ISSN:0935-6304    

DOI:10.1002/jhrc.1240201202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractLinear solvation energy realationships (LSERS) were used to qunatitatively compare the relative contributions of dipolarity/polarizability, hydrogen bonding, and other types of intermolecular interactions to retention and selectivity using various bulk moblie phase component. Using experimental condition which differ only by the compostion of the bulk moble phase component, the factors which cause selctivity to differ between HPLC, subcritical fluid chromatography and supercritical fluid charomatography were decovoluted. Heptance‐based HPLC mobile phases showed superior selectivities towards analytes which differ in hydrogen bond donating ability, gas‐to‐hexadecane partion coefficint and dipolarity/ploarizability. subcritical fluid chromatography with HFC‐134a (1, 1, 1, 2‐tetrafluoroethane) as the bulk fluid produced superior seclectivities for which differ in hydrogen bond accepting ability and execess molar refraction properties. Many of these factors showed temperature dependences which act to attenuate or accenture the particular intermolcular in

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractA detection scheme based on the Post‐column addition of terbium followed by sensitized luminescence detection has been developed. Two model Compounds‐ saliculic acid and diflunisa‐ were separated by capillary electophoresis in an alkaline phosphate buffer. A Solution containing terbium and CTAB was added post‐column via a “home‐built” reactor resulting in the rapid fromation of the strongly luminescent terbium‐salicylic acid and terbium‐diflunisal complexes in a reaction capillary. Following complexationn in the reaction capillarty, the 325 nm line from a HeCd laser was used to excite the analytes which efficiently transfer their energy to terebium. Resuulant luminescence of terebium was liner of 2 orders of magnitude. This novel and practical system enables the detection of micromolar concentrations of diflunisal and salicylic acid‐ a 10 fold improvement over UV absorbance detection in the same system. Post‐column addition of terbium also eliminates the problems associated with strong adsorption of the lanthanide ion to the silica walls of the separation capillary and the formation of metal‐ligand complexes with differe

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractA post‐ column chemiluminescent technique for thedetection of compounds that are poor chromoshores using electorogenerated chemiluminescence following separation by capillartgy electrophoresis is described. The luminrescent signal is generated followintg the reaction of anlyres (e.g. amines) with Ru(bpy)33+, which isx electrochemically generated post‐columan from Ru(bpy)32+. Tripropylamine and proline are used as two model compounds to demostrate the feasibility of the method. Detection limits for the prototype system were in the micromolar rage, suggesting that this technnique offers an alternative to indirect detection of compounds that are poor chromophores with an added selectivity advangage. The system includes the use of a conductive joint to isolate the separation field from the potential necessary to drive the elctrogenerated chemiluminescent reactiion. Addition of the chemiluminescent reagent Ru(bpy)32+post‐column did not decrease the efficiency of the separation. The design and favrication of the novel cell is disc

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractAmino Acids are cations at low PH and can be readily separated by capillarty electrophoresis provided an alkanesulfonic acid is added to the elecrolyte carrier. Formation of a Positive net charge on the bare fused‐silica surface at low PH was confirmed by measurement of an anodic electroosmotic flow. The addition of ethanesulfonic acid or octanesulfonic acid to the electrolyte carrier causes a reversal of the EOF. A mechanism is proposed in which the alkanesulfonic acid adsorbs to the positively‐charged capillary wall through electrostatci attraction. Adsorption of a second molecule of alkanesulfonate by hudrophobic attraction to the carbon chain forms a negatively‐charge coating on the capillary wall. The alkanesuflfonate also imparts selectivety to the system by participation in ionpairing interactions with the native amino acids to improve resolution. The CE separation of a mixture of the twenty common amino acids at PH 2.8 with direct absorabance detection at 185 nm resulted in 17 amino acid peals in 20 minutes with a 30 KV applied voltage. The effect of several variables was studied including electrolyte carrieres containing different alkanesulfonic acids, the influence of PH, applied voltage, and concentration of electrolyte ca

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractMethods for the detectionn of metal cations under acidic conditions, near PH 2, in capillary electrophoresis (CE) were investigatged. Conditions for direct UV detection of UV absorbing metal cations such as Cr3+, Cu2+, Fe3+, UO22+, VO2+, and VO2+were established With aqueous HCl or HClO4as the electroyte carrier. The speciation of vanadium(IV) and vanadium(V) at PH 2.3 by CE was achieved with direct detection at 185 nm. With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations. An indirect UV detrection scheme for acidic conditions was also investigated. Several background carrier electolytes (BCES) were studied including 4‐methylbenzylamince, nicontinamide, pyridazine, guanidine, 3‐picoline, and chromium (III) to determine their effectivencess under very acidic conditions. The efect of ioni c surfactants and the nonionic surfactant, Trition X‐100, on the peak heights and N Values was also st

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractTemperature measurements on the column outer well were used for detecting recondensation or evaporation of solvent inside the precolumn during injection or on‐line transfer of large solvent volumes. This facilitates the choice of the most critical parameter of these techniques, i.e. oven temperature. When using the vaporizer/precolumn solvent split/gas discharge system, the dew point of the solvent is determined, either to just prevent solvent recondensation or to limit it to the capacity of the precolumn to retain liquid. In concurrent eluent evaporation through the loop type LC‐GC interface, temperature measurement enables the determination of whether or not the flooded zone exceeds a given limit. Fanally, when solvent trapping is used (on‐column injector/partially concurrent solvent evaporation evaporation or vaporizer/partial recondensation), temperature measurement near the front end of the flooded zone is used as a signal for accurate closure of the vapor exit shortly before the end of solvent evapor

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractThe extraction of wine bouquet components with solid‐phase microextraction (SPME) using different fibers was studied. Polyacrylate fibers (PA‐85) achieve the most complete bouquet profiles. About ninety substances were identified by capillary gas chromatography‐MS and their retention factors were calculated to allow peak identification in capillary‐GC‐FID chromatograms. The terpene profiles of different wines were recorded by SPME (PA‐

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractAn application of automated on‐line HPLC‐HRGC is described for direct analysis of edible oils for migrated polymer additives. The sample preparation, separating the additive from the oil triglycerides, is carried out using normal phase HPLC. The fraction of the eluent containing the additive is automatically transferred to a HRGC where a second and final separation of the additive from minor oil components takes place. The method compares well with off‐line separation methods. Migration data for Tinuvin 1577 from PET and PC polymers as well as an unspecified experimental polymer is given. The advantages and disadvantages of using different edible oils as food simulants are disc

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY

摘要:

AbstractA reversed‐phase HPLC method for the analysis of cephalexin (7‐[(aminophenylacetyl)amino]‐3‐methyl‐8‐oxo‐5‐thia‐1‐azabicyclo[4.2.0]oct‐2‐ene‐2‐carboxylic acid) by isocratic separation is described. A comparison is made between the ultrafiltration land the extraction procedure developed in our laboratory. The extraction procedure, based on the deproteinization of plasma with perchloric acid followed by the extraction with dichloroethane and separation of cephalexin on a reversed phase column, gave better recovery. Quantitative validation of our method has been performed by an external standard technique. The relative standard deviations were between 1.1 and 1.9% in the within‐day assay and between 1.2 and 2.2% in the inter‐day assay. The limit of detection was 0.14ug/ml and the limit of quantification was 0.28ug/ml. This method is rapid, sensitive, simple, and reproducible. The LC MS/MS technique was successfully used for identification and quantification of cep

ISSN:0935-6304    

DOI:10.1002/jhrc.1240201211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1997

数据来源: WILEY