UV Vis Micro-spectrophotometry Research Articles

Comparative Studies of Changes in Cotton Fabrics and Fibers under the Influence of Disinfection, Sterilization, and DNA Degradation Agents

The purpose of this study was to detect changes in the structure and chemical composition of undyed and dyed cotton fabrics under the influence of six popular agents for disinfection, sterilization, and DNA degradation with different chemical compositions. The original and exposed fabrics and their constituent fibers were subjected to comparative analysis using various optical microscopy methods, infrared spectroscopy, and UV–Vis microspectrophotometry in order to differentiate the exanimated material due to the agents applied. Differences in color, from a slight change to complete discoloration, and in the structure of the tested fabrics, which became more rigid, brittle, or, for example, compact, were noticed. With the use of ATR FTIR, it was possible to identify the presence in the exposed fabrics of residues of these agents that contained quaternary ammonium salts. Bright-field microscopy made it possible to show, above all, changes or lack thereof in the fluorescence properties of single exposed fibers in relation to control ones. With the use of UV–Vis microspectrophotometry, changes in colored fibers following the action of a specific agent on the examined fabrics were monitored. A case study was presented as an application aspect of the research, in which the use of concrete disinfectants was recognized based on changes observed in cotton clothing.

The Effect of Ultraviolet Radiation on Dyed Man-Made Textile Fibers Using UV-Vis Microspectrophotometry (MSP): Technical Aspects on Spectral Alterations in Time

Little is known about changes in dyed man-made fibers caused by environmental conditions, especially exposure to ultraviolet (UV) radiation over long periods of time. Even less known are the deviations of the spectral curves collected from these samples using UV-visible microspectrophotometry (UV-Vis MSP) from the spectral curves collected from unexposed fiber samples. Spectral alterations, however, may derive from undesired causes inherent to the operation of the instrument or the samples themselves. Hence, the primary goal of this research was to study the effect of UV radiation on various combinations of man-made fiber types, color, and dye types. A UV radiation box was constructed as a controlled (indoor) environment and was compared to a dedicated (outdoor) natural exposure facility in Buckeye, AZ. In both settings, the fiber samples were exposed up to 32 weeks and collected and analyzed at intervals of 8 weeks. The undesired causes of UV exposure of induced photobleaching inherent to the xenon source of the spectrophotometer and the latent polarization of the selected fiber samples as a function of their orientation on the stage of the microscope were also evaluated. Although issues due to latent polarization from the samples were not identified, induced photobleaching was observed within 8 seconds of exposure to the xenon source in a few instances. In this study, different types of spectral alterations were observed, which occurred both in the visible and the UV spectral regions. These alterations were the same as observed in the indoor setting, the outdoor setting, and the instrument-induced photobleaching study, although their times of occurrence differed. This study focused on technical aspects related to the proper use of UV-Vis MSP to the analysis of textile fibers exposed to UV radiation. It has led to the formulation of recommended measures that aim at minimizing the risks of spectral alterations resulting from causes other than the environmental UV exposure of interest.

Enzymatic extraction of dyes for differentiation of red cotton fibres by TLC coupled with VSC

The purpose of this work was to assess the usefulness of thin layer chromatography (TLC) for discriminating single cotton fibres dyed with red reactive dyes. An effective enzymatic extraction procedure with the use of cellulase for the red reactively-dyed cotton fibres was developed and used for the discrimination of fibres derived from 21 garments purchased commercially. Discrimination of the fibres relied on the separation of the extracted dyes by thin layer chromatography (TLC). Four eluents were used to develop the plates with the extracted dyes, and the obtained results were analysed using, among others, video spectral comparator (VSC). Observation of TLC plates in visible, ultraviolet and infrared light allowed unambiguous discrimination of 5 and probable discrimination of 6 of the 21 fibres tested. The remaining fibres were divided into several groups. Comparison of the acquired results with those obtained for the same examination material by standard non-destructive methods used in forensic fibres examinations (transmitted light microscopy, fluorescence microscopy, UV–Vis microspectrophotometry and Raman spectroscopy) has shown that efficiency in fibres differentiation is similar for all methods. TLC coupled with VSC was even found to be more effective in differentiation of red cotton fibres. The chemometric analysis was helpful to discriminate dyed cotton fibres, characterized by very similar colour.

