countercurrent distribution


Summary: A method of separation of two or more substances by repeated distribution between two immiscible liquid phases that move past each other in opposite directions. It is a form of liquid-liquid chromatography. (Stedman, 25th ed)

Top Publications

  1. Guan Y, Fisher D, Sutherland I. Model for spiral columns and stationary phase retention in synchronous coil planet centrifuges. J Chromatogr A. 2007;1151:136-41 pubmed
    ..questions such as "in the absence of mobile phase flow, how is the distribution of the two phases in a CCC column determined?" and "for Type-J CCC, do the helical and the spiral columns lead to similar performance?" ..
  2. Guan Y, Fisher D, Sutherland I. Protein separation using toroidal columns by type-J synchronous counter-current chromatography towards preparative separation. J Chromatogr A. 2010;1217:3525-30 pubmed publisher
    ..These results paved the way for further scaling-up toroidal CCC columns for processing larger quantities of samples containing large biomolecules. ..
  3. Sutherland I, Fisher D. Role of counter-current chromatography in the modernisation of Chinese herbal medicines. J Chromatogr A. 2009;1216:740-53 pubmed publisher
    ..It is concluded that CCC is making an increasingly important contribution to the modernisation of Chinese herbal medicines. ..
  4. Guan Y, van den Heuvel R. The three-dimensional model for helical columns on type-J synchronous counter-current chromatography. J Chromatogr A. 2011;1218:5108-14 pubmed publisher
    ..The methodology developed in this work may be regarded as a new platform for designing optimised CCC columns for analytical and engineering applications. ..
  5. Cao X, Hu G, Huo L, Zhu X, Li T, Powell J, et al. Stationary phase retention and preliminary application of a spiral disk assembly designed for high-speed counter-current chromatography. J Chromatogr A. 2008;1188:164-70 pubmed publisher
    ..Acceptable resolutions were achieved when it was used for the separation of peptides such as Leu-Tyr and Val-Tyr, and proteins including cytochrome c and myoglobin, lysozyme and myoglobin, and fresh chicken egg-white proteins. ..
  6. Ito Y. Golden rules and pitfalls in selecting optimum conditions for high-speed counter-current chromatography. J Chromatogr A. 2005;1065:145-68 pubmed
    ..The commercial sources of HSCCC and other CCC instruments are described in detail in the study edited by Berthod [A. Berthod (Ed.), Counter-current Chromatography, Elsevier, Amsterdam, 2003]. ..
  7. Guan Y, Smulders J, Fisher D, Sutherland I. Spiral coils for counter-current chromatography using aqueous polymer two-phase systems. J Chromatogr A. 2007;1151:115-20 pubmed
    ..Wave-like disturbance of the interface near the proximal point was observed and analyses have been made for possible use in protein separation. ..
  8. van den Heuvel R, Sutherland I. Observations of established dual flow in a spiral dual-flow counter-current chromatography coil. J Chromatogr A. 2007;1151:99-102 pubmed
    ..Understanding and then explaining such counter-current flow will significantly help in the prediction of elution behaviour in true moving bed chromatography. ..
  9. Friesen J, Pauli G. Rational development of solvent system families in counter-current chromatography. J Chromatogr A. 2007;1151:51-9 pubmed
    ..The results indicated that the GUESSmix is fit for the purpose of developing and evaluating CCC solvent system families with desired performance characteristics. ..

More Information


  1. Ito Y, Yang F, Fitze P, Powell J, Ide D. Improved spiral disk assembly for high-speed counter-current chromatography. J Chromatogr A. 2003;1017:71-81 pubmed
    ..This new column design substantially improved the separation of both dipeptide and protein samples in terms of stationary phase retention and partition efficiency. ..
  2. Guo M, Liang J, Wu S. On-line coupling of counter-current chromatography and macroporous resin chromatography for continuous isolation of arctiin from the fruit of Arctium lappa L. J Chromatogr A. 2010;1217:5398-406 pubmed publisher
    ..lappa. ..
