Chromatographia: An International Journal for Rapid Communication in Chromatography, Electrophoresis and Associated Techniques (v.57, #7-8)
Determination of biogenic amines in wines and beers by high performance liquid chromatography with pre-column dansylation and ultraviolet detection
by A. Zotou; Z. Loukou; E. Soufleros; I. Stratis (pp. 429-439).
A sensitive high performance liquid chromatographic method for the simultaneous determination of eleven biogenic amines, using 1,7-diaminoheptane as internal standard, has been developed. The method involves pre-column derivatization of the amines with dansyl chloride and subsequent solid phase extraction of the derivatives through C18 cartridges. The derivatization and solid phase extraction procedures were optimized. The separation of dansylamides was achieved on an Inertsil ODS-3 column (250×4 mm I.D. 5 μm) using a 35-min gradient elution method with a binary system of acetonitrile-water, a flow rate of 1 mL.min1 with UV detection at 254 nm. Linearity of derivatization was obtained for concentrations ranging from 0.025 to 3.0 mg.L1. The within- and between-day relative standard deviations ranged from 0.4 to 5.7% and 0.6 to 7.3% respectively. The overall process was successfully applied to identify and quantify biogenic amines in white, red and Retsina Greek wines and Greek beers, after their treatment with polyvinylpyrrolidone.
Keywords: Column liquid chromatography; Dansylation; Biogenic amines; Wines and Beers
Procyanidin size and composition by thiolysis with cysteamine hydrochloride and chromatography
by J. L. Torres; A. Selga (pp. 441-445).
Cysteamine hydrochloride is shown to be an alternative thiol reagent to toluene-α-thiol for the estimation of structural parameters (mean size, galloylation) of plant polymeric procyanidins. Acid depolymerization in the presence of the thiol yields mixtures which may be directly analysed by RPHPLC. Alternatively, the terminal units of the polymer may be separated from the extension units by cation-exchange chromatography previous to RPHPLC. High reaction-recovery yields (ca. 90% thiolysis and RPHPLC, ca. 69% thiolysis, cation exchange and RPHPLC) are obtained and both procedures are precise.
Keywords: Column liquid chromatography; Cation exchange chromatography; Thiolysis with cysteamine; Plant procyanidins; Antioxidants
Simultaneous determination of a new phosphodiesterase-5 inhibitor DA-8159 and its active metabolite in human plasma by high performance liquid chromatography with tandem mass spectrometry
by J. Kim; S. J. Kim; H. Y. Ji; J. K. Jin; S. S. Lee; D. S. Kim; M. Yoo; W. B. Kim; H. S. Lee (pp. 447-450).
An LC-MS-MS method for the simultaneous determination of DA-8159 and its active metabolite, DA-8164 in human plasma was developed. DA-8159, DA-8164 and the internal standard, sildenafil were extracted from human plasma with dichloromethane at basic pH. A reversephase HPLC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-ammonium formate (10 mM, pH 6.0) (60:40,v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring mode. The method showed a satisfactory sensitivity (lower limits of quantification, 2.0 ng mL1), precision, accuracy, recovery and selectivity. The successful determination of DA-8159 and DA-8164 in the plasma of a volunteer who ingested a single dose of 100 mg DA-8159 confirms that the present method can be used for plasma analysis for clinical trial.
Keywords: Column liquid chromatography; Tandem mass spectrometry; Plasma; DA-8159 and metabolite
Using principal component analysis for the study of the retention behaviour of phenol derivatives under reversed-phase conditions
by Z. Kánya; T. Cserháti; E. Forgács (pp. 451-456).
The retention time of 11 ring-substituted phenol derivatives was measured on six different reversed-phase HPLC columns and the log k, theoretical plate number (N) and asymmetry factor (F) values were calculated for each solutes on each column. The similarities and dissimilarities among the columns and solutes were elucidated by principal component analysis followed with nonlinear mapping technique and cluster analysis. Calculations indicated that the retention characteristics of porous graphitized carbon stationary phase considerably deviate from those of octadecyl- and hexyl-coated silica, octadecyl-coated polystyrene-divinylbenzene polymer and polybutadiene-coated alumina. The differences among these columns were markedly smaller. The retention behaviour of aminophenols differed from those of other phenol derivatives proving the importance of molecular polarity in the retention. It was established that the mode of calculation slightly modifies the similarity and dissimilarity among the columns and solutes, therefore, the use of more than one calculation method is proposed.
