UV-Vis Spectrophotometric Analysis

Nanofibers were characterized by UV-Vis spectroscopy. The composite nanofibers were dissolved in DMF, which were PVAc, P0.25, P0.50, P0.75, PI.00, PI.25, and PI.50 (details of compositions are given in Section 4.3.1]. 

As the amount of the PEDOT-PSS increases, absorbance also increases (Fig. 5.14). These results additionally imply that the PEDOT-PSS uniformly incorporated as a composite in the fiber. 

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While the control resins were deep red in color due to the presence of soluble porphyrin complexes, the methacrylate resins obtained after removal of the polyethylene-supported catalysts varied from light yellow to nearly water-white (APHA < 25). UV-Vis spectrophotometric analysis of the yellow resins indicated an absorption signal for the cobalt porphyrin complex Soret band (wavelength of cobalt(ll) porphyrin species appears at -415 nm free porphyrin ligand is formd at -423 tun). Resin samples that visttally appear as water-white show little or no porphyrin species present in the spectrum. Measured catalyst activity and PDl of the polyethylene-supported porphyrin complexes are in the expected range for soluble porphyrin CCT catalysts (PDl = M /Mn - 1.2- 2.0)." The screening resrrlts clearly... 

The high electron density existing inside the CD cavity can grip the electrons of the encapsulated guest molecules, and result in a various spectral properties of both the guest and host [61]. This effect of CDs on the spectral properties of guest molecules has led to their utilization in various spectrometric analyses, such as UV/VIS spectrophotometric analysis, fluorescence and luminescence spectroscopy and NMR spectroscopy. 

Products were characterized by Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), ultraviolet visible (UV-Vis) spectrophotometry, scanning electron microscopy (SEM), and broadband dielectric/impedance spectroscopy (BDS). New absorption bands were observed corresponding to the conjugated pol5mieric units by FTIR-ATR and UV-Vis spectrophotometric analysis. The influence of concentration of PEDOT-PSS and PEDOT on the composite electrospun nanofibers was studied by EIS. Morphologies of electrospun nanofibers were also investigated by SEM. 

Characterization of Synthesized PEDOT in PVAc Matrix by FTIR-ATR, UV-Vis Spectrophotometric Analysis... 

The UV-vis spectrophotometric methods require validation of the method for the analysis of pharmaceutical compounds. Once the method is developed, data regarding precision, accuracy, linear response behavior, limit of quantitation, limit of detection, selectivity, and ruggedness are generated. These terms are very well-defined in many compendial monographs and in ICH, USP, and FDA guidelines. These are not addressed further. However, it should be emphasized that without appropriate validation data and reasonable understanding of how the method results will be affected by minor day-to-day variation of experimental parameters, routine generation of acceptable data may be difficult. 

For the last several years, mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) have determined the trends in the analysis of dyes. Since 1987, various variants of ESI have been used in which droplet formation was assisted by compressed air,[1,2] temperature (e.g. Turbo Ion Spray ) or ultrasound, and they were able to handle flow rates up to 1 2 ml min This made a combination of analytical RPLC and ESI easily and widely used. The reason why it often was (and is) used instead of a traditional UV-Vis detector is the better sensitivity and selectivity of MS in comparison with spectrophotometric detection. Apart from these advantages, MS offers easily interpretable structural information. However, various... 

Although considered a basic technique, ultraviolet-visible (UV-vis) is perhaps the most widely used spectrophotometric technique for the quantitative analysis of pure chemical substances such as APIs in pharmaceutical analysis. For pharmaceutical dosage forms that do not present significant matrix interference, quantitative UV-vis measurements may also be made directly.114,115 It is estimated that UV-vis-based methods account for 10% of pharmacopoeia assays of drug substances and formulated products.116... 

A prevailing problem with neuroactive steroid analysis by HPLC is the lack of sufficient chromaphores or fluorophores within their chemical structures to allow suitable spectrophotometric end-point detection such as with UV/VIS or fluorescence with adequate sensitivity. The multitude of structural isomers of the metabolites also decreases the applicability of RP-HPLC since the chromatographic profiles become very complex with co-eluting peaks. Due to these inherent problems, it is often necessary to derivatize this group of compounds prior to chromatographic separation and suitable end-point detection to allow their direct determination at physiological concentrations. 

In the first spectrophotometric method [22] the measurements were carried out using an Agilent 8453 model UV-Vis spectrophotometer with a DAD. The spectra were recorded from 225 to 475 nm. The quantitative analysis were performed at 376 nm for the zero-order derivative UV spectrophotometric method by measuring the height of the peak from zero and at 302 nm, and 281 nm for the first-order derivative UV... 

Although TLC-MS (mass spectrometry) has been shown to be technically feasible and applicable to a variety of problems, thin-layer chromatography is generally coupled with spectrophotometric methods for quantitative analysis of enantiomers. Optical quantitation can be achieved by in situ densitometry by measurement of UV-vis absorption, fluorescence or fluorescence quenching, or after exctraction of solutes from the scraped layer. The evaluation of detection limits for separated enantiomers is essential because precise determinations of trace levels of a d- or L-en-antiomer in an excess of the other become more and more important. Detection limits as low as 0.1% of an enantiomer in the other have been obtained. 

A significant amount of literature regarding the antioxidant properties of flavonoids and other plant polyphenols is available. As the essence of redox chemistry involves electron transfer, it seems natural that electrochemical detection rivals spectrophotometric detection techniques for the compounds that are supposed to be antioxidants. With the improvements in electrochemical detector geometries and electronics over the last decade, coupled with a requirement for increased sensitivity, the use of electrochemical detectors offers significant additional advantages when combined with the traditional UV-VIS detection in the analysis of flavonoids and other plant polyphenols. ... 

Nowadays, spectrophotometry is regarded as an instrumental technique, based on the measurement of the absorption of electromagnetic radiation in the ultraviolet (UV, 200-380 nm), visible (VIS, 380-780 nm), and near infrared region. Inorganic analysis uses UV-VIS spectrophotometry. The UV region is used mostly in the analysis of organic compounds. Irrespective of their usefulness in quantitative analysis, spectrophotometric methods have also been utilized in fundamental studies. They are applied, for example, in the determination of the composition of chemical compounds, dissociation constants of acids and bases, or stability constants of complex compounds. 

Nprgaard L, Ridder C, Spectrophotometric determination of mixtures of 2-, 3-, and 4-hydroxyben-zaldehydes by flow injection analysis and UV/VIS photodiodearray detector, Talanta, 1994, 41, 59-66. 

The ionization properties of rifamycins have been used in conjimction with UV-VIS spectrophotometry to obtain information on flie chromophoric part of flie molecule and as a quantitative mefliod of analysis. The pK values for rifampin have been determined spectrophotometrically and potentiometrically in solution in water and are reported in the table. Rifampin exists in water solution as the zwitterion with isoelectric point equal to 4.8."... 

During the process, color changes from colorless to light yellow and yellow-brown indicating the formation of silver nanoparticles. After the process, the samples were subjected to spectrophotometric analysis. UV-Vis spectra are shown in Figure 12.3. The peak at 400—450 nm corresponds to the characteristic surface plasmon resonance of silver nanoparticles. Table 12.1 presents the results of nanoparticle size analysis. 

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