Ultraviolet detectors chromatography

Figure 1 Ultraviolet spectra for benzaldehyde and benzoic acid solvent, methanol reference, methanol cell, 1.0 cm. (From Pfeiffer, C. D., Larson, J. R., and Ryder, J. F., Linearity testing of ultraviolet detectors in liquid chromatography, Anal. Chem., 54, 1622, 1983. Copyright American Chemical Society Publishers. With permission.)...

HCN = hydrogen cyanide HPLC = high performance liquid chromatography NaOH = sodium hydroxide GC = gas chromatography ECD = electron capture detector NPD = nitrogen-phosphorus detector UV = ultraviolet detector. 

Lanina et al. 1992 Oishi 1990). These methods include gas chromatography (GC) combined with mass spectrometry (MS) and high-performance liquid chromatography (HPLC) combined with an ultraviolet detector (UV). No comparisons can be made between methods since no data were given regarding sensitivity, recovery, or precision. 

GC = gas chromatography HC1 = hydrochloric acid HPLC = high-performance liquid chromatography MS = mass spectrometry Na2S04 = sodium sulfate NR = not reported UV = ultraviolet detector... 

A high-performance liquid chromatography system can be used to measure concentrations of target semi- and nonvolatile petroleum constituents. The system only requires that the sample be dissolved in a solvent compatible with those used in the separation. The detector most often used in petroleum environmental analysis is the fluorescence detector. These detectors are particularly sensitive to aromatic molecules, especially PAHs. An ultraviolet detector may be used to measure compounds that do not fluoresce. 

Supercritical fluid chromatography provides increased speed and resolution, relative to liquid chromatography, because of increased diffusion coefficients of solutes in supercritical fluids. (However, speed and resolution are slower than those of gas chromatography.) Unlike gases, supercritical fluids can dissolve nonvolatile solutes. When the pressure on the supercritical solution is released, the solvent turns to gas. leaving the solute in the gas phase for easy detection. Carbon dioxide is the supercritical fluid of choice for chromatography because it is compatible with flame ionization and ultraviolet detectors, it has a low critical temperature. and it is nontoxic. 

Figure 25-20 Photodiode array ultraviolet detector for HPLC. (a) Dual-beam optical system uses grating polychromator, one diode array for the sample spectrum, and another diode array for the reference spectrum. Photodiode arrays are described in Section 20-3. (fc>) Reversed-phase chromatography (using C18-silica) of sample containing 0.2 ng of anthracene, with detection at 250 nm. Full-scale absorbance is 0.001. (c) Spectrum of anthracene recorded as it emerged from the column. [Courtesy Perkln-Elmer Corp.. Norwalk. Cl]...

Such AOAC method is a satisfactory method but is thought not to be in current use for various reasons thin-layer chromatography argentation thin-layer chromatography ultraviolet (detector)... 

Arsenite also can be separated by ion chromatography using standard conditions. It elutes early, near the carbonate dip. For this application the ultraviolet detector should be placed between the separator and suppressor columns. 

Carbonate has been determined in high priority water in amounts down to 0.02pg L 1 by ion chromatography on Zipax SAX phthalic acid or mucomic acid at pH 6.5 and 7.2 as eluting agent and an indirect ultraviolet detector set at 321pm [125],... 

Mori [20] has identified and determined very low levels of phthalate esters in river water using reversed phase high performance liquid chromatography using an ultraviolet detector. Phthalates were extracted with n-hcxanc and the uncleaned or concentrated extracts were injected into three chromatographic systems, these being cross-linked porous beads (Shodex HP-225, Showa Penko Co.), porous polymer beads and polystyrene GPC gel. The eluants were respectively / -hexane (system A) and methanol (system B), and chloroform (system C). 

Fig. 9.1 shows the separation of arsenite and arsenate by ion exclusion chromatography using 0.01 mol L 1 hydrochloric acid as the eluent. Arsenious acid is a very weak acid and cannot be detected at low levels by the conductivity detector. However, like sulphide, it is easily detected with the ultraviolet detector. The simultaneous determination of arsenite and arsenate is possible. 

Gel filtration chromatography using Sephadex G100 as column packing and ultraviolet detectors, have been used in studies carried out on the elution of humic acid [8] and in characterisation studies on secondary sewage effluents [9] and in organic substances in river waters [10],... 

Apparatus (See Chromatography, Appendix IIA.) Use a high-performance liquid chromatograph operated at room temperature with a 10-p.m particle size, 30-cm x 4-mm (id), C18 reverse-phase column (jxBondapak C18 column, Waters Corp., 34-T Maple Street, Milford, MA 01757, or equivalent). Maintain the Mobile Phase at a pressure and flow rate (typically 2.0 mL/min) capable of giving the required elution time (see System Suitability in High-Performance Liquid Chromatography). Use an ultraviolet detector that monitors absorption at 254 nm (0.2 to 0.1 AUFS range). 

Chromatographic System (See Chromatography, Appendix IIA.) Use a high-performance liquid chromatograph equipped with an ultraviolet detector measuring at 303 nm and a 25-cm x 4.6-mm (id) column packed with octadecylsilanized silica (Supelcosil LC 18, or equiva-... 

Quantitahve analysis of reaction mixtures was performed by high-performance liquid chromatography (HPLC) and a diode array ultraviolet detector, as reported elsewhere [5, 6, 17]. 

Gel permeation chromatography (gpc) was performed on a Waters GPC-3 with a model 600 solvent delivery system, a 730 data module, a variable wavelength ultraviolet detector (uv), and a refractive index detector (Rl). Calculations were made on the uv detector response with the wavelength set at 325 nm. Three j/Styragel columns of porosities 105, 104, and 103 A were used and calibrated with polystyrene standards. Injection size was 50-125//I of 0.05% solutions with a flow rate of 1.4 ml/min. The solvent was HPLC grade N-methyl pyrrolidone (NMP) obtained from Aldrich Chemical Co. buffered with 0.03 M LiBr and 0.03 M H3P04.(2, 3)... 

LC Separation. Preparative scale liquid chromatography was performed with Waters PrepPak radially compressed silica columns. Fuel charges of 6 to 10 ml were carried through the column with n-pentane at a flow of 200 ml/minute. Refractive index, 254 nm ultraviolet, and 313 nm ultraviolet detectors monitored the LC effluent and keyed the collection of fractions. 

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