摘要:

AbstractThe design and features of an on‐line purge and cold‐trap pre‐concentration device for rapid analysis of volatile organic compounds in aqueous samples are discussed. Excessive water is removed from the purge gas by a condenser or a water permeable membrane in order to avoid blocking of the capillary cold‐trap. Synthetic mixtures covering concentrations ranging from tenths to tens of ppb's and different chemical classes are used to study the effect of various process factors on the efficiency and selectivity of water removal as well as on the purging recovery. The importance of the concentration of the solutes, the flow rate in conjunction with the volume of the purge gas, and the temperature of the condenser, the cold‐trap and the sample is emphasized. Theoretical models describing the purge process and the blocking of the cold‐trap agree fairly well with the highly reproducible experimental results (σ = 2–4%). Both the condenser and the Nafion membrane successfully remove water, although some compounds, dependent on volatility and polarity, are partly or completely lost. It is shown that non‐polar volatile organic compounds are efficiently enriched so that recoveries between 80–100% and a detection limit of 1 ppt can be obtained. The applicability of the system is illustrate

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100202

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe stereodifferentiation of chiral secondary alcohols, 4(5)‐alkyl‐substituted γ (δ)‐lactones via corresponding 1, 4(1, 5)‐diols, chiral 1, 3‐diols, and 1‐thioalkan‐3‐ols was carried out by diastereomeric derivatization with (S)‐O‐acetyllactyl chloride as a chiral auxiliary. This procedure is a convenient and reliable method for screening the enantiomeric composition of these naturally occur

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100203

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

年代:1987

数据来源: WILEY

摘要:

Abstract890 ml of urine of rats treated with [14C] 205–734 was desalted over an Amberlite XAD‐2 adsorption column. The methanol extract dissolved in 10 ml methanol was injected onto an anion exchange column (Nucleosil 10 SB 250 × 16 mm i.d.) equilibrated in methanol. A gradient of decreasing methanol proportionversusa 0.2Mammonium hydrogen carbonate buffer eluted a pure glucuronide of 205–734. Its structure was established by NMR, MS, UV, and IR analyses. This procedure is simple, rapid, and very selective for the compound of in

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100204

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

年代:1987

数据来源: WILEY

摘要:

AbstractLiquid crystalline polyacrylates (LCPAs) are evaluated as stationary phases for capillary gas chromatography (CGC). Aromatic hydrocarbons as well as polar isomeric compounds are used as test solutes to compare the polarity of the LCPAs with a conventional polysiloxane column and a Carbowax 20M column. The relative polarity of the columns with respect to change in the lateral and terminal substituents is also discussed. Lateral substitution, polarity of the terminal group, together with the solute size, affect the LCPA selectivity.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100205

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

年代:1987

数据来源: WILEY

摘要:

AbstractA miniaturized continuous gradient elution system with variable gradient profile was designed. A retention time reproducibility below 1% was achieved. The system was applied to the separation of phenolic compounds with a wide range of polarities.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100206

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

年代:1987

数据来源: WILEY

摘要:

AbstractRacemic gossypol is resolved by HPLC of its amino acid ester Schiff's base derivatives on non‐chiral columns. This provides a rapid and accurate method for determination of optical purity on a small scale and, combined with hydrolysis and fractional crystallization, for the preparation of pure gossypol enantiomers on a multi‐gram sc

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100207

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100208

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100210

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100211

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240100212

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

年代:1987

数据来源: WILEY