Combined Determination of 1,4-Dioxane and Nitrosamine Contaminants in Drinking Water Using a Single SPE Cartridge and Concurrent Solvent Recondensation–Large Volume Splitless Injection (CSR-LVSI) With EI GC-MS

Author(s): Chris Rattray and Jack Cochran
Restek Corporation

Published By: Restek Corporation

Year of Publication: 2014

Link: http://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVAN1922-UNV

Abstract: Global concern over the carcinogenic potential of 1,4-dioxane and several nitrosamines has resulted in increased interest in the development of more efficient testing methods for these contaminants in drinking waters. In the U.S., the current methodologies recommended for the analysis of 1,4-dioxane and nitrosamines in drinking waters are Environmental Protection Agency (EPA) Methods 522 and 521, respectively. EPA Method 522 is a relatively simple gas chromatography–mass spectrometry (GC-MS) method using electron ionization (EI), while Method 521 requires positive chemical ionization (PCI) using liquid methanol or acetonitrile reagent gas, along with tandem mass spectrometry (GC-MS/MS).

The method described here uses the same coconut charcoal sorbent solid phase extraction (SPE) cartridges and dichloromethane eluent recommended in EPA Methods 522 and 521 to concentrate 0.50 L water samples to 10 mL extracts. However, both the extraction and instrumental analysis portions of EPA Methods 522 and 521 have been combined by analyzing a single quantitatively collected SPE tube extract for both 1,4-dioxane and nitrosamines during a single chromatographic run. The benefits of the current combination method include fewer samples to collect, ship, and extract; a reduction in solvent use; and higher sample throughput. Because the final SPE extract cannot be concentrated via evaporation due to volatile compound loss, we employed concurrent solvent recondensation–large volume splitless injection (CSR-LVSI), which uses a standard splitless injector to deliver 50 µL injections of extract to a pre-column connected to a typical GC column for separation followed by EI MS analysis. When combined with selected ion monitoring (SIM), this large volume injection allows for practical quantitation limits (PQLs) as low as 10 ng/L for 1,4-dioxane and 0.5–2.0 ng/L for the nitrosamines.

ChromSoc Food Analysis Conference to Feature Talk by Jaap de Zeeuw

On April 9, 2014, in collaboration with The Chromatographic Society (ChromSoc), Syngenta Research Labs will host “Separating the Wheat from the Chaff; Advances in Natural Product Analysis” at their Jealotts Hill Research Centre in Bracknell, Berkshire, UK. The focus of this conference is the chromatographic and mass spectrometric analysis of foods, vegetables, and natural products. Restek’s International GC Specialist Jaap de Zeeuw will join Professor Pat Sandra (Gent), Dr. Paul Russell (Unilever), Dr. Robin Clery (Givaudan), Dr. Geoffrey Kite (Kew), and other noted industry experts in a full day of valuable presentations.

Considerations for Improved Measurement of Traces in Food Matrices by Minimizing the Injection Bandwidth Using Normal and Large Volume Splitless Injection
Jaap de Zeeuw (presenter)
Restek Corporation

Jaap de Zeeuw

Jaap de Zeeuw

Abstract: In GC, the efficiency of a capillary can only be exploited if the analytes injected are focused as a narrow band. Using a split injection, this is relatively easy as the injection is fast. If trace analysis is required, a bigger sample volume has to be injected. To inject a larger sample, one needs to eliminate the impact of the solvent.

It is possible to remove the solvent via concentration techniques, but this will cause extra sample preparation time. Easier is to inject a larger amount onto the column. Special injection techniques have been developed to introduce larger sample volumes. One of the most used techniques is the splitless technique. In this technique, the sample is introduced in a hot liner with the split line closed. The whole content of the liner is transferred into the column, which takes between 20 and 60 seconds. To get a focused band, one uses the solvent effect by setting the oven temperature about 20 °C below the BP of the solvent. Components will focus here and a narrow band is created.

