Detection dual-wavelength

ABLE (AirBome Lidar Experiment) is a Nd-Yag high energy lidar for the measurement of aerosols and PSC. It will operate in either a dual wavelength configuration 532 nm or 355 nm emissions or at 532 nm with dual polarisation detection capacity. It will detect aerosols, PSC and tropospheric clouds. 

A novel cleanup procedure was used for TMP residues in tissue and milk samples. Tis-sue/milk samples were homogenized/dissolved with phosphate buffer, and the supernatant was purified on a Cl8 SPE cartridge previously conditioned by MeOH, water, and phosphate buffer containing pentanesulphonic acid (PSA). The TMP was eluted with MeOH phosphate buffer and injected directly into the ion-pair chromatographic system followed by dual-wavelength UV detection. The comparison of both signals ratio-enhanced the identification of the TMP peak besides the monitored UV spectra. Recoveries ranging from 73% to 98% were presented, and an LOD below the MRL set for TMP residues was achieved (176,177). 

RP-HPLC with UV dual-wavelength detection at 280 and 343 nm or 254 and 364 nm, N-(4-hydroxy-3-methoxybenzyl)oc-tanamide as the IS. 

Two UV detectors are also available from Laboratory Data Control, the UV Monitor and the Duo Monitor. The UV Monitor (Fig.3.45) consists of an optical unit anda control unit. The optical unit contains the UV source (low-pressure mercury lamp), sample, reference cells and photodetector. The control unit is connected by cable to the optical unit and may be located at a distance of up to 25 ft. The dual quartz flow cells (path-length, 10 mm diameter, 1 mm) each have a capacity of 8 (i 1. Double-beam linear-absorbance measurements may be made at either 254 nm or 280 nm. The absorbance ranges vary from 0.01 to 0.64 optical density units full scale (ODFS). The minimum detectable absorbance (equivalent to the noise) is 0.001 optical density units (OD). The drift of the photometer is usually less than 0.002 OD/h. With this system, it is possible to monitor continuously and quantitatively the absorbance at 254 or 280 nm of one liquid stream or the differential absorbance between two streams. The absorbance readout is linear and is directly related to the concentration in accordance with Beer s law. In the 280 nm mode, the 254-nm light is converted by a phosphor into a band with a maximum at 280 nm. This light is then passed to a photodetector which is sensitized for a response at 280 nm. The Duo Monitor (Fig.3.46) is a dual-wavelength continuous-flow detector with which effluents can be monitored simultaneously at 254 nm and 280 nm. The system consists of two modules, and the principle of operation is based on a modification of the 280-nm conversion kit for the UV Monitor. Light of 254-nm wavelength from a low-pressure mercury lamp is partially converted by the phosphor into a band at 280 nm. 

For all the above reasons, it is to be preferred to measure two solute properties in one detector, especially if both measurements can be performed simultaneously. An example of this is the application of dual-wavelength absorption detection in LC. The application of this technique for the purpose of selectivity optimization has been investigated by Drouen et al. [584]. For the purpose of peak assignment or recognition, ratio recording may be used. The principle of this technique is based on Beer s law and may be explained from the following equation for the absorption ratio Ra ... 

This paper is a progress report on the use of simultaneous dual wavelength (215nm, 280nm)absorbance detection for HPLC analysis of cannabinoids in biological fluids. Work in progress on fluorescence detection of cannabinoids will be the subject of a later report. 

Liquid Chromatography was performed on a Varian 8520 dual syringe pump liquid chromatograph. Two Vari-chrom variable wavelength detectors were used in series to provide a dual wavelength detection system. 

Direct HPLC analysis of urine extracts appears feasible for A -THC. 215nm is the optimum wavelength for detection of THC-class compounds. Dual wavelength at 215 and 280nm serves as a valuable check on cannabinoid retention assignment and as a screen for unknown THC or CBN-class metabolites. The latter feature was demonstrated in the observance of CBN-class peaks in both hexane and E-I extracts. This observation suggests a CBN-metabolic route of A -THC. Evidence of a CBN-metabolic route for A -THC has been reported by McCallum (8) and Green (6) for humans and by Ben Zvi et al (9) for rhesus monkeys. 

Eaulds K, Mackenzie E, Smith WE, Graham D (2007) Quantitative simultaneous multianalyte detection of DNA by dual- wavelength surface-enhanced resonance Raman scattering. Angew Chem Int Ed 46(11) 1829-1831... 

A. Ewen, H. J. Lafontaine, K.-T. Hidesheim, W. H. Stuurmen, Separation and determination of 22 PHAs by minibore HPLC with dual-wavelength UV detection, Int. Chrom. Lab., 14 (1993), 4-8. 

Coc,various alka-loids(Table 2.2 and 2.3) Various drugs Identification by means of dual wavelength detection uBondapak C18 uPorasil... 

C,M,No,P,H,diHC,EtM, totally 101 diHCone,diHMone,nic, drugs of fo- Identification by means of dual wavelength detection pBondapak C18 300x3.9 0.025M NaH,P0. in Me0H-H,0(2 3) pH 7.0 3 3... 

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