Irina Yaroshenko

Determination of urine ionic composition with potentiometric multisensor system

The ionic composition of urine is a good indicator of patients general condition and allows for diagnostics of certain medical problems such as e.g., urolithiasis. Due to environmental factors and malnutrition the number of registered urinary tract cases continuously increases. Most of the methods currently used for urine analysis are expensive, quite laborious and require skilled personnel. The present work deals with feasibility study of potentiometric multisensor system of 18 ion-selective and cross-sensitive sensors as an analytical tool for determination of urine ionic composition. In total 136 samples from patients of Urolithiasis Laboratory and healthy people were analyzed by the multisensor system as well as by capillary electrophoresis as a reference method. Various chemometric approaches were implemented to relate the data from electrochemical measurements with the reference data. Logistic regression (LR) was applied for classification of samples into healthy and unhealthy producing reasonable misclassification rates. Projection on Latent Structures (PLS) regression was applied for quantitative analysis of ionic composition from potentiometric data. Mean relative errors of simultaneous prediction of sodium, potassium, ammonium, calcium, magnesium, chloride, sulfate, phosphate, urate and creatinine from multisensor system response were in the range 3-13% for independent test sets. This shows a good promise for development of a fast and inexpensive alternative method for urine analysis.

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine.

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r(2) = 0.9967 and 0.9972, respectively) from 160 μmol L(-1) to 1.6 mmol L(-1) for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L(-1) and 111 μmol L(-1). Good repeatability was observed for intra-day (1.7-2.9%) and inter-day (3.6-6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.

Exploring bitterness of traditional Chinese medicine samples by potentiometric electronic tongue and by capillary electrophoresis and liquid chromatography coupled to UV detection.

Instrumental bitterness assessment of traditional Chinese herbal medicine (TCM) preparations was addressed in this study. Three different approaches were evaluated, high-performance liquid chromatography coupled to UV detector (HPLC), capillary electrophoresis coupled to UV detector (CE) and a potentiometric multisensor system - electronic tongue (ET). Most studies involving HPLC and CE separations use these as selective instruments for quantification of individual substances. However we employed these techniques to provide chromatographic or electrophoretic sample profiles. These profiles are somewhat analogous to the profiles produced by the ET. Profiles from all instruments were then related to professional sensory panel evaluations using projections on latent structures (PLS) regression. It was found that all three methods allow for bitterness assessment in TCM samples in terms of human sensory panel with root mean squared errors of prediction ca. 0.9 within bitterness scale from 0 (no bitterness) to 6 (maximal bitterness).

Development of a HPLC–MS/MS method for the simultaneous determination of nifedipine and lidocaine in human plasma

The method for simultaneous determination of nifedipine (NIF) and lidocaine (LID) in human plasma by one-step sample preparation has been developed for the first time. Due to the photosensitivity of nifedipine and its low plasma concentrations a precise and reliable method was required. The method involved liquid-liquid extraction (methyl tert-butyl ether, MTBE), and 10μL of the resulting sample was analyzed by HPLC-MS/MS. Chromatographic separation was achieved on an YMC-Triart C18 HPLC column (100×2.0mm; S-5μm 12nm). The mobile phase was methanol:water, 60:40 (v/v) and contained 0.15% acetic acid. The linearity of the method was established in the concentration ranges of 0.5-50ng/mL for NIF and 1.0-500ng/mL for LID. Photodestruction of NIF under ambient light was evaluated. The validated method was successfully applied to analyze human plasma samples after rectal application of the drug (1g) containing 2.0% LID and 0.3% NIF.

A simple design atomic emission spectrometer combined with multivariate image analysis for the determination of sodium content in urine