The focusing will only happen if the solvent used is compatible with the surface polarity of the stationary phase. If there is no compatibility, the solvent will form droplets and multiple injection bands can be formed. The same challenge is observed when larger volumes are introduced. The use of a retention gap helps for generating a focused band, not only when solvent is entering the column, but also when solvent and column phase are not compatible. The retention gap was found to be extremely helpful in operating the large volume splitless injection technique known as CSR-LVSI. This acronym stands for “concurrent solvent recondensation – large volume splitless injection.” With this technique, it is possible to get a focused band while injecting volumes up to 100 µL in standard split/splitless injection systems.

Standard split/splitless systems for injection of larger volumes, avoiding the use of (expensive) PTV-type injection systems and methods, are relatively easy to set up once the process of band-focusing is understood.

Restek has been a leader in the chromatographic analysis of food for over 25 years, so we are proud to be a participant in what is sure to be an informative and worthwhile event. In addition to the long list of distinguished speakers, attendees will also have access to an exhibition of leading manufacturers and suppliers, including Thames Restek UK.

To view the schedule of talks and to register, visit www.chromsoc.com/ChromsocEvents.aspx today.

Misselwitz and Rattray to Speak at the EPA’s 22nd Annual Quality Assurance Conference

Chris Rattray

Chris Rattray

Michelle Misselwitz

Michelle Misselwitz

From October 15–19, 2012, the U.S. Environmental Protection Agency (EPA) will hold its 22nd Annual Quality Assurance Conference in Region 6, Dallas, TX. Two Restek chemists, Michelle Misselwitz and Chris Rattray, will be making the trip south to present some of their latest work, including GCxGC analysis of pesticides and pharmaceutical and personal care products (PPCPs) as well as lowering detection limits for drinking water methods using large volume splitless injection (LVSI). For more details on each presentation, see below.

This free conference has been organized for years by the incredibly dedicated Charles Ritchie and is a great way to network with a wide range of colleagues and get caught up to speed on recent developments in environmental analysis. You can learn more about the Quality Assurance Conference on the EPA’s website (www.epa.gov/earth1r6/qa/index12.htm) and can also re-read Michelle Misselwitz’s blog on last year’s event (blog.restek.com/?p=3916) .

We hope to see you there!

 

Technical Presentations

TUESDAY, OCTOBER 16, 2012

9:30 a.m. / Session E
The QuEChERS Sample Preparation Approach and Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry for the Analysis of Pesticides in Tobacco

Michelle Misselwitz

Tobacco is a high-value production crop for the United States and ranks 6th among the amount of pesticides applied per acre in American agriculture. Even after the processing of tobacco, some pesticide residues remain on the final product. We used the Quick–Easy–Cheap–Effective–Rugged–Safe (QuEChERS) sample preparation approach to isolate pesticide residues from loose cigarette tobacco. Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) was used to determine pesticide residues in the resulting extracts.

3:00 p.m. / Session C
Analysis of Pharmaceutical and Personal Care Products and Other Emerging Environmental Contaminants in Water Using a Highly Efficient GCxGC-TOFMS System

Michelle Misselwitz

Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) is a powerful multidimensional approach to sample analysis that is unmatched by traditional one-dimensional chromatography. By operating the system to maximize efficiency in both the first and second dimension, GCxGC-TOFMS has the ability to detect, identify, and quantify or semi-quantify an unlimited number of target, non-target, and unknown compounds (including emerging compounds of concern) with full mass spectra and sub- to low-pg sensitivity. Using this technique, water samples were collected from the urban river in Las Vegas to analyze a large number of pharmaceutical and personal care products and other emerging environmental contaminants.

4:00 p.m. / Session D
Achieving Lower Detection Limits for Multiple Drinking Water Methods Using Large Volume Splitless Injections on an Unmodified Split/Splitless Injection Port

Chris Rattray
For more information, email Chris Rattray.