  3. Hu R, Dai X, Lu Y, Pan Y. Preparative separation of isoquinoline alkaloids from Stephania yunnanensis by pH-zone-refining counter-current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2010;878:1881-4 pubmed publisher
    ..7 mg isocorydine, 78.2 mg corydine, 583.4 mg tetrahydropalmatine, 36.3 mg N-methylasimilobine, and 47.3 mg anonaine were separated with purities over 90%. Their structures were identified by (1)H NMR, (13)C NMR, ESI-MS data. ..
  4. Ma Z, Ma Y, Sun X, Ye Y, Shen B, Chen X, et al. Purification of optical imaging ligand-Cybesin by high-speed counter-current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2010;878:3039-43 pubmed publisher
    ..7 mg of fractions containing the target compound at 12.8% purity, and in the second run 1 mg of Cybesin was obtained at purity of 94.0% with a sample recovery rate of over 95% based on the LC-MS analysis. ..
  5. Hopmann E, Arlt W, Minceva M. Solvent system selection in counter-current chromatography using conductor-like screening model for real solvents. J Chromatogr A. 2011;1218:242-50 pubmed publisher
    ..A comparison of the experimental and predicted data for five model solutes systems demonstrated the potential of the use of COSMO-RS as a screening tool for the solvent system selection. ..
  6. Su W, Liu Q, Yang Q, Yu J, Chen X. Separation and purification of four compounds from Desmodium styracifolium using off-line two-dimensional high-speed counter-current chromatography. J Sep Sci. 2013;36:3338-44 pubmed publisher
    ..The results illustrated that off-line 2D high-speed counter-current chromatography is an effective way to isolate compounds in complex samples. ..
  7. Xu P, Guan S, Feng R, Tang R, Guo D. Separation of four homoisoflavonoids from Caesalpinia sappan by high-speed counter-current chromatography. Phytochem Anal. 2012;23:228-31 pubmed publisher
    ..The mean recoveries of the four compounds were 83%, 86%, 93% and 85%, respectively. The study has shown that HSCCC is effective for the separation and enrichment of the target compounds at a large scale. ..
  8. Fang L, Liu Y, Yang B, Wang X, Huang L. Separation of alkaloids from herbs using high-speed counter-current chromatography. J Sep Sci. 2011;34:2545-58 pubmed publisher
    ..Based on the data from the literature, the proper solvent systems for the separation of alkaloids by the conventional HSCCC and pH-zone-refining CCC are also summarized. ..
  9. Xiao X, Si X, Yuan Z, Xu X, Li G. Isolation of fucoxanthin from edible brown algae by microwave-assisted extraction coupled with high-speed countercurrent chromatography. J Sep Sci. 2012;35:2313-7 pubmed publisher
    ..5 g dry Undaria pinnatifida (Harv) Sur, and 15.0 g dry Sargassum fusiforme (Harv) Setch, respectively. The purity of fucoxanthin determined by HPLC was over 90% and its structure was further identified by LC-ESI-MS and (1) H-NMR. ..
  10. Huang L, Cao Y, Xu H, Chen G. Separation and purification of ergosterol and stigmasterol in Anoectochilus roxburghii (wall) Lindl by high-speed counter-current chromatography. J Sep Sci. 2011;34:385-92 pubmed publisher
    ..This separation and purification method was more effective than many other conventional techniques. ..
  11. De Beer D, Joubert E, Malherbe C, Jacobus Brand D. Use of countercurrent chromatography during isolation of 6-hydroxyluteolin-7-O-?-glucoside, a major antioxidant of Athrixia phylicoides. J Chromatogr A. 2011;1218:6179-86 pubmed publisher
    ..This is the first report of the isolation of these compounds from A. phylicoides. ..
  12. Ren D, Yang Z, Liang Y, Fan W, Ding Q. Effects of injection volume on chromatographic features and resolution in the process of counter-current chromatography. J Chromatogr A. 2013;1277:7-14 pubmed publisher
    ..In contrast, the resolution between the separated compounds decreases with increase of the injection volume. ..
  13. Chen S, Zhao X, Li Y, Yang D, Zhou T, Fan G. Impurities preparation of sodium tanshinone IIA sulfonate by high-speed counter-current chromatography and identification by liquid chromatography/multistage tandem mass spectrometry. J Chromatogr A. 2013;1288:28-34 pubmed publisher
    ..This research successfully broadened the application of HSCCC and introduced it to the field of impurities preparation of chemical medicine. ..
