Diode array chiral detector

Martens-Lobenhoffer et al. [119] used chiral HPLC-atmospheric pressure photoionization tandem mass-spectrometric method for the enantio-selective quantification of omeprazole and its main metabolites in human serum. The method features solid-phase separation, normal phase chiral HPLC separation, and atmospheric pressure photoionization tandem mass spectrometry. The internal standards serve stable isotope labeled omeprazole and 5-hydroxy omeprazole. The HPLC part consists of Agilent 1100 system comprising a binary pump, an autosampler, a thermo-stated column component, and a diode array UV-VIS detector. The enantioselective chromatographic separation took place on a ReproSil Chiral-CA 5 ym 25 cm x 2 mm column, protected by a security guard system, equipped with a 4 mm x 2-mm silica filter insert. The analytes were detected by a Thermo Scientific TSQ Discovery Max triple quadrupole mass spectrometer, equipped with an APPI ion source with a... 

Fast chiral separations were carried out in a quartz chip using a linear imaging UV detector. Figure 6.11 shows the chiral separation of a tocainide derivative (an antiarrhythmic drug). UV imaging with a diode-array detector located along the 25-mm-long separation channel reveals the separation between the two enantiomers. Another chiral separation of pseudoephedrine was achieved in 13 s. The... 

There are two basic types of chiral detectors for LC, those that measure optical rotation and those that measure circular dichroism. At the time of writing this book, the only commercially available chiral detectors are those that measure optical rotation. Nevertheless, a detector that measures circular dichroism and utilizes a diode array sensor system is thought to be in the design stage and will be briefly described later. 

The value of a chiral detector in the analysis of physiologically active materials is clear, but the methods so far used have been found somewhat insensitive. A more encouraging procedure would be the measurement of circular dichroism and such instrumentation employing diode array detection is presently under development. Details of the device are difficult to obtain due to patent applications pending and particulars are not available. The basic arrangement, however, is thought to be similar to that depicted in figure 11. 

A JASCO model OR-990 chiral detector was tested as a means for assessing racemization in the reference samples. This instrument was equipped with a 44 pi flow cell (25 mm path length), a 150 W Hg-Xe lamp as light source, and an open-loop polarizer/analyzer. Samples were analyzed at 350 nm, with a lOx gain, 0.1 sec response, and 16 mdegree deflection. Separations were performed on a Hewlett Packard HP 1090 HPLC with a diode array detector. 

Polymer particles are suspended in water (25% MeCN) and then slurry-packed into stainless steel columns (250 mm x 4.6 mm i.d.) using an air-driven fluid pump (Haskel, Burbank, CA, USA) and water (25% MeCN) as the packing solvent. The packed columns are washed on-line on a Beckman HPLC system (comprising a solvent module 126 and diode array detector 168) using MeCN (20% acetic acid) to remove the print molecule until a stable base line is obtained. The mobile phase is then changed to a citrate buflfer (pH 3.0, 25 mM citrate) containing 10% MeCN (v/v) at a flow rate of 1 ml. min . For a test of chiral resolution, a racemic mixture of (+)- and ( )-isoproterenol (20 pL at 2 mM in the mobile phase) is injected, and the elution monitored at 280 nm. Acetone can be used as a void marker for the calculation of capacitor factor (k ) and separation factor (oc). 

Chirobiotic T. The authors achieved chiral separation of these pesticides using methanol as the major constituent of the mobile phase, with detection by a diode array detector. The chiral resolution of some environmental pollutants by HLPC is given in Table 7.2. As a specific example, the chromatograms of the resolved enantiomers of crufomate and a-HCH are shown in Figure 7.2. As usual, the enantiomeric resolution is expressed by... 

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