Utilizing a large volume splitless injection is advantageous for many reasons. Some of these include shipping and extracting significantly smaller sample sizes, reducing extract concentration, or decreasing limits of detection for trace-level analysis in drinking water. The drawback for many is that large volume injections typically require a specialized injection port. However, with concurrent solvent recondensation-large volume splitless injection (CSR-LVSI), a large volume injection can be achieved on an unmodified Agilent split/splitless injection port. Here we analyzed multiple drinking water methods using CSR-LVSI on an Agilent 7890/5975C GC-MSD and injected up to 10 µL to achieve lower detection limits.

Restek Chromatographers Lend Their Expertise to NEMC 2012

As in years past, Restek sent a contingent of environmental and air chromatography experts to the National Environmental Monitoring Conference (NEMC). This year’s event took place in Washington, DC, and featured talks from our own Michelle Misselwitz, Jason Herrington, and Chris Rattray. See below to review their abstracts and presentations.

Restek was also involved with NEMC from an organizational standpoint—Joe Konschnik supported Earl Hansen, NEMC’s Technical Program Chair, by serving as Co-Chair of the Air Methods & Monitoring Session. In this role, Joe helped plan, coordinate, and moderate oral presentations by some of the industry’s brightest minds. The session received such unprecedented interest that it was split into three sections!

We are also proud to announce that Joe has been invited to join the steering committee for NEMC 2013. We hope you consider making the trip to San Antonio, TX, on August 5–9 for what is sure to be an enlightening conference.

For more information on NEMC, visit their website at www.nemc.us


Technical Presentations

Characterization of Crude Oils and Tar Balls Using Biomarkers and Comprehensive Two-Dimensional Gas Chromatography

Michelle Misselwitz (presenter), Jack Cochran, Chris English, Barry Burger

Abstract: The analysis of petroleum biomarkers is commonly used to determine the origin of crude oil samples. These biomarkers are “molecular fossils” that are complex hydrocarbon molecules from formerly living organisms in the source rock. Utilizing biomarkers to fingerprint crude oils is advantageous because they are resistant to weathering or degradation and provide a unique profile for oil-to-oil correlations. This information can be used by environmental forensic chemists to pinpoint source oil from spills, or in this case, tar balls washed along the shore of the Gulf of Mexico.

Gas chromatography mass spectrometry (GC-MS) is typically used to monitor the ratios of hopane and sterane isomers. This work will focus on characterizing crude oil samples, including from the broken riser pipe collected via an underwater robot during the Deepwater Horizon oil spill of 2010, by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS). GCxGC is a two-dimensional separation using two columns of different selectivity with thermal modulation. Utilizing a retention plane provides a structured chromatogram that aids in fingerprinting complex oil samples. The hopane/sterane profile of these oils will then be compared to extracts of tar balls that washed ashore on the Gulf of Mexico beaches months after the spill occurred. 

Concerns Regarding 24-Hour Sampling for Formaldehyde, Acetaldehyde, and Acrolein Using 2,4-Dinitrophenylhydrazine (DNPH)-Coated Solid Sorbents

Jason Herrington
For more information, email Jason Herrington.

Abstract: There is high demand for accurate and reliable airborne carbonyl measurement methods due to the human health and environmental impacts of carbonyls and their effects on atmospheric chemistry. Carbonyl sampling methodologies based on derivatization with 2,4-dinitrophenylhydrazine (DNPH)-coated solid sorbents are the current standard. However, these methods present multiple challenges that detract from an accurate understanding of carbonyl-related exposure, health effects, and atmospheric chemistry. Since their original development in the late 1970s, these methods have been extensively evaluated and developed. However, studies have demonstrated formaldehyde interferences from 2,4-dinitrophenylazide (DNPA) and 2,2-dinitrochlorobenze (DNCB); low acetaldehyde collection efficiencies for 24-hour sampling; and numerous acrolein sampling interferences. This presentation will discuss the sampling issues associated with DNPH-coated solid sorbents, the potential for remedies, and will provide recommendations and areas for future research. The presentation of this information is important because it seems clear that carbonyl data produced utilizing DNPH-based methods are being reported without acknowledgment of the method short-comings or how to best address them.