  14. Qiu H, Xiao X, Li G. Separation and purification of furanocoumarins from Toddalia asiatica (L.) Lam. using microwave-assisted extraction coupled with high-speed counter-current chromatography. J Sep Sci. 2012;35:901-6 pubmed publisher
  15. Ito Y, Knight M, Finn T. Spiral countercurrent chromatography. J Chromatogr Sci. 2013;51:726-38 pubmed publisher
  16. Wybraniec S, Jerz G, Gebers N, Winterhalter P. Ion-pair high-speed countercurrent chromatography in fractionation of a high-molecular weight variation of acyl-oligosaccharide linked betacyanins from purple bracts of Bougainvillea glabra. J Chromatogr B Analyt Technol Biomed Life Sci. 2010;878:538-50 pubmed publisher
    ..Structural analysis by analytical LC-ESI-MS/MS in the positive ionization mode detected a total sum of 146 different betacyanin pigments in the CCC fractions of reduced complexity...
  17. Xu J, Luo J, Kong L. Simultaneous separation of triterpenoid saponins and flavonoid glycosides from the roots of Glycyrrhiza uralensis Fisch by pH-zone-refining counter-current chromatography. J Sep Sci. 2013;36:3295-301 pubmed publisher
    ..It is also the first time that the separation of acidic triterpenoid saponins by using pH-zone-refining counter-current chromatography has been reported. ..
  18. Engels C, Ganzle M, Schieber A. Fractionation of Gallotannins from mango (Mangifera indica L.) kernels by high-speed counter-current chromatography and determination of their antibacterial activity. J Agric Food Chem. 2010;58:775-80 pubmed publisher
    ..05-0.1 g/L in Luria-Bertani broth but up to 20 times higher in media containing more iron and divalent cations. ..
  19. He J, Yang R, Zhou T, Boland G, Scott P, Bondy G. An epimer of deoxynivalenol: purification and structure identification of 3-epi-deoxynivalenol. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2015;32:1523-30 pubmed publisher
    ..mutans 17-2-E-8 culture. From the culture where 100 mg DON was applied, 56 mg of 3-epi-DON (purity of 96.8%) was obtained from the HSCCC. The purified 3-epi-DON will be used for toxicological characterisation studies of this chemical...
  20. Yang Z, Hu X, Wu S. Preparative isolation of a cytotoxic principle of a forest mushroom Suillus luteus by sodium dodecyl sulfate based "salting-in" countercurrent chromatography. J Sep Sci. 2016;39:732-40 pubmed publisher
    ..It is very useful for current natural products isolation and drug discovery. ..
  21. Akramipour R, Fattahi N, Pirsaheb M, Gheini S. Combination of counter current salting-out homogenous liquid-liquid extraction and dispersive liquid-liquid microextraction as a novel microextraction of drugs in urine samples. J Chromatogr B Analyt Technol Biomed Life Sci. 2016;1012-1013:162-8 pubmed publisher
    ..5-4.5% and 4-5%, respectively. The method was successfully applied for the determination of amphetamines in the actual urine samples. The relative recoveries of urine samples spiked with amphetamine and methamphetamine are 90-108%. ..
  22. Steinebach F, Müller Späth T, Morbidelli M. Continuous counter-current chromatography for capture and polishing steps in biopharmaceutical production. Biotechnol J. 2016;11:1126-41 pubmed publisher
    ..Based on various examples of applications, primarily monoclonal antibody production processes, conclusions are drawn about the future of these continuous-manufacturing technologies. ..
  23. Dai X, Huang Q, Zhou B, Gong Z, Liu Z, Shi S. Preparative isolation and purification of seven main antioxidants from Eucommia ulmoides Oliv. (Du-zhong) leaves using HSCCC guided by DPPH-HPLC experiment. Food Chem. 2013;139:563-70 pubmed publisher
    ..ulmoides leaves by HSCCC. The results indicated that the combinative methods using DPPH-HPLC and HSCCC could be widely applied for screening and isolation of antioxidants from complex extracts. ..
  24. Ma C, Hu L, Fu Q, Gu X, Tao G, Wang H. Separation of four flavonoids from Rhodiola rosea by on-line combination of sample preparation and counter-current chromatography. J Chromatogr A. 2013;1306:12-9 pubmed publisher
    ..rosea. The purification method was simple, efficient and evaded tedious sample preparation process. ..
