Reactivities of Amino Acids and Proteins with Iodine
Erwin Regoeczi in Iodine-Labeled Plasma Proteins, 2019
A brief outline of the principle of the method is as follows. In analogy to the number of plates used in a column for fractional distillation, the efficiency of a chromatographic column can be described in terms of a “height equivalent to a theoretical plate” (HETP). The spreading of a sample during chromatography in a two-phase (liquid-liquid) system increases with plate height.496 Since the HETP is proportional to the square of the diameter of the particles used to hold the stationary liquid phase,497 a vast improvement in chromatographic resolution (the opposite to spreading) was achieved by the introduction of closely controlled microparticulate (3 to 10 μm) packing materials, mostly based on porous silica.498 The problem thus created for flow was overcome by high-pressure pumps. (There is an optimal flow rate in any chromatography, because diffusion from plate to plate gains in importance as the rate of flow decreases;497 slow flow therefore means an increase in HETP.)
Adulteration of Essential Oils
K. Hüsnü Can Başer, Gerhard Buchbauer in Handbook of Essential Oils, 2020
An even more elaborate technique recently developed not only cuts out one or several parts of the first GC column but virtually cuts the whole 1D chromatogram into small equal pieces (each several seconds long), refocuses each effluent, and separates it on a short second GC column within a very short time (several seconds). Refocusing, which here means stopping the effluent of the first column for several seconds onto a very small area and then releasing the focused substances into the second column, is done with a cryogenic modulator, and this procedure is repeated until all substances are eluted from the first GC column. The overall separation efficiency is calculated by multiplying the theoretical plate numbers of the two columns, which results in rather large figures and a separation efficiency, which cannot be achieved by simple GC alone. Instruments and the appropriate data acquisition software for this comprehensive 2D GC (or GC × GC) are now commercially available. Instead of a 1D chromatogram, a 2D contour plot is generated, and since the “half-widths” of substances are very small, detection must proceed very fast, so in case a mass spectrometer is used as a detector, a fast scanning quadrupole or a time-of-flight MS (TOF-MS) must be chosen. Such an instrument arrangement like GC × GC-TOF-MS leaves almost nothing to be desired for EO analysis (Marsili, 2010).
Current Perspectives and Methods for the Characterization of Natural Medicines
Rohit Dutt, Anil K. Sharma, Raj K. Keservani, Vandana Garg in Promising Drug Molecules of Natural Origin, 2020
High-performance liquid chromatography is also called HPLC. It is an advanced analytical technique over column chromatography. In this technique, the mobile phase is pumped with pressure through a stationary phase of the column which is packed irregularly shaped particles to speed up the analytical procedure. The solvent phase is pumped through a column with a pressure of, 1000–3000 psi. HPLC is effective techniques in the analysis of phytochemical and marine constituents. The approach speeds up the analysis over the traditional column. HPLC is carry small volume of liquid as a sample is injected into the column comprising porous particles (stationary phase). The particle size varies from 5–10 µM. When mixtures of compounds are passed into the column, components are isolated based on their interaction property between the sample and stationary phase by the movement of liquid. The separated components are detected by part of the HPLC device is called detector. Generally HPLC has two method of operation, based on their working principle employed on separation i) normal phase chromatography; and ii) reverse phase chromatography. Normally, chromatography techniques are working based on polar (hydrophilic) stationary phase and non-polar (hydrophobic)mobile phase. In HPLC, it is reverse phase functions, i.e., non-polar stationary phase and polar mobile phase. As many of the pharmaceuticals/drugs are polar in nature, reverse phase HPLC is mainly used in pharmaceutical industries. Based on the principle employed on elution, HPLC is classified into two different categories: (i) isocratic elution; and (ii) gradient elution. The polar component of the mobile phase is constant for isocratic elution. In contrast, the gradient elution pattern, the mobile phase is the reversed process of HPLC analysis. Gradient elution is reduced the retention time and therefore, the components are eluted faster. The approach improves the shape and height of the peak. Further, HPLC is classified into two different modes of operation: (i) analytical HPLC (the compounds are not recovered; (ii) preparative HPLC (the compounds are recovered). The instrumentation of HPLC includes a solvent reservoir, mixing vessel, pressure pump, guard column, a sample injector, column, detector, and collector. Retention time, retention volume, separation factor, resolution, height equivalent theoretical plate, efficiency, and asymmetry factor are the HPLC are employed to detects the components from the test sample. A schematic diagram of the instrumentation of high-performance liquid chromatography is illustrated in Figure 2.5.
