DETERMINATION OF FREE AND TOTAL CHOLESTEROL BY DIRECT CHLOROFORM EXTRACTION

In this paper the use of cholesterol oxidase derivatized with a fluorescein derivative is proposed for the direct determination of total cholesterol in blood serum. The method is based on the changes in the fluorescence of the solution during the enzymatic reaction (λexe = 498 nm and λem 519 nm). A mathematical model which relates the analytical signal to the total cholesterol concentration was developed, and the model can also be used to obtain some of the thermodynamic constants of the process. The method has a linear response range up to 70 mg/L of cholesterol, a detection limit of 2.5 mg/L, and the precision was 1.0% (40 mg/L cholesterol, n = 10). The method was applied to total cholesterol determination in blood serum samples. The results were compared to those obtained by a commercial analyzer, and statistically similar results were obtained. The use of derivatized cholesterol oxidase makes it possible to simplify the methodology normally used in this type of determination (the indicator reaction is avoided and the number of reagents reduced), with the added advantage that the analytical signal is independent of the concentrations of O2 and cholesterol oxidase.

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Automated determination of serum total cholesterol

Clinica Chimica Acta ◽

10.1016/0009-8981(64)90073-7 ◽

1964 ◽

Vol 10 (4) ◽

pp. 381-384 ◽

Cited By ~ 225

Author(s):

J.B. Levine ◽

B. Zak

Keyword(s):

Total Cholesterol ◽

Serum Total Cholesterol ◽

Automated Determination

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Enzymatic Determination of Total Cholesterol in Serum

Clinical Chemistry ◽

10.1093/clinchem/20.6.724 ◽

1974 ◽

Vol 20 (6) ◽

pp. 724-725 ◽

Cited By ~ 26

Author(s):

P N Tarbutton ◽

C R Gunter

Keyword(s):

Total Cholesterol ◽

Enzymatic Determination

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An Ultramicro Method for the Estimation of Plasma Cholesterol

Clinical Chemistry ◽

10.1093/clinchem/8.2.105 ◽

1962 ◽

Vol 8 (2) ◽

pp. 105-112 ◽

Cited By ~ 5

Author(s):

G S Duboff ◽

W W Stevenson

Keyword(s):

Menstrual Cycle ◽

Total Cholesterol ◽

Plasma Cholesterol ◽

Physical Conditioning ◽

Cholesterol Levels ◽

Estrogen Activity ◽

Finger Tip ◽

Consequent Increase ◽

Similar Decrease

Abstract A procedure is outlined for the ultramicro determination of total cholesterol that gives results in excellent agreement with classic methods. The determination requires 40 µl. of plasma obtained from a finger-tip puncture and special handling of precipitated proteins. By the use of the described procedure plasma cholesterol levels have been estimated 4 times daily over a period of 8 weeks in young men undergoing rigorous physical training and 3 times daily in women during the menstrual cycle. A striking fall in total plasma cholesterol was observed in men following physical conditioning in contrast to controls, and a similar decrease was observed in women with normal menstrual cycles in contrast to women with an anovulatory menses. It is suggested that the total cholesterol decrease in the female coincides with the phase in the menstrual cycle when estrogen activity is maximal and that the lowering of total cholesterol in men, following physical conditioning, may be due to an increased production of endogenous androgens with a consequent increase in conversion of these steroids to estrogens.

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Comparison of the Du Pont aca and Dow methods for determination of high-density lipoprotein cholesterol.

Clinical Chemistry ◽

10.1093/clinchem/30.1.127 ◽

1984 ◽

Vol 30 (1) ◽

pp. 127-129 ◽

Cited By ~ 4

Author(s):

N N Rehak ◽

R J Elin ◽

R Chesler ◽

E Johnson

Keyword(s):

High Density Lipoprotein ◽

Disease Control ◽

Total Cholesterol ◽

High Density Lipoprotein Cholesterol ◽

Dextran Sulfate ◽

Density Lipoprotein ◽

High Density ◽

Lipoprotein Cholesterol ◽

Serum Samples

Abstract We compared the Du Pont aca (phosphotungstate-enzymic cholesterol) and the Dow (dextran sulfate/Mg2+-enzymic cholesterol) methods for the determination of high-density lipoprotein cholesterol (HDLC) and total cholesterol in serum from 113 patients. The aca results for both total cholesterol and HDLC were significantly greater (p less than 0.0001) than the Dow results, the aca method overestimating the HDLC concentration (mean recovery 107.2% in serum samples with values assigned by the Centers for Disease Control). The precision of the aca method for HDLC was essentially the same as that of the Dow method. Bilirubin (up to 0.17 g/L), hemoglobin (up to 4 g/L), and slight lipemia (triglycerides up to 5.4 g/L) did not interfere with the aca method.

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Determination of ionized magnesium in platelets and correlation with selected variables

Clinical Chemistry ◽

10.1093/clinchem/42.5.744 ◽

1996 ◽

Vol 42 (5) ◽

pp. 744-748 ◽

Cited By ~ 10

Author(s):

J E Niemela ◽

B M Snader ◽

R J Elin

Keyword(s):

Total Cholesterol ◽

Inverse Correlation ◽

Reference Interval ◽

Cholesterol Concentration ◽

Magnesium Concentration ◽

Serum Electrolytes ◽

Ionized Magnesium ◽

And Gender ◽

Dissociation Constant Kd

Abstract We describe a method for determining the intracellular ionized magnesium concentration ([Mg2+]i) in platelets by using the fluorescent probe FURAPTRA. We determined the dissociation constant (KD) of FURAPTRA for Mg2+ (2.26 +/- 0.29 mmol/L), within-day assay variability (CV = 6.8%), among-day intraindividual variability (CV = 11.0%), variability after a 4-h delay in processing the blood specimen (t = 1.2, P >0.2; F = 6.2, P <0.02), and the reference interval (0.23-0.59 mmol/L) for this assay. We also evaluated the correlation between platelet [Mg2+]i and concentrations of selected serum electrolytes, proteins, and total cholesterol; age; body mass index; and gender. Only the inverse correlation between platelet [Mg2+]i and serum total cholesterol concentration in men was significant (r=-0.66, P <0.005).

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