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Greenhouse plastic contaminations in agricultural soils were studied to quantify and examine the macroplastic and microplastic contaminants on the soil surface, soil profile, and groundwater under greenhouse farmland. Random sampling was used to select three areas in a greenhouse farm where macroplastic and microplastic data were collected. Four composite samples were collected from shallow (0–20 cm) and deep (20–40 cm) soils for each sampling point, respectively. Three soil profiles were dug, and samples were collected at intervals of 20 cm. Groundwater samples were also collected from the same profiles at a depth of 100 cm. Microplastics were extracted using predigestion of organic matter with 30% H2O2 and density separation with ZnCl2. The total mass of macroplastics in the greenhouse farmland was 6.4 kg ha–1. Polyethylene and polyvinyl chloride were the dominant plastic structures, and the dominant sizes were 1–5 and 0.5–1.0 cm, respectively. Overall, the average abundance of microplastics in the greenhouse soil was 225 ± 61.69 pieces/kg, and the dominant size structure was 2–3 mm. The average microplastic concentrations at depths of 0–20 and 20–40 cm were 300 ± 93 and 150.0 ± 76.3 pieces/kg, respectively. The average microplastic concentration in the groundwater was 2.3 pieces/l, and fibers were the dominant plastic structure. Given that microplastics were found in greenhouse soil, soil profiles, and groundwater, we recommend the careful cleaning and disposal of plastics on greenhouse farmland and further research to shed light on the level of microplastic contamination in the soil profiles and groundwater.

Open access

Abstract

A precise, sensitive, specific and accurate stability indicating densitometric method was developed and validated for alpha-lipoic acid (ALA) in bulk and capsule dosage form. The study employed pre-coated silica gel 60F254 TLC plates as stationary phase and toluene: chloroform: methanol: formic acid (5:3:1:0.05; v/v/v/v) as mobile phase. The developed method furnished compact spots of alpha-lipoic acid (Rf 0.28 ± 0.05) after derivatization, offered good linearity in range 80–400 ng/spot with correlation coefficient of 0.998. The values for detection and quantitation were found 18.022 and 54.612 ng/spot respectively. ALA was subjected to stress degradation studies and total 13 degradation products were resolved. Thus, the proposed method offered good results according to ICH guidelines, and can be used for identification, routine quantitative determination as well as for monitoring the stability of ALA in bulk and in capsules.

Open access

Abstract

Modafinil has a strong and long-lasting awakening effect. Short-term use can improve cognitive and work efficiency. Therefore, it has been known to be abused by students and parents as a “smart drug.” It is in the first category of psychotropic drugs and strictly controlled. To detect modafinil in rat plasma and study the differences in the pharmacokinetics of modafinil between oral and sublingual administration in rats, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed. Rats were injected with modafinil by oral gavage and sublingual vein, respectively, blood was collected within a certain period, and the plasma was obtained by centrifugation. Midazolam was used as the internal standard, and the concentration of modafinil in the plasma was determined by UPLC-MS/MS, where a drug-time curve was created to calculate the pharmacokinetic parameters. The standard curve for modafinil ranged from 1 to 2000 ng mL−1 with good linearity. The intra-day accuracy of modafinil was between 86% and 104%, and the intra-day accuracy was between 90% and 103%. Intra-day precision (RSD%) was less than 15%, inter-day precision (RSD%) was less than 15%. The matrix effect was between 93% and 102%, and the recovery was greater than 91%. The UPLC-MS/MS method established in this work has good selectivity and high sensitivity, and the UPLC-MS/MS method was successfully applied to the pharmacokinetics of modafinil by oral gavage and sublingual injection in rats. The bioavailability of modafinil was calculated to be 55.8%.

Open access
Acta Chromatographica
Authors: Qishun Liang, Tianyu Chen, Lvqi Luo, Yizhe Ma, Congcong Wen, and Xueli Huang

Abstract

A UPLC-MS/MS method was developed to determinate curdione in the mouse blood, and the pharmacokinetics of curdione in mice after intravenous (5 mg kg−1) and oral (20 mg kg−1) administration were studied. The HSS T3 column was used for separation, and column temperature was set at 40 °C. Multiple reaction monitoring (MRM) mode were used for determination of curdione. Blood samples were taken from the caudal vein of Institute of Cancer Research (ICR) mice after administration of curdione. It showed a good linear relationship in the range of 1–500 ng mL−1 (r > 0.998); the intra-day precision was <13%, the inter-day precision was <15%, and the accuracy was 90%–105%, the recovery was >77%, and the matrix effect was 97%–107%. The half-life was relatively short, and the bioavailability was 6.5%. The developed method was suitable for the pharmacokinetics of curdione in mice.

