
2. The experience of the analyst is invaluable to the success of the method. Each day that the analysis is performed the daily calibration standards should be evaluated to determine if the chromatographic system is operating properly. Questions that should be asked are: Do the peaks look normal?; Is the response obtained comparable to the response from previous calibrations? Careful examination of the standard chromatogram can indicate whether the column is still good, the injector is leaking, the injector septum needs replacing, etc. If any changes are made to the system (e.g. column changed), recalibration of the system must take place.
3. A quality control reference sample concentrate is required containing each target analyte. The QC reference sample concentrate may be prepared from pure standard materials. This reference sample concentrate is then injected into methylene chloride and the recovery determined prior to analyzing any samples. This will be done at 0.2 mg/l. For each analyte compare the percent recovery to the accepted range in the table below and the range to the valves given in appendix 1.
Compound Ave. %Recovery +/- %*
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1,1,1-trichloroethane 92.29 11.07
benzene 91.66 14.39
trichloroethene 99.77 13.91
toluene 96.14 14.30
ethylbenzene 99.48 11.71
o-xylene 97.59 20.03
decane 103.39 16.65
1,3,5-trimethylbenzene 102.43 37.18
undecane 95.63 27.19
dichlorobenzene 97.95 38.26
naphthalene 97.92 20.93
The average % recovery and the accepted ranges for surrogates and m-xylene have not yet been determined.
* based on three standard deviations of measured percent recoveries.
Appendix 1
Range Tables
Volatile and Semivolatile Organics by Gas Chromatography/Mass Spectrometry (GC/MS): Capillary Column Technique
Compound: 1,1,1-trichloroethane
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.07 0.07 0.09
0.07 - 0.15 1, 2, 3, 0.04, 0.02, 0.01
5, 7 0.01, 0.03 0.07 0.09
0.15 - 0.45 4, 6, 9 0.03, 0.02, 0.02 0.07 0.09
0.45 - 0.89 0.07 0.09
0.89 - 1.62 0.07 0.09
1.62 - 3.32 0.14 0.19
3.32 - 6.84 0.49 0.64
6.84 - 14.71 0.84 1.09
14.71 - 20.22 ---- ----
Compound: benzene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.08 - 0.10 0.08 0.10
0.10 - 0.20 0.08 0.10
0.20 - 0.61 0.08 0.10
0.61 - 1.20 0.28 0.36
1.20 - 2.19 0.31 0.40
2.19 - 4.48 0.78 1.01
4.48 - 9.22 2.33 3.03
9.22 - 12.39 3.00 3.90
Compound: trichloroethene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 1 0.00 0.08 0.10
0.08 - 0.16 2 0.00 0.08 0.10
0.16 - 0.48 4, 5 0.02, 0.05 0.08 0.10
0.48 - 0.95 3 0.06 0.08 0.10
0.95 - 1.70 0.08 0.10
1.70 - 3.57 0.24 0.31
3.57 - 7.35 0.28 0.36
7.35 - 9.22 0.70 0.91
Compound: toluene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 0.07 0.09
0.08 - 0.15 4 0.02 0.07 0.09
0.15 - 0.45 2, 3 0.00, 0.01 0.07 0.09
0.45 - 0.90 0.07 0.09
0.90 - 1.64 1 0.03 0.08 0.10
1.64 - 3.35 0.09 0.12
3.35 - 6.89 0.23 0.30
6.89 - 9.26 5 0.18 0.86 1.12
Compound: ethyl benzene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.05 - 0.07 0.07 0.09
0.07 - 0.14 0.07 0.09
0.14 - 0.43 1, 2 0.03, 0.02 0.07 0.09
0.43 - 0.84 0.07 0.09
0.84 - 1.54 0.07 0.09
1.54 - 3.16 3 0.16 0.16 0.21
3.16 - 6.50 4 0.07 0.29 0.37
6.50 - 8.73 0.90 1.17
Compound: o-xylene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 0.07 0.09
0.08 - 0.15 3 0.02 0.07 0.09
0.15 - 0.46 1, 2, 5 0.02, 0.02, 0.13 0.07 0.09
0.46 - 0.92 4, 7 0.08, 0.07 0.07 0.09
0.92 - 1.68 0.10 0.13
1.68 - 3.44 0.11 0.15
3.44 - 7.06 6 0.40 0.31 0.40
7.06 - 9.50 1.50 1.94
9.22 - 12.39 3.00 3.90
Compound: decane
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.08 - 0.20 0.11 0.14
0.20 - 0.22 0.11 0.14
0.22 - 0.67 3, 4, 5 0.24, 0.18, 0.05 0.11 0.14
0.67 - 1.33 1 0.20 0.11 0.14
1.33 - 2.43 0.12 0.16
2.43 - 4.98 0.29 0.37
4.98 - 10.24 2, 7 0.49, 1.41 0.37 0.48
10.24 - 13.76 6 1.75 1.55 2.02
Compound: 1,3,5-trimethylbenzene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 0.07 0.09
0.08 - 0.15 0.07 0.09
0.15 - 0.46 1 0.04 0.07 0.09
0.46 - 0.91 2, 4 0.09, 0.15 0.07 0.09
0.91 - 1.67 0.10 0.13
1.67 - 3.42 5 0.90 0.14 0.18
3.42 - 7.03 3 0.47 0.33 0.43
7.03 - 9.45 1.16 1.50
Compound: undecane
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 0.11 0.15
0.08 - 0.15 0.11 0.15
0.15 - 0.46 0.11 0.15
0.46 - 0.91 0.11 0.15
0.91 - 1.67 4 0.09 0.14 0.18
1.67 - 3.42 3 0.26 0.12 0.16
3.42 - 7.03 0.32 0.83
7.03 - 9.45 2, 5 0.86, 1.01 0.52 0.68
Compound: o-dichlorobenzene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.06 - 0.08 0.07 0.09
0.08 - 0.15 0.07 0.09
0.15 - 0.46 0.07 0.09
0.46 - 0.92 1 0.29 0.31 0.40
0.92 - 1.68 2, 3 0.22, 0.21 0.17 0.22
1.68 - 3.43 4 0.39 0.76 0.99
3.43 - 7.06 1.29 1.68
7.06 - 9.49 1.74 2.27
Compound: naphthalene
Conc. Range mg/l Sample # Sample Range UWL UCL
----------------------------------------------------------------
0.05 - 0.07 0.07 0.09
0.07 - 0.23 0.07 0.09
0.23 - 0.43 1, 2 0.03, 0.02 0.09 0.11
0.43 - 0.85 0.41 0.54
0.85 - 1.55 0.58 0.75
1.55 - 3.19 3 0.16 1.39 1.81
3.19 - 6.55 4 0.07 2.20 2.86
6.55 - 8.81 4.17 4.42