In clinical analysis the determination of alkali metals in biological samples is often performed by flame emission spectroscopy (FES). Despite its good analytical performance for the determination of trace elements, FES apparatus is often cumbersome, expensive, and energy dependent and thus, not applicable for on-site measurements. In an attempt to address these limitations, a simple digital atomic emission spectrometer built from easily available components is proposed in this study for the quantification of sodium in human urine samples. The system was designed to operate in the absence of electrical power supply with a sample consumption per measurement of about 10 μL. It comprises a traditional Bunsen burner with an air-propane flame embedded in a protective box, a silver wire loop for sample introduction and a smartphone camera for digital recording of the signal emitted by the analyte. The collected video frame is subjected to a multivariate image procedure based on multivariate curve resolution – alternating least squares (MCR-ALS) intended to avoid subjectivity in the selection of the region of interest (ROI) used to build the univariate regression model. The developed platform was evaluated in the context of sodium determination in human urine in the range from 40 to 220 mmol L−1. The system displays a linear response (R2 = 0.990) between the color index and sodium content for standard samples with a detection limit of 10.9 mmol L−1. Performance study for intra-day (2.5–4.1%) and inter-day (1.3–2.5%) measurements, performed on three different days, exhibits good repeatability. The homemade digital atomic emission spectrometer was successfully applied to the determination of (spiked) sodium in human urine samples (R2 = 0.942) with recovery that ranged from 94.8 to 110.4% and an averaged mean relative error below 10%. Selectivity study against potassium, calcium and magnesium revealed high tolerance of the method for these interferents.

A chromatographic-mass spectrometric method for the determination of moxifloxacin in blood plasma for pharmacokinetic studies

A method for the determination of moxifloxacin in human blood plasma has been developed and validated by reversed-phase HPLC on a YMC-Triart C18 (150 × 2.0 mm, 3 μm) column with mass spectrometric detection. Sample preparation has been performed by solid-phase extraction on Waters Sep-Pak cartridges. The recovery of moxifloxacin was 90 ± 3%. A quadrupole mass analyzer with electrospray ionization has been used for detection at m/z 402.2 and 362.2 for moxifloxacin and ofloxacin (internal standard), respectively. The lower limit of the analytical range was 1 ng/mL. The developed method has been used for the pharmacokinetic study of moxifloxacin.

Determination of Rhein in blood plasma by HPLC with UV detection and its application to the study of bioequivalence

A method is proposed for determining rhein (an active metabolite of diacerein) in human blood plasma by reversed-phase high-performance liquid chromatography with UV detection. The analyte was selectively extracted from blood plasma by liquid-liquid extraction with a 5% solution of tert-butyl methyl ether in ethyl acetate. The recovery of rhein is 68 ± 3%, LOQ 100 ng/mL. The stability of the analytes and linearity, selectivity, sensitivity, reproducibility, and accuracy of the developed method are evaluated. The pharmacokinetics of diacerein in the oral administration of drug formulations by 18 healthy volunteers is studied.

Electronic Tongue for Brand Uniformity Control: A Case Study of Apulian Red Wines Recognition and Defects Evaluation †

The potentiometric electronic tongue system has been tested as a potential analytical tool for brand uniformity control of monoculture Apulian red wines (Primitivo and Negroamaro). The sensor array was composed of eight porphyrin coatings obtained by electrochemical polymerization process and was employed for both wines discrimination and quantitative detection of wine defect compounds: “off-odour” 3-(methylthio)-propanol; isoamyl alcohol fusel oil; benzaldehyde (marker of the yeast activity) and acetic acid (marker of vinegar formation). PLS-DA applied to Electronic tongue output data has permitted a correct discrimination of more than 70% of analysed wines in respect to the original brand affiliation. Satisfactory PLS1 predictions were obtained in real wine samples; with R2 = 0.989 for isoamyl alcohol and R2 = 0.732 for acetic acid. Moreover; the possibility to distinguish wine samples on the base of permitted levels of fault compounds content was shown.

Application of chemometric methods to XRF-data – A tutorial review

X-ray fluorescence (XRF) spectrometry is a modern method of element analysis, widely applied in forensic science, archeology, geochemistry and other fields. Chemometric data processing tools and approaches may help XRF to become even more informative. These tools allow for convenient data visualization, exploration of hidden relations in the data, classification of samples and quantitative treatment of noisy and overlapped spectra. This review describes the most popular chemometric techniques employed in XRF studies and provides typical examples of such applications.

Determination of markers of the urinary stone disease

The capabilities of physicochemical methods (chromatographic, electrophoretic, potentiometric, and voltammetric) and also field test methods for the determination of the main markers of the urinary stone disease have been considered. The effect of various factors on the processes of stone formation has been discussed.