共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
Summary The use of over-pressurized thin-layer chromatography in ion pair system using acidic type pairing reagent has been studied.
The most important aspect when reversed phase ion-pair TLC system is used to apply a suitable procedure for pre-treatment
of the sorbents. Because of the acidic type of ion pair reagents cannot be bounded to the surface of the layer by immersion
or pre-development with the reagent solution, double coating technique was used for the pre-treatment, the plate was firstly
immersed in an ethanolic solution of cetrimide, then the immersion has been repeated by an ethanolic solution of acidic ion
pair reagent. The necessary coating of the sorbents can be achieved by this technique.
To find the optimal conditions for reversed phase ion pair TLC separation of organic amines, 10-camphor sulfonic acid as reagent,
different aliphatic, aromatic amines and diamines and heterocyclic nitrogen compounds, respectively as model compounds were
selected. The dependence of the selectivity and efficiency of the separation on the sorbents, on the concentrations of reagents
(cetrimide and camphor sulfonic acid) applied for both immersion and in the eluent were investigated in detail.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
5.
6.
7.
A highly-sensitive analytical method for the detection of p-hydroxymethamphetamine (pOHMA) in urine is presented. The proposed method combines liquid-liquid extraction with acetonitrile and solid-phase extraction by thin-layer chromatography (TLC) with oxidation using potassium hexacyanoferrate(III) and sodium hydroxide to detect the fluorophor of pOHMA. The detection limit for pOHMA is 10 ng (n = 3). The analysis of pOHMA in forensic samples is successfully performed, without interference from endogenous fluorophors, yielding concentrations in the appropriate range for methamphetamine abusers. 相似文献
8.
9.
10.
11.
A simple and rapid method for the identification and quantitation of morphine in urine samples is described. The procedure, which involves conversion of the drug a fluorescent product followed by liquid chromatography, is shown to be highly sensitive and specific. Levels down to 0.01 mug/ml of morphine can be quantitatively detected in urine. A large number of drugs have been tested and shown not to interfere. 相似文献
12.
13.
14.
Summary Tagging techniques with reagents used for fluorescent detection for short and long-chain fatty acids using high-performance
liquid chromatography are evaluated in terms of the tagging reactions, handing, flexibility, stability of the reagents. Emphasis
is given to the applications of the tagging techniques to relatively high molecular mass fatty acids. The fatty acids or carboxylic
compounds were derivatized to their corresponding esters with 9-(2-hydroxy ethyl)-carbazole (HEC) in acetonitrile at 60°C
with N, N′-carbonyldiimidazole (CDI) as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters
of C1−C20 fatty acids was completely separated with 45 min using gradient elution on a reversed-phase C18 column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (λex 293 nm). Studies on derivatization conditions indicated that fatty acids react rapidly and smoothly with HEC in the presence
of CDI and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method
to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility
for fatty acids derivatives. The relative standard deviations (n=6) for each fatty acid derivative are <5.0%. The detection
limits are at 38–57 fmol levels for C14−C20 fatty acids and lower levels for <C14 fatty acids. 相似文献
15.
16.
17.
18.
19.
The nicotine metabolites, cotinine and trans-3′-hydroxycotinine (3HC) are considered as superior biomarkers for identifying tobacco exposure. More importantly, the ratio of 3HC to cotinine is a good indicator to phenotype individuals for cytochrome P450 2A6 activity and to individualize pharmacotherapy for tobacco addiction. In this paper, a simple, robust and novel method based on surface-enhanced Raman spectroscopy coupled with thin-layer chromatography (TLC) was developed to directly quantify the biomarkers in human urine samples. This is the first time surface-enhanced Raman spectroscopy (SERS) was used to detect cotinine and 3HC in urine samples. The linear dynamic range for the detection of cotinine is from 40 nM to 8 μM while that of 3HC is from 1 μM to 15 μM. The detection limits are 10 nM and 0.2 μM for cotinine and 3HC, respectively. The proposed method was further validated by quantifying the concentration of both cotinine and 3HC in smokers’ urine samples. This TLC-SERS method allows the direct detection of cotinine in the urine samples of both active and passive smokers and the detection of 3HC in smokers. Figure
Scheme of the procedure for detection of cotinine and 3HC 相似文献