Thin-Layer Radiochromatography - Raytest

A Field Guide to In stru men ta tion 

Thin-Layer Radiochromatography 

Thin-layer radiochromatography 

(TLRC) involves the use of 

thin-layer chromatography (TLC) 

and high- performance TLC (HPTLC) 

for the separation and qualitative and 

quantitative determination of 

radiolabeled substances in chemical, 

biochemical, biological, pharmaceutical, 

and medicinal samples. The classical 

detection methods for TLRC are 

autoradiography and liquid scintillation 

counting (LSC; also termed zonal 

analysis). In autoradiography, the layer 

containing the separated radioactive 

zones (spots or bands) is put in direct 

contact with a photographic (X-ray) 

film, which shows the image of the 

chromatogram after film development. 

Qualitative assessment of 

chromatograms is made by visual 

inspection of the film to reveal the 

locations of radioactivity as darkened 

zones of varying optical densities. The 

optical density is related to the amount of 

radioactivity in the zone, so 

quantification is done by density 

measurement of the zones with a 

densitometer using a calibration curve 

produced by exposure to radioactive 

standards. Descriptions of applicable slit 

scanning, video, digital camera, and 

flatbed light-based densitometers, which 

are also used for quantification of colored, 

UV absorbing, and fluorescent TLC 

zones, have already been published (1–4) 

and will not be repeated here. 

This article decsribes a selection of 

the most useful methods and instruments 

that are currently available for LSC and 

for detecting and measuring radioactive 

zones in thin layers without the use of 

film or scraping off the layer, and 

selected applications for their use. The 

latest available descriptions of 

instruments for LSC and direct detection 

of radioactivity in TLC were in book 

chapters published in 2001 (5) and 

2003 (6). These chapters included many 

instruments that are outdated and no 

longer commercially available, e.g., the 

digital autoradiograph from EG&G 

Berthold, Wildbad, Germany, and no 

book chapter or journal article on TLC 

has included an updated description of 

current instruments since then. 

The coverage in this article is 

selective rather than exhaustive in terms 

of the number of companies and 

instruments described, as well as 

features, options, and applications 

mentioned for each instrument. 

Information was taken from 

correspondences with manufacturers 

and their Websites and printed 

brochures. Readers are encouraged to 

contact the manufacturers for their 

complete TLRC product offerings, 

detailed instrument specifications, and 

application notes. 

Beckman Coulter LS 6500 

Scintillation Counting System 

In LSC, the zones emitting 

alpha, beta, or gamma 

radioactivity are scraped off 

the layer and mixed with a 

liquid scintillation cocktail (a 

mixture of solvent, emulsifier, 

and flour). The flour in the 

cocktail converts the kinetic 

energy of nuclear emissions 

into photons of light energy 

(blue light flashes) with 

intensity proportional to the 

initial energy of the radioactive 

particle. The photons are 

detected by a photomultiplier 

tube (PMT), converted into proportional 

electrical pulses, and passed into a 

multichannel analyzer covering an 

energy range of, e.g., 0–2000 keV. The 

number of pulses in each channel is 

recorded for sample analysis, and the 

spectrum can be plotted to provide 

information about the energy of the 

radiation or the amount of radioactive 

material dissolved in the cocktail. 

The LS 6500 (Figure 1) is a modern 

scintillation counter incorporating a 

32 678 channel analyzer and Motorola 

host processor and digital signal 

processor that delivers an effective 

resolution of 0.06 keV. Standard window 

settings, expressed in channel units, are 

3 

H 0-4000, 125 

I 0-567, 13 

C 0-670, 35 

S 

0-688, and 32 

P 0-945 for samples in 

liquid scintillation media. The 

H-Number Plus external quench monitor 

provides accurate activity (dpm or 

disintegrations/min) calculations and 

Automatic Quench Compensation that is 

independent of sample volume or 

cocktail composition. It is also the basis 

of instrument calibration, color detection 

and correction, 2-phase monitoring, 

unquenched window determination, and 

Figure 1. LS 6500 liquid scintillation counter (courtesy of 

Beckman Coulter). 

� Copyright 2009 by AOAC INTERNATIONAL. Reprinted with permission. JOURNAL OF AOAC INTERNATIONAL VOL. 92, NO. 1, 2009


Figure 2. BAS-5000 storage phosphor screen imaging 

system (courtesy of Fujifilm Life Science). 

multilabel dpm quench curves. The 

plastic Versa-Rack vial system allows 

counting of samples in any combination, 

up to 336 standard vials (20 mL) and 

648 miniature vials (6 mL); capabilities 

also exist to count 4 mL Bio-Vials and 

Microfuge tubes. Computer-based 

operation is via a combination of easy to 

use menus, context-sensitive help 

screens, and up to 50 user programs. 

Different biodegradable general use and 

specialized cocktails, plastic scintillation 

vials, unquenched LS standards, and 

quenched standards are among the 

available accessories. 

Phosphor Imaging 

Storage phosphor screen imaging is 

often termed filmless autoradiography. 

The phosphor screens are sensitive to 

any source of ionizing radiation, e.g., 

14 C, 3 H, 35 S, 125 I, 32 P, 33 P, 18 F, and 99m Tc. They 

contain small crystals of a 

photostimulable phosphor coated on a 

support in which luminescence is 

produced and stored when exposed to 

radioactive TLC zones. The 

luminescence is evaluated by scanning 

with a laser in a reading device, and 

quantification is carried out by use of a 

calibration curve to exclude the effects 

of the phosphor screen type and 

exposure period. The screens can be 

reused after being erased by 

exposure to visible light. The 

formulation of the phosphor 

screen, chemistry of the detection 

process, mechanism of scanning, 

and software for evaluation of 

images may differ for instruments 

from each manufacturer. 