Open access

Abstract

A rapid and simple ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method was developed and validated for simultaneous determination of six analytes from the Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves (ESL) in beagle dog plasma for the first time, including 3-O-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside-29-hydroxy oleanolic acid, 3-O-β-d-glucopyranosyl-(1→2)-α-l-arabinopyranoside-29-hydroxy oleanolic acid, 3-O-β-d-glucopyranosyl-(1→2)-α-l-arabinopyranosyl-30-norlean-12,20 (29) –dien-28-olic acid, ciwujianoside E, guaianin N, and eleutheroside K. The chromatographic separation was performed using an ACQUITY UPLC BEH C18 column (2.1 × 100 mm, 1.7 μm) using a gradient elution way with a mobile phase of acetonitrile-water containing 0.1% formic acid. Analytes were detected on a triple-quadrupole mass spectrometer equipped with an electrospray ionization (ESI) source with multiple reaction monitoring (MRM) mode. Calibration curves were all linear (r ≥ 0.9933) over the concentration range. The mean extraction recoveries and matrix effect of analytes and I.S. were ranged from 80.26% to 98.32% and from 91.27% to 111.67%, respectively. The intra-day and inter-day precision were ranged from 2.20% to 14.81%, and the accuracy range was 1.60–14.60%. The analytical method was successfully applied for the pharmacokinetic characteristics of the six analytes in beagle plasma after oral administration of ESL extracts. The T 1/2 of six analytes was more than 3.09 ± 0.78 h.

Open access

Abstract

Epilepsy is one of the most prevalent neurological conditions and antiepileptic drugs are the mainstay of epilepsy treatment. High variation in pharmacokinetic profiles of several antiepileptic drugs highlights the importance of therapeutic drug monitoring to estimate pharmacokinetic properties and consequently individualize drug posology. In this work, a simple, rapid and robust liquid chromatography-tandem mass spectrometry method was developed for simultaneous quantification of carbamazepine and its metabolite carbamazepine-10,11-epoxide, gabapentin, levetiracetam, lamotrigine, oxcarbazepine and its metabolite mono-hydroxy-derivative metabolite, phenytoin, topiramate, and valproic acid in human plasma for therapeutic drug monitoring. d 6-Levetiracetam, d 4-gabapentin and d 6-valproic acid were used as internal standards. After addition of internal standards along with two-step protein precipitation and dilution sample preparation, plasma samples were analyzed on a C18 column using a gradient elution in 5 min without interference. The calibration curves were linear over a 100-fold concentration range, with determination coefficients (r 2) greater than 0.99 for all analytes. The limit of quantification was 0.5 μg mL−1 (0.1 μg mL−1 for oxcarbazepine, 2 μg mL−1 for levetiracetam, and 10 μg mL−1 for valproic acid) with precision and accuracy ranging from 3% to 9% and from 94% to 112%, respectively. Intra- and inter-day precision and accuracy values were within 15% at low, medium and high quality control levels. No significant matrix effect was observed in the normal, hemolyzed, lipemic, and hyperbilirubin blood samples. This method was successfully used in the identification and quantitation of antiepileptic drugs in patients undergoing mono- or polytherapy for epilepsy.

Open access

Abstract

A rapid, selective, and precise high performance thin layer chromatographic method was developed and validated for the simultaneous analysis of paracetamol, caffeine, phenylephrine and chlorpheniramine in tablets. The chromatographic analysis was carried out on glass plates pre-coated with silica gel 60 F254 as a stationary phase. The optimized mobile phase was methanol : n-butanol : toluene : acetic acid (8:6:4:0.2 v/v). TLC chamber of 10 × 20 cm was used with saturation time of 15 min. The retardation factor (RF) for chlorpheniramine, phenylephrine, caffeine and paracetamol was found to be 0.15 ± 0.02, 0.29 ± 0.02, 0.50 ± 0.02, 0.68 ± 0.02 respectively. Detection was carried out at 212 nm. Validation study was done following ICH Q2 (R1) guideline. The regression data for the calibration plots showed good linear relationship with R 2 = 0.997 over the concentration range of 300–1,500 ng band−1 for caffeine, R 2 = 0.996 over the concentration range of 100–500 ng band−1 for phenylephrine, R 2 = 0.996 over the concentration range of 200–600 ng band−1 for chlorpheniramine, R 2 = 0.998 over the concentration range of 400–2,400 ng band−1 for paracetamol. The method was validated for precision, accuracy and recovery. Minimum detectable amounts were found to be 304.9 ng band−1, 87.88 ng band−1, 117.18 ng band−1 and 143.06 ng band−1 for caffeine, phenylephrine, chlorpheniramine, and paracetamol respectively while the limit of quantification was found to be 923.95 ng band−1, 266.32 ng band−1, 355.11 ng band−1, and 433.53 ng band−1 in the same order. The method was successfully applied to analyze two marketed tablets in a selective and reproducible manner.

Open access

Egy köles tájfajta műtrágya-reakciójának vizsgálata

Examination of the reaction to fertilization of regional millet variety

Agrokémia és Talajtan
Authors: Zsembeli Zsadány, Sinka Lúcia, Tüdősné Budai Júlia, Kovács Györgyi, Tuba Géza, and Zsembeli József

