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991.
Using cotton as a solid-phase extraction sorbent of the precolumn, an on-line coupled precolumn preconcentration-liquid chromatography system with fluorescence detection was developed for the determination of PAHs in aqueous samples. Four PAHs including fluorene, phenanthrene, fluoranthene and benzo[k]fluoranthene were preconcentrated by a precolumn packed with 30 mg of absorbent cotton and then separated by C18 analytical column. When 100 ml of sample was enriched, the proposed procedure provided detection limits in the range of 0.5-57 ng l−1. Several water samples spiked with PAHs were analyzed with recoveries in the range of 92-119% at spiking level of 100 ng l−1 for fluorene, phenanthrene and fluoranthene, and 10 ng l−1 for benzo[k]fluoranthene, respectively. 相似文献
992.
以万古霉素为流动相添加剂的高效液相色谱法手性分析系统的建立 总被引:2,自引:0,他引:2
以丹酰化苯甘氨酸、丹酰化苯丙氨酸、丹酰化丝氨酸、丹酯化丙氨酸为模型化合物,通过对色谱柱类型、缓冲液类型、pH和盐浓度、万古霉素用量、甲醇用量、柱温等色谱参数进行考察,建立了以万古霉素为手性流动相添加剂在普通色谱柱上进行手性分析的色谱系统,并在该系统中成功地拆分了酮洛芬对映体。 相似文献
993.
采用毛细管气相色谱法对间接电氧化法合成的二甲砜及反应物二甲亚砜进行了分离分析。研究了分离二甲砜、二甲亚砜的最佳条件,内标法定量。两种化合物的线性范围在2-30μg,且有较好的精密度。 相似文献
994.
Summary Tokaj wines (Szamorodni and Aszu wines) of Hungarian origin were investigated on the basis of free amino acids and biogenic
amines. The separation and determination of these compounds was performed by an amino acid analyser equipped with an ion-exchange
resin column. The total amount of free amino acids and biogenic amines was higher in Aszu wines than in Szamorodni wines.
The main amino acids were proline and arginine, while the major biogenic amines were tyramine and putrescine. The free amino
acid and biogenic amine content of Aszu wines depended on the vineyards the wines originated from.
Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001 相似文献
995.
Summary In this study, a rapid and efficient semi-micro extraction procedure is presented for the extraction of some higher n-alkanes
from water and soil samples. In the case of water samples n-hexane was used as the organic phase in a phase volume ratio (volume
of aqueous phase/volume of organic phase) higher than 285, while in the case of soil samples, extraction with n-hexane was
carried out in the presence of an excess of 2 M NaCl solution. The extraction rate from soil samples is very high and is better
than Soxhlet extraction, comparable with supercritical fluid extraction. High preconcentration factor in water samples allows
the limits of detection to be in the ng.mL−1 level with the use of gas chromatographic analysis. Flame ionization detector was used for monitoring the analytes. The obtained
recoveries of all studied compounds from both water and soil samples are higher than 90%. This method was successfully used
to determine some n-alkanes in municipal wastewater and contaminated soil. 相似文献
996.
Vermeiren K 《Journal of chromatography. A》2005,1085(1):66-73
The two-dimensional ion exclusion chromatography/ion chromatography (ICE-IC) approach is considered to be the method of choice for the determination of trace anions in concentrated hydrofluoric acid (48-50%, w/w). In order to achieve lower detection limits, this method was for the first time used with electrolytically generated and purified hydroxide eluents in combination with a low noise electrochemical suppressor. Compared to carbonate based eluents, the achieved gain in peak height sensitivity for chloride, sulfate, nitrate and phosphate is a factor of 6, 7, 16 and 13, respectively. The instrumental detection limits, based on the background noise, are 2, 0.2, 0.4 and 1.4 microg/kg HF 50% (w/w) for the same anions. Their method detection limits, calculated according to SEMI, are all within the 6-10microg/kg HF 50% (w/w) range and thus at least 10 times lower than the current Tier C grade requirements. The chromatographic run time could be shortened with some 10 min by the use of a relatively fast high-capacity hydroxide selective anion exchange column. 相似文献
997.
A chemically bonded cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (CSP) was prepared by a radical polymerization reaction. The prepared CSP was packed into fused-silica capillaries with inner diameter of 75 microm to perform enantiomer separations in CEC. The electrochromatographic behavior of the CSP was investigated. On the prepared CSP, high EOF could be generated under acidic mobile phases, which represented an advantage for the separation of acidic enantiomers. Several neutral, acidic, and basic enantiomers were resolved on the prepared CSP under aqueous mobile phases. The column efficiencies were between 20,000 and 100,000 plates/m, which were much higher than those of HPLC. In addition, it was observed that the separation of some enantiomers benefited from the adoption of THF as mobile phase modifier. 相似文献
998.
We have reported recently that high-speed normal-phase (NP) HPLC separations of a broad range of organic compounds can be performed on cyano columns using gradients of methanol in hexane-like solvent-ethoxynonafluorobutane (ENFB), available commercially. In this communication, we demonstrate that atmospheric pressure chemical ionization (APCI) in combination with mass spectrometry (MS) can be effectively used for detection in such separations. The efficiency of APCI under conditions studied has also been compared to the efficiency of traditional electrospray ionization (ESI) in combination with MS for reversed-phase (RP) HPLC of the same compounds. The compounds included in this study were steroids, benzodiazepines, and other central nervous system-active substances, nonsteroidal anti-inflammatory drugs, tricyclic antidepressants, and beta-adrenergic blocking agents. Non-polar compounds were found to respond stronger when APCI-MS technique was used, whereas APCI and ESI ionization efficiencies were comparable when polar substances were studied. The combination of normal-phase HPLC separation conditions with mass spectral detection may expand the range of LC-MS applications traditionally associated with reversed-phase HPLC and ESI-MS detection. 相似文献
999.
Summary The analysis of several phenylurea herbicides in different waters is described using an immunoaffinity column clean-up and
determination by high performance liquid chromatography. The pesticides were selectively retained on a solid phase extraction
column containing antibodies to chlortoluron and to isoproturon immobilised onto silica. Selected phenylureas were eluted
using a simple phosphate buffered saline/ethanol mixture at low pH. The immunoaffinity approach gave extracts free of interfering
substances and allowed detection limits comparable to those required for pesticides in water in the European Community. The
proposed method was successfully applied to the determination of chlortoluron, isoproturon, linuron and chlorbromuron in tap
and river water.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
1000.
Coexistence Relations, Preparation and Properties of Ternary Compounds in the System Cu/Mo/O The phase diagram of the ternary system Cu/Mo/O is presented at 773 K. The compounds CuMoO4, Cu3Mo2O9, Cu4Mo5O17, Cu6Mo5O18, Cu4–xMo3O12, and CuxMoO3 are found to be thermodynamical stable. The homogeneity range of Cu4–xMo3O12 runs to x = 0.1–0.2. Single crystals of CuMoO4 and Cu3Mo2O9 were grown by chemical transport reactions with TeCl4, Cl2, HCl, and Br2 as transport agent. The results were compared with thermochemical calculations. The decomposition of CuMoO4 and Cu3Mo2O9 was investigated with thermal analysis and decompositon pressure measurements. 相似文献