  25. Sandron S, Nesterenko P, McCaul M, Kelleher B, Paull B. Normal-phase high-performance counter-current chromatography for the fractionation of dissolved organic matter from a freshwater source. J Sep Sci. 2014;37:135-42 pubmed publisher
    ..Where fraction analysis was not suitable for GC-MS, RP-HPLC with UV absorbance detection was used, showing unique chromatograms for each fraction at both 210 and 330 nm. ..
  26. Zhu Q, Liu F, Xu M, Lin X, Wang X. Ultrahigh pressure extraction of lignan compounds from Dysosma versipellis and purification by high-speed counter-current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2012;905:145-9 pubmed publisher
    ..As a result, 73.7 mg podophyllotoxin and 16.5mg 4'-demethylpodophyllotoxin with purities over 96% were obtained from 260 mg crude sample in one-step separation...
  27. Li Y, Li L, Cui Y, Zhang S, Sun B. Separation and purification of polyphenols from red wine extracts using high speed counter current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2017;1054:105-113 pubmed publisher
  28. Ha Y, Kim Y. Preparative isolation of six major saponins from Platycodi Radix by high-speed counter-current chromatography. Phytochem Anal. 2009;20:207-13 pubmed publisher
    ..Their structures were characterized by electrospray ionisation mass spectrometry (ESI-MS), (1)H-NMR and (13)C-NMR. Six of the main bioactive platycosides in Platycodi Radix could be isolated and purified systematically by HSCCC. ..
  29. Qiu F, Luo J, Yao S, Ma L, Kong L. Preparative isolation and purification of anthocyanins from purple sweet potato by high-speed counter-current chromatography. J Sep Sci. 2009;32:2146-51 pubmed publisher
    ..5%, 95.0%, 97.8%, and 96.3%, respectively, as determined by HPLC. Compound 2 was isolated from purple sweet potato for the first time. The chemical structures of these components were identified by 1H NMR, 13C NMR and ESI-MS(n)...
  30. Tong X, Xiao X, Li G. On-line coupling of dynamic microwave-assisted extraction with high-speed counter-current chromatography for continuous isolation of nevadensin from Lyeicnotus pauciflorus Maxim. J Chromatogr B Analyt Technol Biomed Life Sci. 2011;879:2397-402 pubmed publisher
    ..0%. The chemical structure of collected fraction was identified by HPLC, ESI-MS and (1)H NMR. The results indicated that this on-line method was effective and fast for high-throughput isolation of nevadensin from L. pauciflorus Maxim. ..
  31. Tong S, Yan J, Guan Y. Preparative separation of isomeric caffeoylquinic acids from Flos Lonicerae by pH-zone-refining counter-current chromatography. J Chromatogr A. 2008;1212:48-53 pubmed publisher
    ..289g 3,5-dicaffeoylquinic acid and 0.106g 3,4-dicaffeoylquinic acid plus 0.690g 3-caffeoylquinic acid at a high purity of over 92.9%, 94.2% and 97.5%, respectively. ..
  32. Liu S, Cao M, Li D, Zhang J, Feng S, Nie Y, et al. Purification and anticancer activity investigation of pentacyclic triterpenoids from the leaves of Sinojackia sarcocarpa L.Q. Luo by high-speed counter-current chromatography. Nat Prod Res. 2011;25:1600-6 pubmed publisher
    ..57% and 97.33%, respectively. Compared with the same dose of oral 5-fluorouracil with 57.6% inhibition rate, the S(180) tumour inhibition rates of 20 mg kg(-1)d(-1) two compounds were 59.5% and 48.9%, respectively...
  33. Xie J, Deng J, Tan F, Su J. Separation and purification of echinacoside from Penstemon barbatus (Can.) Roth by recycling high-speed counter-current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2010;878:2665-8 pubmed publisher
    ..0%. The structure of our echinacoside confirmed by IR, (1)H NMR and (13)C NMR is identical to the standard sample. This indicates that P. barbatus might be ideal source for preparation of large scale of echinacoside...
