UV Light Conditions Research Articles

Photocatalytic Degradation Characteristics of Organic Compound by Boron-doped TiO2 Catalysts

Boron-doped TiO₂ photocatalysts were synthesized by a modified sol-gel method and their photocatalytic activities were performed and compared with those of pure synthetic and commercial TiO₂ catalysts under UV or visible light conditions. Pure TiO₂ itself exhibited very negligible photocatalytic performance under visible light conditions in the aspects of toluene decomposition reactions, although significant decomposition potential was observed as expected with UV light conditions. However, boron doping over TiO₂ significantly improved photocatalytic activity particularly under visible conditions, where over 95% degradation of toluene was achieved with 1wt% B-TiO₂ within 2 hrs. All the decomposition reactions seemed to follow pseudo firstorder kinetics. The effects of boron-doping and its characteristics are further discussed through the kinetic studies and comparison of results.

Effect of nanoliposomes on the stabilization of incorporated retinol

Nanoliposomes containing retinol were prepared, and the stability of the incorporated retinol was evaluated. Average particle size of nanoliposomes was 98 nm. Retinol was readily incorporated into nanoliposomes with incorporation efficiencies higher than 99%. The bare retinol in the buffer was almost degraded within 2 days of storage, while at least, over 20% of the initial retinol in nanoliposomes was kept until 8 days in all experimental conditions tested. The incorporated retinol in nanoliposomes was more rapidly degraded as temperature increases under both dark and UV light condition during the whole period of storage, and UV light slightly decreased the stability of retinol in nanoliposomes. Key words : Retinol, nanoliposome, stability.

Stability‐indicating ultra‐performance liquid chromatography method for the estimation of thymoquinone and its application in biopharmaceutical studies

Thymoquinone (THQ) is known for its neuroprotective and anti-convulsant properties in preclinical studies. We herewith describe a simple, rapid, selective, sensitive and stability-indicating UPLC method for the estimation of THQ and its application to biopharmaceutical studies such as in vitro release from nanoparticulate system and in vivo pharmacokinetic study. The method employed gradient elution using a Waters Acquity HSS-T3 C(18) (100 × 2.1 mm, 1.8 µm) UPLC column. The mobile phase consisted of water and acetonitrile, pumped at a flow rate of 0.5 mL/min. The injection volume was 5 µL and THQ was monitored at 294 nm wavelength with a total run time of 6 min. In solution as well as in plasma, the method was found to be linear (r ≥ 0.998), precise (CV ≤ 2.45%) and accurate (recovery ≥ 84.8%) in the selected concentration range of 0.1-0.8 µg/mL. Forced degradation studies revealed that THQ undergoes degradation under acidic, basic, oxidation and UV light stress conditions. However, the developed UPLC method could effectively resolve degradation product peaks from THQ. Further, no interference was found at the retention time of THQ from any plasma components, indicating selectivity of the developed method. For solutions, the limits of detection and quantitation of the method were found to be 0.001 and 0.0033 µg/mL, respectively; while in plasma they were 0.006 and 0.02 µg/mL, respectively. The validated method was successfully applied to quantify THQ in dissolution medium as well as oral in vivo pharmacokinetic study of THQ suspension and THQ- solid lipid nanoparticle (THQ-SLN) formulation. A 2-fold increase in the relative bioavailability was observed with the THQ-SLN compared with THQ. The results indicate that the SLN significantly increased plasma concentrations and retention within the systemic circulation.

Solid State Photodegradation Study of Fexofenadine Hydrochloride

The photodegradation of solid-state fexofenadine hydrochloride, H1 receptor antagonist, was investigated under UV light conditions as per option 2 of ICH photostability testing guidelines. The amount of drug remaining intact after photodegradation was estimated using a newly developed and validated HPTLC method employing ethyl acetate: methanol: ammonia (30%) as a mobile phase in proportion of (6:3.5:0.5v/v/v). In solid state, after 1800watt.hrs/m2 of UV light illumination, fexofenadine hydrochloride concentration was reduced to 57% following a first-order kinetic with t1/2 of 2221.5watt.hrs/m2 and a degradation rate constant (k) of 3.12(watt.hrs/m2)−1. The results indicate that fexofenadine hydrochloride should be protected from light.

