Direct determination of the linoleate/oleate ratio in serum cholesterol esters by liquid chromatography.

1982 ◽  
Vol 28 (4) ◽  
pp. 676-680 ◽  
Author(s):  
J T Bernert ◽  
J R Akins ◽  
D T Miller
Keyword(s):  
Liquid Chromatography ◽  
Serum Cholesterol ◽  
Methyl Esters ◽  
Direct Determination ◽  
Reversed Phase ◽  
Cholesterol Esters ◽  
Serum Samples ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract We describe a convenient method for the direct determination of the serum cholesterol linoleate/cholesterol oleate (L/O) ratio by reversed-phase "high-performance" liquid chromatography. After removal of phospholipids by silicic acid chromatography, a serum extract is analyzed on a 5-micrometers particle size Ultrasphere-ODS column, eluted isocratically with acetonitrile/isopropanol (30/70, by vol). Detection is at 200 nm. Cholesterol palmitoleate interferes with the measurement when the analysis is based on peak area, but not when peak height is used. The overall precision of L/O measurements by this method was very similar to that observed with a gas-liquid chromatographic procedure, in which the cholesterol esters are first isolated and transesterified to the methyl esters. In both cases, the within-run CV for six replicate analyses was less than 2%. Analysis of 53 human serum samples by both methods yielded very similar L/O ratios. A plot of the data (our method = y) vs the usual gas-liquid chromatographic procedure gave a correlation coefficient of 0.988 and a regression equation of y = 1.03x + 0.013. Furthermore, direct analysis of serum cholesterol ester L/O ratios by our liquid-chromatographic method is simpler, quicker, and more readily adaptable to automation.

Improved direct determination of alpha- and gamma-tocopherols in plasma and platelets by liquid chromatography, with fluorescence detection.

1982 ◽  
Vol 28 (8) ◽  
pp. 1784-1787 ◽  
Author(s):  
J Lehmann ◽  
H L Martin
Keyword(s):  
Liquid Chromatography ◽  
High Performance ◽  
Limit Of Detection ◽  
Human Subjects ◽  
Direct Determination ◽  
High Performance Liquid Chromatographic ◽  
Reversed Phase ◽  
Liquid Chromatographic ◽  
Chloroform Methanol

Abstract Tocopherols extracted from plasma with methanol or from platelets with chloroform/methanol were injected in methanol on a reversed-phase (C18) "high-performance" liquid-chromatographic column and eluted with water/methanol (2/98, by vol) at a flow rate of 1.4 mL/min. A "high-performance" spectrophotofluorometer was used for detection. Analytical recoveries ranged from 89 to 106%. The response was linear to at least 0.3 micrograms of either tocopherol (alpha- or gamma-) applied to the column, and the limit of detection was 0.1 ng. The method was used to measure tocopherols in plasma and platelets from human subjects, and some values are presented.

Determination of Diacetyl in Butter as 2,3-Diaminonaphthalene Derivative, Using a Fluorometric Procedure or Reverse Phase Liquid Chromatography with Fluorescence Detection

1988 ◽  
Vol 71 (3) ◽  
pp. 462-465
Author(s):  
Pietro Damiani ◽  
Giovanni Burini
Keyword(s):  
Liquid Chromatography ◽  
Fluorescence Detection ◽  
The Other ◽  
Reverse Phase ◽  
Reverse Phase Liquid Chromatography ◽  
Fluorescence Characteristics ◽  
Chromatographic Procedure ◽  
Phase Liquid ◽  
Liquid Chromatographic

Abstract Two procedures, one fluorometric and the other reverse phase liquid chromatographic, for determination of a derivative of diacetyl are described. Exploratory work on diacetyl standard solutions to establish the best conditions for the derivatization with 2,3-diaminonaphthalene (DAN) to yield 2,3-dimethylbenzo[g]-quinoxaline (DMBQ) is discussed, as well as the fluorescence characteristics of the DMBQ derivative. Diacetyl was determined in 10 commercial butter samples by the proposed procedures and by other known methods (determination of o-phenylenediamine and 3,3-diaminobenzidinederivatives). Recoveries from butter samples spiked with known amounts of diacetyl ranged from 96.9 to 101.8% (with CVs ranging from 0.3 to 2.1%) for the fluorometric procedure and from 96.9 to 102.7% (with CVs ranging from 0.5 to 2.4%) for the chromatographic procedure. These results agree well with those obtained with o-phenylenediamine and 3,3-diaminobenzidine methods on the same butter samples. The proposed methods have the advantages of improved detectability and specificity.

