Wavelength Monitoring Research Articles

A 100% Water Mobile Phase HPLC-PDA Analysis of Meamine and Related Analogues

This paper describes a reserved-phase high performance liquid chromatographic method for detecting melamine (MEL) and related analogues, cyanuric acid (CYA), ammeline (AML), and ammelide (AMD), using a 100% water mobile phase. Chromatographic separation was performed an Inertsil? ODS-4 (250 × 4.6 mm, 5 μm) with a water mobile phase and a photodiode-array detector. The monitoring wavelength was adjusted to 210 nm which represents an average maximum for all the analytes. The total run time was < 8 min. The method shows high stability, significant linearity and satisfactory sensitivity. The detection limits were established in the range 23 - 46 ng.mL–1. An inexpensive and harmless method for the simultaneous detection of MEL, CYA, AML, and AMD was developed and may be further applied to the quantification in foods.

Anatomical study of secondary tuberized roots of Harpagophytum procumbens DC and quantification of harpagoside by high-performance liquid chromatography method

Aim and Background:A botanical study is conducted to provide a standard diagnostic tool. In order to improve the quality assurance of the secondary tuberized roots of Harpagophytum procumbens, derived extract and phytomedicine, a simple, rapid, and accurate high-performance liquid chromatography (HPLC) method was developed to assess the harpagoside.Material and Mehods:This HPLC assay was performed on a reversedphase C18 column with methanol and water (50/50–V/V) as the mobile phase with a flow rate of 1.5 mL/min and using a monitoring wavelength at 278 nm.Results and Conclusion:This method was successfully applied to quantify these bioactive iridoid in an aqueous extract of H. procumbens and in its related phytomedicine “harpagophyton”. The result demonstrated that the quantification of harpagoside, indicating that the quality control of the bioactive ingredient in H. procumbens, derived extract and phytomedicine, is critical to ensure its clinical benefits.

Novel Chromatic Technique Based on Optical Absorbance in Characterizing Mineral Hydraulic Oil Degradation

A low cost, compact, real-time, and quick measurement optical device based on the absorbance of white light, which comprised of photodiodes in a 3-element color-sensor, feedback diodes, water and temperature sensing element, and so on, was developed and tested in low absorption mineral oil. The device, a deviation from conventional electrical, mechanical, and electrochemical techniques, uses color ratio (CR) and total contamination index (TCI) parameters based on transmitted light intensity in RGB wavelengths for oil condition monitoring. Test results showed that CR corroborated CIE chromaticity (- Coordinates) and increased with oil degradation unlike Saturation and Hue . CR was found to be independent of the particulate contaminants of oil, but dependent on chemical degradation. TCI depended on both chemical degradation and particulate contaminants in oil, being most sensitive in the blue wavelength range and least in the green. Furthermore, results agreed with those of viscometry, total acid number (TAN), and UV-VIS photospectrometry. CR and TCI gave clearer indication of oil degradation than key monitoring parameters like TAN and were found to be effective criteria for characterizing the degradation of hydraulic mineral oils.

Development and Validation of a Reversed-Phase Ultra-Performance Liquid Chromatographic Method for Assay of Lacidipine and Related Substances

A simple isocratic, RP-ultra-performance LC method was developed and validated for the determination of lacidipine, three process impurities formed during synthesis, and three degradation products present in drug substance and the drug product. An efficient chromatographic separation was achieved on an Acquity BEH C18 column using pH 4.5 ammonium acetate-acetic acid buffer-methanol (70 + 30, v/v) mobile phase. The monitoring wavelength was 240 nm, and the flow rate 0.25 mL/min. Forced degradation studies using acid, alkali, peroxide, water, heat, and light were conducted, and all impurities were separated. The method was validated successfully for specificity, precision, linearity, accuracy, LOD, LOQ, and robustness, according to International Conference on Harmonization guidelines. The linearity of the calibration curve for lacidipine and each impurity was found to be very good (r2 > 0.999). This method is shown to be suitable for analysis of lacidipine to evaluate the quality of drug substance and a drug product.