Development and Validation of a Stability-Indicating HPLC Method for Determination of Voriconazole and Its Related Substances

An isocratic reversed-phase high performance liquid chromatographic (RP-HPLC) method has been developed and validated for the determination of voriconazole and its related substances. The drug substance was subjected to stress conditions of UV light, water hydrolysis, acid, base, oxidation, and deoxidization to observe the degradation products. The successful separation of voriconazole from its synthetic impurities and degradation products formed under stress conditions was achieved using an Agilent Zorbax SB-C18 (250mm x 4.6 mm i.d., 5 microm) column maintained at 25 degrees C with a mobile phase of a mixture of ammonium phosphate dibasic buffer (pH adjusted to 6.0 using diluted orthophosphoric acid; 50 mM)-acetonitrile (52:48, v/v). The mobile phase flow rate was 1.0 mL/min, and the detection wavelength was 250 nm. The stress sample solutions were assayed against the qualified reference standard of voriconazole and the mass balance in each case was close to 99.7%, confirming its stability-indication capacity. The developed HPLC method was validated with respect to linearity, accuracy, precision, specificity, and robustness. The developed HPLC method to determine the related substances and assay determination of voriconazole can be used to evaluate the quality of regular production samples. It can be also used to test the stability samples of voriconazole.

Naturally occurring esterification reactions with bryostatin

Bryostatin structures share a commonality of a central bryophan ring, but each differs due to two groups (R 1 and R 2) that are attached to the bryophan ring via ester bonds. This research examines the impact that conditions such as UV light, acidic and basic conditions can have on the bryostatin structure in the presence of octanoic acid and water. Mass spectrometry (MS) measurements suggest that bryostatin can easily rearrange into various structures under natural conditions by reacting with carboxylates that are ubiquitous in nature. A second set of measurements suggest bryostatin can be hydrolyzed by water, a reaction that has significant implications in both medicinal applications and extraction procedures.

Polymerization of a boronate-functionalized fluorophore by double transesterification: applications to fluorescence detection of hydrogen peroxide vapor

The double transesterification polymerization of 3′,6′-bis(pinacolatoboron)fluoran and pentaerythritol is reported. A model dimeric compound was synthesized to demonstrate the effectiveness of bis-diols to undergo a double transesterification, which is driven by formation of the energetically favored six-membered di-ester ring from a monomer containing a five-membered di-ester ring. This synthetic procedure provides a new route to boronate based polymers, avoiding unstable boronic acid monomers. Formation of poly-3′,6′-bis(1,3,2-dioxaborinane)fluoran, with a molecular weight of 10 000, is complete after 48 h at 50 °C. The thermodynamic stability of the six-membered boronic ester rings present in the polymer backbone also improves the stability of the polymer and its resistance to oxidation under ambient and UV light conditions. A surface detection method for the analysis of H2O2 vapor by a fluorescence turn-on response was explored. The fluorescent response results from oxidative deprotection of the boronate functionalities forming green luminescent fluorescein. Detection limits as low as 3 ppb were observed for H2O2 over an 8 h period. Detection of H2O2 in liquids can also be carried out through spot tests at concentrations as low as 1 ppm after 5 min. This new vapor-phase sensor for H2O2 provides a robust, low-cost alternative to current technology for potential applications as a self-integrating sensor for the detection of H2O2 as well as the direct monitoring of H2O2 levels in areas such as cargo shipments, chemical facilities, and pulp bleaching.

Treatment of wastewater containing Cu(II)-EDTA using immobilized TiO2/solar light

The photocatalytic oxidation (PCO) of Cu(II)-ethylene diamine tetra-acetic acid (EDTA), employing immobilized TiO2, under natural sunlight rather than artificial UV light conditions, was investigated at a latitude 38°. The immobilized TiO2 film was prepared using a sol gel process, the crystalline structure of which was identified, by X-ray diffraction analysis, as a mixture of the rutile and anatase forms. The PCO of Cu(II)-EDTA was examined in a circulating reactor with 20 L of 10− 4 M Cu(II)-EDTA and synthetic and real wastewaters at pH 4 and 6.5, respectively. The removals of both Cu(II) and DOC were initially relatively rapid, but slowed as the reaction proceeded and generally followed first-order kinetics. The rate constants for the removal of Cu(II) and DOC were 1.1 × 10− 3 and 1.6 × 10− 3 min− 1, respectively. The efficiency of the PCO in the decomplexation of Cu(II)-EDTA increased with increasing H2O2 dose using both the synthetic and real wastewaters. Therefore, we suggest the PCO process using the solar/immobilized TiO2 system, with addition of H2O2 as well as filtration for the removal of suspended solids, can be effectively applied to the treatment of Cu(II)-EDTA containing real wastewater.