Simultaneous ultrasound-assisted iodide oxidation and liquid-liquid microextraction for rapid quality control of iodized salts by UV–vis micro-spectrophotometry

In this work, a rapid and simple analytical method for the quality control of iodized salt based on simultaneous ultrasound-assisted iodide oxidation and liquid-liquid microextraction, with the subsequent measurement of the organic phase by UV–vis micro-spectrophotometry is described. An aqueous sample solution along with 50μL of carbon tetrachloride are sonicated with a probe for 2min. CCl4 is used both for intensifying the oxidation capacity of ultrasound and as an extractant, which enables the determination of iodide at trace levels. Chlorine radicals and molecules arising upon sonication react quickly with iodide leading to the formation of iodine, which is simultaneously extracted to yield a purple solution. Relevant variables such as the volume of carbon tetrachloride, sample volume, sample temperature, type of sample vial, sonication parameters (amplitude and time) and pH were studied. The presence of high amounts of NaCl influences the ultrasonic oxidation of iodide, and hence, the use of matrix-matched standard solutions with NaCl was recommended. Under these conditions, the calibration curve was linear up to 20μgmL−1 of iodide. The LOD and LOQ, calculated following the 3σ criteria and 10σ criteria, respectively, were 0.2 and 0.6μgg−1. The repeatability, expressed as relative standard deviation, was 1.9%. The proposed methodology was successfully applied to different salt samples. Quantitative recoveries in the range 95–104% were obtained.

UV–Vis microspectrophotometric study of wool and polyamide fibres dyed with analogous gryfalan dyes

The presented study was dedicated to the comparison between wool and polyamide fibres, dyed with metal-complex (gryfalan) dyes being analogous regarding type and concentration, with the use of UV–Vis microspectrophotometry. The affinity of used dyes to the particular fibre type as well as the influence of fibre polymer on the quality of spectra obtained were subjected to evaluation. The absorbance spectra, obtained with the use of a 20/20 PV™ microspectrophotometer (CRAIC Technologies) for single fibres selected from 15 woolen and 15 polyamide fabrics, were studied. The results indicated that at the same concentration of dye, the dyes' affinity is higher for polyamide fibres than for wool. Thus, the conduction of the examination of single wool fibres in the visible and in the UV-A range can be recommended, and in the case of analysing fibres with similar microscopic colour, the chemometric treatment seems to be an effective way of discrimination.

From protein structure to function via single crystal optical spectroscopy.

The more than 100,000 protein structures determined by X-ray crystallography provide a wealth of information for the characterization of biological processes at the molecular level. However, several crystallographic “artifacts,” including conformational selection, crystallization conditions and radiation damages, may affect the quality and the interpretation of the electron density maps, thus limiting the relevance of structure determinations. Moreover, for most of these structures, no functional data have been obtained in the crystalline state, thus posing serious questions on their validity in infereing protein mechanisms. In order to solve these issues, spectroscopic methods have been applied for the determination of equilibrium and kinetic properties of proteins in the crystalline state. These methods are UV-vis spectrophotometry, spectrofluorimetry, IR, EPR, Raman, and resonance Raman spectroscopy. Some of these approaches have been implemented with on-line instruments at X-ray synchrotron beamlines. Here, we provide an overview of investigations predominantly carried out in our laboratory by single crystal polarized absorption UV-vis microspectrophotometry, the most applied technique for the functional characterization of proteins in the crystalline state. Studies on hemoglobins, pyridoxal 5′-phosphate dependent enzymes and green fluorescent protein in the crystalline state have addressed key biological issues, leading to either straightforward structure-function correlations or limitations to structure-based mechanisms.

The analysis of colored acrylic, cotton, and wool textile fibers using micro-Raman spectroscopy. Part 2: comparison with the traditional methods of fiber examination.

