Quantification of piperine in different varieties of Piper nigrum by a validated high-performance thin-layer chromatography‒densitometry method

JPC – Journal of Planar Chromatography – Modern TLC - Piperine is the most important alkaloid molecule present in Piper nigrum. In this study, a simple, rapid, quantitative...     

Quantification of flavan-3-ols and phenolic acids in milk-based food products by reversed-phase liquid chromatography–tandem mass spectrometry

This article reports the development and validation of a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the comprehensive quantification of flavan-3-ol and phenolic acid constituents of milk-based food products. Isotope dilution-based sample preparation consisted of protein precipitation using acidic methanol enriched with the stable isotope labelled internal standards and ultrafiltration to preserve overall polyphenol composition, but to eliminate milk proteins in order to comply with LC. Reversed-phase liquid chromatography was optimized to achieve separation of 22 analytes in 8 min in order to reduce suppression effects, achieve a wide dynamic range and, most importantly, to resolve isomeric compounds. Negative-ion electrospray mass spectrometric detection and fragmentation of analytes was optimized, final transitions were selected for maximized selectivity, reliable quantification and reduction of false positives. The quantitative performance of the method was validated, the main features include: (1) range of lower limits of detection 5–15 ng/mL for flavan-3-ols, 60–100 ng/mL for procyanidins, 1–60 ng/mL for other phenolic acids, (2) lower limits of quantification 15–45 ng/mL for flavan-3-ols, 200–300 ng/mL for procyanidins, 3–200 ng/mL for other phenolic acids, (3) averaged intra-day precision 9.5%, (4) calibrated range 60–300,000 ng/mL for flavan-3-ols, 900–900,000 ng/mL for procyanidins, 9–225,000 ng/mL for other phenolic acids, (5) averaged accuracy 99.5%. Applications for yoghurt and ice-cream products are given. The presented data suggest that this method will help to better characterize the polyphenol composition of milk-based food products for quality control, assessment of dietary intake and for polyphenol bioavailability/bioefficacy studies.     

Simultaneous quantitative profiling of 20 isoprostanoids from omega-3 and omega-6 polyunsaturated fatty acids by LC–MS/MS in various biological samples

Isoprostanoids are a group of non-enzymatic oxygenated metabolites of polyunsaturated fatty acids. It belongs to oxylipins group, which are important lipid mediators in biological processes, such as tissue repair, blood clotting, blood vessel permeability, inflammation and immunity regulation. Recently, isoprostanoids from eicosapentaenoic, docosahexaenoic, adrenic and α-linolenic namely F₃-isoprostanes, F₄-neuroprostanes, F₂-dihomo-isoprostanes and F₁-phytoprostanes, respectively have attracted attention because of their putative contribution to health. Since isoprostanoids are derived from different substrate of PUFAs and can have similar or opposing biological consequences, a total isoprostanoids profile is essential to understand the overall effect in the testing model. However, the concentration of most isoprostanoids range from picogram to nanogram, therefore a sensitive method to quantify 20 isoprostanoids simultaneously was formulated and measured by liquid chromatography-tandem mass spectrometry (LC–MS/MS). The lipid portion from various biological samples was extracted prior to LC–MS/MS evaluation. For all the isoprostanoids LOD and LOQ, and the method was validated on plasma samples for matrix effect, yield of extraction and reproducibility were determined. The methodology was further tested for the isoprostanoids profiles in brain and liver of LDLR^−/− mice with and without docosahexaenoic acid (DHA) supplementation. Our analysis showed similar levels of total F₂-isoprostanes and F₄-neuroprostanes in the liver and brain of non-supplemented LDLR^−/− mice. The distribution of different F₂-isoprostane isomers varied between tissues but not for F₄-neuroprostanes which were predominated by the 4(RS)-4-F_4t-neuroprostane isomer. DHA supplementation to LDLR^−/− mice concomitantly increased total F₄-neuroprostanes levels compared to F₂-isoprostanes but this effect was more pronounced in the liver than brain.     

Determination of dantrolene sodium in the presence of its process-related impurity by high-performance thin-layer chromatography—spectrodensitometry

JPC – Journal of Planar Chromatography – Modern TLC - Dantrolene sodium (DAN) is widely used as a muscle relaxant drug for the treatment of malignant hyperthermia....     

