Reversed phase HPLC with

Numerous high pressure Hquid chromatographic techniques have been reported for specific sample forms vegetable oHs (55,56), animal feeds (57,58), seta (59,60), plasma (61,62), foods (63,64), and tissues (63). Some of the methods requite a saponification step to remove fats, to release tocopherols from ceHs, and/or to free tocopherols from their esters. AH requite an extraction step to remove the tocopherols from the sample matrix. The methods include both normal and reverse-phase hplc with either uv absorbance or fluorescence detection. AppHcation of supercritical fluid (qv) chromatography has been reported for analysis of tocopherols in marine oHs (65). 

Castro and Canselier [114] similarly used reverse phase HPLC with methanol-water containing a low concentration of nitric acid as eluent. Quantification was made possible by using a moving-wire flame ionization detector. 

The purified sample extracts are concentrated and analyzed by reversed-phase HPLC with fluorescence, MS, or MS/MS detection as described in Sections 2.1 and 2.2. 

Trathnigg, B., Kollroser, M.J. (1997). Liquid chromatography of polyethers using universal detectors V. Quantitative aspects in the analysis of low-molecular mass poly(ethylene glycols) and their derivatives by reversed-phase HPLC with an evaporative light scattering detector. J. Chromatogr. A 768, 223-238. 

A wide variety of methodologies have been employed for the analysis of antioxidants in polymers and some standard methods are available. For high-density polyethylene ASTM method D5524 (ASTM International) — Determination of phenolic antioxidants in high-density polyethylene, describes a method whereby the sample is ground to a small particle size and then extracted by refluxing with cyclohexane. The cyclohexane extract is then examined by reverse-phase HPLC with UV detection. 

Part 20 Determination of epichlorohydrin in plastics Extraction of epichlorohydrin with dioxane, followed by microdistillation and derivitization with 9,10-dimethoxyanthracene-2-sulfonic add followed by reverse phase HPLC with fluorescence detection... 

Determination of organolead metabolites of tetraalkyllead in urine can be carried out after solid-phase enrichment and end analysis using reversed-phase HPLC with chemical reaction detector and by LC-MS (thermospray127). The chemical derivation consists of conversion to the dialky Head form, as shown in reaction 1, followed by complex formation with 4-(2-pyridylazo)resorcinol (11) and spectrophotometic measurement at 515 nm128. 

Enthalpy-entropy compensation has been investigated in reversed-phase HPLC with octylsilica stationary phase [77]. The compensation temperatures were determined for this system, and the results show that their change with the composition of the mobile phase is almost similar to that with octadecylsilica stationary phase. It can be concluded that the retention mechanisms of the separation of alkyl benzenes is the same in both systems with the mobile phase exceeding 20% water content. 

River sediment Alkyltin Reverse phase hplc with ICP mass spectrometric detector 3-I6 pg [83] ... 

Nicoletti I, De Rossi A, Giovinazzo G, Corradini D. Identification and quantification of stUbenes in fruits of transgenic tomato plants (Lycopersicon esculentum Mill.) by reversed phase HPLC with photodiode array and mass spectrometry detection. Journal of Agricultural and Food Chemistry 55, 3304-3311, 2007. 

Lewtas, J., L. King, K. Williams, L. Ball, and D. DeMarini, Bioassay-Directed Fractionation of 1-Nitropyrene Metabolites Generation of Mutagrams by Coupling Reverse-Phase HPLC with Microsuspension Mutagenicity Assays, Mutagenesis, 6, 481-489 (1990b). 

AdoMet and AdoHcy are separated and measured as their etheno derivatives using reverse-phase HPLC with isocratic elution in separate runs, using ion-pairing for AdoMet. In both runs the column is flushed with 100% acetonitrile followed by reequilibration with the mobile phase between sample injections. 

Reversed-phase HPLC with fluorescence detection is the preferred system for the routine determination of total a-tocopherol in vitamin E-supplemented foods after saponification. The use of NARP chromatography with a predominantly hexane mobile phase allows aliquots of hexane extracts of the unsaponifiable matter to be injected directly onto the column, thus avoiding the evaporation step necessary when a semiaqueous mobile phase is used (234). 

JP Langenberg, UR Tjaden, EM de Vogel, DI Langerak. Determination of phylloquinone (vitamin K,) in raw and processed vegetables using reversed phase HPLC with electrofluorometric detection. Acta Alimentaria 15 187-198, 1986. 

The most commonly used stationary phase for the separation of aspartame from synthesis intermediates, stereoisomers, and degradation products is the reverse-phase Cl8 column. As can be seen on Table 2, the main type of the mobile phase used is a phosphate buffer at pH ranging from 2.5 to 5.0 associated with acetonitrile (14,55,80,83). Reverse-phase HPLC with gradient elution of acetonitrile in phosphate buffer has also been used (16,78). 

Reverse-phase HPLC with ion pairing and UV detection at 227 and 210 nm was used to determine sweeteners (acesulfame-K, saccharin, and aspartame), preservatives (BA and SA), and... 