Kutatómunkák általános célja olyan kísérletek végzése, amelyek feltárják az adott régióban perspektivikusan termeszthető fajták, illetve tájfajták optimális műtrágyázási igényeit. Tanulmányunkban a Karcagon nemesített és fenntartott ’Maxi’ köles tájfajta tápanyagreakciójának vizsgálatából származó eredményeinket mutatjuk be a módosított Országos Műtrágyázási Tartamkísérlet (OMTK) 2017. évi és az annak figyelembevételével 2021-ben beállított Műtrágyázási Kísérleti Kert (MKK) adatai alapján. A kísérleteket Karcagon, a MATE Karcagi Kutatóintézetben, egy mélyben szolonyeces réti csernozjom talajon állítottuk be. 2017-ben a módosított OMTK kezelései 4 nitrogén (40, 80, 120, 160 kg ha 1), 4 foszfor (0, 40, 80, 100 kg ha 1) és 3 kálium (0, 60, 90 kg ha 1) dózis kombinációjából adódtak, illetve volt egy műtrágyázás nélküli abszolút kontroll. 2021-ben az MKK kezelései 3 nitrogén (40, 80, 120 kg ha 1), 3 foszfor (0, 40, 80 kg ha 1) és 2 kálium (0, 60 kg ha 1) dózis kombinációját foglalták magukba, illetve mindegyik parcella felére növénykondicionáló szert juttatunk ki. A termesztett növény mindkét évben a karcagi nemesítésű ’Maxi’ kölesfajta volt. A különböző kezeléscsoportok termésre gyakorolt hatásának statisztikai értékelését egytényezős varianciaanalízissel végeztük el. Mindkét vizsgálati évben a 80 kg ha 1 hatóanyag mennyiségben kijuttatott nitrogén műtrágyázás bizonyult a leginkább megfelelőnek. A magas foszfor dózisok a legtöbb esetben termésdepresszióhoz vezettek. Eredményeink alapján még a közepes – jó kálium ellátottságú karcagi talajokon is hasznos lehet a kálium kijuttatása, bár a káliumtrágyázás termésre gyakorolt hatását a varianciaanalízis nem igazolta. Az Algomel PUSH szerrel végzett növénykondicionálás statisztikailag is igazolhatóan, mintegy 10%-kal növelte a termés nagyságát. Kutatómunkánk folytatásával pontosabban meghatározható lesz számos tájfajta tápanyagreakciója és fajtaspecifikus, a helyi agroökológiai viszonyokat is figyelembe vevő tápanyag dózisok és kombinációk ajánlhatók a gazdálkodóknak.

The general objective of our research is to carry out experiments that are suitable to reveal the optimal fertilization demand of regionally bred or potentially producible crop varieties for a specific region. In our recent study, the results gained from the examination of the nutrient reaction of the regional millet variety ‘Maxi’ bred and maintained in Karcag are introduced based on the data originating from the modified Long-term National Fertilization Experiments (OMTK) in 2017 and from the Fertilization Experimental Garden (MKK) established at Karcag in 2021. Both experiments were set up in the MATE Research Institute of Karcag on a meadow chernozem soil salty in the deeper layers. In 2017, there were 4 nitrogen (40, 80, 120, 160 kg ha−1), 4 phosphorus (0, 40, 80, 100 kg ha−1), and 3 potassium (0, 60, 90 kg ha−1) dosage combinations applied and one unfertilized absolute control in the OMTK trial. In 2021, in the MKK experiment, treatments involved 3 nitrogen (40, 80, 120 kg ha−1), 3 phosphorus (0, 40, 80 kg ha−1), and 2 potassium (0, 60 kg ha−1) dosage combinations, furthermore, on half of the plots a plant conditioner was sprayed. Millet variety ‘Maxi’ bred at Karcag was the indicator crop in both years. For the statistical analysis of the effect of the various treatment groups on yields, One-way ANOVA tests were used. We considered the 80 kg ha−1 nitrogen substance dose the most suitable in both years. High dosage of phosphorus application resulted in yield depression in most of the cases. Based on our results, potassium fertilization can be effective even on the soils of Karcag with medium to good potassium supplies, though the analysis of variance did not justify the effect of K-fertilization on yields. The 10% yields increase due to plant conditioning with Algomel PUSH was statistically proven. By continuing or research, the reaction to fertilization of several regional crop varieties can be determined more precisely, and variety-specific nutrient doses and combinations can be determined and suggested to the local famers taking the regional agri-ecological conditions into consideration.

Open access
Acta Chromatographica
Authors: Hao-ran Dai, Ya-hui Hu, Jia-yi Long, Ying Xia, Hong-li Guo, Jing Xu, Xuan-sheng Ding, Jing Chen, Xiao-peng Lu, and Feng Chen

Abstract

Perampanel (PER) is the first clinically available selective antagonist of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor approved globally for the treatment of epilepsy. Studies have recently underlined the significant association between dose-exposure-effect-adverse events of PER in patients with epilepsy, so the therapeutic drug monitoring (TDM) of PER is critical in clinical practices, especially for pediatric patients with drug-resistant epilepsy. Due to several limits in previous published analytical methods, herein, we describe the development and validation of a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) method for monitoring PER in human plasma samples. Protein precipitation method by acetonitrile containing PER-d5 as internal standard was applied for the sample clean-up. Formic acid (FA, 0.2 mM) in both aqueous water and acetonitrile were used as the mobile phases and the analyte was separated by an isocratic elution. Qualification and quantification were performed under positive electrospray ionization (ESI) mode using the m/z 350.3 → 219.1 and 355.3 → 220.0 ions pairs transitions for PER and PER-d5, respectively. Potential co-medicated anti-seizure medications (ASMs) have no interference to the analysis. Calibration curves were linear in the concentration range of 1.00–2,000 ng mL−1 for PER. The intra- and inter-batch precision, accuracy, recovery, dilution integrity, and stability of the method were all within the acceptable criteria and no matrix effect or carryover was found. This method was then successfully implemented on the TDM of PER in Chinese children with drug-resistant epilepsy. We firstly confirmed the apparent inter- and intra-individual PER concentration variabilities and potential drug-drug interactions between PER and several concomitant ASMs occurred in Chinese pediatric patients, which were also in line with previous studies in patients of other race.