Effect of biochar on the mobility and photodegradation of metribuzin and metabolites in soil‒biochar thin-layer chromatography plates

Biochars obtained by biomass pyrolysis have been proposed as a soil amendment to improve soil properties and fertility as well as to retain pesticides and other environmental contaminants. The present study investigates the degradation of metribuzin herbicide and its metabolites deamino- (DA), deaminodiketo- (DADK) and diketo- (DK) metribuzin under simulated solar light and dark conditions as well as their mobility using TLC plates coated with soil and soil?biochar mixtures at 1% and 5% w/w ratio. Biochar was characterised by X-Ray diffraction, porosimetry, scanning electron microscopy and Fourier transform infrared spectroscopy. Degradation under light conditions followed biphasic kinetics, with bi-exponential model fitted better for the soil substrate, while the Gustafson–Holden model was found more appropriate to describe degradation kinetics in 1% soil/biochar mixture. In soil, DA presented the lowest degradation rate (DT₅₀:440.9 h), followed by metribuzin (DT₅₀:208.0 h), DADK (DT₅₀:110.8 h) and DK (DT₅₀:106.5 h). The addition of biochar reduced drastically the degradation or even inhibited the photolytic process for the studied reaction period. The mobility retention factor (Rf) in soil ranged from 0.49 for metribuzin to 0.63 for DADK. The addition of biochar practically immobilises the compounds in the surface layer as Rf ranged from 0.14 to 0.10 for metribuzin and from 0.23 to 0.16 for DADK in soil/biochar mixtures 1% and 5%, respectively. In conclusion, the addition of biochar reduced dramatically the photodegradation rates as well as the mobility of metribuzin and its metabolites due to increased adsorption.     

Quantification of organic acids in particulate matter by coupling of thermally assisted hydrolysis and methylation with thermodesorption-gas chromatography–mass spectrometry

A quantitative method for the determination of organic acids in atmospheric particles is developed. The method couples a derivatisation step (thermally assisted hydrolysis and methylation) and a Curie point pyrolyser as a thermal desorption technique and gas chromatography–mass spectrometry (CPP-GC–MS). Among the reagents tested (tetramethylammonium hydroxide (TMAH), tetramethylammonium acetate (TMAAc) and phenyltrimethylammonium hydroxide (TMPAH)), the best performance was found using TMAAc as a derivatisation reagent for the reaction time of 4 s at 510 °C as heating temperature. Calibration was performed for a series of fatty acids (FA), dicarboxylic acids (DCA) and terpenoic acids (TA) under these conditions. Coefficients of determination (R²) were between 0.94 and 0.98. Limits of detection (LOD) were in the nanogram-range between 0.1 and 3.6 ng. The method is applied on atmospheric particle samples to obtain the quantification reproducibility and quantification limits. Reproducibility was determined in terms of relative standard deviations (RSD) for ambient aerosol samples collected by a high-volume-sampler (HVS, RSD = 6–45%, n = 10) and a Berner impactor (BI, RSD = 5–34%, n = 10). Based on 24 h sampling time the developed method enables quantification of all three classes of acids for both sampling techniques. Calibration data and presented volume concentrations are compared with literature data. A comparison with an off-line methylation-GC–MS using BF₃ as a derivatisation reagent and capillary electrophoresis coupled mass spectrometry (CE-MS) showed a good agreement. Minimal sample preparation is the main advantage of the developed method. Depending on the sensitivity requirements the present method can be a fast and simple alternative to GC–MS techniques with conventional sample preparation steps for semi-volatile organic acids.     

Analysis of fatty acids in sputum from patients with pulmonary tuberculosis using gas chromatography–mass spectrometry preceded by solid-phase microextraction and post-derivatization on the fiber

A method based on solid-phase microextraction (SPME) and post-derivatization on the fiber coupled to gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of fatty acids in sputum from patients with pulmonary tuberculosis. The sputum specimens were digested, hydrolyzed, extracted, derivertized, injected and analyzed without cultivation or isolation of the microorganism. Under optimized conditions, the relative standard deviations (RSD, n = 5) for all analytes were below 17% and the limits of detection varied from 1.68 (C_24:0) to 150.4 μg L⁻¹ (C_12:0). Good linearity was observed for all the fatty acids studied except for C_12:0 within a wide concentration range of three orders of magnitudes with the correlation coefficients ranging from 0.91 (C_24:0) to 0.99 (C_14:0). Fatty acids in sputum specimens from 21 persons were directly analyzed using the proposed method. The results show that in all the sputum specimens from patients, who were clinically diagnosed with tuberculosis (TB), tuberculosis stearic acid (TBSA) was detected, while in all the sputum samples from persons without TB, TBSA was not found. The possibility of using the proposed method to detect mycobacterium tuberculosis (MTB) via the identification of TBSA in sputum was discussed. The comparison with other methods including sputum culture and microscopy of direct smears indicated that the proposed method is fast and sensitive for the analysis of fatty acids in sputum and offers an alternative for the detection of MTB in sputum.     

