Ultraviolet Monitoring Research Articles

Conference Report: WORKSHOP ON CRITICAL ISSUES IN AIR ULTRAVIOLET METROLOGY Gaithersburg, MD May 26-27, 1994.

This workshop was held at NIST/Gaithersburg, Maryland on May 26 and 27, 1994. One of the goals of this workshop was to identify the needs of the UV measurement communities for standards and instrumentation necessary for absolute measurements of irradiance and radiance. Another purpose of this conference was to compile a list of specific recommendations to improve the nations`s UV measurement capabilities, and to determine NIST`s role in supporting these efforts. Session 3 focused on: Measurement requirements of solar ultraviolet monitoring and ozone depletion. Session 4 focused on: Quantitation of ultraviolet biological effects and hazard evaluation.

Determination of synovial fluid hyaluronate concentration and polymerisation by high performance liquid chromatography.

High performance liquid chromatography (HPLC) with a size exclusion column and ultraviolet monitoring was used to study the effect of synovial fluid hyaluronate concentration and degree of polymerisation on viscosity and mucin clot formation. Rotational viscometry measurements showed an exponential relation between the synovial fluid hyaluronate concentration and relative viscosity, the viscosity increasing particularly steeply with hyaluronate concentrations exceeding 2-2.5 mg/ml. The scattering of individual values observed around the expected curve was eliminated when both the hyaluronate concentration and its degree of polymerisation were taken into account. Hyaluronate concentration and degree of polymerisation also correlated with the quality of mucin clot, though only HPLC provided more detailed quantitative information about this association. Because HPLC allows reproducible and rapid simultaneous analysis of the synovial fluid hyaluronate concentration and the degree of polymerisation in small volumes of unprocessed samples it can be used in well equipped rheumatological units to replace other methods used previously.

Chemical measurements with optical fibers for process control

Several aspects of remote in situ spectrophotometric measurement by means of optical fibers are considered in the context of chemical process control. The technique makes it possible to measure a species in a particular oxidation state, such as plutonium(VI), sequentially, under the stringent conditions of automated analysis. For the control of several species in solution, measurements at discrete wavelengths on the sides of the absorption peaks serve to increase the dynamic range. Examples are given concerning the isotopic separation of uranium in the Chemex process. The chemical control of complex solutions containing numerous mutually interfering species requires a more elaborate spectral scan and real-time processing to determine the chemical kinetics. Photodiode array spectrophotometers are therefore ideal for analysing the uranium and plutonium solutions of the Purex process. Remote on-line control by ultraviolet monitoring exhibits limitations chiefly due to Rayleigh scattering in the optical fibers. The measurement of pH in acidic (0.8–3.2) and basic media (10–13) has also been attempted. Prior calibration, signal processing and optical spectra modeling are also discussed.

An on-line clean-up procedure for large sample volume analysis of serum aminoglycoside antibiotics by reversed-phase high-performance liquid chromatography.

A reversed-phase (RP) liquid chromatography procedure using column switching was applied to assay one of the aminoglycoside antibiotics, sisomicin. The drug in serum was derivatized with o-phthalaldehyde (OPA) and β-mercaptopropionic acid (β-MP) in 0.05M borate buffer (pH 9.0), then directly injected onto a RP pre-column (ODS-silica, 50×4 mm i.d.) to remove protein and interfering compounds (confirmed by ultraviolet monitoring at 280nm). The sisomicin derivatives retained on the pre-column were desorbed by back-flushing onto an analytical column (5μm ODS-silica 200×4mm i.d.) with 0.05M potassium dihydrogen phosphate-0.05M disodium hydrogen phosphate buffer (pH 7) and were separated by elution with a mixture of methanol, ethylene glycol and counter ion solution (sodium 1-heptanesulfonate/acetic acid/water, 2.5g/42ml/208ml). This system could be utilized for more than 50 samples with a 1ml injection volume. A good linear response curve was found between the injected sample amounts and the peak heights for the concentration range of 0.5 to 5μg/ml of sisomicin. The limit of detection for sisomicin in serum was 62.5.ng/ml for 0.1ml of sample. The mean recovery from serum was 97.5%.