Preparation and Luminescence Properties of the Nano- Composite Materials LaF3 - SiO2: Eu3+

Eu3+doped LaF3-SiO2nano-composite material were synthesized by sol-gel method at room temperature, and the structure and properties were characterized by XRD, TG-DTA, IR, excitation and emission spectrum. The structure indicated that the optimal doping formula for preparing nano-materials was La5Si95that transformed into a stable mineral structure of cerium fluoride, and mainly found Si-O-Si bonds when the temperature was above 500 °C. Luminous property researches showed that the optimum annealing temperature was 500 °C. The best excitation wavelength was 395 nm when the monitoring wavelength was 612 nm, and the optimal doping molar concentration of Eu3+was 0.35 mol %.

A New Method for Preparation and Luminescence of YBO&lt;sub&gt;3&lt;/sub&gt; :Eu&lt;sup&gt;3&lt;/sup&gt;&lt;sup&gt;+&lt;/sup&gt; Phosphor

The pure phase red phosphor yttrium borate doped with Eu3+ was prepared by a new solid state reaction named high temperature ball milling method. The phosphor was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectra. The results show that the single phase YBO3:Eu3+ phosphor was obtained at 600°C, which is obviously decreased in contrast to conventional solid state reaction method. The particles are approximately nanometer size with narrow distribution range and spherical morphology. In emission spectra, the strongest peak at 597nm is due to the transition 5D0→7F1 of Eu3+ ions under 394nm monitoring wavelength. The luminescent properties of YBO3:Eu3+ phosphor with 25 mol% doping concentration of Eu3+ is optimal.

Application of high-performance liquid chromatography diode array detection and mass spectrometry to the analysis of characteristic compounds in various essential oils

A high-performance liquid chromatography (HPLC) method was established using an analytical reversed-phase column and gradient elution to achieve chromatographic separation of typical compounds in essential oils. For detection, a diode array detector monitoring different wavelengths simultaneously as well as a mass spectrometer (MS) were used. Atmospheric pressure chemical ionization operating in the positive mode turned out to be a suitable tool to detect volatiles of different chemical classes and to identify them in essential oil matrices. Characteristic fingerprints of eucalyptus, lavender, may chang, pine, rosemary, thyme, and turpentine essential oils monitored at a representative wavelength (220 nm) demonstrated the suitability of HPLC in essential oil analysis. Additional monitoring wavelengths (210, 250, and 280 nm) provided useful information about the identity of the specific component and opened the possibility to differentiate presumably coeluting compounds by means of their distinct absorption behavior. Finally, peak assignment in seven essential oils was performed on the basis of characteristic retention times and UV and MS data of a broad set of reference volatiles.

OES monitoring of sequential deposition of C/W layers by PECVD/magnetron sputtering techniques

An innovative sequential plasma deposition method suitable for deposition of carbon/metal nanocomposite or multilayer films is presented. The method is based on cyclic exposure of a substrate, for predefined time intervals, to two totally independent plasma deposition sources, working in alternative sequences: magnetron sputtering (MS) for metal deposition and Plasma Enhanced Chemical Vapor Deposition (PECVD) for hydrogenated amorphous carbon (a-C:H) deposition. This paper presents a study of the a-C:H/W nanocomposite deposition method by optical emission spectroscopy (OES), focusing on identifying the useful wavelengths for optical monitoring of the process. On the basis of optical monitoring, the optimal pumping out and precursor gas admission conditions are established.

Coherent control of the isomerization of retinal in bacteriorhodopsin in the high intensity regime