Detection of dimetridazole in pork by thin-layer chromatography and surface-enhanced Raman scattering spectroscopyEI北大核心CSCD

The thin-layer chromatography coupled with surface-enhanced Raman scattering spectroscopyTLC-SERSwas used to detect dimetridazole in pork. The diatomite was used as stationary phase to construct TLC plate. The mixture containing dimetridazole was directly spotted on the diatomite plate to realize TLC separation without complicated pre-treatment process. The ratio shift valueRf was determined after TLC separation. Au nanoparticles were dropped onto the corresponding position for SERS measurement. The sensitivity of dimetridazole could reach 10 μµmol/L and the detection limit was 4.16 mmol/Lwhich was lower than the maximum residue limit of dimetridazole in food. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Determination of trace volatile fatty acids in ambient air by capillary gas chromatography–mass spectrometry in SIM mode

A simple, rapid and sensitive method was developed and validated for the analysis of C₂–C₅ volatile fatty acids (VFAs) in ambient air. This method involves preconcentration of VFAs with a sodium carbonate-impregnated silica gel tube, ultrasonic extraction with pure water, partition of VFAs to diethyl ether and determination using gas chromatography with a mass selective detector in the selected ion monitoring mode. A water-resistant free fatty acid phase capillary column was used to directly separate C₂–C₅ VFAs without the time-consuming derivatisation process. The limits of detection ranged from 0.001 to 0.003 µg m^?3 and the limits of quantification ranged from 0.003 to 0.010 µg m^?3. The validated method was successfully applied to the analysis trace-level VFAs in ambient air and in air samples from a landfill with perceived odour pollution.     

Simultaneous quantification of vasicine and vasicinone in different parts of Justicia adhatoda using high-performance thin-layer chromatography‒densitometry: comparison of different extraction techniques and solvent systems

JPC – Journal of Planar Chromatography – Modern TLC - The present study was carried out for screening an efficient extraction method and extracting solvent in different plant parts of...     

Quantification of low molecular weight fatty acids in cave drip water and speleothems using HPLC-ESI-IT/MS — development and validation of a selective method

This study presents a novel method for the analysis of low molecular weight (LMW) fatty acids in cave drip water and speleothems. The method development included optimization of sample preparation procedures, e.g., blank reduction, solid phase extraction, concentration of extracts as well as liquid chromatography coupled to electrospray ion-trap mass spectrometry (HPLC-ESI-IT/MS) measurement parameters. Retention times for five analytes (lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid) were between 5 and 13.5 min. Spiking experiments were performed to accomplish external calibrations which ranged from 12.5 to 75 ng per spiked water sample. The correlation coefficient ranged from 0.9558 to 0.9989. Inter-batch precision, expressed as the relative standard deviation of three replicates, was <7 %. Limits of detection ranged from 0.77 to 55.97 ng for the diverse analytes; obtained recoveries varied from 30 to 103 %. For a first application, cave drip water and stalagmite samples from Herbstlabyrinth-Adventhöhle cave system were analyzed. Concentrations ranged from 38.37 to 9,982.54 ng L^?1 for water samples and 2.52 to 1,344.96 ng g^?1 for the stalagmite. Thereby, the different fatty acids showed a distinctive variation. Whereas shorter-chained fatty acids exhibited similarities, arachidic acid showed opposite trends. Diverse correlations were found, which could improve the understanding of different organic sources of the lipids transported by drip water and preserved in speleothems. This new method provides a more selective extraction process, particularly adjusted to LMW fatty acids and therefore reduces the required sample size. Furthermore, it is applicable to stalagmite as well as cave drip water samples.     