Ethoxyquin, a synthetic antioxidant, is not generally allowed for human consumption in foods, but it is being added to animal feed and to fruits as an antiscald agent (94,143). Ethoxyquin is also used in the spice industry to prevent carotenoid loss during postharvest handling. However, ethoxyquin-treated paprika is unacceptable for some markets and some consumers (129). Perfetti et al. (130) described a method for determination of ethoxyquin in paprika and chili powder. Ethoxyquin was extracted from the spice with hexane and partitioned into 0.3 N HC1. After adjusting the solution to pH 13-14, ethoxyquin was extracted into hexane, and the hexane layer was evaporated to dryness. An acetonitrile solution of the residue was then analyzed by reversed-phase HPLC, with detection at 254 nm. The mobile phase was water/acetonitrile with ammonium acetate buffer. Recoveries from samples fortified at 50, 100, and 200 ppm averaged 92%, with a coefficient of variation of 2.3%. The method was applied to a number of commercial samples of paprika and chili powder. Ethoxyquin was found in paprika samples at levels up to 63 ppm and in chili powder samples at levels up to 20 ppm. 

Two predominant phenolic compounds (neochlorogenic and chlorogenic acids) in prunes and prune juice can be analyzed by reversed-phase HPLC with diode array detection along with other phenolic compounds (65). Phenolic compounds were extracted from prunes with methanol and aqueous 80% methanol and analyzed by HPLC. Ternary-gradient elution (a) 50 mM NaH4H2P04, pH 2.6, (b) 80% acetonitrile/20% (a), and (c) 200 mM phosphoric acid, pH 1.5, was employed for an 80-min run time. Four wavelengths were monitored for quantitation 280 nm for catechins and benzoic acids, 316 nm for hydroxycinnamates, 365 nm for flavonols, and 520 nm for anthocyanins. Phenolic analysis of pitted prune extract is presented in an HPLC chromatogram in Fig. 9, which is based on work done by Donovan and Waterhouse (65). 

Scudamore [52] determined 2-aminobutane in potatoes by HPLC. This substance is used to control certain potato tuber diseases. The amine was distilled from potatoes, dansylated and determined using reverse-phase HPLC with fluorescence detection. Recovery of 2-aminobutane by distillation was about 95% from standard solutions and 92% from treated potatoes. The lower limit of detection was below 0.2 pg/kg. 

Taylor EW, Qian MG, Dollinger GD. Simultaneous online characterization of small organic molecules derived from combinatorial libraries for identity, quantity, and purity by reversed-phase HPLC with chemiluminescent nitrogen, UV, and mass spectrometric detection. Anal Chem 1998 70 3339-3347. 

Air is drawn through a midget impinger or a bubbler containing 0.1 ANaOH solution. Phenol and ciesols are trapped as phenolates. The pH of the solution is adjusted <4 by H2S04. The compounds are determined by reverse-phase HPLC with UV detection at 274 nm. An electrochemical or fluorescence detector may also be used. The solution may be analyzed by colorimetric or GC-FID technique. 

Aqueous samples buffered with citrate and pH adjusted to 3. Acidified sample derivatized with 2,4-dinitrophenylhydrazine (DNPH) derivative analyzed by GC-NPD or reverse phase HPLC with UV detection at 360 nm. 

Air drawn through a midget impinger containing 10 mL of 2% aniline in toluene (by volume) phosgene reacts with aniline forming carbanilide (1,3-dipheny-lurea) solvent evaporated at 60°C under N2 flow residue dissolved in 1 mL acetonitrile carbanilide analyzed by reverse-phase HPLC with an UV detector set at 254 nm (EPA Method T06) recommended flow rate 200 mL/min sample volume 20 L. 

Orsulak, P. J., Kenney, J. T., Debus, J. R., Crowley, G., Wittman, P. D. Determination of the Antidepressant Fluoxetine and Its Metabolite Norfluoxetine in Serum by Reversed-Phase HPLC, with Ultraviolet Detection. Clin. Chem. 1988, 34, 1875-1878. 

Szpunar, J., Chassaigne, H., Donard, O.F.X., Bettmer,J. and Lobinski, R. (1997) Specia-tion of protein-bound cadmium in biological materials by size-exclusion and reversed-phase HPLC with ICP-MC detection. Spec. Publ. — Roy. Soc. Client., 202, 131-144. 

Chong, B. E. Hamler, R. L. Lubman, D. M. Ethier, S. P. Rosenspire, A. J. Miller, F. R. 2001. Differential screening and mass mapping of profiles from premalignant and cancer cell lines using nonporous reversed phase HPLC with on-line detection by ESI-TOFMS. Anal. Chem., 73, 1219-1227. 

Figure 3.20. Analysis of carboxylic acids and alcohols by reversed phase HPLC, with indirect UV detection, (a) Carboxylic acids. Chromatography conditions mobile phase, 3 X 10 4 M l-phenethyl-2-picolinium in acetate buffer (pH 4.6) column, ju-Bondapak phenyl detection, indirect UV absorbance at 254 nm. Peaks 1, acetic acid 2, propionic acid 3, butyric acid 4, valeric acid 5, caproic acid S, system peak, (b) Aliphatic alcohols. Chromatography conditions mobile phase, 4 x 10 4 M nicotinamide in water column. Ultrasphere ODS detection, indirect UV absorbance at 268 nm. Peaks 1, methanol 2, propylene glycol 3, ethanol 4, 2-propanol 5, 1-propanol 6, system peak 7, 2-butanol 8, 2-methyl-l-propanol 9, 1-butanol. (Redrawn from Refs. 23 and 24 with permission.)...

Palaniswamy, U.R., Caporuscio, C. and Stuart, J.D. (2003) A chemical analysis of antioxidant vitamins in fresh curry leaf (Murraya koenigii) by reversed phase HPLC with UV detection. Acta Horticulturae 620, 475 178. 

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