Coherent control protocols provide a direct experimental determination of the relative importance of quantum interference or phase relationships of coupled states along a selected pathway. These effects are most readily observed in the high intensity regime where the field amplitude is sufficient to overcome decoherence effects. The coherent response of retinal photoisomerization in bacteriorhodopsin to the phase of the photoexcitation pulses was examined at fluences of 10(15) - 2.5 × 10(16) photons per square centimeter, comparable to or higher than the saturation excitation level of the S(0) - S(1) retinal electronic transition. At moderate excitation levels of ∼6 × 10(15) photons/cm(2) (<100 GW/cm(2)), chirping the excitation pulses increases the all-trans to 13-cis isomerization yield by up to 16% relative to transform limited pulses. The reported results extend previous weak-field studies [Prokhorenko et al., Science 313, 1257 (2006)] and further illustrate that quantum coherence effects persist along the reaction coordinate in strong fields even for systems as complex as biological molecules. However, for higher excitation levels of ∼200 GW/cm(2), there is a dramatic change in photophysics that leads to multiphoton generated photoproducts unrelated to the target isomerization reaction channel and drastically changes the observed isomerization kinetics that appears, in particular, as a red shift of the transient spectra. These results explain the apparent contradictions of the work by Florean et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 10896 (2009)] in the high intensity regime. We are able to show that the difference in observations and interpretation is due to artifacts associated with additional multiphoton-induced photoproducts. At the proper monitoring wavelengths, coherent control in the high intensity regime is clearly observable. The present work highlights the importance of conducting coherent control experiments in the low intensity regime to access information on quantum interference effects along specific reaction coordinates.

Quantification of six bioactive compounds in Zhenqi Fuzheng preparation by high-performance liquid chromatography coupled with diode array detector and evaporative light scattering detector

A simple and accurate high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD) and evaporative light scattering detector (ELSD) was established for the determination of six bioactive compounds in Zhenqi Fuzheng preparation (ZFP). The monitoring wavelengths were 254, 275 and 328 nm. Under the optimum conditions, good separation was achieved, and the assay was fully validated in respect of precision, repeatability and accuracy. The proposed method was successfully applied to quantify the six ingredients in 31 batches of ZFP samples and evaluate the variation by hierarchical cluster analysis (HCA), which demonstrated significant variations on the content of these compounds in the samples from different manufacturers with different preparation procedures. The developed HPLC method can be used as a valid analytical method to evaluate the intrinsic quality of this preparation.

Kinetic Investigation of the Autocatalytic Reaction between Potassium Permanganate and Hydrogen Peroxide with Soft-modeling Methods

The complex autocatalytic reaction between potassium permanganate (KMnO(4)) and hydrogen peroxide (H(2)O(2)) was studied by online UV-Vis spectra methods. The kinetic profiles of the absorptive components, including KMnO(4) and two intermediates, were obtained by resolving the spectra-kinetic matrix with iterative target transformation factor analysis (ITTFA). But for the product Mn(II), which is not absorptive in the monitoring wavelength range, this was not applicable. Therefore, local mass balance region (LMBR) technique was proposed to get all of the scaled profiles, especially the non-absorptive components. Influences of various reaction conditions, such as concentrations of H(2)O(2) and sulfuric acid (H(2)SO(4)) and reaction temperatures, were also investigated. Contrary to most other reactions, when initial concentrations of hydrogen peroxide ([H(2)O(2)](0)) are largely excessive ([H(2)O(2)](0)/[KMnO(4)](0) >40), higher [H(2)O(2)](0) will decrease the degradation rate, while the higher temperature makes the reaction go much slower.

Characterisation and performance of a Terfenol-D coated femtosecond laser inscribed optical fibre Bragg sensor with a laser ablated microslot for the detection of static magnetic fields

We present a novel device for the characterisation of static magnetic fields through monitoring wavelength shifts of femtosecond inscribed fibre Bragg grating and micromachined slot, coated with Terfenol-D. The device was sensitive to static magnetic fields and can be used as a vectoral sensor for the detection of magnetic fields as low as 0.046 mT with a resolution of ± 0.3mT in transmission and ± 0.7mT in reflection. The use of a femtosecond laser to both inscribe the FBGs and micromachine the slot in a single stage prior to coating the device significantly simplifies the fabrication.