Open access

Abstract

Gluten-free (GF) breads are often described with low quality, rapidly staling, dry mouthfeel and crumbling texture attributes. In lack of recent texture profile data on commercially available, preservative-free, freshly-baked GF bread, this study aimed to compare different types of GF products with their wheat-based counterparts during a 4-day-long storage test. Texture analysis data showed that GF loaves performed better than or comparable to the wheat-based ones in hardness, springiness and cohesiveness. Among sensorial properties mouth-feel, softness and aroma were evaluated as significantly better or similar for GF versus wheat-based products. GF cob had a saltier taste, which reduced the flavour experience. Both the texture results of the storage test and sensory data showed that the quality of GF bread products improved in recent years; they stayed comparable with their wheat-based counterparts even during a 4-day-long storage period.

Open access

The selectivity of the separation of five antihistamines has been investigated by TLC on silica gel 60 F254 and on aluminium oxide 60 F254 with a variety of mobile phases in horizontal chambers. The best separation selectivity and retention differences for the drugs on the two types of plate were obtained with the mobile phases chloroform–ethyl acetate, 1 + 1 (v/v), ethyl acetate, and butan-2-one–toluene, 7 + 3 (v/v).

The plates were visualized by illumination at l = 254 nm and by reaction with different reagents. The greatest detection sensitivity – 0.06 mg for cetirizine, 0.1 mg for chloropyramine, and 0.2 mg for antazoline, doxylamine, and ketotifene – was obtained by spraying with potassium iodoplatinate reagent.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Alka J.M. Horvat, Jasenka Živko-Babić, Danijela Ivanković, Sandra Babić, and Marija Kaštelan-Macan

Knowledge of the composition of an incorporated alloy is a precondition for avoiding polymetallism in subsequent prosthetic treatment, or detection of the cause of an allergic reaction attributed to a metallic component of the prosthesis restoration. The method proposed in this paper can be a very useful means of determining the presence of Ni–Cr or Co–Cr dental alloys, and, especially, beryllium in Ni–Cr alloys which, despite its toxicity, gives the alloy desirable properties. Nickel is also a well-known allergen. This paper reports an analytical procedure for detection and identification of cobalt-and nickel-based dental alloy components. The method involves anodic sampling, and separation and identification of the components by thin-layer chromatography on precoated microcrystalline cellulose layers. Computer-assisted optimization was used to choose the mobile-phase composition. Excellent detection and identification of nickel, chromium, cobalt, molybdenum, and beryllium, on the basis of different RF values and spot colors, was achieved after anodic sampling in-situ.

Microanodic dissolution of dental alloys enables intra-oral, in-situ, and almost non-destructive sampling of a permanent prosthesis restoration.

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The object of this study was determination of the content and composition of the essential oil of the fruits of three varieties of stalk celery – Helios, Zefir, and Orient. We also investigated hexane extracts obtained from the fruits of two varieties of stalk celery – Helios and Zefir. The essential oils and the extracts were examined by TLC and GC–MS.

Analysis showed the presence of terpene (mono- and sesquiterpene) and non-terpene (phthalide) fractions in the oils and extracts investigated. The combined amount of limonene, α- and β-pinene and myrcene in the monoterpene fraction of the essential oils ranged from 79.1 to 82.9%. The amount of the sesquiterpene fraction (α-and β-selinene) was from 15.7% to 18.8%. The phthalide fraction (3-n-butylphthalide, dehydrosedanolide, and sedanolide) was found in trace amounts. The amounts of these fractions in the hexane extracts ranged from 40.2 to 43.6% for the monoterpene fraction, from 19.4 to 20.7% for the sesquiterpene fraction, and from 35.7 to 37.7% for the phthalide fraction.

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The conditions used for TLC and HPTLC analysis of catechins have been optimized. Chemically modified stationary phases (HPTLC CN, HPTLC NH2, and HPTLC RP-18W) were used for qualitative examination of polyphenol fractions obtained by an SPE–RP 18 method from Uncaria tomentosa bark. Although the best separation of catechin from epicatechin was achieved on octadecyl plates, silica gel plates are good enough for preliminary investigations of crude plant extracts.

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A high performance thin layer chromatographic method has been developed for the determination of idebenone in pharmaceutical preparations. The method uses silica gel 60 F254 as the stationary phase, toluene–diethyl ether–methanol–triethylamine, 4 + 4 + 1.5 + 0.5 (v/v) as mobile phase, and detection at λ = 279 nm, the wavelength of maximum absorption of idebenone. Diclofenac sodium was used as internal standard. The response was found to be linearly dependent on amount of idebenone between 100 and 1000 ng mL–1. The method was validated to determine its accuracy and precision and the repeatability of the method was also determined. System suitability tests were conducted to verify that the resolution and reproducibility of the chromatographic system are adequate for the analysis. The determination of idebenone in tablets is described.

