Beta-carotene determined in serum by liquid chromatography with an internal standard.

1983 ◽  
Vol 29 (6) ◽  
pp. 1042-1044 ◽  
Author(s):  
W J Driskell ◽  
M M Bashor ◽  
J W Neese
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Methylene Chloride ◽  
Internal Standard ◽  
Beta Carotene ◽  
Solvent System ◽  
Peak Height ◽  
Reversed Phase ◽  
Human Populations ◽  
Relationship Of

Abstract We describe a procedure for quantitative determination of beta-carotene in human serum. The 0.1-mL serum sample is precipitated with ethanol containing the internal standard, dimethyl-beta-carotene, then extracted with hexane. This extract is injected onto a reversed-phase, "high-performance" liquid-chromatography column, and the carotenes are resolved and eluted with an acetonitrile/methylene chloride isocratic solvent system. They are quantified from the peak-height ratios of their absorbance at 450 nm. About 14 min is required for each chromatogram. The procedure has excellent precision and is appropriate for routine use in analysis of large numbers of samples. The method should be particularly useful for clinical studies on the relationship of serum beta-carotene and cancer incidence in human populations.

Liquid chromatography and radioimmunoassay compared for determination of cortisol and corticosterone in plasma after a dexamethasone suppression test.

1987 ◽  
Vol 33 (9) ◽  
pp. 1639-1642 ◽  
Author(s):  
K Oka ◽  
M Noguchi ◽  
T Kitamura ◽  
S Shima
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Internal Standard ◽  
Solvent System ◽  
Peak Height ◽  
Peak Height Ratio ◽  
Analytical Recovery ◽  
Suppression Test ◽  
Dexamethasone Suppression

Abstract We developed sensitive, specific "high-performance" liquid chromatography (HPLC) for determining suppressed cortisol and corticosterone in human plasma and compared its efficacy with that of conventional radioimmunoassay (RIA) at concentrations in the nanogram per liter range. Steroids from a 0.5-mL aliquot of plasma were extracted by rapid-flow fractionation, with diethyl ether as mobile-phase solvent, diatomaceous earth granules as stationary-support material. Analytical recovery of the steroids approached 100%. Concentrations in plasma were determined from peak-height ratio calibration (dexamethasone internal standard). The analytical column contained silica gel and the solvent system was water/methanol/dichloromethane/n-hexane (0.1/3/30/66.9 by vol). We could measure the steroids before and 20 h after oral administration of 0.5 mg of dexamethasone. The detection limit was 300 ng per liter of plasma for corticosterone, 500 ng/L for cortisol, with CVs of less than 4%. Determining corticosterone after administration of dexamethasone, in four of 20 such samples we could determine concentrations greater than 300 ng/L; the others contained corticosterone between 100 and 300 ng/L, but these values could not be certified analytically. Mean concentrations of these hormones as determined by RIA substantially exceeded those by HPLC. Some cross reactions in RIA could not be considered negligible in spite of pre-column treatment of the extracts.

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.

A high-performance liquid-chromatographic method for routine simultaneous determination of nicotine and cotinine in plasma.

1988 ◽  
Vol 34 (4) ◽  
pp. 724-729 ◽  
Author(s):  
M Hariharan ◽  
T VanNoord ◽  
J F Greden
Keyword(s):  
Simultaneous Determination ◽  
Mobile Phase ◽  
High Performance ◽  
Methylene Chloride ◽  
Internal Standard ◽  
High Performance Liquid Chromatographic ◽  
Reversed Phase ◽  
Standard Curve ◽  
Liquid Chromatographic

Abstract We describe a rapid, sensitive method for the routine simultaneous determination of nicotine and cotinine in 1 mL of plasma. Extraction in 10-mL screw-capped Teflon tubes with methylene chloride after deproteinization with trichloroacetic acid eliminated emulsion formation. The extract, after evaporation and reconstitution in 30 microL of mobile phase, is injected into a reversed-phase C-18 ion-pair column of an isocratic high-performance liquid-chromatographic unit. Absorbance is monitored at 256 nm. The mobile phase is a citrate-phosphate (30 mmol each per liter) buffer mixture containing 50 mL of acetonitrile and 1 mmol of sodium heptanesulfonate per liter. 2-Phenylimidazole is the internal standard. The detection limit is 1 microgram/L for nicotine and 3 micrograms/L for cotinine. The standard curve is linear from 0 to 700 micrograms/L for both compounds. The average CV for nicotine in the concentration range 0-100 micrograms/L is 6.5%, and that for cotinine in the concentration range 50-700 micrograms/L is 4%.

