UV detector diode array

Simultaneous quantification of the herbicides atra2ine, sima2ine, terbut5la2ine, propa2ine, and prometryne and their principal metabohtes has been reported in natural waters at 3—1500 ng/L concentration (104). The compounds were enriched on graphiti2ed carbon black and analy2ed with hplc and a diode array uv detector. 

A more definitive identification may be obtained by combining retention characteristics with more specific information from an appropriate detector. Arguably, the most information-rich HPLC detectors for the general identification problem are the diode-array UV detector, which allows a complete UV spectrum of an analyte to be obtained as it elutes from a column, and the mass spectrometer. The UV spectrum often allows the class of componnd to be determined but the... 

Diode-array UV detector A UV detector which monitors all wavelengths simultaneously and therefore allows a complete UV spectrum to be obtained instantaneously. The alternative, a dispersive UV detector, monitors one wavelength at a time and thus requires a considerable amount of time to record a complete spectrum. 

The use of a fixed wavelength UV detector for liquid chromatographic separations was first described by Horvath and Lipsky in 1966 [1], and is possibly the most popular HPLC detector in general use today. Although other detection techniques are more sensitive, the UV detector provides a simple and universal answer to the majority of HPLC applications [2]. Developed in 1982, the diode array UV detector measures the full absorption spectrum of each analyte peak, and was a... 

For the majority of analyses of drugs in formulations, variable wavelength UV or diode array UV detectors are used. A typical UV dector has a narrow cell about 1 mm in diameter with a length of 10 mm, giving it an internal volume of about 8. ... 

Figure 9.13 A diode array UV detector light path.

It is also seen that the direction of rotation is clearly and unambiguously indicated by the direction of the peak. The peaks represent between 20 and 40 pg of material, which also indicates reasonable sensitivity. From approximate calculations made from the chromatogram the sensitivity for peak (6) appeared to be about 1.4 x 10 g/ml, which is only a factor of 2-4 less than that obtainable from the diode array UV detector. However it is extremely difficult to estimate the noise from the chromatogram shown in figure 9. A more... 

All HPLC analyses were carried out on a Hitachi system model 6200A, equipped with an L-4500 diode array UV detector. A SynChropak reverse-phase C4 column (0.46 X 25 cm) was employed. Elution was accomplished with a linear gradient of 0-60% acetonitrile containing 0.1% TEA over a period of 30 min at a flow rate of 1.0 ml/min. 

High-performance liquid chromatography is performed using a Hewlett-Packard 1090 chromatograph equipped with a ternary-solvent delivery system, an autoinjector with a 0 -20- u.L injection loop, an oven compartment, and a diode-array UV detector. An ELS detector (Alltech Associates, Deerfield, IL) is connected in series to the UV detector. Hexane, 2-propanol, and water were used for the analysis of nonionic surfactants. Water and tetrahydrofuran (THF) are used for the analysis of anionic surfactants. No preliminary sample preparation is used other than dilution. The nonionic surfactants are diluted 1 40 (v/v) with hexane. The anionic surfactants (alkyl ether sulfates and synthetic and petroleum sulfonates) are diluted 1 20 (v/v) with water-THF (50 50). The calcium sulfonate surfactants were diluted 1 20 (v/v) with a THF-38% hydrochloric acid solution of pH 1. Hydrochloric add is required to prevent salt precipitation by converting any excess water-insoluble caldum carbonate into water-soluble calcium chloride. All diluted samples are... 

Figure 7.15 HPLC-UV diode array instrument and chromatograms, (a) HPLC diode array UV detector system (b) UV spectra recorded at three points on an HPLC peak to enable peak purity to be determined (c) Isometric map obtained by plotting successive spectra from an HPLC separation of polynuclear aromatics. A, naphthalene B, fluorene C, anthracene D, chrysene.

The LACCC and LAC experiments were conducted on a Hewlett-Packard (HP 1090) HPLC system using a diode array UV Detector and an evaporative light-scattering detector. SEC measurements were performed on a modular... 

Miller et al. (36) studied the MW distribution of polycarbonates and aromatic polyesters blends using two solvents selectively. A blend of methylene chloride/HFIP (70 30) dissolves both polymers, but THF dissolves only polycarbonate. Separations were performed on a column set comprising a PL gel 5 pm mixed bed, a 100 A column, and a 5 pm precolumn. Although these two polymers coeluted, use of a diode array UV detector set at 285 nm allowed detection of the polyester because absorption is 20 times greater for PET versus polycarbonate. 

The UV spectrum recorded by the liquid chromatograph s diode array UV detector shows an intense maximum at 236 nm. This indicates that the impurity contains the 4-ene-3-oxo moiety. However, the slightly hypsochromic shift (see Table 1), and especially the broadening of the peak as compared to that of norgestrel, indicate the presence of a double bond in the skeleton, presumably in the 8(14) position, which is not in conjugation with the... 

Stock solutions of taxol in methanol (5mg/ml) was added with a weight ratio of 0.2 1 to 1 ml of OCL worm micellar solutions at different concentrations and vortexed for 5 minutes. The small amount of methanol was removed by dialysis at 4 °C for 2 hours. Unloaded taxol precipitate was centrifuged down at 3000 rpm for 5 min and further removed from the micelle supernatant by filtering with a 0.45 pm pore-sized syringe filter. The amount of taxol loaded into OCL worm micelles was then determined by HPLC. A Waters Breeze HPLC equipped with a diode array UV detector set at A, = 220 nm, connected with a Symmetry C-18 column, methanol as the mobile phase, and a flow rate of 0.8 mL/min was used. Taxol is well resolved from OCL peak, and the amount of taxol was estimated from its calibration curve that correlates peak area with amount. 

The easiest hyphenated system consists of an LC instrument with a multi-wavelength (e.g. diode-array) UV detector. Such a system is excellent for characterizing copolymers consisting of two or more types of monomeric units, all of which exhibit (different) UV activity. Unfortunately, this is hardly ever the case. A combination of a UV detector and a refractive-index (RI) detector connected in series does in principle provide sufficient information for copolymers (two different monomeric units). However, the interdetector volumes and band broadening are a complicating factor, as are the different background and blank signals (solvent peaks) provided by the two instruments. 

The diode array UV detector (DAD) has been employed for preparative SFC [13] and this has the advantage that the eluting materials may be partially characterised by acquisition of their UV absorption spectrum directly in the flowing stream. The light scattering detector (LSD) is a recent detector development that has found useful application in SFC. 

---