4-(5,6-dimethoxy-2-phthalimidinyl)phenylsulfonyl semipiperazide as a fluorescent labelling reagent for determination of carboxylic acids in precolumn high-performance liquid chromatography

Design and synthesis of a novel fluorescent reagent, 6-oxy-(ethylpiperazine)-9-(2'-methoxycarbonyl) fluorescein, for carboxylic acids and its application in food samples using high-performance liquid chromatography

A novel derivatization reagent for carboxylic acids, 6-oxy-(ethylpiperazine)-9-(2'-methoxycarbonyl)fluorescein (EPMF) has been well designed and synthesized. It was used to label 13 fatty acids, n-butyric acid (C4), n-valeric acid (C5), n-hexanoic acid (C6), n-heptanoic acid (C7), n-octanoic acid (C8), n-nonanoic acid (C9), n-decanoic acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), oleic acid (C18:1) and linoleic acid (C18:2), successfully. The derivatization reaction with fatty acids was completed at 50 degrees C, 50 min. The derivatives of fatty acids were separated on a C18 reversed-phase column with gradient elution and fluorescence detection at lambda(ex)/lambda(em)=469/518 nm. The detection limits obtained were 0.4-2 nmol L(-1) (signal-to-noise ratio of 3). The proposed method has been applied to the quantification of fatty acids in edible oil with recoveries over 93%. It has been demonstrated that EPMF is a prominent derivatization reagent for fatty acids and is suitable for HPLC.

Development of Highly Sensitive Determination of Biogenic Compounds by High-performance Liquid Chromatography with Pre-column Fluorescence Derivatization

A sensitive fluorescent labeling reagent, 4-(5,6-dimethoxy-2-phthalimidinyl)-2-methoxyphenylsulfonyl chloride (DMS-Cl), for the determination of amino compounds in HPLC was developed. DMS-Cl reacted with amino compounds in the basic medium to produce the corresponding fluorescent sulfonamides (excition 318 nm, emission 406 nm in aqueous acetonitrile). When amino acids were analyzed using reverse-phase HPLC, the detection limits (signal-to-noise ratio = 3) of almost all amino acids labeled with DMS-Cl were less than 5 fmol/injection. DMS-Cl was utilized for highly sensitive determination of amino compounds in biological samples and HPLC methods for determination of prolyl dipeptides, Pro and Hyp, in serum and urine, pipecolic acid in serum, taurine in plasma, and free and N-acetylated polyamine in urine were established. As these proposed methods are highly sensitive and reproducible and require only a small amount of biological sample, they may be useful for clinical and biochemical research.

Analysis of carboxylic acids in biological fluids by capillary electrophoresis

This review article addresses the different capillary electrophoretic methods that are being used for the study of both short-chain organic acids (including anionic catecholamine metabolites) and fatty acids in biological samples. This work intends to provide an updated overview (including works published until November 2004) on the recent methodological developments and applications of such procedures together with their main advantages and drawbacks. Moreover, the usefulness of CE analysis of organic acids to study and/or monitor different diseases such as diabetes, new-borns diseases or metabolism disorders is examined. The use of microchip devices and CE-MS couplings for organic acid analysis is also discussed.

An HPLC-MS approach for analysis of very long chain fatty acids and other apolar compounds on octadecyl-silica phase using partly miscible solvents

A novel approach for analyzing underivatized very long chain fatty acids (C16-C26) and other apolar compounds such as triacylglycerols is described. It is based on reversed-phase HPLC separation followed by mass spectrometric detection. Partly miscible solvents are used for stepwise gradient elution starting with a methanol/water and ending with a methanol/n-hexane binary mixture. The developed technique does not need derivatization, and analysis is fast (fatty acids were separated in 2-min-long chromatograms) and robust. The developed method is also very sensitive; a quantitation limit in the low-picogram range was achieved for fatty acids. The separation mechanism and advantages of the suggested technique are discussed and illustrated in the case of blood analysis and plant oil characterization.

A fluorogenic reagent, 4-mercapto-7-methylthio-2,1,3-benzoxadiazole for carboxylic acids, designed by prediction of the fluorescence intensity

During the course of our studies of the development of fluorogenic reagents having a 4,7-disubstituted benzofurazan structure, we previously proposed 7-acetylamino-4-mercapto-2,1,3-benzoxadiazole (AABD-SH) as a fluorogenic reagent for carboxylic acids. Since then, progress has made it possible to estimate the fluorescence quantum yields of the 4,7-disubstituted benzofurazan compounds on the basis of the PM3 calculation of their S1-T2 energies. Subsequently, a new fluorogenic reagent, 4-mercapto-7-methylthio-2,1,3-benzoxadiazole (MTBDSH) was designed and synthesized. In the presence of condensation reagents, triphenylphosphine (TPP) and 2,2'-dipyridyl disulfide (DPDS), MTBD-SH readily reacted with n-caprylic acid within 1 min at room temperature. The derivatives of five carboxylic acids (n-caprylic acid, n-capric acid, lauric acid, myristic acid, and palmitic acid) were well-separated on a reversed-phase column and were fluorimetrically detected at 519 nm with excitation at 391 nm. The detection limits (S/N = 3) were 2.4-5.0 fmol. Thus, MTBD-SH had properties that were considered to be superior. For carboxylic acids, itwas superior not only to AABD-SH, but also to many other conventional reagents. The superiority was examined in terms of its reactivity and sensitivity and the avoidance of interfering peaks that were derived from the reagent itself or degradation products in the chromatogram.

Determination of plasma free fatty acids by high-performance liquid chromatography with electrochemical detection

Determination of free fatty acids (FFAs) in control serum and human plasma was carried out by high-performance liquid chromatography with electrochemical detection. Peak height for palmitic, palmitoleic, stearic, oleic, linoleic, and arachidonic acids at a detection potential of -415 mV vs a saturated calomel electrode showed a linear relation to acid amount in the range 50-1600 pmol. The present method for plasma free fatty acid determination required only 10 microL of plasma sample. The method is simple and the time for blood pretreatment is short. Change in plasma FFA with blood glucose level was monitored before and after meal ingestion by this method, using one male and one female subject. It was possible to rapidly reduce plasma FFA and increase blood glucose subsequent to the meal. The present method is thus shown to have potential for clinical application.