Ultraviolet UV Detector

Responds to the relatively low energy levels produced at wavelengths between 0.185 and 0.245 microns. This wavelength is outside the range of normal human visibility and outside that of sunlight. 

It responds to electric arcs from welding operations. It can be affected by deposits of grease and oil on the lens. This reduces it s ability to see a fire. Lightning with long duration strikes can cause false alarm problems. Some vapors typically those with unsaturated bonds may cause signal attenuation. Smoke will cause a reduction in signal level seen during a fire. It may produce a false alarm response when subject to other forms of radiation such as from NDT operations. 

This detector responds to infrared emissions from the narrow CO2 band at 4.4. microns. It requires the satisfaction of a flicker frequency discrimination at between 2 and 10 Hz. 

It responds well to a wide range of hydrocarbon fires and is blind to welding arcs except when very close to the detector. It can see through smoke and other contaminates that could blind a UV detector. It generally ignores lightning, electrical arcs and other forms of radiation. It is blind to solar radiation and resistant to most forms of artificial lighting. 

There are few models with automatic test capability. Testing is usually limited to hand held devices only 2 meters (7 ft.) from the detector or directly on the lens test unit. It can be ineffective if ice forms on the lens. It is sensitive to modulated emissions from hot black body sources. Most of the detectors have fixed sensitivities. The standard being under five seconds to a petroleum fire of 0.1 square meter (1.08 sq. ft.) located 20 meters (66 ft.) from the device. Response times increase as the distance increases. It cannot be used in locations where the ambient temperatures could reach up to 75 °C (167 °F). It is resistant to contaminants that could affect a UV detector. Its response is dependent on fires possessing a flicker characteristic so that detection of high pressure gas flames may be difficult. 

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Kratos Spectroflow 400 LC pumps ABI Model 783 variable-wavelength ultraviolet (UV) detector... 

HPLC) system equipped with an ODS column and ultraviolet (UV) detector for quantitative determination. 

Collect fractions starting from the bottom of the gradient, while recording an absorbance profile at 254 nm (which is dominated by the very abundant ribosomal RNA). We use a setup consisting of a peristaltic pump, ultraviolet (UV) detector, and fraction collector commonly used for chromatography experiments (GE Healthcare Life Sciences). 

Collecting the correct fraction is greatly facilitated by the use of a continuous ultraviolet (UV) detector, such as the ISCO UA-6 system. The OD254 reading allows accurate determination of the sedimentation of various complexes (e.g., 40S, 80S, and various polysomal complexes Fig. 9.1, step 3a). This information can be used to correct for small variations in sedimentation. Importantly, in many cases, it enables the determination of the number of ribosomes on the mRNA or on the resulting fragments, thereby allowing more accurate conclusions. 

From the available analytical techniques, the most commonly employed is HPLC coupled with an ultraviolet (UV) detector, which provides a rapid, relatively cheap and easy routine analysis of conjugated BAs from serum samples. HPLC with UV detection determination does not require sample derivatisation, but the sensitivity of... 

In the beginning, the refractive index detector was the most used detection system, although it has two important drawbacks (1) solvent gradients cannot be used, and (2) it has low sensitivity and different responses to saturated and highly unsaturated TGs (112). Moreover, use of the ultraviolet (UV) detector is difficult, because the most adequate solvents also absorb in the same range and therefore cause an important baseline drift with gradient elution systems (106). 

Fig. 45 Reversed-phase HPLC of autoxidized trilinolenin (peroxide value = 236.4 meq/kg). Nova-Pak C18 cartridge column (Waters, Milford, MA) (3.9 X 150 mm, 60 A, 4 yam), mobile phase acetonitrile/ dichloromethane/methanol (80 10 10). Ultraviolet (UV) detector (235 nm) and evaporative light-scattering detector (ELSD). Primary oxidation products, double peak at 3.6 min secondary oxidation products elute before primary oxidation products.

Verhaar et al.18 described the HPLC analysis of reaction mixtures of lactose (oxidation and degradation). In this work, a refractive index (RI) detector coupled with a variable wavelength ultraviolet (UV) detector at 212 nm was used to monitor the... 

Pressure sensors were used initially but were not successful because of their slow response and the rapid pressure buildup due to the speed of the flame propagation. Ultraviolet (UV) detectors were determined to be the only type suitable for this purpose. 

All these methods require the use of the refractive index of mass spectrometry (MS) detectors, since the detection of the isotopes is not possible with conventional ultraviolet (UV) detectors. 

Disadvantages. Neither the MS and ultraviolet (UV) detectors provide a complete solution alone. UV spectra simply are not unique enough to differentiate between closely related compounds. Under the conditions typically used for liquid chromatography, compounds may fail to give... 

Variable-wavelength detector using a deuterium or tungsten lamp with wavelength selection by a monochromator Filter photometer using a deuterium lamp with wavelength selection by filters Scanning ultraviolet (UV) detector Photodiode array detector... 

With respect to chromatography, electrochemical detection means amperometric detection. Amper-ometry is the measurement of electrolysis current versus time at a controlled electrode potential. It has a relationship to voltammetry similar to the relationship of an ultraviolet (UV) detector to spectroscopy. Whereas conductometric detection is used in ion chromatography, potentiometric detection is never used in routine practice. Electrochemical detection has even been used in gas chromatography in a few unusual circumstances. It has even been attempted with thin-layer chromatography (TLC). Its practical success has only been with liquid chromatography (LC) and that will be the focus here. 

DNA fragments separated by polymer networks are detected by ultraviolet (UV) detector or laser-induced fluorescence (LIF) detection. UV detection of DNA fragments is based on the UV absorption of the DNA bases that is, the wavelength and the molar absorption coefficient for the UV absorption maxima of DNA bases are 260 nm for A, 254 nm for G, 267 nm for T, and 271 nm for C, respectively. 

As far as the conversion of the analytical response is concerned, the most used detectors in GrFFF have been, until now, conventional ultraviolet (UV) detectors commonly used for HPLC. With this type of detector, the amount of particles with diameter di is proportional to the detector response at the zth point. With particulate samples, in fact, because of UV detector optics, the response is a turbidity signal read within an angle between the incident light and the photosensor (i.e., usually smaller than —10°) rather than the absorbance. This turbidity signal can be assumed to be directly proportional to the sum of all cross-sectional areas of the particulate sample components at any time. The validity of the above assumption, in the case of particles which are about 10-fold larger than the incident wavelength, is discussed elsewhere [6]. The mass frequency function can thus be expressed as [7]... 

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