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A quantitative instrumental high-performance thin-layer chromatographic (HPTLC) method has been developed for assessment of the photodegradation of bensulfuron-methyl on silica gel. The method uses automated band application on to silica gel plates with fluorescent indicator, direct development after irradiation, and scanning densitometry of fluorescence-quenched zones of samples and standards. The accuracy of the analyses was confirmed by performing recovery studies with preanalyzed samples and a blank sample fortified with the analytes. Precision was determined by analyzing samples in replicate; loaded amounts of 500–2000 ng per spot were suggested for assessing the photodegradation of the pesticides. The simplicity of sample preparation and the chromatographic techniques, high sample throughput, high reproducibility, and the strong possibility of separating the photoproducts seem to make the test on HPTLC plates highly suitable for estimation of the photodegradability of pesticides in the adsorbed state.

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Homologous series of higher fatty acids, higher alcohols, and methyl esters of higher fatty acids have been separated by RPTLC. The values of RM and of the log PRek partition coefficient from Rekker for the compounds of the homologous series could be correlated with numerical values of topological indexes based on the adjacency matrix (M, °χ, 1χ, °χν, 1χν), and on the distance matrix (W, A, °B,1B). The most accurate prediction of the RM and log PRek values of the compounds investigated was achieved by use of monoparametric equations containing one topological index based on the adjacency matrix.

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Two-dimensional thin layer chromatography of twelve flavonoids and three phenolic acids from Betula sp. leaves has been performed in normal-phase systems. Plots showing the dependence of RM on modifier concentration in some non-aqueous systems were used to optimize the chromatographic separation. RM values were correlated for all the chromatographic systems investigated and optimum pairs of systems were then selected for use in two-dimensional TLC separations. Complete separation of the compounds investigated was achieved by use of two optimum non-aqueous mobile phases on silica plates.

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The normal-phase (NP) and reversed-phase (RP) thin-layer chromatographic separations of aminoglycosides (streptomycin, kanamycin, gentamycin, and tobramycin) have been investigated on silica gel and C18 plates, respectively. The mobile phase acetone–2% sodium acetate–acetic acid–butanol, 7 + 6 + 4 + 1 (v/v) was successful for NPTLC and acetonitrile–5 mM sodium acetate buffer (pH 4.6) 4 + 18 (v/v) for RPTLC. The spots were located by use of iodine vapor. The minimum detection limits were in the range 0.4–0.6 μg. The method is a simple and direct approach for detection which does not require pre- or post-chromatographic derivatization.

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Complexes of hydroxy- and alkyloxytetraphenylporphyrins with Cu (II), Zn (II), and Ni (II) have been prepared and their chromatographic behavior in adsorption and partition thin-layer chromatography has been investigated. Gutman topological indexes, Mν, and the screening effect, SE, of the hydrocarbon chains on the electron pairs of the oxygen atoms of –OR groups have been calculated for the metalloporphyrin derivatives studied. The correlation between these and chromatographic retention, expressed as RM values, has been studied.

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Planar electrochromatography (PEC) is a mode of planar chromatography in which the mobile phase is driven by electroosmotic flow. The variables that affect the performance of PEC with an aqueous mobile phase on a bonded octadecylsilyl layer are discussed. These include the magnitude of the applied electric field, the concentration of the buffer salt, the pH of the mobile phase, and the concentration of acetonitrile used as the organic modifier. The effect of changing each of these variables is illustrated by model separations of a mixture of four compounds of diverse structure.

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Planar chromatographic methods thin-layer chromatography (TLC) and over-pressure thin-layer chromatography (OPLC) have been developed for the determination of pigments in plant leaves. Plants with variegated leaves, which sometimes contain both anthocyanins and chlorophyll, are a reasonable material for investigation. Multicolored Coleus, Prunus cerasifera, and Rhus hirta leaves were taken for quantitative determination of anthocyanins and chlorophyll. The separation of pigments from plant leaves, which depends on compound polarity was optimized by appropriate selection of mobile and stationary phases and chromatographic conditions.

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The chromatographic behavior of fullerene C60 has been studied on silica gel layers impregnated with solutions of glucose, sucrose, fructose, and dextrans of MW 20, 40, and 110 kDa, and with hexane as mobile phase. It was found that the RF of fullerene decreases as the concentration of impregnating solution is increased. The retention of fullerene C60 changes to a smaller extent when dextran solutions are used.

The solid-phase interaction of fullerene with the carbohydrates sucrose and dextran was studied by use of differential scanning calorimetry (DSC) and by NMR and UV-vis spectroscopy. The interaction with sucrose is greater than that with the dextrans.

Correlation was observed between the chromatographic behavior of C60 fullerene and the solid-phase interaction of the compound with carbohydrates.

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Carbohydrates have been examined by TLC on layers modified with metal ions, in the form of salts, by dipping commercial plates in methanolic solutions or by use of mobile phase additives; the mobile phases were mixtures of acetonitrile, propan-2-ol, or acetone with water or aqueous solutions of the metal salts. The effect on spot shape and retention of the identities and concentrations of the metal ions used for impregnation are discussed, and the selectivity of the different systems investigated are compared. The chromatographic properties of the adsorbents used were compared by consideration of the relationships between RM values measured on the different layers.