Click here to download a PDF of the full presentation.

Lowering Detection Limits for 1,4-Dioxane in Drinking Water using EPA 522 with Concurrent Solvent Recondensation – Large Volume Splitless Injection

Christopher Rattray (presenter), Jack Cochran, Scott Grossman, Chris English
For more information, email Christopher Rattray.

Abstract: The third Unregulated Contaminant Monitoring Regulation (UCMR 3) is scheduled to begin next year and includes a requirement for 1,4-dioxane analysis using EPA Method 522. EPA Method 522 was originally written to be performed using a standard gas chromatograph (GC) equipped with a single quadrupole mass spectrometer (MS). However, a recent reevaluation of 1,4-dioxane’s carcinogenic risk resulted in the EPA lowering the suggested minimum reporting limit from 0.3 to 0.07 µg/L, and even when operating in selected ion monitoring (SIM) mode, most GC-MS instruments would be hard pressed to meet this lower 0.07 µg/L limit. One way to lower detection limits is to inject more sample, but large volume splitless injection (LVSI) for gas chromatography typically requires a special injection port such as a programmable temperature vaporizer (PTV). The technique described here for the analysis of 1,4-dioxane in drinking water uses an unmodified split/splitless inlet with LVSI to lower reporting limits without concentrating extract. With an injection volume of 10 µL, we achieved a linear calibration range exceeding 3 orders of magnitude, with levels ranging from 5 to 10,000 pg on column. We saw 89% recovery when 1 L of bottled water fortified at 0.005 µg/L was extracted using coconut charcoal SPE tubes and analyzed according to EPA Method 522 with LVSI, matching the method performance data published by the EPA. This LVSI technique requires absolutely no changes to standard laboratory instrumentation.

Click here to download a PDF of the full presentation.

Air Methods/Monitoring Sessions

• Data Interpretation and Policy Development

• Developments in Analytical Methods

• Sorbent Based Sampling Methods

Session Chairs & Moderators: Joe Konschnik1, George Lucier2, Deb Gaynor3, Michael Flournoy4, Nicola Watson5
1. Restek Corporation, 2. Battelle Memorial Institute, 3. Phoenix Chemistry Services, 4. SGS-Analytical Perspectives, 5. Markes International

For more information, visit www.nemc.us/meeting/2012/nemc-program.php

Lowering Detection Limits for 1,4-Dioxane in Drinking Water Using Large Volume Injection in an Unmodified Splitless GC Inlet

Author(s): Chris Rattray, Jack Cochran, Chris English

Published By: LCGC North America

Issue: June 2012

Year of Publication: 2012

Abstract: Recent work analyzing 1,4-dioxane in drinking water using large volume splitless injection is summarized in this  LCGC North America application note. Concurrent solvent recondensation–large volume splitless injection (CSR-LVSI), an alternative to programmed temperature vaporization (PTV), typically requires a special GC inlet. The technique described here uses an unmodified split/splitless inlet with CSR-LVSI to lower detection limits for the analysis of 1,4-dioxane in drinking water. The complete version of this application is also available and can be found here: http://www.restek.com/Technical-Resources/Technical-Library/Environmental/env_EVAN1548-UNV

Large Volume Splitless Injection Using an Unmodified Split/Splitless Inlet and GC-TOFMS for Pesticides and Brominated Flame Retardants

Author(s): Michelle Misselwitz, Jack Cochran

Published By: Restek Corporation

Year of Publication: 2011

Link: http://www.restek.com/Technical-Resources/Technical-Library/Environmental/ev_an1331

Abstract: Concurrent solvent recondensation large volume splitless injection (CSR-LVSI) GC/MS is used here for analyzing pesticides and brominated flame retardants in drinking water based on EPA Method 527. CSR-LVSI allows a time-consuming sample extract concentration step to be eliminated, but can also be used with extract concentration for lower detection limits.