Yuta Yasaka

2-(2,3-Naphthalimino)ethyl trifluoromethanesulphonate as a highly reactive ultraviolet and fluorescent labelling agent for the liquid chromatographic determination of carboxylic acids

Abstract The use of 2-(2,3-naphthalimino)ethyl trifluoromethanesulphonate in the preparation of 2-(2,3-naphthalimino)ethyl ester derivatives of carboxylic acids for ultraviolet and fluorescent detection in high-performance liquid chromatography is described. The reagent is easily synthesized in two steps from 2,3-naphthalenedi-carboxylic anhydride and is stable at least for 6 months at room temperature. Reactions of carboxylate potassium salts (10 −5 M ) with a 10-fold equivalent excess amount of the reagent proceed to completion within 10 min in acetonitrile at room temperature in the presence of 18-crown-6 as a catalyst. The derivatization procedure with this reagent has been applied succesfully to the determination of some carboxylic acids in mouse brain. The detection limits (signal-to-noise ratio = 3) with ultraviolet and fluorescent detection are 100 fmol (at 259 nm) and 4 fmol (λ ex = 259 nm, λ em = 394 nm), respectively.

Labeling of free carboxyl groups

The latest trends in the labeling of free carboxyl groups for high-performance liquid chromatography are reviewed. The labeling reagents for fluorescence detection are mainly discussed according to their reaction type (or functional group). Attention is also paid to the reagents used for ultraviolet detection and for enantiomeric separation. The reactivity and sensitivity of the reagents used for the labeling of carboxylic acids are described.

(S)-(+)-1-Methyl-2-(6,7,-dimethoxy-2,3-naphthalimido)ethyl trifluoromethanesulfonate as a fluorescence chiral derivatizing reagent for carboxylic acid enantiomers in high-performance liquid chromatography

A new triflate-type fluorescence chiral derivatizing reagent, (S)-(+)-1-methyl-2-(6,7-dimethoxy-2,3-naphthalimido)ethyl trifluoromethanesulfonate, [S-(+)-MDNE-OTf], has been developed for the determination of the enantiomers of carboxylic acids. By introducing the two methoxy groups on the naphthalimido ring moiety, the red shift in the fluorescence spectrum and a high resolution in reversed-mode separation of the diastereomers of chiral carboxylic acids have been achieved. The detection limits (S/N=3) with ultraviolet and fluorescence detection are 8 fmol (λmax=283 nm) and 4 fmol (λex=283 nm, λem=467 nm), respectively.

Double-chain surfactants with two sulfonate groups as micelle-forming reagents in micellar electrokinetic chromatography of naphthalene derivatives

Three surfactants having two sulfonate groups and two lipophilic chains, disodium 5,12-bis(dodecyloxymethyl)-4,7,10,13-tetraoxa-1-16-hexadecanedisulfonate (DBTHX), 5,13-bis(dodecyloxymethyl)-4,7,11,14-tetraoxa-1-17-heptadecanedisulfonate (DBTHP) and 5,13-bis(dodecyloxymethyl)-4,7,11,14-tetraoxa-9,9-dimethyl-1-17-heptadecanedisulfonate (DBTDMHP), were used in micellar electrokinetic chromatography (MEKC) to separate eight naphthalene derivatives as model analytes. Their capacity factors linearly increased as the concentration of each surfactant increased from 1 to 10 mM at pH 7.0. These double-chain surfactants exhibited different selectivity and wider migration time windows when compared with sodium dodecyl sulfate (SDS), which is used widely in MEKC. The eight naphthalene derivatives were baseline separated at 5 mM DBTHX and 2.5 mM DBTHP, respectively, and nearly baseline separated at 2.5 mM DBTDMHP. However, SDS at 60 mM could not completely resolve three of the analytes.

New ultraviolet labelling agents for high-performance liquid chromatographic determination of monocarboxylic acids

New UV-labelling agents have been synthesized, which are designed to convert monocarboxylic acids into their highly UV-absorbing derivatives for enhancement of the sensitivities of UV detection in high-performance liquid chromatography. The reagents are p-nitrobenzyl, 3,5-dinitrobenzyl and 2-(phthalimino)ethyl p-toluenesulphonates. Each has been prepared by reaction of p-toluenesulphonyl chloride with p-nitrobenzyl alcohol, 3,5-dinitrobenzyl alcohol or N-(hydroxyethyl)phtalimide, respectively, in the presence of sodium hydroxide, and they are stable in the solid state for at least 6 months. Monocarboxylic acids were derivatized to their p-nitrobenzyl, 3,5-dinitrobenzyl or 2-(phthalimino)ethyl esters with each of the above reagents, respectively, then determined by high-performance liquid chromatography with UV detection. In the UV-labelling with each reagent, 18-crown-6 was used as the catalyst. The effects of the reaction solvent, reaction temperature and time and the concentrations of each reagent and the catalyst were also examined.