Quantification of protein concentration by the Bradford method in the presence of pharmaceutical polymers

We investigated how the Bradford assay for measurements of protein released from a drug formulation may be affected by a concomitant release of a pharmaceutical polymer used to formulate the protein delivery device. The main result is that polymer-caused perturbations of the Coomassie dye absorbance at the Bradford monitoring wavelength (595 nm) can be identified and corrected by recording absorption spectra in the region of 350–850 mm. The pharmaceutical polymers Carbopol and chitosan illustrate two potential types of perturbations in the Bradford assay, whereas the third polymer, hydroxypropylmethylcellulose (HPMC), acts as a nonperturbing control. Carbopol increases the apparent absorbance at 595 nm because the polymer aggregates at the low pH of the Bradford protocol, causing a turbidity contribution that can be corrected quantitatively at 595 nm by measuring the sample absorbance at 850 nm outside the dye absorption band. Chitosan is a cationic polymer under Bradford conditions and interacts directly with the anionic Coomassie dye and perturbs its absorption spectrum, including 595 nm. In this case, the Bradford method remains useful if the polymer concentration is known but should be used with caution in release studies where the polymer concentration may vary and needs to be measured independently.

Long-Lived Charge Separation in Gold Nanoparticles Encapsulated inside Cucurbit[7]uril and Its Relevance for Photocatalysis

Gold nanoparticles (average size 1 nm) encapsulated inside cucurbit[7]uril exhibit, upon 532 nm excitation in water, an intense transient absorption spectrum. The temporal profiles of the signals were different depending on the monitoring wavelength and extended beyond 1.2 ms. Quenching experiments using electron donors and acceptor molecules support that the transient spectra correspond to species arising from electron ejection from gold clusters to the solution. Photochemical generation of positive gold clusters has been advantageously used to effect the catalytic dimerization of phenylacetylene and to minimize the spurious decomposition of H2O2 promoted by Au@CB[7] in the dark.

M2-CYCLE: An optical layer algorithm for fast link failure detection in all-optical mesh networks

To achieve fast link failure detection in all-optical networks, monitoring-cycles (m-cycles) are introduced at the optical layer to reduce the number of required monitoring devices (or monitors). Each m-cycle is equipped with a monitor and a pair of optical transceivers to transmit an optical supervisory signal. A set of m-cycles can be found to form a cycle cover of the network. If a link fails, optical supervisory signals inside the m-cycles passing through this link will be disrupted, and the corresponding monitors will alarm due to Loss of Light (LoL). This gives an alarm code to localize the failed link. The accuracy of the failure localization is measured by localization degree, and the amount of monitoring resources required is measured by the number of cycles/monitors, cover length, and monitoring wavelength requirement. The best known m-cycle construction algorithm HST [11] adopts a spanning tree-based approach. In this paper, we propose a new algorithm M2-CYCLE to construct a cycle cover consisting of a set of minimum-length m-cycles (or m2-cycles). We prove that M2-CYCLE achieves the same localization degree as the spanning tree-based approach, but requires less amount of monitoring resources no matter how the spanning tree is generated. Numerical results confirm our theoretical analysis, and show that the monitoring resources required by M2-CYCLE are dramatically cut down.

ChemInform Abstract: The Detection of Ionic Intermediates During the Bromination of 5H- Dibenz(b,f)azepine-5-carboxamide in 1,2-Dichloroethane.

The bromination of 5H-dibenz[b,f]azepine-5-carboxamide (carbamazepine)(1) in 1,2-dichloroethane gives only the trans-dibromide 2. The reaction, followed spectrophotometrically, obeys a third-order rate law (second-order in Br2), but the value of k3 changes considerably depending on the monitoring wavelength. It is shown that this is due to the presence of reversibly formed Br3– salt intermediates, that make a more important contribution to the absorbance in the lower wavelength range of the monitored 360–540 nm region. A significant conductivity is also measured during the course of the bromination. Both spectrophotometric and conductimetric measurements are consistent with the presence of Br3– salt intermediates at a maximum concentration amounting to ca. 2% of that of the initial reagents. The structure of dibromide 2, determined by X-ray diffraction, shows a considerable angle strain at carbons bearing bromine. This strain is responsible for an easy spontaneous debromination of 2, as well as for a relatively high barrier for the formation of 2 from the bromonium–tribromide intermediate, that makes possible the accumulation of the intermediate itself during the bromination of 1.

