Rapid Determination of Azo Dyes from Textile Samples Using Dionex ASE and U3000 HPLC-UV Instruments with MSQ Plus Detection

Azo dyes are used widely in the manufacture of various consumer goods such as leather, textiles, plastics, paper, hair care products, and cosmetics. On September 11, 2003, the European Union enacted European Parliament Directive 2002/61/EC, prohibiting the manufacture and sale of consumer goods containing specified azo dyes (1). The azo dyes of concern are those that can be reduced to aromatic amines. There are 22 aromatic amines classified as carcinogenic or potentially carcinogenic to humans.

Current sample preparation and analysis methods for these compounds are time and labor intensive and consume large volumes of solvent (2). Combining an Accelerated Solvent Extraction (ASE®) system for sample preparation with an UltiMate® 3000 HPLC-UV-MS system for analysis has proven to be an advantageous alternative to previous methods, saving time, labor, and solvent. This article describes methods for extracting textile samples using ASE as well as analytical methods for determination of aromatic amines, including the 22 restricted aromatic amines.

Equipment

ASE 200 system

UltiMate 3000 HPLC system consisting of:

SRD-3600 solvent rack degasser

LPG-3600 low pressure gradient pump

WPS-3000T well plate autosampler

TCC-3000 thermostatted column compartment

UVD 340U UV detector

MSQ™ Plus MS detector

Chromeleon® 6.80 Chromatography Workstation

Glass fiber filters

ASE Conditions

Preheat: 20 min (purge closed)

Pressure: 1500 psi

Static: 5 min

Temp: 100 °C

Cycles: 2

Purge: 100 s

Flush: 30%

Solvent: 90% CH₃OH with 10% 1 M KOH

Extraction time per sample: 40 min

Solvent amount used per sample: 17 mL

Analytical Conditions

Column: Acclaim® 120 C18, 3 μm, 120 Å, 2.1 × 150 mm

Column Temperature: 30°C

Injection Volume: 10 μL

Gradient: See Dionex Application Note 360 (3)

UV: 240 nm, 278 nm

Ionization Mode: APCI, positive polarity

Nitrogen: 3 bar

Corona Current: 10 μA

Source Temperature: 400°C

Cone Voltage: Varies per analyte. See Table I.

Sample Prep

Soak 1.0 gram of material in 3 mL citrate buffer (pH 6.0) and 3 mL of sodium dithionite (200 mg/mL) for two min. Transfer the mixture and solution to an ASE 11 mL cell containing a glass fiber filter.

Extraction

Place the extraction cells onto the ASE 200 and extract with the ASE conditions listed above. When the extraction is complete, record total volume of the extract and inject 10 μL onto the UltiMate 3000 HPLC-MS-UV.

Results and Discussion

Experimentation with the photodiode array detector demonstrated that wavelengths 240 and 278 nm were best suited for aromatic amine detection. A standard comprising 22 aromatic amines at 5 mg/L concentrations (Azo Dyes Mix-6, Ehrenstorfer Laboratories) was separated on the Acclaim 120 column and detected at UV wavelength 278 nm. (Figure 1). The 22 restricted azo dyes are labeled.

Figure 1

Individual standards of the Ehrenstorfer dyes were ordered from Sigma-Aldrich. These standards were run to determine the optimal mass spectrometer detection conditions (Table 1).

Table I: Optimized detection conditions of Azo Dye standards for amine analysis

A leather sample known to contain a forbidden dye was prepared, extracted, and determined using UV and MS detection (Figure 2). The presence of 2-anisidine and o-toluidine peaks in single ion monitoring (SIM) detection mode confirmed the identification of the peaks in the UV trace.

Figure 2

Conclusions

Extracting aromatic amines from samples is a bottleneck for most azo dye test procedures. ASE in combination with the UltiMate 3000 HPLC-MS-UV is a powerful tool in extraction and analysis of azo dyes, saving both time and solvent.

References

(1) Directive 2002/61/EC of the European Parliament and of the Council of 19 July 2002 Amending for the Nineteenth Time Council Directive 76/769/EEC Relating to Restrictions on the Marketing and Use of Certain Dangerous Substances and Preparations (Azocolourants). Official J. Eur. Commun. 2002, 45 (L243), 15–18.

(2) Ahlström, L.; Eskilsson, C. S.; Björklund, E. "Determination of Banned Azo Dyes in Consumer Goods." Trends in Analytical Chemistry 2005, 24, 49–56.

(3) Dionex Corporation. "Application Note 360: Rapid Determination of Azo Dyes in Textiles Using Dionex ASE and UltiMate 3000 HPLC Systems with MSQ Plus and UV Detection." Sunnyvale, CA, 2008.

Acclaim, ASE, Chromeleon, and UltiMate are registered trademarks of Dionex Corporation. MSQ is a trademark of Thermo Fisher Scientific Inc.

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