UV-fluorescence

Note that in liquid phase chromatography there are no detectors that are both sensitive and universal, that is, which respond linearly to solute concentration regardless of its chemical nature. In fact, the refractometer detects all solutes but it is not very sensitive its response depends evidently on the difference in refractive indices between solvent and solute whereas absorption and UV fluorescence methods respond only to aromatics, an advantage in numerous applications. Unfortunately, their coefficient of response (in ultraviolet, absorptivity is the term used) is highly variable among individual components. 

The sample is pyrolyzed in an 80/20 mixture of oxygen and nitrogen at from 1050 to 1100°C the combustion gases are analyzed by iodine titration or by UV fluorescence. Up to 20% of the sulfur can escape analysis, however. 

Despite their importance, gas chromatography and liquid chromatography cannot be used to separate and analyze all types of samples. Gas chromatography, particularly when using capillary columns, provides for rapid separations with excellent resolution. Its application, however, is limited to volatile analytes or those analytes that can be made volatile by a suitable derivatization. Liquid chromatography can be used to separate a wider array of solutes however, the most commonly used detectors (UV, fluorescence, and electrochemical) do not respond as universally as the flame ionization detector commonly used in gas chromatography. 

Sulphur compounds Flame photometry Coulometry UV fluorescence... 

The choice of detector is often crucial to the success of a particular HPLC method. A number are in routine use, including the UV, fluorescence, electrochemical, conductivity and refractive index detectors, and each has particular advantages and disadvantages, details of which can be found elsewhere [2-4],... 

HPLC with various detection methods (UV, fluorescence)... 

At this point, the anaiyte may not be amenabie to UV, FL, or EC detection. In this case, the best course of action may be to choose LC/MS (see Section 4.2). However, one other option is to use a pre- " or post-coiumn derivatization step to increase the detectabiiity of the anaiyte with respect to FL or UV. Fluorescent or UV labels are available for carboxylic acids," amines, phenols, and thiols. The decision to use pre- or post-column derivatization is predicated upon the functionality of the analyte available for derivatization and the rate and extent of the reaction between each derivatizing agent and the analyte. 

HPLC and LC/MS. HPLC methodology coupled with ultraviolet (UV), fluorescence (FL), photodiode-array (PDA) and/or a mass spectrometry (MS) detection has been developed. In general, neonicotinoids can be determined by HPLC/UV. Typical HPLC operating conditions are given in Table 2. 

The detection of the migrating sample boundary in CE can be accomplished by UV, fluorescent, electrochemical, radiochemical, conductivity, and mass spectrometry (MS) means. The use of high-sensitivity detection systems is always a key issue in CE applications. The sensitivity of HPCE detectors may be at least 2 to 3 orders of magnitude better than that of HPLC detectors. Since the detection cell volume is very small, the concentration sensitivity... 

Detection mode microcoulometric titration. c Detection mode UV fluorescence. 

Hartel S, Tykhonova S, Haas M, Diehl HA (2002) The susceptibility of non-UV fluorescent membrane dyes to dynamical properties of lipid membranes. J Fluoresc 12(3) 465 179... 

Decisive for the success of the assay is the finding that the rate of oxidation constitutes a direct measure of the ee (Figure 8). High throughput was demonstrated by analyzing 100 samples in a 384-well format using a UV/fluorescence plate reader. Each sample contained 1 pmol of... 

The IPCF camera can be used in UV reflectivity and UV fluorescence mode, illuminating the object with UV light and choosing the proper acquisition mode by software. The light source used for UV reflectivity and fluorescence measurements was a 150 W Wood lamp illuminating the sample at a distance of 50 cm from the surface. 

The near UV spectral range is divided in three bands the short wave band or UV-C emission runs from 180 to 280 nm with a peak at 254 nm. The medium wave band or UV-B runs from 280 to 320 nm with a peak at 312 nm, while the UV-A long wave band runs from 320 to 380 nm with a peak at 365 nm. The long wave emission is commonly called "Black light" or "Wood s light". Only the UV-A portion of the lamp spectrum is useful for UV reflectivity measurements, since wavelengths under 400 nm are cut off by the glass optics of the objective. However, the full power of the lamp is used for UV fluorescence measurements. 

UV light, others do not. Figure 13.6 demonstrates a plate applied with a UV fluorescent compound and how it appears under 366 nm UV light. 

---