Studies on the degradation of blue gel pen dyes by ion-pairing high performance liquid chromatography and electrospray tandem mass spectrometry

Ion-pairing high performance liquid chromatography (IP-HPLC) was utilized to monitor the composition changes of blue gel pen ink entries on paper stored in different light conditions and natural environment. The chromatographic conditions were optimized by comparing the separation efficiencies of the blue gel pen inks using a series of ion-pairing reagents, including ammonium carbonate, ammonium acetate, triethylamine acetate, tributylamine acetate, tetrabutylammonium bromide and dihexylammonium acetate. It has been found that tributylamine acetate was a suitable ion-pairing reagent for separation of the inks on the common C 18 column. The analysis results of the ink entries on paper in different aging conditions showed that the tendency of composition change in natural aging condition was similar with those in fluorescent light and UV light conditions, respectively. One main component dye of the blue gel pen ink, Acid Blue 9, and its degradation products were identified by ion-pairing high performance liquid chromatography coupled with electrospray tandem mass spectrometry. The results showed that the main degradation products originated from the Acid Blue 9. It gave a reasonable explanation for the changing rules of the relative content of the dyes in the blue gel pen ink. The results obtained can provide scientific evidences for dating of the blue gel pen ink entries on documents.

Modeling of an external light irradiation slurry photoreactor: UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II with natural mineral tourmaline powder

A model for design and scale-up of an external light irradiation slurry photoreactor was developed on the basis of a model for the average light intensity in the photoreactor. In order to assess the design parameters in the proposed model, experiments for UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II in water with iron ion eluted from the natural mineral tourmaline powder containing 4.49 wt% Fe 2O 3 were conducted using an external light irradiation cylindrical column photoreactor. The efficiency of discoloration increased as initial Orange II concentration decreased and the tourmaline concentration and UV light intensity increased. It was found that the optimal hydrogen peroxide concentration and pH are 500 mg L - 1 and 3, respectively. The proposed model, in which the change of light intensity with degradation time due to the discoloration of Orange II and the light scatter due to solid photocatalysts are taken into account, could simulate the experimental results both for UV light and sunlight irradiation conditions reasonably well. The model is applicable commonly both for UV light and sunlight irradiation. The results will be very useful for designing slurry photoreactors in the treatment of textile effluents.

Influence of PET and PET/PEN Blend Packaging on Ascorbic Acid and Color in Juices Exposed to Fluorescent and UV Light

ABSTRACT: Apple and orange juices packed in polyester bottles were stored in dark, intense fluorescent (1500 lux), and UV light conditions in temperature-controlled (22 °C) chambers and monitored more than 7 mo for ascorbic acid content and color changes. Polyester beverage bottles were made of polyethylene terephthalate (PET), or PET blended with 0.25%, 1%, and 4% polyethylene naphthalate (PEN). The cut-off wavelength ranged from 322 nm for PET to 373 nm for the 4% PEN/PET blend. Spectral irradiance, visible light intensity, and light distribution were evaluated in the light chambers and compared with supermarket display lighting and outdoor daylight conditions. Only the UV chamber and sunlight showed significant irradiance at wavelengths below 400 nm. Ascorbic acid (AA) degradation and concurrent color changes occurred in both juices during storage in all 3 lighting conditions and in all 4 bottle types. Zero-order reaction kinetics described the AA degradation rate for all treatments. Apple juice stored in UV had a significantly higher (P < 0.05) AA degradation rate than juice stored in the dark or in fluorescent light. Under UV conditions, apple juice in PET/ PEN bottles had a lower AA degradation rate than the juice in PET bottles. AA degradation in orange juice was less affected by UV exposure than in apple juice. Both juices darkened over time when stored in dark and fluorescent conditions, whereas UV exposure caused some initial bleaching of color before darkening. The bleaching effect was reduced in apple juice stored in the PET/PEN bottles.

