There is no doubt that high-performance thin-layer chromatography (HPTLC) can be applied as a quantitative method if the technique is properly used. Densitometry is a commonly used detection mode for quantitation in HPTLC. The influence of instrumental settings on signal intensity, peak resolution, and peak positioning was rarely described in literature. Especially, quantitation of adjacent substance zones was critical when improper combinations of these settings merge. Future trends regarding ultrathin-layer chromatography and hyphenation to scanning or imaging mass spectrometry required the consideration of these delicate points. The influence of different instrumental settings on the obtained signal intensities was demonstrated for four separated parabens (each 150 ng band−1). The maximum mean signal deviations of all four compounds were 6.9% by the optical system, 16.8% by the scan slit dimension, 7.5% by the scan speed, and 1.5% by the data resolution. The influence of these settings on the quantitation of three parabens in two skin protection creams was investigated. Depending on the selected settings, deviations of the calculated substance amount of up to 5.6% were yielded, whereby determination coefficients of the polynomial calibration curves (60–300 ng band−1) varied between 0.9985 and 0.9999. The setting of integration markers between two adjacent peaks was demonstrated to be deficient if low spatial data resolution is applied; however, this challenging task will rise in interest due to the trend towards miniaturization.
Authors:T. Fukumoto, P. S. Thomas, B. H. Stuart, P. Simon, G. Adam, R. Shimmon, and J.-P. Guerbois
solutions were prepared from NaOH pellets (97%, Ajax Finechem, Australia).
Synthesis of DMU
DMU was synthesised according to a method described in the literature [ 13 ]. A sodium phosphate buffer with pH 8 was prepared by
Authors:Miha Vivoda, Robert Roškar, and Vojko Kmetec
development of a suitable method which could be compared to previous literature data [ 14 , 15 ] and nifedipine was chosen as its amorphicity/crystallinity properties are of prime importance for its performance and pharmacological use. The amorphous lactose
Authors:Pankajkumar B. Nariya, Vinay J. Shukla, Rabinarayan Acharya, and Mukeshkumar B. Nariya
The aim of this study was to isolate and identify three biologically active flavonoids, quercetin, kaempferol, and apigenin, from the hydrolyzed methanolic extract of three indigenous medicinal Cordia species, i.e., Cordia macleodii, Cordia dichotoma, and Cordia rothi barks using preparative thin-layer chromatography (TLC) and high-performance (HP)TLC methods. The isolation of flavonoid fraction was accomplished by preparative TLC method using reference standard. For achieving good separation, a mobile phase of toluene–ethyl acetate–GAA–formic acid (5:5:0.5:1) was used. The ultraviolet (UV)-based densitometry determination was carried out at 254 nm in reflection—absorption mode. The antioxidant compounds in the samples were screened through 2,2-diphenyl-1-picrylhydrazyl (DPPH) derivatization method. The method was partially validated in terms of linearity, specificity, and sensitivity. All three standards showed good linearity in the range of 2500–7500 ng with respect to area. Limit of detection (LOD) and limit of quantitation (LOQ) for quercetin were 9.4 and 28 ng; for apigenin, 30 and 92 ng; and for kaempferol, 57 and 173 ng. From the analysis, quercetin (0.21%) and kaempferol (0.19%) in C. rothi and apigenin (0.28%) in C. dichotoma were found to be the highest. The isolation and identification of these flavonoids have not yet been found in the literature and they are reported in this study for first time. From this, it is concluded that planar chromatography has a potential as a rapid and simple tool for the identification and quantification of phytochemicals in complex mixtures and marker-based samples.
Authors:Eva Kranjc, Alen Albreht, Irena Vovk, Vesna Glavnik, and Damjan Makuc
High-performance thin-layer chromatography (HPTLC) is a powerful separation technique which is often overlooked. In this study, we comprehensively assessed the applicability, ease, and performance of HPTLC in combination with densitometry and mass spectrometry (MS) to characterize physalins — relatively polar secondary metabolites from Physalis alkekengi L. HPTLC silica gel plates were evaluated in combination with 14 developing solvents (13 published in the literature). Bonded stationary phases (HPTLC RP-18, RP-18 W, CN F254S) were also tested. Four detection reagents (sulfuric acid, anisaldehyde, 4-dimethylaminocinnamaldehyde (DMACA), and molybdatophosphoric acid) were compared to ascertain which one is the most suitable. For all chromatographic analyses, a commercial standard physalin L and a P. alkekengi L. crude extract were used. In some cases, physalin L standard appeared as two clearly resolved bands on silica plates, but only after derivatization, where sulfuric acid reagent provided the best selectivity and sensitivity. Physalin L standard impurity was found to belong to the physalin family as confirmed by HPTLC–MS/(MS) and nuclear magnetic resonance (NMR) spectroscopy. Compared to high-performance liquid chromatography (HPLC), our HPTLC method showed extremely high sensitivity for standard impurity (ca. 4% determined by NMR) as it was clearly visible on the plate during image analysis after derivatization. Unlike (ultra)-high-performance liquid chromatography ((U)HPLC), HPTLC was also able to separate physalin L standard from its impurity. We show that (HP)TLC is a suitable chromatographic technique for the analysis of physalins and can even surpass the performance of (U)HPLC, namely, due to a wide array of different developing solvents available.
Authors:Sudharshan Sekar, Surianarayanan Mahadevan, Sathish Sundar Dhilip Kumar, and Asit Baran Mandal
is found out. Table 3 lists the biokinetic parameters for five different glucose concentrations. It may be noted that the parameters are within the range reported in the literature [ 10 ].
onset in the Ni + Zr + PTFE mixture coincides with PTFE decomposition (about 500 °C). Note, that thermal decomposition onset of PTFE was reported to be at 500–600 °C [ 18 , 19 ]. According to the literature data [ 19 – 21 ] at inert atmosphere, the
Authors:S. Materazzi, S. Vecchio, L. W. Wo, and Curtis S. De Angelis
the literature [ 23 ], the synthesis and the thermoanalytical study of bis(1-methylimidazl-2yl)ketone(BIK) complexes with divalent manganese having a general formula Mn(BIK) 2 X 2 are reported (X = Cl, Br, NO 3 , or ClO 4 ). The thermal stability and