Keywords: Column liquid chromatography; stationary phases; Phenol derivatives; Principal component analysis
Chiral resolution of diphenylalanine by high-performance liquid chromatography on a crown-ether-based chiral stationary phase and by NMR spectroscopy
by W. Lee; E. Bang; W. Lee (pp. 457-461).
The enantiomers of diphenylalanine (DPA) were well separated by chiral HPLC and NMR spectroscopy on the chiral stationary phase (CSP) derived from (18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA). The chromatographic parameters such as separation factors and retention times were greatly influenced by the mobile phase conditions. The (+)-18-C-6-TA used in the CSP was also employed as a chiral solvating agent for the enantiodiscrimination of the DPA enantiomers by NMR spectroscopy. The proton of the DPA analyte showing the chemical shift nonequivalences was used in determining the enantiomeric composition of the analyte.
Keywords: Column liquid chromatography; NMR spectroscopy; Chiral solvating agent; 18-Crown-6-tetracarboxylic acid
Influence of various factors on the chromatographic behavior of cytostatic antibiotics of rubomicin derivatives in micellar liquid chromatography
by A. U. Kulikov; L. P. Loginova; L. V. Samokhina (pp. 463-469).
Micellar liquid chromatography has been adopted for separation of cytostatic antibiotics of rubomicin derivatives. The influence of the kind of organic modifier (normal and iso-alcohols) and its concentration, sodium dodecyl sulfate micelle concentration and column temperature on the chromatographic characteristics of rubomicin derivatives have been investigated. 1-pentanol and iso-propanol were shown to be the most suitable for providing optimum selectivity, good tailing factor and column efficiency with minimum reagent consumption.
Keywords: Column liquid chromatography; Micellar chromatography; Sodium dodecy sulfate; Cytostatic antibiotics of rubomicin derivatives
Electrochemically generated multifunctional suppressor for ion chromatography
by R. Z. Hu; Y. H. Weng; L. M. Lai; J. C. Chen; Q. Lin (pp. 471-474).
A multifunctional suppressor for both anion and cation chromatography has been designed. The suppressor comprises five thin chambers—an anion eluent suppressive chamber, a cation eluent suppressive chamber, a cathode chamber, an anode chamber, and a common electrode chamber, all of which are clipped together. An electrochemical process—electrolysis of deionized water or detector effluent—is used to regenerate the suppressor for continuous operation. Two power sources are used to supply current. The device can work as an anion suppressor, a cation suppressor, or as both anion and cation suppressors, with high suppression capacity (60 mmol L−1) and good reproducibility (RSD=0.80–0.91%) and linearity (r=0.9992).
Keywords: Column liquid chromatography; Ion chromatography; Multifunctional suppressor; Anions and cations
Observations on the effect of temperature on performance and stability of anion exchange columns in ion chromatography
by R. Dybczyński; K. Kulisa (pp. 475-484).
The influence of column temperature on elution behaviour of several ions on anion-exchange resin beds of the Dionex Ion Pac type was investigated. Iodate, bromate, bromide and iodide ions were separated on Ion Pac AS9SC column in the temperature range of 10°C–55°C, using NaHCO3/Na2CO3 and NaHCO3 eluents. Free energy, enthalpy and entropy changes for respective ion exchange reactions were calculated and compared with literature data for classical gel type exchangers. In most cases the enthalpy change was a function of temperature. The work at elevated temperatures caused progressing resin degradation i.e. loss of strongly basic groups, accompanied by formation of weakly basic groups and also some weakly acidic groups. Similar resin degradation was observed for Ion Pac AS5 column. Observations on the changes of the plate height with the retention factor and temperature lead to conclusion that in some circumstances longitudinal diffusion in the resin phase also contributes to the total plate height.
Keywords: Column liquid chromatography; Ion chromatography; Effect of temperature; Resin bed degradation; Mechanism of zone spreading
Application of open tubular electrochromatography for acidic and basic analytes
by S. Dube; R. M. Smith (pp. 485-492).