  34. Deng S, Deng Z, Fan Y, Peng Y, Li J, Xiong D, et al. Isolation and purification of three flavonoid glycosides from the leaves of Nelumbo nucifera (Lotus) by high-speed counter-current chromatography. J Chromatogr B Analyt Technol Biomed Life Sci. 2009;877:2487-92 pubmed publisher
    ..nucifera. The chemical structures of all the three compounds were identified by MS, (1)H NMR, (13)C NMR. Astragalin was obtained from N. nucifera for the first time. ..
  35. Zhang Y, Guo L, Liu C, Fu Z, Cong L, Qi Y, et al. Pressurized liquid extraction coupled with countercurrent chromatography for systematic isolation of chemical constituents by preprogrammed automatic control. J Chromatogr B Analyt Technol Biomed Life Sci. 2013;935:16-25 pubmed publisher
    ..The separation results prove that the PLE/HSCCC parameters calculated via mathematical model and formulas were accurately and scientifically. This research has opened up great prospects for industrial automation application. ..
  36. Yang Y, Gu D, Liu Y, Aisa H, Ito Y. Compact type-I coil planet centrifuge for counter-current chromatography. J Chromatogr A. 2010;1217:1313-9 pubmed publisher
    ..75 and 2.16 within 90 min at a flow rate of 0.4 ml/min. We believe that the compact type-I coil planet centrifuge has a high analytical potential. ..
  37. Kukula Koch W, Koch W, Angelis A, Halabalaki M, Aligiannis N. Application of pH-zone refining hydrostatic countercurrent chromatography (hCCC) for the recovery of antioxidant phenolics and the isolation of alkaloids from Siberian barberry herb. Food Chem. 2016;203:394-401 pubmed publisher
    ..Additionally, fractionation of alkaloids was achieved resulting isolation of pharmacologically important alkaloids: magnoflorine and berberine. ..
  38. Xu J, Guo S, Du L, Wang Y, Sugawara T, Hirata T, et al. Isolation of cytotoxic glucoerebrosides and long-chain bases from sea cucumber Cucumaria frondosa using high speed counter-current chromatography. J Oleo Sci. 2013;62:133-42 pubmed
    ..Moreover, CFC-3 was most effective in four glucocerebrosides to Caco-2 cell viability. The inhibition effect of CF-LCB was much stronger than glucocerebrosides...
  39. Yin H, Zhang S, Luo X, Liu Y. Preparative isolation and purification of two benzoxazinoid glucosides from Acanthus ilicifolius L. by high-speed counter-current chromatography. J Chromatogr A. 2008;1205:177-81 pubmed publisher
    ..A 100-mg amount of the n-butanol extracts of A. ilicifolius was separated to yield 5.8 mg of HBOA-Glc and 4.8 mg of DIBOA-Glc with purities of 97.1% and 94.8%, respectively, which were directly used for NMR analyses. ..
  40. Mekaoui N, Chamieh J, Dugas V, Demesmay C, Berthod A. Purification of Coomassie Brilliant Blue G-250 by multiple dual mode countercurrent chromatography. J Chromatogr A. 2012;1232:134-41 pubmed publisher
    ..The purified CBB gave total satisfaction in testing amine content in polyclonal antibody containing monolith pipettes. ..
  41. Mbeunkui F, Grace M, Lila M. Isolation and structural elucidation of indole alkaloids from Geissospermum vellosii by mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci. 2012;885-886:83-9 pubmed publisher
    ..vellosii. ..
  42. Xu S, Sun Y, Jing F, Duan W, Du J, Wang X. [Separation and purification of flavones from Nelumbo nucifera Gaertn. by silica gel chromatography and high-speed counter-current chromatography]. Se Pu. 2011;29:1244-8 pubmed
    ..It is effective in the separation of flavones from N. nucifera, and provides theoretical foundation for the further development and use of N. nucifera resources. ..
  43. Gao L, Yu B, Yang H. [Preparative isolation and purification of five non-volatile compounds from Fructus caryophylli and Flos caryophylli by high-speed counter-current chromatography]. Se Pu. 2011;29:1112-7 pubmed
    ..The results indicate that HSCCC is a powerful technique for the purification of non-volatile compounds from different parts of Eugenia caryophylla Thunb. ..