Determination of Cymiazole Residues in Honey by Liquid Chromatography

1993 ◽  
Vol 76 (1) ◽  
pp. 92-94 ◽  
Author(s):  
Paolo Cabras ◽  
Marinella Melis ◽  
Lorenzo Spanedda
Keyword(s):  
Liquid Chromatography ◽  
Chromatographic Analysis ◽  
Mobile Phase ◽  
Chromatographic Method ◽  
Reversed Phase ◽  
Limit Of Determination ◽  
Liquid Chromatographic Method ◽  
Liquid Chromatographic ◽  
Control Samples

Abstract A liquid chromatographic method is described for the determination of cymiazole residues in honey. This acaricide is determined on a reversed-phase (C18) column, with a CH3CN-O.OOIN HCI-NaCI mixture (950 mL + 50 mL + 0.3 g/L) as the mobile phase, and UV detection at 265 nm. Cymiazole is extracted with n-hexane from aqueous alkalinized (pH 9) honey solutions. No further cleanup of the honey extract was required before chromatographic analysis. Recoveries on control samples fortified with 0.01,0.10, and 1.00 ppm cymiazole ranged from 92 to 102%. The limit of determination was 0.01 ppm.

Determination of Aspartame and Its Major Decomposition Products in Foods

1993 ◽  
Vol 76 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Jacques Prodolliet ◽  
Milene Bruelhart
Keyword(s):  
Soft Drink ◽  
Food Additives ◽  
Reversed Phase ◽  
Food Samples ◽  
Phase Detection ◽  
Decomposition Products ◽  
Coefficients Of Variation ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic

Abstract A liquid chromatographic procedure already evaluated in a preceding study for the analysis of acesulfam-K is also suitable for the determination of the intense sweetener aspartame in tabletop sweetener, candy, fruit beverage, fruit pulp, soft drink, yogurt, cream, cheese, and chocolate preparations. The method also allows the determination of aspartame’s major decomposition products: diketopiperazine, aspartylphenylalanine, and phenylalanine. Samples are extracted or diluted with water and filtered. Complex matrixes are centrifuged or clarified with Carrez solutions. An aliquot of the extract is analyzed on a reversed-phase μBondapak C18 column using 0.0125M KH2P04 (pH 3.5)-acetonitrile ([85 + 15] or [98 + 2]) as mobile phase. Detection is performed by UV absorbance at 214 nm. Recoveries ranged from 96.1 to 105.0%. Decomposition of the sweetener was observed in most food samples. However, the total aspartame values (measured aspartame + breakdown products) were within -10% and +5% of the declared levels. The repeatabilities and the repeatability coefficients of variation were, respectively, 1.00 mg/100 g and 1.34% for products containing less than 45 mg/100 g aspartame and 4.11 mg/100 g and 0.91 % for other products. The technique is precise and sensitive. It enables the detection of many food additives or natural constituents, such as other intense sweeteners, organic acids, and alkaloids, in the same run without interfering with aspartame or its decomposition products. The method is consequently suitable for quality control or monitoring.

Elimination of caffeine interference in HPLC determination of urinary nicotine and cotinine.

1989 ◽  
Vol 35 (7) ◽  
pp. 1456-1459 ◽  
Author(s):  
N T Thuan ◽  
M L Migueres ◽  
D Roche ◽  
G Roussel ◽  
G Mahuzier ◽  
...  
Keyword(s):  
Reversed Phase ◽  
Gas Liquid Chromatography ◽  
Tobacco Exposure ◽  
Coefficients Of Variation ◽  
Chromatographic Procedure ◽  
Phase Liquid ◽  
Liquid Chromatographic ◽  
Minimum Detectable Amount ◽  
Column Extraction

Abstract We report an analytical reversed-phase liquid-chromatographic procedure for quantifying nicotine and cotinine in urine, taking into account the presence of interfering caffeine frequently encountered in such specimens. These analytes are extracted from the alkalinized urine with chloroform. After evaporation of the chloroform, the residue is dissolved in methanol and injected into a chromatographic C18 column. Extraction recoveries averaged 80% to 97%. Chromatographic conditions were investigated to obviate caffeine interference. The proposed eluent mobile phase is a polar mixture of water, acetonitrile, methanol, and a pH 4 acetoacetate buffer (65/2/29/4 by vol) adjusted to pH 4.30 +/- 0.02 with triethylamine. High resolution and linearity were obtained for each analyte up to a concentration of 200 mg/L. The minimum detectable amount of each compound was 20 ng per injection, corresponding to 10 micrograms per liter of urine. Correlation with results of gas-liquid chromatography was excellent (r = 0.99). This simple, rapid procedure allows routine screening of tobacco exposure with acceptable precision: within- and between-run coefficients of variation were less than 2% and less than 5%, respectively.