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In normal TLC practice, migration of the mobile phase through the layer is controlled by capillary forces. Under these conditions the velocity at which the solvent front moves is a function of the distance of the front from the solvent entry position, and this velocity declines as the distance increases. In this work we have proved that the velocity and migration distance of the mobile-phase front in porous media can be increased by application of an external electric field. We have called this displacement effect on liquids ‘dielectroosmotic flow’ (DEOF), because of its similarity with electrokinetic phenomena. Capillary tubes were used to enable understanding of the flow phenomena which occur in porous media.

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A stand-alone argentation TLC (Ag-TLC) procedure has been established for rapid estimation of the authenticity and densitometric quantitation of fatty acid groups in milk fats. The applicability of methyl (ME) and isopropyl (IPE) ester derivatives for accurate short-chain fatty acid analysis by Ag-TLC and GLC was compared and a correction coefficient compensating for loss of C4–C10 saturated fatty acids has been proposed. To check its accuracy and reproducibility the method was applied to model mixtures and to real margarine and butter samples. Low levels of trans fatty acids can be unequivocally detected and amounts down to 0.2% can be measured precisely. The method gives a good estimate of the diversity of isomeric fatty acids in the samples and when precautions are taken to avoid overloading, it provides reliable results with good accuracy.

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A simple and reliable HPTLC method has been developed and validated for the determination of dexamethasone (as the sodium phosphate salt) and xylometazoline (as the chloride). Assay of the compounds was performed on silica gel HPTLC plates with spherical particles by development with the mobile phase ethyl acetate–acetonitrile–diethylamine–water, 3 + 3 + 1 + 1 (v/v). A TLC scanner set at λ = 240 nm was used for direct evaluation of chromatograms in reflectance/absorbance mode. The validation data linearity (R > 0.996), precision (RSD = 1.67–2.77%), accuracy (recovery = 95.95–100.69%) and LOD and LOQ (ng levels) were determined and found to be satisfactory.

Assay of dexamethasone and xylometazoline in nasal drops was performed simultaneously with assay of preservatives such as methyl para-hydroxybenzoate. The effect of the most commonly used preservative, benzalkonium chloride on the concentrations of active substances was investigated; it was found that this compound led to a significant reduction of the dexamethasone sodium phosphate content of nasal drops.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Irina V. Marutsenko, Tatyana V. Polenova, Eduard D. Virus, Andrew G. Borzenko, and Igor A. Revelsky

A method developed for quantitative determination of the total amount of polyaromatic hydrocarbons (PAH) in human hair has been applied to the analysis of smokers’ hair. The procedure involves washing the hair with dichloromethane, acid decomposition of the hair matrix, micro-liquid extraction, and HPTLC determination of total PAH concentrations in the whole extract. The concentrations of PAH in human hair were in the range 0.005–0.3 μg g–1 hair.

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High-performance thin-layer chromatography (HPTLC) on silica plates, with two successive mobile phases, has been used for analysis of seven amine azo dye isomers prohibited under a German ban. Dichloromethane was used for the first development, to a distance of 4.5 cm. After drying, the second development was performed with toluene–tetrahydrofuran, 10 + 1 (v/v), to a distance of 8.5 cm. Spots were visualized at λ = 254 nm. Eighteen amines have been studied by use of the method. The limit of determination (X) and the correlation coefficient in the range X to 5X are reported for each amine. To increase the sensitivity of detection, the UV spectrum was acquired for each amine and the wavelength of maximum absorbance (λmax) was used to establish the limit of determination. Synthetic mixtures and dye samples have been resolved and quantified.

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This paper reports a recently developed technique, coupling of optimum-performance laminar chromatography (OPLC) with online radioactivity detection (OPLC–RD). Sample preparation for purification of urinary metabolites of a 14C-labeled drug candidate was performed on octadecyl-modified silica solid-phase extraction columns. Optimum-performance laminar chromatography was conducted on aluminum-backed silica gel layers with butanol– acetic acid–water as mobile phase. Eluate radioactivity was detected by use of a flow-cell radioactivity detector equipped with solid scintillator, and eluate fractions containing radioactivity were collected. Strongly retained radioactive components were detected off-line after development by use of digital autoradiography (DAR).

The isolated fractions containing metabolites were further purified by reversed-phase high-performance liquid chromatography coupled with radioactivity detection; this provided a second dimension for additional selectivity. Purified metabolite fractions were submitted to structure elucidation by spectroscopic methods.

The novel on-line optimum-performance layer chromatography with radioactivity detection, combined with high-performance liquid chromatography with radioactivity detection and digital autoradiography techniques, the advantages and disadvantages of which are discussed in detail in this paper, provides a rapid, effective, and economic tool which can be applied to advantage in metabolism research.

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In this paper we report our most recent experimental results relating to the thermal instability of selected alkyl chemically bonded stationary phases. The phenomenon of the thermal instability of such phases, as a result of their irradiation with a high-power neodymium laser, the light source of a Raman spectrometer, has been demonstrated in a series of our earlier publications. We even established a novel method of estimating the density of coverage of the silica matrix with alkyl ligands by utilizing the thermal instability of the phases discussed. The mechanism of the thermal transformation of alkyl chemically bonded ligands remained rather obscure, however, vague speculations only were made about the possible aromatization of these ligands.