The causes of skin cancer: A comprehensive review

Skin cancer is the most common type of cancer in fair-skinned populations around the world. The incidence and mortality rates of skin cancers are dramatically increasing and thus pose a threat to public health. Understanding the etiology and pathogenesis of skin cancer remains a goal for healthcare systems. A clearer understanding of causative factors is an essential step in the prevention of skin cancer. This article comprehensively reviews the causative agents which play a role in the development of skin cancer. Ultraviolet radiation (UV) from sun exposure is the most important cause of skin cancer. Sunburns and excessive exposures cause cumulative damage which induces immunosuppression and skin cancers. Ozone depletion, the level of UV light, elevation, latitude, altitude and weather conditions influence the emission of UV radiation reaching the earth's surface. Organ transplant recipients and AIDS patients have an increased incidence of skin cancers. Some treatment modalities, including radiation therapy, phototherapy and psoralen and long-wave ultraviolet radiation (PUVA) can also predispose to skin cancers. Viral infections such as the human papilloma virus can cause squamous cell carcinomas. Individuals with familial genetic syndromes are susceptible to specific types of skin cancers. Ionizing radiation, environmental pollutants, chemical carcinogens and work-related exposures have been associated with skin cancers. Exposure to artificial UV radiation (tanning beds and lamps), aging, skin color, diet and smoking are attributable risks. Skin cancers have been found in dermatoses and various types of keratoses, chronically injured or nonhealing wounds, and scars. This article provides a comprehensive and thorough overview of skin cancer, with an emphasis on understanding its epidemiology, incidence, etiology and related risk factors.

A validated chiral LC method for the enantioselective analysis of Levetiracetam and its enantiomer R-α-ethyl-2-oxo-pyrrolidine acetamide on amylose-based stationary phase

A new, simple chiral HPLC method was developed for the enantiomeric separation of Levetiracetam, [( S)-α-ethyl-2-oxo-pyrrolidine acetamide], an antiepileptic drug in pharmaceutical formulations and in bulk materials. Enantiomeric separation was achieved on a chiralpak AD-H column using a mobile phase consisting of hexane and isopropanol in the ratio (90:10, v/v) at a flow rate of 1.0 ml/min. The resolution between the enantiomers was found to be not less than 7 in the optimized method. Interestingly, unwanted enantiomer, namely R-α-ethyl-2-oxo-pyrrolidine acetamide (( R)-enantiomer), was eluted prior to its mirror image in the developed method. The developed method was found to be selective in the presence of related impurities of Levetiracetam, namely N-(1-carbamoyl-propyl)-4-chloro-butyramide (Imp-1) and 1-ethyl-2-oxo-1-pyrrolidine acetic acid (Imp-2), and also under exposed conditions of UV light and 60 °C. The limit of detection (LOD) and limit of quantification (LOQ) of ( R)-enantiomer were found to be 900 and 2250 ng/ml, respectively, for 10 μl injection volume. The method precision for ( R)-enantiomer at limit of quantification level was within 8% R.S.D. Calibration curve for ( R)-enantiomer was linear over the studied ranges (2250–9000 ng) with correlation coefficient greater than 0998. The active pharmaceutical ingredient was extracted from its finished dosage form (tablet) using isopropanol. The percentage recoveries of ( R)-enantiomer were ranged from 94.2 to 102.6 and from 93.5 to 104.1 in spiked bulk and formulation samples of Levetiracetam, respectively. Levetiracetam sample solution and mobile phase are found to be stable for at least 48 h. The developed method was found to be rugged and robust. The proposed method was found to be suitable and accurate for the quantitative determination of ( R)-enantiomer in bulk drugs and commercial formulations. Chiralcel OD-H column can also be used as an alternative column for the above purpose.

