One of the current challenges facing researchers is the search for alternative biological material, as opposed to routinely and invasively collected (such as blood), as the analysis of the former would provide information about the state of human health, allowing for the diagnosis of diseases in their early stages. With the search for disease biomarkers in alternative materials, the development of newer analytical solutions has been observed. This study aims to develop a reliable analytical method using the capillary isotachophoresis technique for the determination of organic acids in children’s saliva, the presence/elevation of which can be used in the future for diagnostic purposes. Organic acids such as formic, lactic, acetic, propionic, and butyric acid, were determined in the saliva of healthy children without carious lesions. The limit of quantification determined in the validation process was found to vary from 0.05 to 1.56 mg/L, the recoveries at the two levels were determined to vary between 90% and 110% for level I, while for level II the corresponding values of 75% and 106% were found; the presentation, expressed as relative standard deviation values (RSD), did not exceed 5%. The parameters determined while validating the results method indicated that the obtained are reliable. The Red–Green–Blue (RGB) additive color model was used for the evaluation of the method. This comparative analysis allowed us to define the color of the method, which expresses whether it meets the given assumptions and requirements. According to the RGB model, the isotachophoresis method developed requires less reagent input, shorter sample preparation times, and results with lower energy consumption. Thus, the subject procedure may provide an alternative, routine tool for determining organic acids in human saliva, to be applied in the diagnosing of diseases of various etiological origins.

Breast milk is the most appropriate food for an infant in the first months of life - it provides the essential nutrients required for proper growth, with breast milk oligosaccharides (HMOs) being the third most abundant component. HMO concentrations vary based on factors like lactation stage and maternal health. They play crucial roles in infant health, acting as prebiotics, antimicrobials, and immune modulators. Analytical methods like capillary electrophoresis and liquid chromatography are the most often used in HMOs qualitative and quantitative analysis. Continuing research aims to enhance analytical techniques for comprehensive HMOs analysis, this work presents the development of a capillary electrophoresis method with laser-induced fluorescence detection along with derivatization and solid-phase extraction steps for the characterisation of major oligosaccharides in colostrum samples. Validation parameters, such as linearity (0.9949–0.9989), limits of detection (5.49–16.40 ng cm⁻³) and quantification (18.30–54.67 ng cm⁻³), intra- and inter-day precision (2.41–9.78% and 1.27—14.5%, respectively), trueness (− 8.4 to − 2.0%), and recovery (70.02–113.5%) and repeatability (2.22–10.58%) for solid-phase extraction stage were assessed. The method was evaluated using RGB additive colour model regarding the analytical and practical effectiveness and greenness of the method (achieving a brilliance score of 67.1%). Moreover, the developed method was successfully applied to determine three oligosaccharides (DSLNT, 3’SL, and 6’SL) in colostrum samples. Considering its effectiveness, the method has promise for this type of application. Graphical abstract