Recurrent episodic mass loss in a B2e star - 66 Ophiuchi, 1982-1985

view Abstract Citations (24) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Recurrent Episodic Mass Loss in a B2e Star: 66 Ophiuchi, 1982--1985 Grady, C. A. ; Sonneborn, George ; Wu, Chi-Chao ; Henrichs, H. F. Abstract The results of three intensive ultraviolet monitoring campaigns for 66 Oph in September-October 1982, September 1983, and September 1984, supplemented by the available IUE archival data from April, 1982 to June, 1985 are reported. The stellar wind went through at least two and probably three episodes of weak-wind absorption. At wind minimum, the resonance profiles and equivalent widths of C IV, Si IV, Si III, and Al III are similar to those observed in normal B stars of comparable luminosity, effective temperature, and v sin i. The strong-wind absorption profiles show one or more shortward-shifted discrete components superposed upon the weak-wind absorption profiles. Significant profile variations are seen on time scales spanning over two orders of magnitude, ranging from small-amplitude changes detected on time scales of hours to the transitions from wind minimum to maximum, which take months. Publication: The Astrophysical Journal Supplement Series Pub Date: December 1987 DOI: 10.1086/191239 Bibcode: 1987ApJS...65..673G Keywords: B Stars; Metallic Stars; Satellite Observation; Stellar Mass Ejection; Stellar Spectra; Iue; Line Spectra; Linear Polarization; Ultraviolet Spectroscopy; Astrophysics; LINE PROFILES; STARS: BE; STARS: INDIVIDUAL CONSTELLATION NAME: 66 OPHIUCHI; STARS: MASS LOSS; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (5) MAST (1)

HPLC Analysis of Capsaicins and Simultaneous Determination of Capsaicins and Piperine by HPLC‐ECD and UV

ABSTRACTA highly sensitive liquid chromatographic procedure with electrochemical detection (ECD) was developed to separate and quantitate major capsaicins, the pungent principles of red and green pepper. Although complete chromatographic separation of capsaicins from piperines was not achieved, electrochemical (EC) monitoring at 0.4V applied potential detected only the electroactive capsaicins. Ultraviolet (UV) monitoring at 340 nm detected only the strongly absorbing piperine. Thus, simultaneous determination of capsaicins and piperine were achieved by the applications of both EC and UV detections.

Assessment of a two-step high-performance liquid chromatographic assay using dual-wavelength ultraviolet monitoring for 25-hydroxyergocalciferol and 25-hydroxycholecalciferol in human serum or plasma

The technique of dual-wavelength monitoring was used to verify the purity of high-performance liquid chromatographic (HPLC) peaks quantified as 25-hydroxyergocalciferol and 25-hydroxycholecalciferol. The data obtained show the need for a second HPLC step prior to quantitation. Potential inaccuracy arising from inadvertent collection of radio-labelled decomposition products was assessed. Between-day coefficients of variation were 7.3, 5.0 and 3.6%, respectively for 11.3 ( n = 12), 17.1 ( n = 14), and 32.9 ( n = 8) ng/ml of 25-hydroxycholecalciferol. For 25-hydroxyergocalciferol, these values were 6.4 and 3.8% for 11.4 ( n = 12) and 20.1 ( n = 8) ng/ml concentrations, respectively. Comparison of total 25-hydroxycalciferol with a competitive protein binding assay was made. The comparison produced a correlation coefficient ( r) of 0.94 and a relationship of y = 1.03 x + 3.3. Four of the samples contained more than 10 ng/ml of 25-hydroxyergocalciferol and the results are consistent with the reported 100% cross-reactivity of the competitive binding protein method for 25-hydroxyergocalciferol and 25-hydroxycholecalciferol. A simple regeneration procedure is also described which enables Sep-Pak C 18 cartridges to be reused up to eighteen times. Samples may be stored at −18° C for upto several months before assay and either serum or plasma may be used.

Pyrimidine nucleoside phosphorylase assay by automated high-performance liquid chromatography

A new assay for pyrimidine nucleoside phosphorylase is reported. This method utilizes an isocratic reversed-phase high-performance liquid chromatographic system for separation of nucleosides and bases. Product detection is accomplished by ultraviolet monitoring and radioactive flow detection. Use of an automated sample injector allows for the analysis of a series of samples, with data recorded onto a microprocessor-based cassette recorder. Data can then be downloaded into computer memory. The velocity of uridine phosphorylase (E.C. 2.4.2.3) was a linear function of enzyme concentration. The Michaelis constant for uridine at pH 8.0 was found to be in close agreement with the value obtained by a thin-layer chromatographic assay method.

High-performance liquid chromatography of carbapenem antibiotics in complex biological samples with column switching and simultaneous multichannel ultraviolet monitoring

During fermentative production of new carbapenem compounds of the OA-6129 type, many interfering by-products, exhibiting physicochemical properties very similar to the main components, are produced. The compounds of interest, especially OA-6129 A, B1, B2 and C, are difficult to quantify because of the complex biological matrix and the broad spectrum of by-products. High-performance liquid chromatography (h.p.l.c.) is used to quantify OA-6129 B2. In order to assign the chromatographic peaks clearly to the wanted substances, h.p.l.c., t.l.c, and a selective chemical degradation method proved to be necessary. This procedure was considerably simplified by combined use of a column-switching technique and a diode-array detector. The polar by-products and much of the interfering matrix were eliminated by column switching. Positive identification of OA-6129 B2 was feasible by monitoring chromatograms simultaneously at different wavelengths and by use of the diode-array detector. Additional information on uniformity and purity of the peaks was obtained by u.v.-absorbance ratio recording.

