•Application of experimental design methodology in non-aqueous HILIC and SFC.•Evaluating the retention behaviour on two different stationary phases.•Application of MLR, PCA, and PARAFAC analysis to ...understand the retention mechanism.•Interpretation of retention based on molecular characteristics of tested compounds.
The experimental design methodology based on central composite design of experiments was applied to compare the retention mechanisms in supercritical fluid chromatography (SFC) and non-aqueous hydrophilic interaction liquid chromatography (NA-HILIC). The selected set consists of 26 compounds that belong to imidazoline and serotonin receptor ligands. The different chemometric tools (multiple linear regression, principal component analysis, parallel factor analysis) were used to examine the retention, as well as to identify the most significant retention mechanisms. The retention mechanism was investigated on two different stationary phases (diol, and mixed-mode diol). In NA-HILIC, the mobile phase contains acetonitrile as a main component, and methanolic solution of ammonium formate (+ 0.1% of formic acid) as a modifier. The same mobile phase modifier was used in SFC, with a difference in the main component of the mobile phase which was CO2.
The retention behaviour differs significantly between HILIC and SFC conditions. The retention pattern in HILIC mode was more partition-like, while in SFC the solute-sorbent interactions allowed retention. The retention mechanism between mixed-mode diol and the diol phases varies depending on the applied chromatographic mode, e.g., in HILIC the type of stationary phase significantly affects the elution order, while in SFC this was not the case. The HILIC retention behaviour was influenced by the number of tertiary amines-aliphatic, and N atom-centred fragments in tested compounds. On the other hand, the number of pyrrole and pyridine rings in the structure of the compound showed correlation with their SFC retention, simultaneously increasing the molecular weight and rapid elution of larger compounds. It was found that temperature surprisingly plays a major role in SFC mode. The increase in temperature reduces the relative contribution of enthalpy factors to total retention, so the separation in SFC was more entropy-controlled. For further pharmaceutical research and optimization, the SFC would be considered more beneficial compared to HILIC since it gives good selectivity in separation of chosen impurities.
New adsorbents based on silica and polystyrene–divinylbenzene (PS–DVB) for hydrophilic interaction liquid chromatography (HILIC) with eremomycin in functional layers were obtained. The ...chromatographic properties of the new adsorbents were assessed using the Tanaka test for hydrophilic stationary phases and by studying the retention of substances of various classes in HILIC, chiral, and reversed-phase chromatography modes. It was shown that the use of eremomycin to create functional layers leads to an increase in the hydrophilicity of the adsorbents on different types of substrates and ensures the shielding of their charge. Eleven nitrogenous bases, nucleosides with an efficiency of up to 25 000 tp/m, or seven vitamins with an efficiency of up to 40 000 tp/m can be separated on a modified sorbent based on aminopropyl silica, and three different HPLC modes can be implemented on the sorbent with eremomycin based on PS–DVB.
The ultrasound-assisted extraction method for isolation of 17 sugars and sugar alcohols from conifers with a subsequent hydrophilic interaction liquid chromatography-tandem mass spectrometry method ...for their determination is proposed. The optimization of extraction parameters was carried out using Taguchi – L9 (34) orthogonal array experimental design for the following parameters—a methanol concentration in the extraction solution, an extraction time, a type of plant sample and an extraction temperature. The optimal ultrasound-assisted extraction conditions were—MeOH concentration – 30% (water – 70%), extraction time – 30 min, type of plant sample – II (grinded leaves 2–4 mm long), extraction temperature – 60 °C. Pure water and acetonitrile were used as eluents in gradient elution mode to separate the analytes. Direct determination of multiple sugars and sugar alcohols was carried out using a mass spectrometric detector operated in a multiple reaction monitoring mode, providing detection limits in the range between 0.1 and 20 ng/mL and good analytical characteristics of the method without derivatization. The developed approach was validated by multiple successive extraction method applied to test its performance on a series of 10 samples, i.e. 2 samples per each of 5 genera: Abies, Larix, Picea, Pinus (Pinaceae) and Juniperus (Cupressaceae), widely distributed in the boreal conifer forests of Eurasia. The novel strategy can be used for profiling of sugars and sugar alcohols in a wide range of plant species.
•Optimization & validation of HPLC-MS/MS method for sugars and polyols determination.•Sugars and polyols isolation from conifers by ultrasound assisted extraction.•Optimization of ultrasound assisted extraction parameters by orthogonal array design.•Method applicability was verified in the analysis of 5 conifers.
Adsorbents based on various substrates—silica and a copolymer of styrene with divinylbenzene—are developed for the determination of amino acids by hydrophilic interaction liquid chromatography—mass ...spectrometry. The optimal version of the structure of the functional layer in two series of the obtained stationary phases was chosen, which provides the best hydrophilization for each substrate. Retention mechanisms were studied and the conditions for the mass-spectrometric detection, separation, and determination of 16 amino acids were chosen. The applicability of the obtained adsorbents and a method for determining amino acids for the analysis of soil extracts were estimated.
New stationary phases for hydrophilic chromatography (HILIC) with functional layers formed by the multicomponent Ugi reaction have been obtained. Acetone, glycolic acid, ethyl isocyanacetate, and ...3‑aminopropyl silica, which also act as adsorbent matrices, were used as reaction components. The study of the effect of solvent on the reaction yield showed that a high degree of coverage of the matrix was achieved when the reaction was carried out in ethanol. The new adsorbents’ chromatographic properties compared with the initial matrix were assessed using the Tanaka tests for hydrophilic phases and by studying the retention of polar analytes from various classes. The synthesized adsorbents have demonstrated high efficiency and selectivity in separating model mixtures of sugars, amino acids, and water-soluble vitamins in the HILIC mode.