In the second part of this survey, the ability of micro-Raman spectroscopy to discriminate 180 fiber samples of blue, black, and red cottons, wools, and acrylics was compared to that gathered with the traditional methods for the examination of textile fibers in a forensic context (including light microscopy methods, UV-vis microspectrophotometry and thin-layer chromatography). This study shows that the Raman technique plays a complementary and useful role to obtain further discriminations after the application of light microscopy methods and UV-vis microspectrophotometry and assure the nondestructive nature of the analytical sequence. These additional discriminations were observed despite the lower discriminating powers of Raman data considered individually, compared to those of light microscopy and UV-vis MSP. This study also confirms that an instrument equipped with several laser lines is necessary for an efficient use as applied to the examination of textile fibers in a forensic setting.

Ultrasensitive, simple and solvent-free micro-assay for determining sulphite preservatives (E220–228) in foods by HS-SDME and UV–vis micro-spectrophotometry

A new method based on headspace single-drop microextraction in combination with UV-vis micro-spectrophotometry has been developed for the ultrasensitive determination of banned sulphite preservatives (E220-228) in fruits and vegetables. Sample acidification was used for SO2 generation, which is collected onto a 5,5'-dithiobis-(2-nitrobenzoic acid) microdrop for spectrophotometric measurement. A careful study of this reaction was necessary, including conditions for SO2 generation from different sulphating salts, drop pH, 5,5'-dithiobis-(2-nitrobenzoic acid) concentration and potential interference effects. Variables influencing mass transfer (stirring, sample volume and addition of salt) and microextraction time were also studied. A simple sulphite extraction was carried out, and problems caused by oxidation during the extraction process were addressed. A high enrichment factor (380) allows the determination of low levels of free SO2 in fruits and vegetables (limit of detection 0.06 μg g(-1), limit of quantification 0.2 μg g(-1)) with an adequate precision (repeatability, relative standard deviation 5 %). In addition, the sulphiting process was studied through the monitoring of residual SO2 in a vegetal sample, thus showing the importance of a sensitive tool for SO2 detection at low levels.

Operator care and eco-concerned development of a fast, facile and economical assay for basic nitrogenous drugs based on simplified ion-pair mini-scale extraction using safer solvent combined with drop-based spectrophotometry

A fast, facile, and economical assay for basic nitrogenous drugs has been developed based on the mini-scale extraction of the drug–dye ion pair complex combined with the use of safe-for-analyst and eco-friendlier organic extractant and drop-based micro-spectrophotometry. Instead of using large volume devices, the extraction was simply carried out in typical 1.5mL microcentrifuge tubes along with the use of micropipettes for accurate transfer of liquids, vortex mixer for efficient partitioning of solutes and benchtop centrifuge for rapid phase separation. In the last step, back-extraction was performed by using the microvolume of acidic solution in order to concentrate the colored species into a confined aqueous microdrop and to keep the analyst away from unwanted contact and inhalation of organic solvents during the quantitation step which was achieved by using cuvetteless UV–vis micro-spectrophotometry without any prior dilutions. Using chlorpheniramine maleate as a representative analyte and n-butyl acetate as a less toxic and non-ozone depleting extractant, the miniaturized method was less laborious and much faster. It was accurate, precise and insensitive to the interferences from common excipients. Notably, it gave the assay results of drug in tablets and oral solution comparable to the large-scale pharmacopeial method while the consumption of organic solvents and the release of wastes were lowered by 200–400 folds.

Ion pair-based liquid-phase microextraction combined with cuvetteless UV–vis micro-spectrophotometry as a miniaturized assay for monitoring ammonia in waters

A miniaturized method based on liquid-phase microextraction (LPME) in combination with microvolume UV–vis spectrophotometry for monitoring ammonia in waters is proposed. The methodology is based on the extraction of the ion pair formed between the blue indophenol obtained according to the Berthelot reaction and a quaternary ammonium salt into a microvolume of organic solvent. Experimental parameters affecting the LPME performance such as type and concentration of the quaternary ammonium ion salt required to form the ion pair, type and volume of extractant solvent, effect of disperser solvent, ionic strength and extraction time, were optimized. A detection limit of 5.0μgL−1 ammonia and an enrichment factor of 30 can be attained after a microextraction time of 4min. The repeatability, expressed as relative standard deviation, was 7.6% (n=7). The proposed method can be successfully applied to the determination of trace amounts of ammonia in several environmental water samples.

