, Volume 400, Issue 7, pp 2141-2147
Date: 08 Apr 2011

Determination of phenylenediamine isomers in hair dyes by coal cinders micro-column extraction and MEKC

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A new micellar electrokinetic chromatography (MEKC) method using beta-cyclodextrins (β-CDs) and 1-butyl-3-methylimidazolium hexafluorophosphates (ionic liquids) as additives was successfully developed for determination of para-, meta-, and ortho-phenylenediamines isomers (p-P, m-P, and o-P) in hair dyes. To improve the sensitivity of the MEKC-UV, a simple and cheap flow injection (FI) technique using a micro-column packed with coal cinders (the by-products from combustion in a boiler) as solid-phase extractant was also investigated. In the presence of 20 mmol L−1 phosphates at pH 5.5, addition of 12 mmol L−1 ionic liquids and 8 mmol L−1 β-CDs greatly improved the separation efficiency. The three analytes could be quantitatively adsorbed by coal cinders, and desorbed readily with 0.15 mL of 0.01 mol L−1 NaOH. Under the optimum conditions, an enrichment factor (EF) of 33.3 was obtained, and determination limits of p-P, m-P, and o-P were 1.97 × 10−7, 0.99 × 10−7, and 0.61 × 10−7 mol L−1, respectively. The adsorption capacities of the coal cinders micro-column for p-P, m-P, and o-P were all 1.20 mg g−1. The presented procedure was successfully applied to the determination of p-P, m-P, and o-P in hair dyes with satisfactory results.


Electropherograms of 0.1 mmol L−1 p-P, m-P, and o-P obtained by a direct MEKC and b SPE-MEKC; SPE conditions: sample solution flow rate 0.30 mL min−1, eluent flow rate 0.45 mL min−1, desorption by 0.15 mL of 0.01 mol L−1 NaOH; MEKC conditions: 20 mmol L−1 phosphates containing 12 mmol L−1 ionic liquid and 8 mmol L−1 β-CD at pH 5.5; injection time 50 s