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. 2020 Jul 17;10(7):296. doi: 10.3390/metabo10070296

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© 2020 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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This figure shows the comparison between the two lipid extraction techniques regarding their extraction efficiency of the stable isotope internal standards from the rat liver samples (Folch liquid–liquid extraction: chloroform: methanol: water, ~7:3:4 , and Protein precipitation liquid extraction: chloroform: methanol: acetone, ~7:3:4 ). n = 34 rat liver samples per extraction method. The intensity of the internal standards were measured by liquid chromatography with mass spectrometry. The significance of the difference between the two extraction protocols are shown by the p-value star system; where p ≤ 0.05 was considered statistically significant (* p < 0.05, ** p < 0.01, *** p < 0.001). Error bars represent ± standard deviation. Lipid internal standard include: Butyryl-d7-L-carnitine (abbreviated to IS_Car_4:0-d7), N-tetradecylphosphocholine-d42 (abbreviated to IS_LPC_14:0-d42), hexadecanoyl-L-carnitine-d3 (abbreviated to IS_Car_16:0-d3), heptadecanoic-d33 acid (abbreviated to IS_FA_17:0-d33), 1,2-dimyristoyl-d54-sn-glycero-3-[phospho-L-serine] (abbreviated to IS_PS_28:0-d54), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphoinositol (abbreviated to IS_PI_34:1-d31), N-palmitoyl-d31-D-erythro-sphingosylphosphorylcholine (abbreviated to IS_SM_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (abbreviated to IS_PG_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphate (abbreviated to IS_PA_34:1-d31), N-palmitoyl-d31-D-erythro-sphingosine (abbreviated to IS_Cer_16:0-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphocholine (abbreviated to IS_PC_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphoethanolamine (abbreviated to IS_PE_34:1-d31), glyceryl tri(pentadecanoate-d29) (abbreviated to IS_TG_45:0-d87).

Inline graphic — This figure shows the comparison between the two lipid extraction techniques regarding their extraction efficiency of the stable isotope internal standards from the rat liver samples (Folch liquid–liquid extraction: chloroform: methanol: water, ~7:3:4 , and Protein precipitation liquid extraction: chloroform: methanol: acetone, ~7:3:4 ). n = 34 rat liver samples per extraction method. The intensity of the internal standards were measured by liquid chromatography with mass spectrometry. The significance of the difference between the two extraction protocols are shown by the p-value star system; where p ≤ 0.05 was considered statistically significant (* p < 0.05, ** p < 0.01, *** p < 0.001). Error bars represent ± standard deviation. Lipid internal standard include: Butyryl-d7-L-carnitine (abbreviated to IS_Car_4:0-d7), N-tetradecylphosphocholine-d42 (abbreviated to IS_LPC_14:0-d42), hexadecanoyl-L-carnitine-d3 (abbreviated to IS_Car_16:0-d3), heptadecanoic-d33 acid (abbreviated to IS_FA_17:0-d33), 1,2-dimyristoyl-d54-sn-glycero-3-[phospho-L-serine] (abbreviated to IS_PS_28:0-d54), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphoinositol (abbreviated to IS_PI_34:1-d31), N-palmitoyl-d31-D-erythro-sphingosylphosphorylcholine (abbreviated to IS_SM_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (abbreviated to IS_PG_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphate (abbreviated to IS_PA_34:1-d31), N-palmitoyl-d31-D-erythro-sphingosine (abbreviated to IS_Cer_16:0-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphocholine (abbreviated to IS_PC_34:1-d31), 1-palmitoyl-d31-2-oleoyl-sn-glycero-3-phosphoethanolamine (abbreviated to IS_PE_34:1-d31), glyceryl tri(pentadecanoate-d29) (abbreviated to IS_TG_45:0-d87).