  44. Wang J, Wen Y, Chen X, Lin Y, Zhou J, Xie Y, et al. Preparative separation of six antimycin A components from antimycin fermentation broth by high-speed counter-current chromatography. J Chromatogr A. 2010;1217:5687-92 pubmed publisher
    ..2, 98.6, 96.2, 94.1, 94.9 and 96.7%, respectively, determined by high-performance liquid chromatography (HPLC), were yielded from 200mg crude sample only in one HSCCC run. ..
  45. Urbain A, Corbeiller P, Aligiannis N, Halabalaki M, Skaltsounis A. Hydrostatic countercurrent chromatography and ultra high pressure LC: Two fast complementary separation methods for the preparative isolation and the analysis of the fragrant massoia lactones. J Sep Sci. 2010;33:1198-203 pubmed publisher
    ..In parallel, an easy and efficient ultra high pressure LC method was developed for the ultra-fast analysis of massoia lactones, as an alternative to long GC-MS methods...
  46. Wu D, Jiang X, Wu S. Direct purification of tanshinones from Salvia miltiorrhiza Bunge by high-speed counter-current chromatography without presaturation of the two-phase solvent mixture. J Sep Sci. 2010;33:67-73 pubmed publisher
    ..As a result, over 98% pure tanshinone IIA and over 94% pure tanshinone I have been obtained by using less solvent volume. Their structures have been identified by ESI-MS, NMR spectra. ..
  47. Fuereder M, Panke S, Bechtold M. Simulated moving bed enantioseparation of amino acids employing memory effect-constrained chromatography columns. J Chromatogr A. 2012;1236:123-31 pubmed publisher
  48. Kato T, Hatanaka K. Purification of gangliosides by liquid-liquid partition chromatography. J Lipid Res. 2008;49:2474-8 pubmed publisher
    ..Moreover, various kinds of gangliosides (GM1, GD1a, GD1b, GT1b) could be separated individually by using the lower phase as stationary phase by CPC. The sample can be recovered without loss by these systems. ..
  49. Maryutina T, Soin A, Katasonova O. Counter-current chromatography for oil analysis: retention features and kinetic effects. J Chromatogr A. 2009;1216:4232-6 pubmed publisher
    ..The extraction recoveries of Zn, Mn, Fe, Ni, V, Cu, Cd, Pb and Ba by CCC in dynamic mode are in the range of 75-95% while they are lower than 35% under batch conditions. ..
  50. Costa F, Garrard I, da Silva A, Leitão G. Changes in the mobile phase composition on a stepwise counter-current chromatography elution for the isolation of flavonoids from Siparuna glycycarpa. J Sep Sci. 2013;36:2253-9 pubmed publisher
    ..Results showed a gradual variation of the composition of the mobile phase emerging after the step gradient, favoring the selectivity of the solvent system. ..
  51. Gu J, Feng R, Wu Z, Guan S, Guo J, Cheng C, et al. A rapid and convenient method for preparative separation of three indissolvable polyphenols from Euphorbia pekinensis by the flexible application of solvent extraction combined with counter-current chromatography. J Sep Sci. 2013;36:2366-72 pubmed publisher
    ..The recoveries were calculated as 84.6, 85.7, and 89.5%, respectively. The result demonstrated that the present isolation method was rapid, economical and efficient for the preparative separation of polyphenols from E. pekinensis. ..
  52. Li X, Li X, Song S, Zhang B, Liu X, Ye X. [Preparative isolation and purification of scopoletin from Lycium barbarum L. by high-speed countercurrent chromatography]. Se Pu. 2012;30:971-4 pubmed
    ..These results suggested that the TLC-F method is useful in measuring the partitioning coefficients of the target compound in HSCCC solvent systems and HSCCC is a fast and convenient method for the separation of scopoletin. ..
  53. Weisz A, Witten J, Zeng Y, Mazzola E, Ito Y. Preparation of two novel monobrominated 2-(2',4'-dihydroxybenzoyl)-3,4,5,6-tetrachlorobenzoic acids and their separation from crude synthetic mixtures using vortex counter-current chromatography. J Chromatogr A. 2012;1237:106-14 pubmed publisher
    ..The isolated compounds were characterized by high-resolution mass spectrometry and proton nuclear magnetic resonance spectroscopy. ..