Formation and stability of rare earth metalloporphyrin monolayer films on amino-terminated silanized quartz surfaces studied by ultraviolet–visible and X-ray photoelectron spectroscopy

We investigated the fabrication of self-assembled monolayers of 5,10,15,20-tetra-( p-chlorophenyl)-porphyrin metal hydroxyl compounds (MOH; M=Gd, Tb, Er, Lu) on amino-terminated silanized quartz surfaces using ultraviolet–visible (UV–vis) and X-ray photoelectron spectroscopy (XPS). The orientation of MOH molecules in the films, the kinetics of the adsorption of MOH from a chloroform solution on an amino-terminated quartz substrate, and the stability of the metalloporphyrin films under natural light, UV light, and acidic and basic conditions were studied by UV–vis spectroscopy. The results indicate that the central metal is crucial in the formation of self-assembled porphyrin films and that the stability of the MOH SAMs also depends on the central metal. Under natural and UV light irradiation conditions, the stability of the MOH SAMs depends on the strength of the MN bonds between the central metal and pyrrole nitrogens or between the central metal and the axial ligand. In the acidic conditions, the UV–vis spectra of the MOH SAMs show decreases in the absorbance and blue shifts. These spectral changes lead us to suggest that the four MN bonds between the central metal and the pyrrole nitrogens of the porphyrins are cleaved and the resulted porphyrins are protonated under acidic conditions. Thus, it is likely that the protonated porphyrins and MOH form π− π complexes with a parallel stacking of the macrocycles through the electrostatic attractive interaction in the SAMs, resulting in the blue shifts of the Soret bands of the SAMs.

신팔달콩 유래 IFS (isoflavone synthase)유전자 클로닝 및 기능 규명

Two genes, SinIFS1 and SinIFS2 from Korean soybean cultivar, Sinpaldalkong known as one of isoflavonerich cultivars, were cloned with PCR and degenerate primers. The sequences of two genes were analyzed with previously reported IFS genes of leguminous plants and their expression pattern in various environmental conditions was surveyed. The genomic clone of SinIFS1 contained 1,828bp nucleotides and encoded a polypeptide of 521 amino acids, and 1912bp nucleotides and a polypeptide of 521 amino acids for SinIFS2. Both genes included several conserved motifs, oxygen binding and activation (A/G-G-X-E/D-T-T/S), ERR triad (E...R....R), and heme binding (F-X-X-G-X-R-X-C-X-G) domain, which are typical in any member of cytochrome P45O superfamily. Very high sequence homology (>98%) was observed in the comparison with other IFSs of legumes. In the northern blot analysis to check the expression and increase of SinIFS1 to various environmental renditions (low temperature, light, dark, UV, and fungal elicitor), the most significant induction, more than 6 times of transcript level compared to the dark treatment as a control, was observed from the fungal elicitor treatment. The next up-regulated expression was from UV treatment (4), low temperature and light conditions.

Photochemical degradation of solid-state nisoldipine monitored by HPLC

The photochemical degradation of solid-state nisoldipine, 1,4-dihydropyridine calcium antagonist, was investigated under daylight and UV light conditions. Degradation products were identified by using the retention times of corresponding standards and quantified by high-performance liquid chromatographic method. The daylight illumination induced appearance of nitrosophenylpyridine, while formation of second degradation product, nitrophenylpyridine, was observed only upon UV light illumination. The photodegradation kinetics of solid-state nisoldipine under daylight and UV light illumination belongs to class of zero-order reactions. The rate constants of disappearance of nisoldipine upon illumination were determined for raw material as well as pharmaceuticals (tablets, film-tablets and capsules).

Photostability of extended-release matrix formulations

The photostability of drugs has been widely studied while less attention is devoted to the possible modifications that UV light may induce on the excipients of a dosage form, in particular, on the functional polymers used to modulate drug delivery. In this work we have evaluated the effect of UV light on the release characteristics of extended-release matrix tablets containing hydroxypropylmethylcellulose (HPMC) or polyethylene oxide (PEO) as retarding polymers. Two different model drugs have been used: nifedipine (insoluble and photolabile drug) and diltiazem (soluble and photostable drug). Photodecomposition of nifedipine was evaluated and the formation of the photoproducts was followed during the dissolution process. Regarding the dissolution stability, the matrix tablets containing HPMC exposed to UV light have not shown significant differences in drug release profiles compared to the same non-irradiated formulation, while the matrix tablets containing PEO and exposed to the same conditions of UV light have shown a remarkable increase of drug release rate within the first minutes of the dissolution test (burst effect) which is particularly critical because it can cause the loss of the desired therapeutic control.