Determination of triclosan by cuvetteless UV–vis micro-spectrophotometry following simultaneous ultrasound assisted emulsification–microextraction with derivatization: Use of a micellar-ionic liquid as extractant

Two ultrasound-assisted emulsification–microextraction procedures based on the use of a micellar ionic liquid as extractant are proposed for triclosan determination in troublesome matrices such as cosmetics and wastewaters. Microvolume UV–vis spectrophotometry was used in order to quantify the yellow azoderivative formed. This compound is polar and water-soluble and hence, it is not extractable into conventional organic solvents. Two imidazolium based ionic liquids were used as extractants. An improvement in the extraction of the derivative was achieved when SDS was mixed with the ionic liquid. The use of ultrasound energy allows a fast emulsification of the system. All the parameters related to the emulsification–microextraction were carefully optimized (i.e., ionic liquid type and volume, SDS concentration, sonication time and amplitude, salt addition, disperser solvent, cooling of ionic liquid and centrifugation time). Matrix effects were assessed and external calibration was used in all cases. Several advantages such as high sample throughput, simplicity and low reagent consumption can be emphasized.

Simultaneous ultrasound-assisted emulsification–derivatization as a simple and miniaturized sample preparation method for determination of nitrite in cosmetic samples by microvolume UV–vis spectrophotomety

A simple and miniaturized approach based on ultrasound-assisted emulsification–derivatization is proposed for the determination of nitrite in cosmetic samples by UV–vis micro-spectrophotometry. Oil/water emulsions were formed using 15 mg of cosmetic sample and 1 mL of an aqueous medium containing 0.5% w/v SDS and 1% v/v acetic acid. When powerful sonication systems were used to make emulsions, i.e. probe or cup-horn sonoreactor, stable and transparent emulsions were obtained in one or half minute per sample, respectively. The Griess reaction in these special conditions (i.e. sonication and the presence of an organized medium) was investigated. The absence of matrix effects allows external calibration with aqueous standards for nitrite quantification. Analytical features were compared to those of the European official method 82/434/EEC. Detection limit, sample throughput and reagent consumption were significantly improved.

Ultrasound-assisted emulsification microextraction with simultaneous derivatization coupled to fibre optics-based cuvetteless UV–vis micro-spectrophotometry for formaldehyde determination in cosmetic samples

In this work, ultrasound-assisted emulsification microextraction in combination with fibre optics-based cuvetteless UV–vis micro-spectrophotometry has been proposed as a novel method for the determination of formaldehyde in water-based cosmetics such as shampoo, conditioner and shower gel. The use of a powerful cup-horn sonoreactor allows simultaneous extraction and derivatization of the samples without any pre-treatment. The type and volume of organic extractant solvent, need for a disperser solvent, sonication conditions (sonication time and amplitude), ionic strength and centrifuging time have been carefully studied. Matrix effects were also evaluated. The European official method for quantification of formaldehyde in cosmetic products was used for comparison purposes. An important improvement in sensitivity and sample throughput as well as miniaturization was achieved. A limit of detection of 0.02 μg g −1 of formaldehyde and a repeatability expressed as relative standard deviation of 5.9% were obtained.

Griess micro-assay for the determination of nitrite by combining fibre optics-based cuvetteless UV–Vis micro-spectrophotometry with liquid-phase microextraction

A novel, simple and low cost method for the determination of nitrite using headspace single-drop microextraction and cuvetteless ultraviolet–visible micro-spectrophotometry is described. A Griess reagent-containing aqueous microdrop exposed to the headspace was used as extractant of the volatile nitrogen oxides generated from nitrite by direct acidification of the aqueous sample. Experimental parameters affecting the headspace single-drop microextraction performance such as composition and volume of the extractant phase, sample volume, concentration of acetic acid, ionic strength, sample agitation, temperature and microextraction time were systematically examined. Measurements were carried out at 540 nm under optimized conditions. A detection limit of 1.5 μg L −1 and an enrichment factor of 193 were achieved. Intra-day repeatability and inter-day reproducibility, expressed as relative standard deviation, were 3.5% ( n = 7) and 10.6% (three consecutive days), respectively. The proposed method, characterized by its enhanced sensitivity and selectivity in comparison with the standardized colorimetric assay, was successfully applied to the analysis of several environmental water samples.

