The applicability of capillary electrophoresis (CE) with light-emitting diode-induced fluorescence detection (LEDIF) for the separation of sugars in honey samples was studied. An amount of 25 mM ammonium acetate (pH 4.5) with 0.3% polyethylene oxide (PEO) was found to be optimal for the efficient separation of carbohydrates. 8-aminopyrene-1,3,6-trisulfonic acid (APTS) was used for the labeling of the carbohydrate standards and honey sugars for fluorescence detection. The optimized method was applied in the quantitative analysis of fructose and glucose by direct injection of honey samples. Apart from the labeling reaction, no other sample preparation was performed. The mean values of the fructose/glucose ratio for phacelia honey, acacia honey and honeydew honey were 0.86, 1.61 and 1.42, respectively. The proposed method provides high separation efficiency and sensitive detection within a short analysis time. Apart from the labeling reaction, it enables the injection of honeys without sample pretreatment. This is the first time that fluorescence detection has been applied for the CE analysis of sugars in honeys.

The preparation of linear polyacrylamide (LPA)-coated capillary is a multistep, laborious process. In this study, five different LPA-coating procedures were compared regarding the capillary pretreatment (incubation time and temperature), the formation of the intermediate silyl layer and the attachment of the polymer top layer. LPA coatings were examined by the analysis of a standard mixture solution of insulin, rituximab and hemoglobin using a background electrolyte (BGE) of 50 mM HCOOH (pH 2.6). The results were contrasted with those that were obtained using the bare fused-silica capillary. The reproducibility of the simplest LPA-coating preparation was tested. The long-term stability of the capillary coating was evaluated through inter-day precision data using a large number of injections of the three-protein test mixture solution. The implementation of a short-term procedure at elevated temperature, guided by a comprehensive review of various conditions documented in the literature, yielded an efficiently functional LPA coating.

This paper demonstrates the study of the use of single or multiple (2–4) internal standards for the improvement of the repeatability of the micellar electrokinetic capillary chromatographic measuremen