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Identify and control nitrosamines with Agilent’s Dual Plasma Nitrogen Chemiluminescence Detector

By Thomas Daniels
Agilent Sulfur and Nitrogen Chemiluminescence Product Manager

For many years, concern has grown regarding the health effects of nitrosamines, formed from naturally occurring or added nitrates, nitrites, and amines. Nitrosamines potentially appear in cured meat products, tobacco, rubber products, distilled spirits, cosmetics, and other consumer products and environmental matrices. Several of these N-nitroso compounds are known or suspected carcinogens, and studies have indicated that certain nitrosamines are mutagens and can cause birth defects, even at very low concentrations. Clearly, many industries need effective analytical techniques to measure these toxic compounds. Capillary gas chromatography combined with the Agilent 255 Nitrogen Chemiluminescence Detector (NCD) is a rapid and selective means to perform nitrosamine analysis.

The 255 NCD allows you to optimize burner conditions to selectively measure nitrosamines. The 255 NCD response is proportional only to the presence of the thermally unstable nitroso moiety. With Dual Plasma Technology, the detector provides an equimolar response and is not subject to quenching. The 255 NCD is linear over at least four orders of magnitude and offers good stability over time.

Figure 1. Each shipment includes a chromatogram of a low-level nitrosamine standard, which demonstrates performance verification at the factory. (Click here to see this image larger.)

Agilent 7890A GC system Oven  program 60 °C for 1 min, then 10 °C/min to 120 °C for 4 min, then 15 °C/min to 230 °C for 5 min Run time 23.33 min Inlet Cool on-column, oven tracking mode Column Agilent J&W DB-Wax, 30 m x 530 µm x 1 µm Column flow 3.5 mL/min Agilent Dual Plasma Controller for the 255 NCD Hydrogen flow N/A Oxygen flow 7.5 SCCM Typical pressure 70 – 80 torr Burner temperature 450 °C

Table 1. Chromatographic conditions for nitrosamine analysis

Figure 2. Switching from TEA (left) to NCD (right) reduced analysis time by 63%. Chromatograms show a reference material that nominally contained 100 ng/mL of nitrosamines. (Click here to see this image larger.)

Optimized GC/NCD solution

Agilent now offers a dedicated, factory-tested GC system for nitrosamines analysis. It consists of a specially configured 7890A GC system with an optimized Agilent 255 NCD, and is supplied with nitrosamine test results (as shown in Figure 1) for each system. Table 1 lists the chromatographic conditions for the checkout standard for this dedicated solution.

Successful adoption shows advantages of 255 NCD over TEA

A major supplier of cGMP analytical services with expertise in nitrosamines analysis successfully switched from thermal energy analyzers (TEAs) to the Agilent 255 NCD. The lab had problems with maintenance of aging TEAs and sought an alternative to reduce repair expenses and improve reliability.

The analytical services company sent samples to the application laboratory for a demonstration. After receiving encouraging results, the company purchased two Agilent 255 NCDs for nitrosamines analysis. The company has since completed extensive bridging studies, and the results have allowed them to retire the aging TEAs.

Not only have the Agilent NCDs proved to be more reliable, they have yielded higher resolution and faster run times. This is illustrated in Figure 2, where the TEA run (left) took 27 minutes, while the 255 NCD run (right) took only 10 minutes. This large improvement comes from the ability to switch from the packed columns that were used with the TEA to the capillary columns used with the 255 NCD. The NCD chromatogram in Figure 2 took advantage of a 0.53 mm internal diameter Agilent J&W DB-Wax column, with conditions similar to those described in Application Note 5989-6773EN.

The bridging study demonstrated essentially equivalent results, but with slightly higher recoveries for the 255 NCDs. The study showed that use of Thermo Scientific CTR (molecular sieve) traps with both detection systems lead to more stable baselines, and that traps required replacement after approximately 50 analyses. Further, the more stable baseline of the Agilent 255 NCD yielded easier peak integration.

Gas chromatography combined with nitrogen chemiluminescence detection offers a reliable, sensitive, and specific means for nitrosamine analysis. Learn more about the advantages of the Agilent Dual Plasma Nitrogen Chemiluminescence Detector. Then talk with your Agilent Representative about how you can use the Agilent 255 NCD to gain greater confidence in your results. To order a dedicated GC solution for nitrosamines, please request SP-1 7890-0460 for nitrosamine analysis.

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