•Very simple sample pretreatment was developed.•Alkyl methylphosphonic acids unlike methylphosphonic acid did not react with p-bromophenacyl bromide under chosen conditions.•Low limits of detection ...(0.005–0.2ngmL−1) for methylphosphonic acid and alkyl methylphosphonic acids were achieved.•Developed approach was successfully applied to the real samples of dust and ground mixed samples from the territory of former chemical weapons plant
Once exposed to the environment organophosphate nerve agents readily degrade by rapid hydrolysis to the corresponding alkyl methylphosphonic acids which do not exist in nature. These alkyl methylphosphonic acids are finally slowly hydrolyzed to methylphosphonic acid. Methylphosphonic acid is the most stable hydrolysis product of organophosphate nerve agents, persisting in environment for a long time. A highly sensitive method of methylphosphonic acid and alkyl methylphosphonic acids detection in dust and ground mixed samples has been developed and validated. The fact that alkyl methylphosphonic acids unlike methylphosphonic acid did not react with p-bromophenacyl bromide under chosen conditions was discovered. This allowed simultaneous chromatographic separation and mass spectrometric detection of derivatized methylphosphonic acid and underivatized alkyl methylphosphonic acids using HILIC–MS/MS method. Very simple sample pretreatment with high recoveries for each analyte was developed. Methylphosphonic acid pre-column derivate and alkyl methylphosphonic acids were detected using tandem mass spectrometry with electrospray ionization after hydrophilic interaction liquid chromatography separation. The developed approach allows achieving ultra-low detection limits: 200pgmL−1 for methylphosphonic acid, 70pgmL−1 for ethyl methylphosphonic acid, 8pgmL−1 for i-propyl methylphosphonic acid, 8pgmL−1 for i-butyl methylphosphonic acid, 5pgmL−1 for pinacolyl methylphosphonic acid in the extracts of dust and ground mixed samples. This approach was successfully applied to the dust and ground mixed samples from decommissioned plant for the production of chemical weapons.
Eleutherococcus senticosus
is a plant with medicinal properties due to the presence of glycosides, called eleutherosides А, В and В
1
, C, D, E, and F, in its roots and rhizomes. In this paper, a ...procedure for the simultaneous determination of Eleutheroside B and Eleutheroside E in dry samples of
Eleutherococcus senticosus
roots from different manufactures by high performance liquid chromatography/tandem mass spectrometry was proposed. The quantification of eleutheroside B and eleutheroside E was performed using electrospray ionization in the negative ion mode with detection by multiple reaction monitoring (MRM), which ensured a better signal-to-noise ratio. To isolate eleutherosides from plant materials, simple and rapid methods of sample preparation were used, including extraction in an ultrasonic bath with various solvents. The calibration curve was linear in the concentration range from 40 to 4000 ng/mL.
The efficiency of the extraction of the terpene fraction from the greenery of common juniper (
Juniperus communis
L.) by sub- and supercritical extraction methods is compared with the efficiency of ...conventional methods. The effect of the extraction parameters on the qualitative composition of the extracts is studied. The components of the obtained extracts are identified by gas chromatography–mass spectrometry. It is determined that the studied extracts are similar in qualitative composition, but differ markedly in the quantitative ratio of groups of components. It is shown that monoterpenes are best extracted with butane under subcritical conditions and by hydrodistillation.
We proposed a method for determining the presence of trace amounts of adducts of isopropylmethylphosphonic acid (IMPA) and cyclohexylmethylphosphonic acid (CMPA), biomarkers of exposure to sarin and ...cyclosarin in a body, with a tripeptide (
Tyr-Thr-Lys
). The method is based on plasma trypsinolysis with the formation of stable adducts IMPA–
Tyr-Thr-Lys
and СMPA–
Tyr-Thr-Lys
and their detection by high-performance liquid chromatography (HPLC) with high-resolution tandem mass spectrometry detection. The following conditions for the sample preparation of human blood plasma exposed to sarin and cyclosarin were optimized: aliquot portion volume, enzymatic hydrolysis conditions, mass spectrometric detection (selection of optimal pairs of ion reactions and detection modes), and gradient elution programs in the HPLC separation of the test mixture. The limit of detection for sarin and cyclosarin in human blood plasma was 5 ng mL
–1
. The proposed approach was tested in the analysis of blood plasma samples submitted to analysis in the framework of the Fourth Official Biomedical Test of the Organization for the Prohibition of Chemical Weapons; the results showed good determination specificity.
Scutellariae baicalensis
is one of the most popular herb in the traditional Chinese medicine. It is used for the treatment of inflammatory process, hypertension, cardiovascular diseases, and also in ...the treatment of bacterial and virus infections because of such active components as wogonin, scutellarin, baicalin, and baicalein, which are contained in this herb
.
A sensitive and selective method of the simultaneous determination of these compounds in the extracts from plant raw materials using high-performance liquid chromatography–tandem mass spectrometry with electrospray ionization was developed. The proposed method has been successfully tested on commercially available samples of the
Scutellariae baicalensis
root
.
Analysis of samples was carried out using reversed-phase chromatography with an Acclaim RSLC C18 adsorbent. Using multiple reactions monitoring the following limits of detection were achieved: 1 ng/mL for wogonin and baicalin, 3 ng mL
–1
for scutellarin, and 4 ng mL
–1
for baicalein. It was found that the calibration curve was linear in the concentration range 20 ng mL
–1
and 2000 ng mL
–1
for scutellarin and 20 ng mL
–1
and 500 ng mL
–1
for wogonin, baicalin, and baicalein.