High-performance liquid chromatography for determination of adenosine-5'-triphosphate in biological materials

A high-performance liquid chromatographic method for the determination of adenosine-5'-triphosphate (ATP) in the biological materials, blood, heart, liver and kidney is described. The organs were frozen in liquid nitrogen immediately after the removal in situ with precooled tongs and homogenized with cold 10% trichloroacetic acid and 0.1 N HCl. The chromatographic analysis utilized an anion exchange (Polygosil N (CH3)2) column with a mobile phase of 0.35 M KH2PO4 buffer (pH3.35) and ultraviolet monitoring at 260 nm. This method was applied to the determination of ATP in the blood, heart, liver and kidney. The minimum detectable quantity of ATP was 10 pmol (about 55 ng) and the coefficient of variation was about 1%.

Sensitive ultraviolet monitoring of aldoses in automated borate complex anion-exchange chromatography with 2-cyanoacetamide

A convenient method for postcolumn carbohydrate labeling has been developed. Eluates of borate complex anion-exchange columns are mixed with a reagent solution prepared from an aqueous solution of 2-cyanoacetamide and a borate buffer (pH 10.5), and the mixture is heated in a 10-m reaction coil at 100°C. Measurement of the absorbance of the product at 276 nm permits high reproducibility determination of 5 to 500 nmol of aldoses. Some carbonyl compounds are positive to this reaction, but most do not interfere with the analysis because their peaks do not appear in the aldose region. Ascorbate gives a small peak between those of mannose and fucose, but interference is negligible for equimolar amounts of ascorbate and these aldoses. This method is applied to and gives satisfactory results in the analysis of monosaccharides from various types of glycoconjugates.

High-performance liquid chromatographic separation of ascorbic acid, erythorbic acid, dehydroascorbic acid, dehydroerythorbic acid, diketogulonic acid, and diketogluconic acid

High-performance liquid chromatography on a Zorbax NH 2 analytical column, with acetonitrile: 0.05 m KH 2PO 4 (75:25, w w ) used as eluant, has allowed the separation, in less than 14 min, of ascorbic acid, erythorbic acid, dehydroascorbic acid, dehydroerythorbic acid, diketogulonic acid, and diketogluconic acid. Ultraviolet monitoring at 268 nm allows ascorbic acid and erythorbic acid to be detected at the 25-ng level, while refractive index detection monitors the elution of all six compounds. Tyrosine is a good internal standard, being well separated from the other compounds and having an adequate ultraviolet absorption at 268 nm. We have found dithiothreitol to be effective in rapidly reducing dehydroascorbic acid to ascorbic acid, providing the basis for indirectly determining dehydroascorbic acid after its reduction. The potential of this high-performance liquid chromatographic procedure for evaluating the levels of these compounds in orange juice and urine is demonstrated.

Ultraviolet, optical and X-ray monitoring of the continuum of NGC 4151

Ultraviolet, optical and X-ray monitoring of the continuum of NGC 4151

Combined ultraviolet absorbance and fluorescence monitoring: an aid to identification of polycyclic aromatic hydrocarbon metabolities by high-pressurre liquid chromatography

Combined ultraviolet absorbance and fluorescence monitoring: an aid to identification of polycyclic aromatic hydrocarbon metabolities by high-pressurre liquid chromatography

Application of thin-layer and high-performance liquid chromatography to the separation of polycyclic aromatic hydrocarbons in bituminous materials

The application of high-performance liquid chromatography (HPLC) on microparticulate silica gel with selective ultraviolet monitoring at four wavelengths has led to a rapid method for the reliable analysis of polycyclic aromatic hydrocarbons (PAH) in tar and petroleum materials. Preliminary separation of the PAH fraction is accomplished, if necessary, by a new form of thin-layer chromatography which incorporates the organo-clay Bentone 34 and which has been shown to be selective for PAH. This selectivity has been utilised in additional separations of HPLC fractions to facilitate their identification by UV spectroscopy. The operation of a “stop-start” liquid chromatograph is described in which the UV spectra of peaks can be scanned during chromatography for identification purposes.

Separation and determination of opiates and diluents in illicit narcotic mixtures

A semi-automated method for the separation and determination of opiates in illicit narcotic preparations is described. The procedure involves resolution of the mixtures on SE-Sephadex ion-exchanger, continuous ultraviolet monitoring of the column effluent and colorimetric assay of lactose and mannitol. Peak elution volumes ( V e ) for compounds of forensic importance are presented. The differences in V e 's for the most commonly encountered opiates and diluents are great enough to permit identification and determination with ease. Examples of analyses of contraband preparations are also discussed.