The separation of charged analytes by electrochromatography has been examined on porous-layer open tubular capillaries prepared using the sol gel method. An electroosmotic flow of about 2.10×104 cm2V1s1 was obtained using between 10 and 30% acetonitrile in the mobile phase. Acidic diuretic drug compounds were successfully separated at high pH as were theN-alkylanilines in their basic and neutral forms. The limitation of open tubular columns was observed on separating some basic pharmaceutical drugs. These components showed severe peak tailing and were not resolved on a 20 μm i.d. porous silica layer open tubular column. Strongly acidic components could not be detected on these columns due to their higher counter electromobilities. The successful separation of neutral aryl alkyl ketones with an efficiency of 101,533 plates m1 for butyrophenone was an indication of the improved phase ratio on this type of open tubular columns.
Keywords: Capillary electrochromatography; Open tubular liquid chromatography; Acidic and basic analytes; Diuretic drugs
Direct capillary electrophoretic determination of three chemotherapeutic drugs in human urine
by J. Rodríguez Flores; J. J. Berzas Nevado; G. Castañeda Peñalvo; M. I. Rodríguez Cáceres (pp. 493-496).
Capillary zone electrophoresis (CZE) has been used for direct determination of 6-thioguanine, methotrexate, and 5-fluorouracil in human urine, by use of a fused-silica capillary (60.2 cm×75 μm i.d.). Separation was performed after hydrodynamic injection for 7 s; the separation potential and capillary temperature were 25 kV and 35°C, respectively. A 45mm borate buffer solution (pH 9.2) was used as separation electrolyte. Under these conditions the analysis takes approximately 10 min and interday precision of migration times and corrected peak areas is satisfactory. A linear response over the concentration range 3.0–20.0 mg L1 was observed for the three chemotherapeutic drugs in diluted human urine. Detection limits (s/n=3) for 6-thioguanine and methotrexate were approximately 1.60 mg L1 in diluted human urine; that for fluorouracil was 2.60 mg L1. A 2-ml volume of human urine was diluted with 2-mL of water and introduced directly into the electrophoresis system. CZE was shown to be a good method with regard to simplicity, satisfactory precision, and sensitivity. This method resulted in especially excellent recoveries for determination of methotrexate in all the different urine samples analysed (n=10).
Keywords: Capillary electrophoresis; Chemotherapeutic agents in urine; 6-Thioguanine, methotrexate, 5-fluorouracil
Application of capillary electrophoretic immunoassay to analysis of estradiol in women's serum
by Ping Su; Xin-Xiang Zhang; Wen-Bao Chang (pp. 497-500).
A rapid and sensitive capillary electrophoretic immunoassay is described for determination of estradiol in women's serum. Addition of thermally reversible hydrogel in the buffer, serving as a replaceable packing material, improved the reproducibility of the method. Using a laser-induced fluorescence detector this method can be applied to the determination of estradiol at concentrations as low as 30.6 pg mL1. Estradiol levels in 16 normal women's serum were measured at the range 115≈370 pg mL1. The results of this method have been found to correlate well with those of chemiluminescent immunoassay.
Keywords: Capillary electrophoretic immunoassay; Laser-induced fluorescence; Hydrogel; Estradiol in Serum
Capillary electrophoretic resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit
by T. Raab; U. Schmitt; T. Hauck; A. Knecht; U. Holzgrabe; W. Schwab (pp. 501-504).
A simple capillary electrophoretic method with UV detection has been developed for resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit. The separation was performed in fused-silica capillaries (30/40.2 cm long×50μm i.d.) with running buffer consisting of 50mm ammonium acetate, pH 4.0, containing 20mm heptakis-(2,3-O-diacetyl-6-O-sulfato)-β-cyclodextrin (HDAS-β CD). The applied potential was 10 kV, the temperature 25°C, and detection was at 280 nm. The method was used to determine the enantiomer ratio of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) isolated from strawberry fruits and from the yeastZygosaccharomyces rouxii. The formation of enantiomerically enriched(+)-DMHF byZ. rouxii was demonstrated for, the first time.
Keywords: Capillary electrophoresis; Chiral separation; 2,5-Dimethyl-4-hydroxy-3(2H)-furanone; Strawberry flavor
Fast separation and determination of carnosic acid and rosmarinic acid in different rosemary (Rosmarinus officinalis) extracts by capillary zone electrophoresis with ultra violet-diode array detection
by M. Bonoli; M. Pelillo; G. Lercker (pp. 505-512).