In this paper we provide additional experimental evidence in support of our earlier hypothesis about possible aromatization of alkyl ligands on the surface of the acidic/basic silica matrix under the influence of high temperature. This evidence was obtained by use of instrumental techniques such as Raman spectroscopy, differential scanning calorimetry (DSC), and UV absorption spectroscopy. Although all these techniques supply indirect evidence only, the results reported furnish a convincing confirmation of our earlier intuitions.

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The effect of cold-stress (2°C, 7 days cold-hardening) on the level of polyamines in different varieties of wheat and genetically modified wheat samples (chromosome substitution lines, deletion lines, recombinant lines) has been investigated. Biogenic amines (spermine, spermidine, putrescine, and agmatine) were determined as the dansyl derivatives by stepwise gradient elution with the Personal OPLC BS 50 Chromatograph. Short-term cold-hardening caused characteristic changes in free polyamine content of wheat genotypes. The total free polyamine content was significantly lower in the cold-hardened samples than in the control samples. It seems that accumulation of spermine and agmatine might be good markers of cold sensitivity.

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A quantitative thin layer chromatographic (TLC) method on silica gel, with ethyl acetate–acetone–alcohol, 62 + 40 + 3 (v/v) as mobile phase, has been developed for the determination of olaquindox at ppm levels in animal feed. Preliminary purification consists of extraction with water, adsorption on XAD-4, washing, and elution with acetonitrile. Before the elution step acetylolaquindox is added as internal standard. The residue obtained after evaporation of acetonitrile is dissolved in a small volume of methanol. Quantitation is performed by densitometry at λ = 360 nm.

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Abstract

A modified QuEChERS method using a GC-ECD to determine the multiple residues of pyraclostrobin, difenoconazole, dimethomorph and azoxystrobin and to indirectly determine the total residues of maneb, mancozeb and propineb by a GC-FPD (with an S filter) was established and validated. Meanwhile, field trials were conducted in accordance with good agricultural practice (GAP) to study their characteristics of residue degradation under the agricultural climate and cropping system of Guangxi Province. The separation effect of each target peak was good with a linearity range of 0.01–5 mg L−1, a limit of detection (LOD) of 0.003–0.015 mg kg−1 and a limit of quantification (LOQ) of 0.01–0.05 mg kg−1. The average recovery ranges of vegetable tomatoes and cherry tomatoes were 70.5–120.0% and 70.8–119.8%, respectively, with relative standard deviations (RSDs) of less than 7.1%. Field trials of seven fungicides in vegetable and cherry tomatoes showed that the half-lives (t 1/2) of the dithiocarbamate fungicides (metiram, mancozeb, and propineb, defined as total residues determined as CS2), pyraclostrobin, difenoconazole, dimethomorph, and azoxystrobin were in the ranges of 5.2, 12.7–17.8, 7.6–7.9, 6.6–6.9, and 6.3–6.6 d in vegetable tomatoes, respectively. The cherry tomatoes presented ranges of 4.3–4.5, 10.8–11.8, 6.7–7.0, 5.4–5.5, and 5.9–6.2 d, respectively. Combined with the final residue and market monitoring results, the results show that cherry tomatoes have significantly higher terminal residues, initial deposits, and maximum residues of seven fungicides than vegetable tomatoes, and these seven pesticides can be detected in cherry tomatoes purchased from three markets. Therefore, cherry tomatoes may be regarded as representative varieties of tomatoes in realizing residual extrapolation for the establishment of the maximum residue limit (MRL) value of fungicides in tomatoes and for conducting market monitoring.

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The chromatographic behavior of six macrocyclic antibiotics (erythromycin, troleandomycin, tylosin, vancomycin, rifamycin B, and rifampicin) has been examined on Polyamide 11F254 TLC plates as stationary phase with five binary solvent mixtures (methanol–water, ethanol–water, propanol–water, acetonitrile–water, and tetrahydrofuran–water) as mobile phases in which the concentration of the organic modifier was from 0 to 100% (v/v). Chromatographic retention data and a possible retention mechanism are discussed.

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The retention behavior of twenty-four alkaloids has been investigated in normal-phase systems on thin layers of aminopropylsilica and bare silica developed with a variety of binary mobile phases prepared from n-hexane and polar modifiers – 2-propanol, ethyl acetate, methyl ethyl ketone, tetrahydrofuran, dioxane – in different concentrations. The retention factors obtained were fitted to the logarithmic Snyder–Soczewiński equation; the results are presented as the equation parameters and the statistical coefficients which prove the goodness of fit of the results with the displacement theory of retention.

The retention behavior of the alkaloids was also investigated in reversed-phase systems with buffered aqueous–acetonitrile mobile phases (pH 9.15) and the cyanopropyl- and octadecylsilica as stationary phases. Retention factors obtained for use of different concentrations of acetonitrile in the mobile phase were fitted to the semi-logarithmic equation or to quadratic polynomial equation selected for RP systems and are also presented as equation parameters and statistical coefficients which prove the goodness of fit of the results obtained with the theories derived for RP systems.