Characterization and ex vivo evaluation of curcumin nanoethosomes for melanoma treatment
Published in Pharmaceutical Development and Technology, 2022
Rajesh Sreedharan Nair, Nashiru Billa, Lim Yang Mooi, Andrew P. Morris
At low, medium, and high curcumin concentrations, the system suitability parameters such as capacity factor, resolution, theoretical plates, peak symmetry, and signal to noise ratio (S/N) were determined. (Table 2). An excellent resolution above 2.0 and a capacity factor of >3.0 were seen for all the peaks corresponding to curcumin which satisfies the criteria for good separation. The theoretical plate number (n) was >13 000 for all the concentrations analysed. As expected, the S/N ratio increased as the concentration of the analyte increased. The tailing factor was found to be between 1.02 and 1.03. The accuracy of analysis decreases with the increase in peak tailing; a tailing factor close to 1.00 is considered optimal; however, a tailing factor of ˂2.0 is acceptable (ICH 2005).
Erzhi pills ameliorate cognitive dysfunction and alter proteomic hippocampus profiles induced by d -galactose and Aβ1–
40 injection in ovariectomized Alzheimer’s disease model rats
Published in Pharmaceutical Biology, 2021
Yongyan Xie, Bo Yan, Min Hou, Maofu Zhou, Chao Liu, Mengsheng Sun, Kun He, Cong Fang, Yaohui Chen, Liping Huang
High-performance liquid chromatography (HPLC) was used to detect the content of specnuezhenide in Erzhi pills in order to evaluate their quality. According to the Pharmacopoeia of China (2015), the content of specnuezhenide in qualified Erzhi pills is above 4.0 mg/g. Erzhi pills sample solution and specnuezhenide reference substance were prepared according to the Pharmacopoeia of China (2015). These solutions were filtered using a syringe filter (0.4 µm), and the filtrates were transferred to HPLC analysis. Samples were analyzed on Zorbax Eclipse XDB columns (4.6 × 150 mm2, 5 µm, Agilent, Santa Clara, CA, USA). The mobile phase consisted of methanol and water (36:64). Each sample (10 μL) was injected for analysis, and the profile was recorded at an ultraviolet detection wavelength of 224 nm. The theoretical plate number was not less than 7000, according to the peak of specnuezhenide. Three parallel experiments were performed for each sample, and three parallel injections were performed for each sample.
Optimization and validation of RP-HPLC method for simultaneous estimation of palbociclib and letrozole
Published in Toxicology Mechanisms and Methods, 2018
Yuvraj Dange, Somnath Bhinge, Vijay Salunkhe
The chromatographic systems used for analysis must pass the system suitability limits before sample analysis can commence (The United States Pharmacopoeia 2012). The tailing factor (T), theoretical plate number (N), retention time (RT) and Asymmetry factor (As) for the principle peak were evaluated using PB and LT of 10 mg mL−1. Typically, at least two of these criteria are required to demonstrate system suitability for the proposed method. Some of the tests were carried out on fresh standard solutions prepared including drug compounds. Tailing factors were 0.6660 ± 0.0171 for PB and 0.8273 ± 0.0157 for LT. The theoretical plate number (N) was 6469.67 ± 178.15 for PB and 43.69.00 ± 203.512 for LT, respectively. The chromatographic conditions described ensured adequate retention and asymmetry for drug compounds. The retention time of drug PB and LT were 3.3283 ± 0.0147 and 8.5266 ± 0.0186 min, respectively. Asymmetry factor was found to be 0.8627 ± 0.0180 for PB and 0.9498 ± 0.0366 for LT. The variation in retention time for six replicate injections of drug compounds gave %CV of 0.4422% for PB and 0.2183% for LT. The results obtained from the system suitability tests (Table 1) satisfy the USP and ICH standards (Q2A ICH guideline 2003; The United States Pharmacopoeia 2012).
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