Combining poly(dimethyldiphenylsiloxane) and nitrile phases for improving the separation and quantitation of benzalkonium chloride homologues: In-tube solid phase microextraction–capillary liquid chromatography–diode array detection-mass spectrometry for

• Combination of poly(dimethyldiphenylsiloxane) and nitrile phase.
• Screening of four homologues of benzalkonium chloride.
• The more carbon atoms of the chain length of the homologue, the longer retention time.
• Industrial samples are processed directly without any sample pretreatment.
• This work provides findings that could explain the difficulties encountered by other authors.

The retention and separation of four homologues of benzalkonium chloride (alkyl (C12, C14, C16, C18) dimethylbenzylammonium chloride) have been studied in poly(dimethyldiphenylsiloxane) (TRB) and nitrile capillary phases, respectively. Under the optimized conditions (50% acetonitrile in processed samples, 35% of diphenyl content of the TRB, capillary length 43 cm and water:methanol 60:40 as replacing solvent), the extraction efficiency was similar for all the homologues with satisfactory reproducibility and independently of the amount and proportion of homologues. Industrial samples with high viscosity or with complex composition and washes waters have been analyzed without previous treatment. The coupling of IT-SPME–CapLC–DAD to MS detection allowed the determination of the minority homologues (C16 and C18) in the industrial samples and washes waters. No matrix effect was found.