Determination of iodate in waters by cuvetteless UV–vis micro-spectrophotometry after liquid-phase microextraction

The combination of liquid-phase microextraction and microvolume UV-vis spectrophotometry has been applied to the determination of iodate in natural water samples. The method is based on the reduction of iodate into vapor iodine and extraction of this volatile onto a single drop of N,N'-dimethylformamide. The following derivatization reaction was employed: Optimum conditions employed for iodate determination were as follows: 2.5 microL N,N'-dimethylformamide exposed to the headspace of a 10 mL acidic (HCl 0.2 mol L(-1)) aqueous solution stirred at 1400 rpm for 7 min after addition of 1 mL of KI 10(-3)mol L(-1) for in situ iodine generation. The limit of detection was determined as 1.1 microg L(-1). The repeatability, expressed as relative standard deviation, was 4.2% (n=6). A large preconcentration factor (i.e. 396) was obtained in only 7 min.

Forensic Fibre Analysis by UV-Visible Microspectrophotometry

ABSTRACTThis study evaluated various aspects of UV-VIS microspectrophotometry for routine colour analysis of fibres in a forensic laboratory, and was compared to visible microspectrophotometry. Quartz plates and glycerine mounting medium do not absorb within the spectral range of 240 nm to 380 nm. However, glass and XAM™ mounting medium, which are routinely used for microscopic fibre analysis and visible microspectrophotometry, were found to absorb substantially below 320 nm. The spectral interference from the polymeric composition of fibres was also studied. Wool, silk, polyester and acrylics with methylvinylpyridine(MVP) are highly absorbing below 310 nm, so dye colour analysis could not be applied in that region for these fibre types. Acetates, nylons, modacrylics and acrylics with polyvinylpyrrolidone (PVP) have low or moderate absorbance below 310 nm, which causes some interference. Cotton, rayon, and olefins do not absorb in the UV range. Analysis of glass-mounted fibres in the UV-VIS range can provide increased discrimination over analysis in the visible range. A flowchart decision tree was developed to guide the analyst in the application of UV-VIS microspectrophotometry for fibre analysis. Dyed fibres could initially be analysed under glass mount by UV-VIS microspectrophotometry from 320 nm to 770 nm. For fibre types with little or no polymeric UV spectral interference, additional spectral information could be obtained from UV-VIS analysis on quartz slides, measured from 240 nm to 770 nm.

Can soaked-in scavengers protect metalloprotein active sites from reduction during data collection?

One of the first events taking place when a crystal of a metalloprotein is exposed to X-ray radiation is photoreduction of the metal centres. The oxidation state of a metal cannot always be determined from routine X-ray diffraction experiments alone, but it may have a crucial impact on the metal's environment and on the analysis of the structural data when considering the functional mechanism of a metalloenzyme. Here, UV-Vis microspectrophotometry is used to test the efficacy of selected scavengers in reducing the undesirable photoreduction of the iron and copper centres in myoglobin and azurin, respectively, and X-ray crystallography to assess their capacity of mitigating global and specific radiation damage effects. UV-Vis absorption spectra of native crystals, as well as those soaked in 18 different radioprotectants, show dramatic metal reduction occurring in the first 60 s of irradiation with an X-ray beam from a third-generation synchrotron source. Among the tested radioprotectants only potassium hexacyanoferrate(III) seems to be capable of partially mitigating the rate of metal photoreduction at the concentrations used, but not to a sufficient extent that would allow a complete data set to be recorded from a fully oxidized crystal. On the other hand, analysis of the X-ray crystallographic data confirms ascorbate as an efficient protecting agent against radiation damage, other than metal centre reduction, and suggests further testing of HEPES and 2,3-dichloro-1,4-naphtoquinone as potential scavengers.