Determination of lipoic acid in human plasma by HPLC-ECD using liquid–liquid and solid-phase extraction: Method development, validation and optimization of experimental parameters

Khan, Abad; Khan, Muhammad Imran; Iqbal, Zafar; Ahmad, Lateef; Shah, Yatrik M.; Watson, David

doi:10.1016/j.jchromb.2010.08.022

Cited by 31 publications

(22 citation statements)

References 20 publications

(43 reference statements)

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“…Table 2 shows comparative recoveries of the two analytes with various extraction solvents/procedures. Recovery of the a-LA with the liquidliquid extraction (LLE) procedure using dichloromethane as the extraction solvent was comparable with that obtained with the selected PP method [13]; however, DHLA was not efficiently extracted by LLE as compared to PP, which may be attributed to its poor partitioning into non-polar solvents because of its greater polarity [16]. Other disadvantages of the LLE methods over PP methods are that these procedures are multi-step, laborious, and time consuming.…”

Section: Optimization Of Sample Preparationmentioning

confidence: 70%

“…Other disadvantages of the LLE methods over PP methods are that these procedures are multi-step, laborious, and time consuming. Solidphase extraction (SPE) procedures have also been reported for the extraction of the a-LA from complex sample matrices [12,13,15,17,20], and these procedures offer comparable recoveries and clear chromatograms. However, SPE is a much more expensive procedure than the LLE and PP, so it was not utilized in this study.…”

Section: Optimization Of Sample Preparationmentioning

confidence: 99%

“…Although, the use of a longer column (250 mm) has also been reported for analysis of the a-LA [13], but a shorter column offered the advantages of lesser mobile phase consumption and shorter run time over the longer column without affecting peaks resolution.…”

Section: Stationary Phasementioning

confidence: 99%

“…Several papers have been published on the chromatographic analysis of total, free, or bound a-LA in various sample matrices such as foodstuffs [9], dietary supplements [10], and biological samples [11][12][13][14][15][16]. Similarly, very few methods [17][18][19][20][21][22][23] are available for simultaneous determination of the total a-LA and its reduced form, DHLA, in biological samples after oral administration.…”

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confidence: 99%

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Simultaneous Determination of the Endogenous Free α-Lipoic Acid and Dihydrolipoic Acid in Human Plasma and Erythrocytes by RP-HPLC with Electrochemical Detection

et al. 2011

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A highly sensitive, precise, and accurate reversed-phase high-performance liquid-chromatography/ electrochemical detection method for simultaneous determination of the endogenous free a-lipoic acid and dihydrolipoic acid in biological matrices was developed and validated. The two analytes were extracted from the samples with acetonitrile/10% metaphosphoric acid solution (aqueous) (50/50 v/v). To determine the total lipoic acid, samples were treated with tris(2-carboxyethyl)phosphine solution in phosphate buffer, pH 2.5 with 85% orthophosphoric acid prior to deproteination. The two analytes were separated on a C 18 (150 9 4.6 mm, 5 lm) analytical column using acetonitrile-50 mM phosphate buffer, pH 2.5 with 85% orthophosphoric acid (35/65 v/v) as the isocratic mobile phase pumped at a flow rate of 2.0 mL min -1 at the column oven temperature of 35°C. The column eluents were monitored at a potential of 0.9 V. These analytes were efficiently resolved in \7 min. The present method was sufficiently robust and specific for simultaneous determination of the two analytes and demonstrated acceptable values for linearity (r 2 = 0.999 in the range of 0.1-500 and 0.25-1,000 ng mL -1 for a-lipoic acid and dihydrolipoic acid, respectively), recovery ([97%), precision (RSD% \2), and sensitivity (on column limit of detection, 150 and 375 fg for a-lipoic acid and dihydrolipoic acid, respectively and limit of quantification: 0.5 and 1.25 pg for a-lipoic acid and dihydrolipoic acid, respectively), indicating that the proposed method was more sensitive, precise, economical, and versatile, and has higher throughput than the previously reported methods for simultaneous determination of the two analytes.

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Section: Optimization Of Sample Preparationmentioning

confidence: 70%

Section: Optimization Of Sample Preparationmentioning

confidence: 99%

Section: Stationary Phasementioning

confidence: 99%

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confidence: 99%

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Simultaneous Determination of the Endogenous Free α-Lipoic Acid and Dihydrolipoic Acid in Human Plasma and Erythrocytes by RP-HPLC with Electrochemical Detection

et al. 2011

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“…Chemically it is, 1,2-dithiolane-3-valeric acid or 6,8-dithiolane octanoic acid, or 6,8-thioctic acid. It is found naturally in both plants and animals [1][2][3][4]. Alpha-lipoic acid (LA) and its reduced form dihydrolipoic acid (DHLA) is the crucial universal antioxidant redox couple of human body [4,5].…”

Section: Introductionmentioning

confidence: 99%

Simultaneous determination of lipoic acid (LA) and dihydrolipoic acid (DHLA) in human plasma using high-performance liquid chromatography coupled with electrochemical detection

Khan

Iqbal

Watson

et al. 2011

Journal of Chromatography B

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Least median of squares and iteratively re‐weighted least squares as robust linear regression methods for fluorimetric determination of α‐lipoic acid in capsules in ideal and non‐ideal cases of linearity

et al. 2018

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This study outlines two robust regression approaches, namely least median of squares (LMS) and iteratively re-weighted least squares (IRLS) to investigate their application in instrument analysis of nutraceuticals (that is, fluorescence quenching of merbromin reagent upon lipoic acid addition). These robust regression methods were used to calculate calibration data from the fluorescence quenching reaction (∆F and F-ratio) under ideal or non-ideal linearity conditions. For each condition, data were treated using three regression fittings: Ordinary Least Squares (OLS), LMS and IRLS. Assessment of linearity, limits of detection (LOD) and quantitation (LOQ), accuracy and precision were carefully studied for each condition. LMS and IRLS regression line fittings showed significant improvement in correlation coefficients and all regression parameters for both methods and both conditions. In the ideal linearity condition, the intercept and slope changed insignificantly, but a dramatic change was observed for the non-ideal condition and linearity intercept. Under both linearity conditions, LOD and LOQ values after the robust regression line fitting of data were lower than those obtained before data treatment. The results obtained after statistical treatment indicated that the linearity ranges for drug determination could be expanded to lower limits of quantitation by enhancing the regression equation parameters after data treatment. Analysis results for lipoic acid in capsules, using both fluorimetric methods, treated by parametric OLS and after treatment by robust LMS and IRLS were compared for both linearity conditions.

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Determination of lipoic acid in human plasma by HPLC-ECD using liquid–liquid and solid-phase extraction: Method development, validation and optimization of experimental parameters

Cited by 31 publications

References 20 publications

Simultaneous Determination of the Endogenous Free α-Lipoic Acid and Dihydrolipoic Acid in Human Plasma and Erythrocytes by RP-HPLC with Electrochemical Detection

Simultaneous Determination of the Endogenous Free α-Lipoic Acid and Dihydrolipoic Acid in Human Plasma and Erythrocytes by RP-HPLC with Electrochemical Detection

Simultaneous determination of lipoic acid (LA) and dihydrolipoic acid (DHLA) in human plasma using high-performance liquid chromatography coupled with electrochemical detection

Least median of squares and iteratively re‐weighted least squares as robust linear regression methods for fluorimetric determination of α‐lipoic acid in capsules in ideal and non‐ideal cases of linearity

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