Derivatization of inorganic anions with pentafluorobenzyl methanesulphonate for gas chromatography

A new derivatizing reagent, pentafluorobenzyl methanesulphonate, has been synthesized and used to determine inorganic anions by gas chromatography. Bromide, iodide, cyanide, thiocyanate, nitrite and sulph iodide, cyanide, thiocyanate, nitrite and sulphide in water at mM levels could be simultaneously pentafluorobenzylated in dichloromethane, using tetra-n-amylammonium chloride as a phase-transfer catalyst. The resulting derivtives were subsequently determined by gas chromatography with flame ionization detection. In water at μM levels, except for cyanide and nitrate, the anions could also be derivatized to their pentafluorobenzyl derivatives in the biphasic reaction system and be detected by gas chromatography with electron-capture detection. In addition to the biphasic reaction method, bromide, iodide and thiocyanate were simultaneously pentafluorobenzylated in an homogen in an homogeneous reaction system of aqueous acetone or aqueous methanol, without the use of a phase-transfer catalyst.

Impacts of converting from leaded to unleaded gasoline on ambient lead concentrations in Jakarta metropolitan area.

Total suspended particulate mater (TSP) concentrations were monitored for one year from July 2000 and for one year from April 2003 in Jakarta City. Thirteen elemental TSP components, aluminum (Al), sodium (Na), iron (Fe), lead (Pb), potassium (K), zinc (Zn), titanium (Ti), manganese (Mn), bromine (Br), copper (Cu), chromium (Cr), nickel (Ni), and vanadium (V) were analyzed by a sequential X-ray fluorescence spectrometer. Al, Na, Fe, K, and Pb were major components at most of the sampling locations in 2000. However, only Pb in 2003 dramatically decreased to one tenth. The phase-out of leaded gasoline began on July 1, 2001 in Jakarta City and lead content in gasoline decreased to one tenth, too. The decrease in Pb concentration was a result of the phase-out of leaded gasoline, as lead emissions mainly are exhaust gas from vehicles.

Strontium isotope effect in DMSO-water system by liquid chromatography using a cryptand polymer

The strontium isotope effect in the chemical exchange reaction of chromatography using a cryptand (2B, 2, 2) polymer as a solid phase was investigated. Isotope enrichment factors were decreased with DMSO contents in water. The enrichment factor ε84,88 for 84Sr in comparison to 88Sr in pure water system was ε84,88 = (6.33 ± 0.48) × 10−3 and that in 100% DMSO system was ε84,88 = (10.14 ± 1.08) × 10−3. In almost all systems except for 50 v% DMSO–water system, the enrichment factors were not scaled with Δm/mm′, where Δm is the mass difference for the isotopes m and m′. In these systems, the difference of nuclear size and shape, namely the field shift was found to dominate the isotope effects of strontium. In the water system, the contribution of the nuclear size and shape was 7.47 × 10−3, and that in the DMSO was −17.97 × 10−3. Those values were larger than the contribution of the mass effect.

Polymeric pentafluorobenzylating reagent for gas chromatography of inorganic anions with electron-capture detection

Abstract Poly(pentafluorobenzyl p -styrenesulphonate) was synthesized as a pentafluorobenzylating reagent for inorganic anions. Bromide, iodide, cyanide, thiocyanate, nitrite and sulphide anions in water were readily converted into their pentafluorobenzyl derivatives by reaction with the reagent dissolved in dichloromethane in the presence of tetra- n -amylammonium chloride as phase-transfer catalyst. The replacement of dichloromethane with tert. -butyl methyl ether can precipitate the reagent and prevent its interference. The injection of the derivatives into a gas chromatograph equipped with an electron-capture detector, without introducing the derivatizing reagent, can be achieved only by injecting the supernatant solutions. The use of the polymeric reagent has greatly facilitated this process and resulted in the sensitive determination of inorganic anions at ng/ml levels.

Effect of Counter Anion in Isotope Exchange Reaction of Strontium

Abstract The effect of counter anion in isotope exchange reaction of strontium was investigated by liquid chromatography using a cryptand (2B, 2, 2) polymer as a stationary phase. Isotope enrichment factors were assumed to be in the order: perchlorate > chloride > nitrate > bromide. The maximum isotope enrichment factor of 84Sr was (13.2 ± 2.2) × 10−3 and the minimum was (4.2 ± 1.2) × 10−3. No isotope enrichment factor showed a linear relation to the difference of atomic masses. The contribution of the field shift in atomic electrons was greater to the isotope enrichment factor than the vibrational frequency shift between an isotope and a ligand. Chloride as a counter anion to strontium was the largest isotope enrichment factor. # This work was mainly carried out at the Department of Nuclear Engineering, Graduate School of Osaka University.