Measurement of gliclazide in plasma by radial compression reversed-phase liquid chromatography.

1984 ◽  
Vol 30 (11) ◽  
pp. 1789-1791 ◽  
Author(s):  
B G Charles ◽  
P J Ravenscroft
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Limit Of Detection ◽  
Internal Standard ◽  
Reversed Phase ◽  
Radial Compression ◽  
Reversed Phase Liquid Chromatography ◽  
Minimal Sample ◽  
Precise Analysis ◽  
Phase Liquid

Abstract We describe a rapid, specific, and precise analysis for gliclazide in plasma by radial compression, reversed-phase, "high-performance" liquid chromatography. Gliclazide and the internal standard, 3-chlorogliclazide, are eluted after 4.4 and 6.8 min, respectively. Only 100 microL of plasma and minimal sample workup are required. The limit of detection for gliclazide in plasma is 0.5 mg/L (1.55 mumol/L) at 229 nm. Precision (CV) of the assay for 10 and 1 mg of gliclazide per litre is 2.1% and 6.4%, respectively.

Liquid-chromatographic determination of vanillylmandelic acid in urine.

1985 ◽  
Vol 31 (6) ◽  
pp. 819-821 ◽  
Author(s):  
G M Anderson ◽  
F C Feibel ◽  
D J Cohen
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Internal Standard ◽  
Chromatographic Determination ◽  
Reversed Phase ◽  
Urine Samples ◽  
Vanillylmandelic Acid ◽  
Analytical Recovery ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract Urinary vanillylmandelic acid (VMA) was determined by "high-performance" liquid chromatography with fluorometric (LC-F) and amperometric (LC-EC) detection. Urine samples were first purified on a small, open-bed, reversed-phase preparatory column. VMA and the internal standard (iso-VMA) were then separated by reversed-phase ion-pair liquid chromatography. Analytical recovery of VMA was high (98.3%, SD 3.3%, n = 8), and concentrations measured by LC-F and LC-EC were in excellent agreement (r = 0.996). The LC-F chromatograms of urine samples had fewer late peaks; however, detection limits were lower (15 vs 120 micrograms/L) for the LC-EC method. Typical concentrations of 1-10 mg/L in urine can be measured easily with either method.

Quantification of alprazolam in serum or plasma by liquid chromatography.

1984 ◽  
Vol 30 (10) ◽  
pp. 1652-1655 ◽  
Author(s):  
S R McCormick ◽  
J Nielsen ◽  
P Jatlow
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Isoamyl Alcohol ◽  
High Performance Liquid Chromatographic ◽  
Peak Height ◽  
Reversed Phase ◽  
Internal Standards ◽  
Steady State Serum ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract A reversed-phase "high-performance" liquid-chromatographic assay for the quantification of alprazolam in serum or plasma is described. Serum or plasma is extracted with toluene/isoamyl alcohol (99/1 by vol), evaporated, and reconstituted in the mobile phase. The latter is washed with hexane, then subjected to reversed-phase liquid chromatography and ultraviolet detection at 202 nm. Either U-31485, an alprazolam analog, or lorazepam, a 3-hydroxybenzodiazepine, is satisfactory as internal standards. Major alprazolam metabolites and various other commonly used drugs do not interfere. The useful lower limit of sensitivity for quantification is 2.5 micrograms/L. Peak height and alprazolam concentration are linearly related from 2.5 to 100 micrograms/L. For 10 and 20 micrograms/L concentrations, within-run CVs were 1.4% and 0.9% and the between-runs CVs 4.8% and 3.2%. Steady-state serum concentrations ranged from 25 to 55 micrograms/L in patients taking 1.5 to 6.0 mg per day, orally. Preliminary data suggest the method is also suitable for analysis of the structurally similar triazolobenzodiazepine, triazolam.

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