High-Pressure Liquid Chromatography of Benzo (a) pyrene and Benzo(ghi)perylene in Oil-Contaminated Shellfish

1976 ◽  
Vol 59 (5) ◽  
pp. 989-992 ◽  
Author(s):  
Humberto Guerrero ◽  
Edward R Biehl ◽  
Charles T Kenner
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Petroleum Ether ◽  
Silica Gel ◽  
High Pressure Liquid Chromatography ◽  
High Pressure Liquid Chromatographic ◽  
Chromatographic Procedure ◽  
Liquid Chromatographic ◽  
Polynuclear Aromatics

Abstract A high-pressure liquid chromatographic procedure is described for the determination of benzo (a) pyrene and benzo(ghi)perylene. These polynuclear aromatics are extracted with acetonitrile and partitioned into petroleum ether, the petroleum ether is removed, and the residue is saponified. The compounds are purified and isolated by passing the residue through a silica gel column and a high-pressure liquid chromatographic column, and detected by their ultraviolet absorption. Recoveries of standards through the procedure averaged 104%.

Liquid-chromatographic determination of 4-hydroxyproline in urine.

1986 ◽  
Vol 32 (6) ◽  
pp. 1002-1004 ◽  
Author(s):  
H Hughes ◽  
L Hagen ◽  
R A Sutton
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Present Method ◽  
High Performance ◽  
Protein Hydrolysate ◽  
Chromatographic Determination ◽  
Reversed Phase ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract In this method for 4-hydroxyproline in urine, hydroxyproline is derivatized with 4-chloro-7-nitrobenzofurazan, with subsequent estimation by reversed-phase "high-performance" liquid chromatography. The ranges for excretion of free and total hydroxyproline while the subjects were ingesting unrestricted diets were 2-29 and 122-374 mumol/24 h (n = 21), respectively, with no significant sex-related difference. A comparison with results by colorimetry indicated no significant differences: mean (n = 18) concentrations (mumol/L) of hydroxyproline in urine were 180 (SD 149) by the present method, 163 (SD 166) by colorimetry. For protein hydrolysate the respective values were 5.9 (SD 2.7) and 6.7 (SD 2.9).

scholarly journals Liquid Chromatographic Determination of Fosthiazate Residues in Environmental Samples and Application of the Method to a Fosthiazate Field Dissipation Study

2005 ◽  
Vol 88 (6) ◽  
pp. 1827-1833 ◽  
Author(s):  
Nicholas G Tsiropoulos ◽  
Dimitrios T Likas ◽  
Dimitrios G Karpouzas
Keyword(s):  
Liquid Chromatography ◽  
Solid Phase ◽  
Chromatographic Determination ◽  
Physicochemical Characteristics ◽  
Reversed Phase ◽  
Subsequent Elution ◽  
Water And Soil Samples ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic

Abstract A method was developed and validated for the determination of residues of the organophosphorus nematicide fosthiazate in soil and water by using reversed-phase liquid chromatography with UV detection. Good recoveries (>85%) of fosthiazate residues were obtained from water samples (drinking water, groundwater, and liquid chromatography water) after passage of 0.5–2 L water through solid-phase extraction (SPE) C-18 cartridges and subsequent elution with ethyl acetate. Residues in soil were extracted with methanol–water (75 + 25, v/v) on a wrist-action shaker, and the extract was cleaned up on C-18 SPE cartridges before analysis. The method was validated by analysis of a range of soils with different physicochemical characteristics; recoveries exceeded 87% at fortification levels ranging from 0.02 to 5.0 mg/kg. The precision values obtained for the method, expressed as repeatability and reproducibility, were satisfactory (<11%). Fosthiazate detection limits were 0.025 μg/L and 0.005 mg/kg for water and soil samples, respectively. The decline in the levels of fosthiazate residues in soil was measured after application of fosthiazate to protected tomato cultivation. The dissipation of fosthiazate residues followed first-order kinetics with a calculated half-life of 21 days.

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