Separation selectivity was presented as the RF spectrum for the aminopropyl phase, comparing the separation selectivity obtained by use of different mobile phases, and as RF1 vs RF2 correlation diagrams for different systems, enabling selection of the most selective systems for separation of particular pairs or groups of alkaloids. Such correlation diagrams are presented for the aminopropyl phase and silica with four non-aqueous mobile phases and also for CN-silica and C18 phases, and for CN-silica and diol phases with aqueous mobile phases.

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The thin-layer chromatography of eighteen anions has been performed on silica layers with mixed aqueous–organic mobile phases. Binary mobile phases consisting of distilled water and acetone or acetonitrile were found suitable for resolving hexacyanoferrate(II) from hexacyanoferrate(III) or thiocyanate whereas ternary solvent systems consisting of distilled water, carbon tetrachloride, and acetonitrile was found most suitable for separating ternary mixtures of hexacyanoferrate(II), hexacyanoferrate(III), and thiocyanate. Distilled water–acetonitrile–carbon tetrachloride, 10 + 80 + 5, was the best mobile phase for separation of three-component mixtures of these anions in the presence of heavy metal cations and amino acids. The proposed method works well for the separation of Fe(CN)64–, Fe(CN)63–, and SCN from industrial waste water, saline water, hard water and fixer and bleach samples.

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Combined technology for the synthesis, separation, screening, and analysis of combinatorial libraries is described. The technique enables a rapid route from synthesis to the testing of chemical compounds. Chemistry can be rapidly optimized and vital information obtained by testing by-products and reagents simultaneously if desired. Screening can be performed without need for reaction work-up and without the need for undesired chemical manipulation, or further handling. Emphasis has been given to bioautographical/agar overlay screening methods for the testing of antimicrobial agents.

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Abstract

There has been a lively interest on macrocyclic polyamine alkaloids due to their remarkable pharmacological activities such as anti-tumor, anti-inflammatory, anti-Alzheimer's disease and anti-parasitic. Tripterygium wilfordii is a widely used traditional Chinese medicine, which is abundant in alkaloids including macrocyclic polyamine alkaloids. However, there are rarely studies on macrocyclic spermidine alkaloids of T. wilfordii so far. In this article, we use three known macrocyclic spermidine alkaloids celafurine, celabenzine and celacinnine, and successfully develop a simple and sensitive HPLC method for simultaneous quantification of macrocyclic spermidine alkaloids in root, stem and leaf of T. wilfordii.

Open access

Abstract

β-sitosterol (BS) and lupeol (LU) exhibit a number of biological activities and are the important bioactive marker compounds in pharmaceutical science. In the present study, a simple, precise, accurate and validated high performance thin layer chromatographic (HPTLC) method was developed for simultaneous quantification of these two compounds in leaves, stem and roots of Uraria picta, a critically endangered medicinal plant and one of the important constituents of ten plants ayurvedic formulation called Dashmoola. Standards and test samples were applied on TLC aluminum plate precoated with 0.2 mm layer of silica gel 60F254. The plate was run in a twin glass chamber comprising toluene: methanol: chloroform (8:1:1, v/v/v) as a mobile phase. The plates were immersed in anisaldehyde-sulfuric reagent and then heated at 105 °C for 5 min in CAMAG TLC plate heater for appearance of bands. Densitometric scanning was performed at λ max = 525 nm using tungsten light source in CAMAG TLC Scanner4 armed with WinCATS software. R F values of BS and LU standards and those of test samples were found to be 0.53 ± 0.01 and 0.63 ± 0.01 respectively. The method was further validated by following the International Conference of Harmonization (ICH) guidelines. For BS and LU, the linear regression data for the calibration plots revealed a satisfactory linear association with r 2 = 0.995 and 0.998, respectively. Linear range for both BS and LU was 200–600 ng/band. Accuracy of the method was evaluated by performing recovery study at three different levels by standard addition methods with an average recovery of 99.86% and 101.07%. The results revealed that the leaf samples of U. picta contained highest concentration of BS (0.150 ± 0.02%) while its root samples confined the highest concentration of LU (0.149 ± 0.01%). The developed method can be applied for routine and quality control analysis in different herbal formulations containing U. picta species.

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A new simple, precise, rapid, and selective high–performance thin-layer chromatography (HPTLC) method has been developed for the analysis of finasteride in pharmaceutical formulations. The method uses loratadine as an internal standard. The stationary phase was silica gel 60F254 prewashed with methanol; chloroform–ethyl acetate, 6 + 4 (v/v) was used as mobile phase. Detection and quantification were performed densitometrically at λ = 228 nm. The linear range of the analysis was 0.2–2.0 μg and the percentage recovery was 101.8%.

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A high-performance thin-layer chromatographic method with densitometric detection has been used to determine the convallatoxine content of extracts from the various parts (flowers, leaves, and underground parts such as the rhizomes and buds on the rhizomes) of the plant. Plant extracts were separated on thin layers of silica gel Si 60F254 by multiple gradient development. The convallatoxine content was determined by densitometry and the results were evaluated statistically.

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This review covers the use of topological indexes based on the adjacency and distance matrixes to predict the RF and RM values, and the physicochemical properties, of a variety of groups of organic compounds investigated by TLC. This review indicates that further investigations on the application of the topological indexes in TLC are justifiable.

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