Analysis of lichens under environmental stress using TMAH thermochemolysis–gas chromatography

Plants often react to various kinds of stress by changes in their organic composition as the result of defense or stress-induced metabolism. This study investigated the use of lichens as stress monitors by examining changes in their chemistry under various environmental conditions. A micro-scale acetone extraction of dried and ground lichen sample was necessary to observe significant compositional differences in lichen extractives compared to no extraction. The extract was dissolved in solvent and treated with 10% methanolic TMAH. The sample was pyrolyzed and the products identified by GC/MS. A GG–FID was used for quantitative analysis. The lichens Cladina mitis and Cladina rangiferina exposed to laboratory conditions (3 days) of visible and/or UV light were examined. Small differences in total unsaturated fatty acid, and atranorin and rangiformic acid composition were observed according to conditions. Usnea dasypoga samples were collected from sites of various ground-level ozone conditions in New Brunswick, Canada. Reduction in unique lichen acid, salazinic acid, was detected in sites having higher cumulative ozone exposure. Alectoria sarmentosa was collected from sites of varying sulfur dioxide exposure (from oil refinery) in Newfoundland, Canada. In general, lichen acids decreased with increased levels of stress exposure except for Usnea dasypoga which showed increased concentrations of salazinic acid at the highest level of ozone measured indicating a defensive biochemical response. Unsaturated fatty acid markers decreased in lichens collected close to the refinery (SO 2) and increased for those exposed to higher levels of ozone.

Non-oxidative modification of lens crystallins by kynurenine: a novel post-translational protein modification with possible relevance to ageing and cataract

In humans, the crystallin proteins of the ocular lens become yellow-coloured and fluorescent with ageing. With the development of senile nuclear cataract, the crystallins become brown and additional fluorophores are formed. The mechanism underlying crystallin colouration is not known but may involve interaction with kynurenine-derived UV filter compounds. We have recently identified a sulphur-linked glutathionyl-3-hydroxykynurenine glucoside adduct in the lens and speculated that kynurenine may also form adducts with GSH and possibly with nucleophilic amino acids of the crystallins (e.g. Cys). Here we show that kynurenine modifies calf lens crystallins non-oxidatively to yield coloured (365 nm absorbing), fluorescent (Ex 380 nm/Em 450–490 nm) protein adducts. Carboxymethylation and succinylation of crystallins inhibited kynurenine-mediated modification by approx. 90%, suggesting that Cys, Lys and possibly His residues may be involved. This was confirmed by showing that kynurenine formed adducts with GSH as well as with poly-His and poly-Lys. NMR studies revealed that the novel poly-Lys-kynurenine covalent linkage was via the ϵ-amino group of the Lys side chain and the βC of the kynurenine side chain. Analysis of tryptic peptides of kynurenine-modified crystallins revealed that all of the coloured peptides contained either His, Cys or an internal Lys residue. We propose a novel mechanism of kynurenine-mediated crystallin modification which does not require UV light or oxidative conditions as catalysts. Rather, we suggest that the side chain of kynurenine-derived lens UV filters becomes deaminated to yield an α,β-unsaturated carbonyl which is highly susceptible to attack by nucleophilic amino acid residues of the crystallins. The inability of the lens fibre cells to metabolise their constituent proteins results in the accumulation of coloured/fluorescent crystallins with age.

Automated Detection of Fluorescent Spray Deposits with a Computer Vision System

An automated computer vision system was developed to characterize spray deposit features. This system characterized water-soluble fluorescent tracer spray deposits on artificial targets and also on leaf images on which tracer deposit images had been digitally superimposed. In an automated fashion, the system positioned samples, focused the camera, acquired images, and processed and analyzed the images. Components for the computer vision system were selected to discern small and low intensity particles under low level UV light conditions. After an image was acquired, a set of feature parameters related to spray coverage, tracer intensity, droplet shape, and droplet size distribution were extracted by using custom-developed image processing and analysis algorithms. In the performance evaluation of this system, relatively good statistical correlations were found between the known deposit feature parameters and deposit feature measurements extracted from digitally treated leaf surfaces. This acquisition system represents an improvement on previously reported deposit analysis systems because it can view a wide range of feature sizes within the same sampling area. It is also better able to work in conditions of low contrast between water-soluble tracer deposits and a plant leaf background. The system hardware and software could be applied as a means to compare spray quality on plant targets treated with either a water-soluble or water-insoluble tracer.