An isotope-labeled chemical derivatization method for the quantitation of short-chain fatty acids in human feces by liquid chromatography–tandem mass spectrometry

Short-chain fatty acids (SCFAs) are produced by anaerobic gut microbiota in the large bowel. Qualitative and quantitative measurements of SCFAs in the intestinal tract and the fecal samples are important to understand the complex interplay between diet, gut microbiota and host metabolism homeostasis. To develop a new LC-MS/MS method for sensitive and reliable analysis of SCFAs in human fecal samples, 3-nitrophenylhydrazine (3NPH) was employed for pre-analytical derivatization to convert ten C₂–C₆ SCFAs to their 3-nitrophenylhydrazones under a single set of optimized reaction conditions and without the need of reaction quenching. The derivatives showed excellent in-solution chemical stability. They were separated on a reversed-phase C₁₈ column and quantitated by negative-ion electrospray ionization – multiple-reaction monitoring (MRM)/MS. To achieve accurate quantitation, the stable isotope-labeled versions of the derivatives were synthesized in a single reaction vessel from ¹³C₆-3NPH, and were used as internal standard to compensate for the matrix effects in ESI. Method validation showed on-column limits of detection and quantitation over the range from low to high femtomoles for the ten SCFAs, and the intra-day and inter-day precision for determination of nine of the ten SCFAs in human fecal samples was ≤8.8% (n = 6). The quantitation accuracy ranged from 93.1% to 108.4% (CVs ≤ 4.6%, n = 6). This method was used to determine the SCFA concentrations and compositions in six human fecal samples. One of the six samples, which was collected from a clinically diagnosed type 2 diabetes patient showed a significantly high molar ratio of branch-chain SCFAs to straight-chain SCFAs than the others. In summary, this work provides a new LC-MS/MS method for precise and accurate quantitation of SCFAs in human feces.     

Fate of tris(2-chloroethyl)amine in water and alkaline environment determined by thin-layer chromatography and gas chromatography–mass spectrometry

Tris(2-chloroethyl)amine is a chemical warfare agent which is considered to be a persistent contaminant highly resistant to decontamination. The time dependence of tris(2-chloroethyl)amine degradation on the water pH value is observed to determine decontamination options using the decontamination of hydroxide-based mixtures which are used by a number of armed forces. The kinetics was observed using thin-layer chromatography and gas chromatography. The time development of tris(2-chloroethyl)amine concentration decrease in the environment with the pH ranging from 7.5 to 12.5 was recorded. The reaction rate constants were established at all observed pH values, half-lifes of reactions and the influence of temperature on the reaction rate at a slightly alkaline pH of 8.5. The equation to estimate the rate constant of the first step of tris(2-chloroethyl)amine hydrolysis at various temperatures was formed. The rate of triethanolamine formation in the samples of neutral to alkaline pH was recorded. The results indicate the substantial influence of pH on tris(2-chloroethyl)amine hydrolysis. The rate constant was significantly increased from a neutral environment to the pH of 12.5 reaching 500% of the original value using alkalisation. The hydrolysis in a neutral environment was also influenced by the analyte concentration. The concentrated solutions hydrolysed more slowly as a result of hydrochloric acid release as the acid lowered the pH value of the environment. The results demonstrate that there is an important kinetic difference between sulphur and nitrogen mustard hydrolysis in an alkaline environment.

     

Speciation analysis of arsenic in prenatal and children's dietary supplements using microwave-enhanced extraction and ion chromatography–inductively coupled plasma mass spectrometry

A study was conducted to develop a microwave-enhanced extraction method for the determination of arsenic species in prenatal and children's dietary supplements prepared from plant materials. The method was optimized by evaluating the efficiency of various solutions previously used to extract arsenic from the types of plant materials used in the dietary supplement formulations. A multivitamin standard reference material (NIST SRM 3280) and a prenatal supplement sample were analyzed in the method optimization. The identified optimum conditions were 0.25 g of sample, 5 mL of 0.3 mol L⁻¹ orthophosphoric acid (H₃PO₄) and microwave heating at 90 °C for 30 min. The extracted arsenic was speciated by cation exchange ion chromatography–inductively coupled plasma mass spectrometry (IC–ICP-MS). The method detection limit (MDL) for the arsenic species was in the range 2–8 ng g⁻¹. Ten widely consumed prenatal and children's dietary supplements were analyzed using the optimized protocol. The supplements were found to have total arsenic in the concentration range 59–531 ng g⁻¹. The extraction procedure recovered 61–92% of the arsenic from the supplements. All the supplementary products were found to contain arsenite (As³⁺) and dimethylarsinic acid (DMA). Arsenate (As⁵⁺) was found in two of the supplements, and an unknown specie of arsenic was detected in one product. The results of the analysis were validated using mass balance by comparing the sum of the extracted and non-extracted arsenic with the total concentration of the element in the corresponding samples.     

