HPLC high performance liquid secondary

GC-gas chromatography, HPLC-high performance liquid chromatography, SFC-supercritical fluid chromatography, TLC-thin layer chromatography, MS-mass spectrometry, MF-mass fragmentography, Cl-chemical ionization, El-electron ionization, ECI-electron capture ionization, IS-ionspray, FAB-fast atom bombardment, ESI-electrospray, SIMS-secondary ion mass spectrometry. 

B. L. Karger, J. N. LePage, N. Tanaka, Secondary chemical equilibria in HPLC, in Cs. Horvath (Ed.) High-Performance Liquid Chromatography, Vol. 1, Academic Press, New York, 1980. 

Often, treatment of samples with fluorescence labeling agent reacts with primary and secondary amines to give a fluorescent compound. This is especially important for detecting amino acids in protein hydrolyzates. Fluorescence detectors may also be integrated into a high performance liquid chromatographic (HPLC) system. 

To suppress enamine-derived side products, we explored addition of benzotriazole (BtH) to the reaction mixture. The premise behind these experiments was the ability of BtH to form stable adducts with imines,23,24 thereby blocking tautomerization of 19 to 20 through in situ formation of the benzotriazolyl derivative 21. It was hoped that subsequent hydride displacement of the Bt moiety would afford the desired mono alkylated products 23. Indeed, analytical high-performance liquid chromatography (HPLC) revealed a remarkable improvement in terms of product purity, especially for reactions carried out at room temperature, with the desired secondary anilines 23 being essentially the only products detected. In... 

Amadori compounds (N-substituted-l-amino-l-deoxy-2-ketoses) are potential precursors to the formation of many of these heterocyclic volatile products. The secondary nitrogen in most Amadori compounds is weakly basic and is therefore a likely site for rapid nitrosation reactions via normal reactions with nitrous acid, under mildly acidic conditions. However, purified Amadori compounds are usually obtained only after tedious isolation procedures are invoked to separate them from the complex mixtures of typical Maillard browning systems. Takeoka et al. ( 5) reported high performance liquid chromatographic (HPLC) procedures to separate Amadori compounds in highly purified form on a wide variety of columns, both of hydrophilic and hydrophobic nature. They were able to thus demonstrate that reaction products could be followed for kinetic measurements as well as to ensure purity of isolated products. 

Porphyrophora hameli BRANDT (Armenian cochineal) contains nearly exclusively carminic acid. It has been reported that high-performance liquid chromatography (HPLC) has also identified a trace of kermesic acid, but TLC has not provided any clear proof of the presence of this secondary component in Armenian cochineal, even after previous concentration. 

The process of analyte retention in high-performance liquid chromatography (HPLC) involves many different aspects of molecular behavior and interactions in condensed media in a dynamic interfacial system. Molecular diffusion in the eluent flow with complex flow dynamics in a bimodal porous space is only one of many complex processes responsible for broadening of the chromatographic zone. Dynamic transfer of the analyte molecules between mobile phase and adsorbent surface in the presence of secondary equilibria effects is also only part of the processes responsible for the analyte retention on the column. These processes just outline a complex picture that chromatographic theory should be able to describe. 

The first concern in the selection of the sample preparation solvent is to optimize recovery. However, a secondary consideration is the sample solvent s effect on the analysis. This is true whether the analytical technique is ultraviolet spectroscopy (UV), high-performance liquid chromatography (HPLC), or gas chromatography (GC). The method development sequence can be described as (a) development of the chromatographic separation, (b) development of the sample preparation method, and then (c) evaluation and optimization of the interaction of the sample preparation with the instrumental method. 

Certain secondary amine compounds are commonly used for chemical derivation of isocyanates which, like phosgene, form substituted urea compounds amenable to chromatographic determination. One of the most common of these reagents is 1—(2—pyridyl)-piperazine (PYP) PYP reacts on a one-to-one basis with isocyanate compounds yielding a stable urea derivative which can be quantified specifically and sensitively with reversed phase, high performance liquid chromatography (HPLC) and ultraviolet absorbance detection. 

Apparatus. High performance liquid chromatographic separations were achieved on a binary gradient microbore HPLC systems primary pump (A) Model 305, secondary pump (B) Model 306, monomclric module Model 805, and a dynamic mixer Model 811C from Gilson Inc. (Middleton. Wl). Sample injections were achieved with a 20 pL loop on a Model EQ-36 injection valve from Valeo Instruments Co. Inc. (Houston, TX). A stainless steel Y-splitter also from Valeo was used in order to achieve a post-column split of the mobile phase Dow to the CLND. A Supelcosil LC-18S analytical HPLC column was purchased from SUPELCO Inc. (Bellefonte. PA). The Y-splitter was attached to the analytical column by a SLIPFREE connector, available from Keystone Scientific Inc. (Bellefonte, PA). Analyses of nor-dihydrocapsaicin, capsaicin and dihydrocapsaicin in spices as well... 

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