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The study focuses on the development of a new procedure for the preparation of reference samples with a given concentration for X-ray fluorescence analysis by adding certain volume of analyzed elements solutions with a known concentration to certified reference rock materials and further fusion with borate fluxes. The presented method of preparing emitters allows not only to obtain samples with the required concentrations for the elements to be determined, but also to preserve the influence that other elements have on the analytical signal. A set of 12 certified reference samples of rocks was used to construct calibration dependencies. The preparation of multicomponent modified reference samples (MRS) was carried out on the basis of certified reference materials (CRM) included in the set for constructing calibration curves. The concentration dependences on the analytical signal were established for the main oxides (SiO2, TiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O, P2O5) and minor elements (Cr, Cu, Ba, Ni, Sr, V, Zr, and Zn) using an X-ray fluorescence spectrometer with wavelength dispersion. With the help of modified reference samples, the calibration curves were expanded and supplemented both for major oxides (P2O5, MnO) and for minor elements (Zn, Sr). Also, in the course of the research, a comparison was made of the homogeneity of the emitters obtained according to the MRS preparation procedure presented in the work and reference samples (RS) made of CRM prepared according to the standard method for rocks, and the composition of inclusions on the surface of the fused disks was determined.

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Solvent front position extraction procedure was used to prepare biological samples containing selected antihypertensive drugs (ramipril, lercanidipine, indapamide, valsartan, hydrochlorothiazide, perindopril, and nebivolol). Substances separated from the biological matrix components (bovine serum albumin) were quantified by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Sample preparation process was performed with the use of a prototype horizontal chamber with a moving pipette driven by a 3D printer mechanism enabling a controlled eluent flow velocity. Application of this device was advantageous for simultaneous preparation of several samples for further quantitative analysis, with a synchronized reduction of manual operations and solvent consumption. Quantitative results obtained for the majority of the investigated antihypertensive drugs in a complex biological matrix were satisfactory. The values of the %RSD were around 5% for six of the seven substances (with the exception of indapamide). The method exhibits a suitable accuracy (the relative error percentage was below 10% for most drugs). The values of LOD and LOQ were in the range of 1.19 µg/L-8.53 µg/L and 3.61 µg/L-25.8 µg/L, respectively.

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Accurate analysis using a simple and rapid procedure is always the most important pursuit of analytical chemists. In this study, a new sample preparation procedure, namely the shaker cup (SH) method, was designed and compared with two sample preparation procedures, commonly used in the laboratory, from three aspects: homogeneity of the sample-flux mixture, potential for sample contamination, and sample preparation time. For the three methods, a set of 54 certified reference materials (CRMs) was used to establish the calibration curves, while another set of 19 CRMs was measured to validate the results. In the calibration procedures, the matrix effects were corrected using the theoretical alpha coefficient method combined with the experimental coefficient method. The data of the major oxides (SiO2, TiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O, and P2O5) and minor elements (Cr, Cu, Ba, Ni, Sr, V, Zr, and Zn) obtained by wavelength dispersive X-ray fluorescence spectroscopy (WD-XRF) were compared using two derivative equations based on the findings by Laurence Whitty-Léveillé. The results revealed that the WD-XRF measured values using the SH method best agreed with the values recommended in the literature.

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Solvent Front Position Extraction (SFPE) procedure has been recently introduced as a novel concept for multi-component sample preparation. According to the procedure, thin-layer chromatography (TLC) is used to separate the compounds of interest from matrix components, and to focus them into a common zone from which the compounds are extracted and transferred to apparatus for instrumental analysis. In the paper, we investigate different adsorbent types of the chromatographic plates and various mobile phases, including pH of their buffers, in respect of optimization conditions of the SFPE procedure. The research was carried out using a test sample containing 9 compounds characterised by different chemical properties, hence the conclusions from the obtained results can be applied to other multi-component samples. Under the optimal conditions, all target compounds are separated from other compounds (matrix), and evenly distributed along a narrow strip, which is advantageous for their quantitation. The determination results are good, the percentage values of relative error and relative standard deviation do not exceed 6%.

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An azo coupling-based derivatization method is reported for high-sensitivity liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation of tetrahydrocannabinol (THC) and other aromatic compounds, i.e. phenols and amines. Through the azo coupling of a diazonium to an analyte, it produces a derivatized analyte which has enhanced ionization efficiency and results in high-response fragments in tandem mass spectrometry. The derivatization method was applied to six typical aromatic compounds using three different diazonium salts as derivatization reagents, demonstrating its applicability to a variety of analytes and reagents. The derivatization reaction can be directly carried out in neat samples, and after derivatization the samples can be immediately sent to the LC-MS/MS instrument for analysis. These advantages facilitate a one-step sample preparation procedure that can be completed in less than one hour, allowing for a "derivatize & shoot" lab workflow. The derivatization method was applied to establish an LC-MS/MS assay for the quantitation of THC in human breath samples. The derivatization conditions were studied in this application, including the effects of acidity, organic solvent, and diazonium concentration in the reaction. The THC derivatization assay was validated and achieved a limit of quantitation (LOQ) of 0.50 pg/ml using either of the two regio-isomers of the azo-derivative of THC (THC-DRV). To prove that the derivatization method has compatibility with complex-matrix samples, a THC derivatization assay for serum samples was established, in which the azo coupling reaction was directly carried out in crude protein-precipitated supernatants. An LOQ of 5.0 pg/ml was achieved. In addition, excellent correlation between THC derivatization and non-derivatization assays was found in the analysis of whole blood samples.

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