Determination of lipoic acid in dietary supplement preparations by capillary electrophoresis

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

“…Among the reported analytical methods for the determination of lipoic acid in the body fluids include thin layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography (GC), polarography, colorimetric and microbiological assay, liquid chromatography mass spectrometry (LC-MS) [1,3,18,19], gas chromatography mass spectrometry (GC-MS) and capillary electrophoresis [20,21]. Though GC-MS has been reported to be a suitable and powerful tool for the quantification of LA in body fluids but it is expensive and its use is not common in most of the laboratories [5,15].…”

“…HPLC with fluorescence detection, offers a good method for the determination of ␣-lipoic acid in biological fluids but its lengthy and time consuming derivitization and sample preparation steps are laborious [5,24]. HPLC with electrochemical detection method is therefore seems to be an ultimate choice in terms of sensitivity, shorter analysis time and lower cost for most of the standard research laboratories to quantify ␣-lipoic acid in biological fluids in comparison with other literature reported methods [3,5,15,[18][19][20][21]23,24]. To our knowledge only a few HPLC methods with fluorescence detection have been reported for the simultaneous determination of LA and DHLA in biological fluids and pharmaceuticals samples [5,13], and no HPLC-ECD method for the simultaneous determination of LA and DHLA in biological fluids has been reported so for.…”

The quality of commercially available nutraceutical supplements and food sources

“…Branched-chain amino acids [15] Italy MEC 3/3 97-104% Carnitine [16] Czech † CE 1/3 50-104% Carnitine [16] USA † CE 0/1 35% Carnitine [17] Greece † HPLC 2/2 capsules 98% each Carnitine [17] Greece † HPLC 5/5 oral solutions 96-100% b Carotene [18] Germany † HPLC 1/11 61-137% b Carotene [19] Canada HPLC 2/6 86-111% Coenzyme Q10 [20] Japan HPLC 10/10 96-106% Coenzyme Q10 [21] New Zealand HPLC 1/7 100-130% Coenzyme Q10 [22] USA HPLC 100%, number not stated 95-105% Coenzyme Q10 [23] USA HPLC 4/4 98-103% Coenzyme Q10 [24] Japan HPLC 36/61 5-123% Creatine [25] USA TLC 1/8 83-106% Creatine [26] USA † HPLC 2/2 Effervescent powders 99-100% Creatine [26] USA † HPLC 0 'Serum' formulation, 1.7% of claimed level Creatine [27] USA † HPLC 4/6 94-126%, 100% in four DHEA [28] USA HPLC 6/16 Three contain 0%, and one 150% DHEA [29] USA HPLC 14/45 74-110%, plus one of 0% Docosahexaenoic acid [30] USA † GLC 1/8 57-115% Eicosapentanoic acid [30] USA † GLC 0/8 75-94% g-Linolenic acid [31] Germany † GLC 5/19 73-107% g-Linolenic acid [32] Australia † GLC 12/16 36-109% Lipoic acid [33] Austria CE 3/5 87-110% Lipoic acid [34] Austria HPLC 1/6 40-97% Lutein [35] USA HPLC 0/3 134-194% Lutein/zeaxanthin [36] German HPLC 0/7 16-136% Lutein/zeaxanthin [36] USA HPLC 2/7 11-22% Lutein [19] Canada † HPLC 0/2 109-125% Lycopene [37] Canada HPLC 1/6 6-143% Melatonin [38] Italy HPTLC 5/6 93-102% Oxyresveratrol [39] USA HPLC -Three of four contained 0% Policosanol [40] USA GC-MS Tablet 53% Octacosanol 58% Capsule 54% 16% Capsule 40% 24% Proanthocyanidins [41] Japan grape seed oil HPLC 0/2 ND Resveratrol [42] USA HPTLC 2/4 94-97% SAMe…”

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

“…Various analytical methods are currently reported for the analysis of lipoic acid in the body fluids including thin layer chromatography (TLC), high performance liquid chromatography (HPLC), gas chromatography (GC), polarography, colorimetric and microbiological assay, liquid chromatography-mass spectrometry (LC-MS) [1,11,12], gas chromatography-mass spectrometry (GC-MS), and capillary electrophoresis [13,14]. Although GC-MS is a powerful technique for the quantification of LA in biological fluids but it is expensive and beyond the reach of many laboratories [2,9].…”

“…HPLC with fluorescence detection, proved to offer a good method for the determination of ␣-lipoic acid in biological fluids but require lengthy derivatization and laborious sample preparation steps [2,17]. HPLC with electrochemical detection seems to be a method of choice in terms of sensitivity, short run time and low cost for most of the standard laboratories to quantify ␣-lipoic acid in biological fluids as compared with other reported analytical methods [1,2,9,[11][12][13][14]16,17].…”