Selective and quantitative analysis of 4-hydroxybenzoate preservatives by microemulsion electrokinetic chromatography

Recent advances in the development and application of microemulsion EKC

“…Buffers up to pH 12 have been used for basic compounds [59] to eliminate ionisation and for acidic compounds, a low pH buffer is required (pH 1.2-1.4). Because at low pH there is little or no EOF generated, a negative voltage needs to be applied across the capillary in order to move the droplets through the detector, which results in the most retained compounds being detected first [31,60]. Although utilisation of a high pH buffer is most common in MEEKC, low pH buffers have been used to separate priority endocrine disrupting compounds [34], parabens from parahydroxybenzoic acid [60], a range of insoluble vitamins [61], a range of pharmaceuticals [62] and green tea catechins [46].…”

“…For example, a MEEKC method has been developed and validated for the determination of naproxen and rizatripan benzoate in pharmaceutical formulations [87]. The same microemulsion electrolyte was used for a validated MEEKC method to determine a range of paraben preservatives in a liquid formulation [60]. Fig.…”

Separation and determination of psoralen and isopsoralen by microemulsion electrokinetic chromatography

“…Consequently, separations can be faster, because a lower concentration of surfactant can be used, which makes it possible to apply higher voltage across the capillary without generating excessive current. Since analytes are able to penetrate the surface of oil droplets more easily compared with micelles' more rigid surfaces, MEEKC has also been demonstrated as a reliable separation tool for both highly hydrophobic and hydrophilic compounds (Altria et al, 2004;Mahuzier et al, 2001). Most papers comparing separations obtained by MEEKC and MEKC have concluded that MEEKC has a greater separation capability for highly hydrophobic compounds than MEKC, because highly hydrophobic compounds tend to be strongly retained by the micelles (Hilder et al, 2001;Klampfl, 2003).…”

A comparative study of microemulsion electrokinetic capillary chromatography and micellar electrokinetic capillary chromatography for the analysis of UV‐absorbing compounds in human urine

“…To date, MEEKC has been used for a variety of separations, e.g., natural products [9], sugars [10], fatty acids [11], hop acids [12], preservatives [13], bases and nucleosides [14], proteins [15], agrochemicals [16,17], ketones and diketones [6,18], steroids [19][20][21], vitamins [22][23][24][25][26], and a range of pharmaceuticals [23,[27][28][29][30][31][32][33][34][35]. All these separations involved standard solutions in relatively simple matrices.…”