Carnosol, carnosic acid, rosmarinic acid and other not identified phenolic compounds were separated by capillary zone electrophoresis (CZE) using a 40-cm long capillary and a 20 mM tetraborate buffer (pH 9.0), within 3 min. A UV-diode array detector was employed to collect spectra of phenolic compounds. The effect of some separation parameters on peak resolution and migration time of phenolic species present in a refined rosemary extract was studied. The repeatability of the method was also investigated: the intraday relative standard deviation on total peak area was less than 4%, while the intraday relative standard deviation on migration time was less than 0.6%. Moreover the CZE method showed good sensitivity (0.0007 μg mL1 for carnosic acid and rosmarinic acid). Carnosic acid and rosmarinic acid have been quantified in different commercial extracts of rosemary. Finally, the optimized method was also applied to evaluate the recovery of these two compounds when different organic solvents were employed during the extraction procedure.
Keywords: Capillary zone electrophoresis; Rosemary; Carnosic and rosmarinic acid; Polyphenols
Ultrasound-assisted derivatization of phenolic compounds in spiked water samples before pervaporation, gas chromatographic separation, and flame lonization detection
by E. Priego-López; M. D. Luque de Castro (pp. 513-518).
A fully automated method, based on continuous ultrasound-assisted derivatization coupled with pervaporation before gas chromatographic separation and flame ionization detection, has been developed for the determination of phenol and cresols in water. Spiked water samples were doped with acetic anhydride and dipotassium hydrogen phosphate, before introduction into the flow system, to achieve catalytic acetylation of the target compounds. A multivariate study was performed to optimize the main factors affecting the derivatization process. The correlation coefficients, r, of the calibration plots obtained were better than 0.999 for cresols and better than 0.99 for phenol. Detection limits were 0.02 μg mL1 for phenol, o-cresol, andp-cresol, and 0.05 μg mL1 form-cresol. Reproducibility and repeatability, expressed as relative standard deviation, ranged from 2.0–3.9% and from 1.0–3.5% respectively.
Keywords: Gas chromatography; Ultrasound assisted derivatization; Phenols and cresols in water; Acetyl derivatives; Automated method
Identification of isopropyl substituted β-blocking agents in human urine by gas chromatography and tandem mass spectrometry
by G. Forsdahl; T. Geisendorfer; G. Gmeiner (pp. 519-524).
A method for the sensitive detection of isopropyl substituted β-blocking agents in human urine is presented. The sample preparation step involves enzymatic hydrolysis, solid phase extraction and derivatisation withN-methyl-N-trimethylsilyl-trifluoroacetamide. The instrumental analysis was performed using gas chromatography-mass spectrometry with an ion trap mass spectromeler. The mass spectrometer was operated in the scan as well as in the MS-MS mode.
Keywords: Gas chromatography-mass spectrometry; Solid phase extraction; Beta-blocking agents; Urine samples; Doping
Solid-phase microextraction coupled with gas chromatography and gas chromatography—Mass spectrometry for public health pesticides analysis
by C. BorFuh; Y. C. Yang; H. Y. Tsai; L. S. Ho (pp. 525-528).
Public health pesticides in two-component mixed solutions were analyzed using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography—mass spectrometry (GC-MS). The two-component mixed solutions used were allethrin mixed with cyfluthrin, cypermethrin mixed with tetramethrin, and transfluthrin mixed with cyfluthrin. Quantitative SPME-GC and SPME-GC-MS analyses using calibration and standard addition methods were evaluated. Using SPME pretreatment saved several tens to hundreds of mL of organic solvent. Quantitative analyses of the SPME-GC and SPME-GC-MS using the calibration and standard addition methods showed promise for simple, fast, and solventless public health pesticide analysis.
Keywords: Gas chromatography—mass spectrometry; Solid phase microextraction; Public health pesticides
Solubility parameter determination of cationic surfactants by inverse GC
by S. M. Bardavid; P. C. Schulz; E. L. Arancibia (pp. 529-532).
The solubility parameters of cationic surfactants were obtained using the inverse gas chromatographic technique. The surfactants didodecyl dimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide and dodecyl pyridinium chloride were used as stationary phase and retention data of different probe solutes were measured at different temperatures. The results were analysed by the combination of Flory-Huggins and Hildebrand theories, and the solubility parameters of the surfactants were obtained in a range of temperatures between 80–120°C.
Keywords: Gas chromatography; Inverse gas chromatography; Cationic surfactants; Solubility parameter
The search for reactive peroxides and hydroquinones in an acrylic copolymer blend via supercritical fluid extraction-chromatography
by D. Johnston; M. Ashraf-Khorassani; L. T. Taylor (pp. 533-537).
