Determination of alkyltrimethylammonium surfactants in hair conditioners and fabric softeners by gas chromatography–mass spectrometry with electron-impact and chemical ionization

doi:10.1016/j.chroma.2003.10.047

Journal of Chromatography A

Volume 1027, Issues 1–2, 20 February 2004, Pages 103-108

https://doi.org/10.1016/j.chroma.2003.10.047 Get rights and content

Abstract

The commercial hair conditioners and fabric softeners were analyzed for the content of alkyltrimethylammonium compounds (ATMACs) by gas chromatography–mass spectrometry (GC–MS) with electron impact (EI) and low-pressure positive-ion chemical ionization (PICI) modes. The method involves mixed diluted samples (adjust pH to 10.0) with potassium iodide to enhance the extraction of iodide–ATMA⁺ ion pairs by direct liquid–liquid extraction. The iodide–ATMA⁺ pairs were then demethylated to their corresponding nonionic alkyldimethylamines (ADMAs) by thermal decomposition in a GC injection-port. A high abundance of ADMAs was detected at the temperature above 300 °C in the GC injection-port. The enhanced selectivity of quasi-molecular ion chromatograms of C₁₂–C₁₈-ADMA, obtained using methanol PICI-MS enables ADMAs to be identified. The accuracy and precision of the method was validated and was successfully applied to determine contents of ATMAC in commercial hair conditioners and fabric softeners. The contents of total measured ATMAC ranged from 0.4 to 6.9% for hair conditioners, and from 3.3 to 4.6% for fabric softeners.

Introduction

Cationic surfactants are applied in many commercial hair conditioners and fabric softeners as softeners, antistatics and bactericides. Alkyltrimethylammonium compounds (ATMACs) are one of the most important softening agents as a mixture of linear alkyl homologues of dodecyl- (C₁₂), tetradecyl- (C₁₄), hexadecyl- (C₁₆) and octadecyl- (C₁₈) trimethylammonium chlorides or bromides. After use, ATMAC are normally discharged via wastewater treatment facilities to surface waters. Hence, they can disturb the ecosystem due to their toxicity to aquatic organisms [1], [2], [3]. However, information on the content of ATMAC in most commercial hair conditioners and fabric softeners in Taiwan is unavailable. None of them was labeled ATMAC in the products, and some products were only labeled as containing “cationic surfactants”. Therefore, the concentration of ATMAC in hair conditioners and fabric softeners and the associated environmental risk are not assessable, and concentrations of ATMAC in municipal effluents and sewage could not be evaluated. The widespread use of ATMAC, and the increasing public concern over environmental issues have stimulated our interest to investigate the content and distribution of ATMAC in commercial hair conditioners and fabric softeners.

Numerous analytical methods for cationic surfactants have been developed. Typically, cationic surfactants are treated with anionic dyes, to form ion-pair complexes, which can be then extracted by solvents and followed by spectrophotometry [4], [5], [6]. However, these methods lack specificity to differential individual homologues, and suffer from many interfering compounds. HPLC is the most promising method for the analysis of these cationic surfactants. However, due to the lack of UV absorption by long-chain quaternary ammonium surfactants, electrical conductivity detection or indirect detection were usually employed with HPLC [7], [8], [9], [10], [11], [12], [13]. LC–MS with electrospray may represent a powerful method for determining of QACs [14], [15], [16], but the required equipment is expensive and not easily available. GC or GC–MS is not only more readily available in many analytical laboratories, but also provides a higher chromatographic resolution with a capillary column. GC and GC–MS has been used for determination of long-chain cationic surfactants by converting them to the corresponding tertiary amines by thermal decomposition in the injection-port, or by the Hofmann elimination to decompose them [17], [18], [19], [20], [21], [22], [23]. Currently, demethylation of alkyltrimethyl ammonium bromides in Bayer process liquors with potassium iodide in injection-port has been reported [24]. However, quantitative determination of content of C₁₂–C₁₈-ATMACs by GC–MS in commercial product samples has yet to be achieved.

As part of a larger effort to characterize the impact of ATMACs in the environment, a simple and rapid method for routinely determining the contents of ATMAC homologues in various hair conditioners and fabric softeners was developed. The method involves sample dilution, liquid–liquid extraction and GC–MS analysis of their corresponding alkyldimethylamines (ADMAs) using various MS techniques. In addition to the EI studies, the methanol as CI reagent gas was also applied to facilitate molecular weight determination of these corresponding ADMAs in hair conditioners and fabric softeners [25]. This work undertakes a preliminary study of the ATMAC content in hair conditioners and fabric softeners sold in Taiwan, to support the surface water pollution prevention and control programs.

Section snippets

Chemicals and reagents

Dodecyltrimethyl ammonium bromide (99% purity) was from Sigma (St. Louis, MO, USA). Hexadecyl- and octadecyltrimethyl ammonium bromides (all above 98% purity) were obtained from ChemServices. Tetradecyl trimethyl ammonium bromide and undecyldimethylamine (C₁₁-ADMA, as an internal standard) were purchased from Aldrich (Milwaukee, WI, USA). All other high purity chemicals and solvents were purchased from Aldrich, Tedia (Fairfield, OH, USA) and Merck (Darmstadt, Germany), and were used without

Method optimization

According to our previous experience with thermal demethylation, injecting the iodide–ATMA⁺ ion-pairs could improve the chromatograms and produce the highest average peak areas and quantitative results [25]. The peak response was increased by more than one order of magnitude and peak tailing was reduced. Therefore, an exchange of ATMA⁺ from bromide or chloride salts to iodide salts was employed as reported elsewhere [24], [25]. The effect of injection temperature on the formation of ADMAs was

Conclusion

The analytical procedure developed herein demonstrates that the liquid–liquid extraction and GC–MS methods that involve a thermal demethylation reaction are reliable, sensitive and offer convenient analytical techniques for determination of ATMAC in commercial product samples. The iodide salts enhanced the extraction and the thermal demethylation of ATMA⁺ in GC injection-port. Using methanol as the reagent gas for PICI-MS provides high-intensities of protonated molecular signals, enabling

Acknowledgements

This research was supported by a grant from the National Science Council of Taiwan under contract No. NSC 91-2113-M-008-020.

References (26)

M.A. Lewis et al.
Water Res.
(1986)
T. Sakai et al.
Talanta
(1986)
V.T. Wee
Water Res.
(1984)
S. Suzuki et al.
J. Chromatogr.
(1989)
S. Suzuki et al.
J. Chromatogr.
(1986)
A.R. Hind et al.
J. Chromatogr. A
(1997)
W. Knauf
Tens. Deterg.
(1973)
R.S. Boethling, D.G. Lynch, in: O. Hutzinger (Ed.), The Handbook of Environmental Chemistry, vol. 3, Part F, Springer,...
R.A. Llenado et al.
Anal. Chem.
(1981)
S. Motomizu et al.
Analyst
(1992)

V.T. Wee et al.

Anal. Chem.

(1982)

K. Levsen et al.

Fresenius’ J. Anal. Chem.

(1993)

E. Matthijs et al.

Vom Wasser

(1987)

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Determination of alkyltrimethylammonium surfactants in hair conditioners and fabric softeners by gas chromatography–mass spectrometry with electron-impact and chemical ionization

Abstract

Introduction

Section snippets

Chemicals and reagents

Method optimization

Conclusion

Acknowledgements

Water Res.

Talanta

Water Res.

J. Chromatogr.

J. Chromatogr.

J. Chromatogr. A

Tens. Deterg.

Anal. Chem.

Analyst

Anal. Chem.

Fresenius’ J. Anal. Chem.

Vom Wasser