Simplified Yet Sensitive Determination of Aniline and Nitroanilines

Aniline is an organic compound widely used in the polymer, rubber, pharmaceutical, and dye industries. Aniline and its derivatives (e.g., nitroanilines) are suspected carcinogens and are highly toxic to aquatic life. Because these compounds are thermolabile and polar, the traditional analytical methods require a derivatization step prior to GC analysis. Most of these procedures are time-consuming and complicated. HPLC analysis is a good alternative because derivatization is not needed. To gain enough sensitivity for UV detection, either liquid-liquid partitioning or off-line SPE must be used prior to HPLC analysis. Here an on-line SPE HPLC system is used to fulfill the simple and sensitive determination of aniline and four nitroanilines (o-nitroaniline, m-nitroaniline, p-nitroaniline, and o,p-dinitroaniline) in tap and pond water. Various trap columns and separation columns were tested (best performing are shown here).

Method Conditions and Sample Preparation

The experimental configuration, more experimental results, references, and sample preparation procedures are described in Dionex Application Note 292 (now part of Thermo Fisher Scientific Inc.).

Results

Linearity was tested using standards with concentrations of 1–100 µg/L undergoing on-line SPE under the specified chromatographic conditions (r value better 0.9999). Recoveries for each standard in both sample sets ranged from 98 to 108% for the 10 µg/L standard spiked samples, and ranged from 93 to 147% (contaminant excluded after DAD spectra review, pond water only) for the 1 µg/L standard spiked samples. The samples had no detectable aniline or nitroanilines. Method detection limits were 0.1–0.2 µg/L and are therefore 10–100 times more sensitive (analyte dependant) compared to the limits reported in EPA Method 8131. Reproducibility for a 10 µg/L spiked standard was very good with values better than or equal to 0.3% area RSD.

Figure 1: Chromatograms of A) pond water sample, B) A spiked with 1.0 µg/L aniline and nitroanilines standard, and C) A spiked with 10 µg/L. Peaks: 1. Aniline; 2. p-Nitroaniline; 3. m-Nitroaniline; 4. o-Nitroaniline; 5. o,p-Dinitroaniline

Chromatograms of tap and pond water samples, as well as the same samples spiked with aniline and related standards (1.0 µg/L each and 10 µg/L each, respectively), are shown in Figure 1. A Thermo Scientific Dionex SolEx on-line solid-phase extraction (SPE) HRP cartridge, 12–14 µm, 2.1 × 20 mm, was used for the enrichment. A Thermo Scientific Acclaim 120 C18, 3 µm Analytical, 3 × 150 mm column was used for the separation. Under the optimized chromatographic conditions, the complete analysis required 15 min (30 min including column reconditioning).

Conclusion

This work describes an on-line SPE system using the Dionex SolEx™ HRP cartridge to enrich aniline and nitroanilines, followed by HPLC with UV detection. The enrichment of aniline and nitroanilines in tap and pond water is sufficient, and baseline separation on the Acclaim™ 120 C18 column is achieved. With excellent linearity, sensitivity, and reproducibility, on-line SPE HPLC provides full automation, eliminates operator-related variation, and can help enforce strict process control.

Receive the complete application note at: www.thermoscientific/AN292

Thermo Fisher Scientific Inc. (formerly Dionex Corp.)

1228 Titan Way, P.O. Box 3603, Sunnyvale, CA 94088-3603

tel. (800) 532-4752

Website: www.thermoscientific.com/dionex