Analysis of dinitro- and amino-nitro-toluenesulfonic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A reversed-phase LC–MS method with quadrupole-time of flight (QTOF) detection has been developed for the determination of four dinitro-toluenesulfonic acids and two amino-nitro-toluenesulfonic acids in groundwater. The analytes were separated by HPLC with 0.1% (v/v) formic acid as mobile phase modifier compatible with mass spectrometric detection. QTOF-MS analysis with negative ion electrospray ionization afforded good selectivity and sensitivity for analysis of the dinitro- and amino-nitro-toluenesulfonic acids. Structure elucidation and confirmation were accomplished by tandem mass spectrometry. Characteristic ions resulting from the loss of NO, NO₂, and SO₂ from the [M–H]^– ions were detected. An intense fragment ion at m/z 80 representing the [SO₃]^– ion was detected for all dinitro- and amino-nitro-toluenesulfonic acids. Solid-phase extraction using a co-polymer cartridge was developed for preconcentration of the analytes from water. Good recovery (>85%) was achieved when 0.1% formic acid was added into the water samples before extraction. Method detection limits ranged from 10 to 76 ng L^–1 for the targeted compounds when 10 mL water was analyzed. Groundwater samples collected from wells close to a former ammunition plant in Stadtallendorf, Germany, were analyzed for the dinitro- and amino-nitro-toluenesulfonic acids.     

Systematization of the results of the chromatography–mass spectrometry identification of the products of quercetin oxidation by atmospheric oxygen in aqueous solutions

The coordination of the results of different works for the systematization of the structures of products previously detected in the complex samples is an important stage in the interpretation of the results of the identification of the components of complex samples of natural origin by chromatography–mass spectrometry with the low reproducibility of their mass spectra under the conditions of electrospray ionization and limited reference information. The data processing of this kind was carried out for the products of the oxidation of the most common natural flavonoid quercetin (3,5,7,3',4'-pentahydroxyflavone) by atmospheric oxygen in weakly alkaline aqueous alcohol solutions. For the correlation of peaks in chromatograms with the structures of oxidation products, their reversed-phase HPLC retention indices in the scale of reference n-alkyl phenyl ketones were determined for the first time. It was confirmed that not all of the oxidation products are stable in solution; some of them can accumulate or disappear during the storage of the samples.     

Solution chemistry in fused monochloroacetic acid—V: Solvolytic reactions of Lewis acids in monochloroacetic acid and the nature of the solvolysed products

Tetrachlorides of tin, titanium, zirconium, thorium and silicon form compounds of composition SnCl₂(CH₂ClCOO)₂, Ti(CH₂ClCOO)₄, Zr(CH₂ClCOO)₄, Th(CH₂ClCOO)₄ and Si₂O(CH₂ClCOO)₆ when refluxed with excess of monochloroacetic acid. From i.r., molecular weight and conductance studies, their structures have been elucidated. Their Lewis acid character is established by isolating and characterising their adducts with organic tertiary bases. Antimony pentachloride, aluminium trichloride and ferric chloride form compounds of composition SbCl₂(CH₂ClCOO)₃, Al(CH₂ClCOO)₃, FeCl(CH₂ClCOO)₂ and Fe(CH₂ClCOO)₃ when refluxed with excess of solvent and these have been characterised by i.r. studies.     

Determination of five nitrobenzoic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A method involving solid-phase extraction (SPE) and reversed-phase liquid chromatography–mass spectrometry (LC–MS) has been developed for determination, in groundwater, of nitrobenzoic acids associated with 2,4,6-trinitrotoluene production. Pre-concentration on a co-polymer-based SPE cartridge enabled quantitative extraction of the analytes from water. Investigation of negative ion electrospray and atmospheric-pressure chemical ionization mass spectrometry indicated the sensitivity of APCI was more than twice that of ESI. An ¹⁵N-labeled internal standard was used to achieve more accurate quantitation and mass assignment. Recovery was better than 80% when 10 mL water was extracted with the SPE cartridge. Combination of SPE with LC–MS analysis resulted in method detection limits of less than 5 μg L⁻¹. The method has been used for analysis of groundwater samples collected from a site of a former ammunition plant. Contamination with nitrobenzoic acids was determined at μg L⁻¹ levels.