A simple and sensitive HPLC fluorescence method for determination of tadalafil in mouse plasma

A simple and sensitive high-performance liquid chromatographic (HPLC) method utilizing fluorescence detection was developed for the determination of the phosphodiesterase type 5 inhibitor tadalafil in mouse plasma. This method utilizes a simple sample preparation (protein precipitation) with high recovery of tadalafil (∼98%), which eliminates the need for an internal standard. For constituent separation, the method utilized a monolithic C 18 column and a flow rate of 1.0 mL/min with a mobile phase gradient consisting of aqueous trifluoroacetic acid (0.1% TFA in deionized water pH 2.2, v/v) and acetonitrile. The method calibration was linear for tadalafil in mouse plasma from 100 to 2000 ng/mL ( r > 0.999) with a detection limit of approximately 40 ng/mL. Component fluorescence detection was achieved using an excitation wavelength of 275 nm with monitoring of the emission wavelength at 335 nm. The intra-day and inter-day precision (relative standard deviation, RSD) values for tadalafil in mouse plasma were less than 14%, and the accuracy (percent error) was within −14% of the nominal concentration. The method was utilized on mouse plasma samples from research evaluating the potential cardioprotective effects of tadalafil on mouse heart tissue exposed to doxorubicin, a chemotherapeutic drug with reported cardiotoxic effects.

Independence and inverted dependence on temperature of rates of photoinduced electron transfer in double-linked phthalocyanine-fullerene dyads

Photoinduced electron transfer reactions of phthalalocyanine-fullerene dyads, in which donor and acceptor moieties are covalently linked to each other, with one or two malonic linkers, were studied. In the dyads with two linkers, phthalocyanine and fullerene have mutual orientations, face-to-face or face-to-tail, which differ from each other and influence photoinduced electron transfer processes. Quantitative spectroscopic and time-resolved spectroscopic measurements were done in polar and non-polar solvents at room temperature and at several reduced temperatures. The emission spectra of the double-linked dyads were different from that of the reference phthalocyanine showing a shoulder at the red part of the spectrum, emission decays were two-exponential and emission lifetimes depend on monitoring wavelengths. These facts support, for the dyads with two linkers, the formation of an emissive intramolecular exciplex preceding the charge separated state. For these dyads the formation times of the charge separated state, approximately 0.4 ps and 0.8 ps for the face-to-face and face-to-tail isomers, respectively, were independent of temperature and the reaction is considered to be quantum tunneling in nature. The charge recombination times were temperature dependent, but decreased with the decrease of temperature from roughly 1.2 ns at room temperature to 0.7 ns at 190 K.

Simultaneous Determination of Seven Components in Qibaomeiran Pill by HPLC-DAD

A high-performance liquid chromatography coupled with photo diode array detection method is developed for simultaneous determination of seven active components in Qibaomeiran pill, including rutin, 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glycoside, ferulic acid, psoralen, isopsoralen, emodin, and physcion. The analysis is performed on a C(18) column using a mobile phase composed of A (0.1% acetic acid) and B (acetonitrile) with linear gradient elution. Four wavelengths at 245, 290, 320, and 350 nm were chosen as the monitoring wavelength to determine seven active components, respectively. All the compounds show good linearity (r > 0.999). The developed method is fully validated in respect to precision, repeatability, and accuracy. The proposed method is successfully applied to quantify the seven active components in different Qibaomeiran pill samples. The results indicate that the developed assay could be considered as a suitable quality control method for the Qibaomeiran pill.

Monitoring error compensation in general optical coatings

Error compensation in optical monitoring was demonstrated many years ago for narrow bandpass and edge filters. It is shown here that the compensation effects can apply to a broader range of more general coatings. This is illustrated with a very broadband antireflection coating design of 20 layers and a ramp design of 13 layers. The choice of monitoring wavelength and monitoring strategy are important, and suggestions are made concerning those choices. The results are derived from and demonstrated by computer simulations of the monitoring processes. The importance of monitoring directly on only one part and with one wavelength throughout the process in order to obtain the benefits of error compensation is emphasized.