The objective of this work was to extract, identify, and quantify dibenzoyl peroxide (DBPO), N,N-dimethyl-p-toluidine (DMPT), hydroquinone (HQ), and the methylether of hydroquinone (MEHQ) in an ethyl and methyl methacrylate copolymer blend cured at 35°C for two different time periods. The reactivity of BPO, HQ, and MEHQ made working with supercritical fluids most advantageous. Exactly 0.85 gram of cured polymer was placed in a 5 mL extraction vessel. In order to obtain efficient collection of the analyte after supercritical fluid extraction, a solid phase trap (C18) was used. Various polymer samples were cured at different times and then extracted and analyzed. The level of DMPT decreased by 50% (0.22% to 0.12%) as the cure time increased from 30 minutes to 24 hours. The BPO level did not vary with increasing cure time (0.44% vs 0.43%). The MEHQ level could not be ascertained since it was below our detection limit for MEHQ.
Keywords: Supercritical fluid chromatography; Supercritical fluid extraction; Acrylic co-polymer; Additive residues
Sensitive determination of phloroglucinol in human plasma by liquid chromatography-tandem mass spectrometry
by Hohyun Kim; Sang Beom Han (pp. 539-542).
A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry (LC-MS-MS) was developed for the quantification of phloroglucinol in human plasma. Resorcinol was used as internal standard, with plasma samples extracted using ethyl acetate. A centrifuged upper layer was then evaporated and reconstituted with mobile phase. The reconsituted samples were injected into a C18 XTerra MS column (2.1×100 mm) with 3.5 μm particle size. The analytical column lasted for at least 500 injections. The mobile phase was 15% acetonitrile (pH 3.0), with a flow rate at 100 μL min1. The mass spectrometer was operated in positive ion mode using electrospray ionization. Using MS-MS in multiple reaction monitoring (MRM) mode, phloroglucinol was detected without severe interferences from the plasma matrix. Phloroglucinol produced a parent molecule ([M+H]+) atm/z 127 and a corresponding product ion atm/z 8l. Detection of phloroglucinol in human plasma was accurate and precise, with quantification on limit at 0.5 ng mL1. The method has been successfully applied to a study of phloroglucinol in human specimens.
Keywords: Column liquid chromatography-MS-MS; Electrospray ionization; Multiple reaction monitoring; Pholoroglucinol; Resorcinol
Determination of sulfides in synthesis and isomerization systems by reversed-phase ion-pair chromatography with a mobile phase containing tetramethylene oxide as organic modifier
by XiuYan Pang; HanWen Sun; YanHuan Wang (pp. 543-547).
A reversed-phase ionpair chromatographic method with tetramethylene oxide as organic modifier has been developed for the simultaneous separation and detection of the sulfides NH2CSNH2, (NH4)2CS3, (NH4)2S, and NH4SCN. The optimized separation conditions were determined by means of a U7 (76) uniform design experiment, and tetramethylene oxide played an important role in adjusting the retention behavior of (NH4)2S and NH4SCN. The linearity of the calibration plots for the four components was investigated; correlation coefficients were from 0.9989–0.9999. The proposed method was successfully applied to the determination of NH2CSNH2, (NH4)2CS3, (NH4)2S, and NH4SCN in synthesis and isomerization samples.
Keywords: Column liquid chromatography; Ion-pair chromatography; Sulfides; Tetramethylene oxide; Synthesis and isomerization system
Synthesis and the reversed-phase HPLC analysis ofcis andtrans-dichlorobis(ethylenediamine-ruthenium) chloride isomers
by N. S. Gonçalves; L. C. G. Vasconcellos; S. E. Mazzetto (pp. 549-552).
In this work we report the monitoring of the synthesis ofcis andtrans-dichlorobis(ethylenedia-mine)ruthenium chloride isomers by HPLC. The preparation of thecis andtrans complexes were as described in the literature with modifications arising from reversed-phase HPLC results. Thecis andtrans complexes were separated with retention times of 3.0 min and 5.5 min respectively using an ODS column (250 mm×4.6 mm i.d. 5 μm particles, Alltech) and methanol/water 45/55 ratio as mobile phase. According to HPLC results the reaction time to completion is 48 h and not 72 h as previously described. The shorter time resulted in better yield 82% and reduced by-products.
Keywords: Column liquid chromatography; Reaction monitoring; cis andtans-Dichlorobis(ethylenediamine-ruthenium) chloride