A sensitive internal standard method for the determination of melatonin in mammals using precolumn oxidation reversed-phase high-performance liquid chromatography

2004 ◽  
Vol 811 (2) ◽  
pp. 237-241 ◽  
Author(s):  
K HAMASE ◽  
J HIRANO ◽  
Y KOSAI ◽  
T TOMITA ◽  
K ZAITSU
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Standard Method ◽  
High Performance ◽  
Internal Standard ◽  
Reversed Phase ◽  
Internal Standard Method

Determination of cocaine concentrations in plasma by high-performance liquid chromatography

1990 ◽  
Vol 36 (8) ◽  
pp. 1436-1439 ◽  
Author(s):  
P Jatlow ◽  
H Nadim
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Plasma Concentrations ◽  
Internal Standard ◽  
Reversed Phase ◽  
Dilute Acid ◽  
Nitrogen Detection ◽  
Chromatographic Procedure

Abstract We describe a procedure for measuring concentrations of cocaine in plasma by reversed-phase high-performance liquid chromatography, with ion-pairing. The procedure involves solvent extraction followed by back-extraction with dilute acid. The n-propyl ester of benzoylecgonine is used as an internal standard. An evaporation step is not required, and concentrations as low as 5 micrograms/L can be quantified. Plasma concentrations of cocaine determined by high-performance liquid chromatography correlated well with those determined by a previously reported gas-chromatographic procedure with nitrogen detection.

scholarly journals Determination of the total tryptophan in food by high performance liquid chromatography combined with enzyme hydrolysis

2019 ◽  
Vol 2 (2) ◽  
pp. 37-43
Author(s):  
Huyen Trang Luu Thi ◽  
Trang Vu Thi ◽  
Ngan Le Viet ◽  
◽  
◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
High Performance ◽  
Limit Of Detection ◽  
Internal Standard ◽  
Standard Addition ◽  
Reversed Phase ◽  
Enzyme Hydrolysis ◽  
Protease Enzyme

High performance liquid chromatography was applied for the determination of tryptophan in food. The sample was hydrolyzed in a duration from 16 to 24 hour by protease enzyme at 50 oC. The extract was separated on the C8 reversed phase column with mobile phase of NaH2PO4 50mM pH 2.3: Methanol (82:18; v/v). The linearity of the method was kept in the range of 0.5 - 50 mg/L. Limit of detection was found to be 4.6 mg/100g. Recovery was determined by standard addition method, giving values of recovery in the range of 97 - 103% and RSD (n = 6) in the range of 0.077 - 2.27%. Internal standard was used to reduce the errors in analysis process and good reproducibility.

scholarly journals Determination and Separation of Diarylheptanoids From Alder Growing in Latvia

2015 ◽  
Vol 1 ◽  
pp. 329 ◽  
Author(s):  
Liga Roze ◽  
Oskars Bikovens ◽  
Galina Telysheva
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Quantitative Determination ◽  
High Performance ◽  
Internal Standard ◽  
Extraction Methods ◽  
Internal Standard Method ◽  
Black Alder ◽  
Phenolic Components

The composition of diarylhepatnoids fraction isolated from bark of two alder species (grey alder and black alder) was studied. The efficiency of three extraction methods used for isolation of diarylhepatnoids from alder bark was compared. Two diarylhepatnoids: 1,7-bis-(3,4-dihydroxyphenyl)-heptan- 3-one-5-O-β-D-xylopyronoside (oregonin) and 1,7-bis-(3,4-dihydroxyphenyl)-3-hydroxyheptane-5-O-β-D- xylopyranoside were isolated from the bark of grey alder. The phenolic components of the extracts were analyzed by high-performance liquid chromatography (HPLC). Quantitative determination of oregonin was performed using an internal standard method. The results obtained show that alder barks are rich source of diarylhepatnoids.

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