BAS-5000 Bioimaging 

Analyzer 

The BAS-5000 bioimaging 

analyzer from Fujifilm Life 

Science USA (Figure 2) uses a 

patented phosphor imaging plate (IP) 

with a scanner for IP reading for the 

sensitive, 2-dimensional (2D) detection 

of radioactive TLC zones by the 

photostimulated luminescence (PSL) 

phenomenon. The instrument features a 

confocal laser, light-collecting optics, 

dynamic range up to 5 orders of 

magnitude, and a pixel size as small as 

25 �m. A 20 � 25 cm IP with the images 

of chromatograms from a 20 � 20 cm 

TLC plate can be scanned at 50 �m in as 

manufacturing process. The exposed IP 

is scanned with a laser beam of red light 

(633 nm) focused by a mirror while 

being moved in the reader; the PSL 

released by the laser as photons of blue 

light (390 nm) is collected onto a PMT 

through a light collection guide and is 

converted to electrical signals. 

Cyclone Plus Phosphor Imager 

The PerkinElmer benchtop Cyclone 

Plus quantitative radiometric phosphor 

imager (Figure 3) operates with the same 

storage phosphor and scanning process 

(Figure 4), except that confocal optics 

and a helical scanning mechanism are 

used with the flexible phosphor screen 

loaded into a cylindrical carousel that 

spins at 360 rpm. This allows the 

instrument to be more compact and less 

expensive than the BAS-5000, in which 

the phosphor screen is kept on a flat 

plane during scanning. The phosphor 

screen is scanned by the system’s laser 

focused to less than 50 �m, and the latent 

image is detected by the instrument 

optics to create a high-resolution 

digitized image of the layer with 

quantitative data in the form of an image 

file. The image is displayed on the 

computer screen for analysis with 

OptiQuant software and can be printed, 

exported, and archived for future use. 

The following storage phosphor screens 

little as 5 min; the detection limit is 

0.11 dpm/mm 2 

/h for P 32 

. Compared to 

X-ray film, sensitivity is about 100 times 

higher, processing is 10–100 times 

faster, and quantitative accuracy is 

greater. 

The IP consists of 5 �m crystals of 

barium fluorobromide containing a trace 

amount of bivalent europium 

(BaFBr:Eu +2 ) as a 

bioluminescence center 

coated on a polyester support 

film. When the crystal is 

exposed to a radiolabeled 

zone, the energy of the 

radioisotope ionizes the Eu +2 

to Eu +3 

, liberating electrons 

to the conduction band of the 

phosphor crystals. The 

electrons are trapped in the 

bromine vacancies Figure 3. Cyclone Plus phosphor imager (courtesy of 

introduced during the 

PerkinElmer). 

JOURNAL OF AOAC INTERNATIONAL VOL. 92, NO. 1, 2009. � Copyright 2009 by AOAC INTERNATIONAL. Reprinted with permission.


Figure 4. Schematic representation of the storage phosphor process (courtesy of PerkinElmer). 

are available in 12.5 � 19.2, 12.5 � 25.2, 

or 12.5 � 43 cm sizes: multisensitive 

(MS) general purpose, super resolution 

(SR) made with the finest grain particles 

of phosphor, and tritium sensitive (TR) 

uncoated for the detection of 3 

H. Specific 

TLC applications cited by PerkinElmer 

are imaging of 3 

H, 125 

I, 14 

C, 32 

P, 33 

P, 18 

F, 90 

Y, 

99m 111 177 

Tc, In, and Lu; nucleotide 

metabolism studies with 

32 P- and 

33 

P-labeled adenosine triphosphate 

(ATP) or guanosine triphosphate (GTP); 

14 

C-uridine-5�-diphospho-glucuronic 

acid (UDPGA) glucuronidation assay; 

quality control (QC) of 

177 Lu- and 

90 Y-DOTA-D-phenylalanine(1)-tyrosine 

(3)-octreotide (TOC); 18 F silica gel TLC 

for analysis of positron emission 

tomography (PET) radiochemicals; QC 

of 99m Tc; and radiochemical purity of 90 Y 

Zevalin (Figure 5). 

Radioscanners for Direct 

Measurement of TLC Plates 

Bioscan AR-2000 TLC Imaging 

Scanner 

The AR-2000 imaging scanner 

(Figure 6) uses a resistive anode 

single-element position sensing 

windowless gas-filled proportional 

detector for direct digital counting of all 

beta and gamma emitting isotopes, 

including 3 H, on TLC or HPTLC plates. 

The process involves ionization of the 

counting gas by interaction with 

radioactive TLC zones, producing a 

pulse of electrons that is proportional to 

the amount of radioactivity. An entire 

lane can be imaged in under 1 min, and 

multiple lanes can be measured in a 

single automated run without operator 

intervention. The instrument is linear 

over 4–5 decades of activity; has 

resolution of 0.5–3 mm depending on 

the isotope; and has a sensitivity of less 

than 1000 dpm for 3 H and 125 I and less 

than 100 dpm for 14 C, 32 P, and most other 

isotopes in a 10 min analysis. Models are 

available that hold one, two, or three 20 

� 20 cm TLC plates. Single-lane or 2D 

color imaging and automated 

quantification can be performed with 

WinScan software, and Bio-Chrom 

software can be used in place of 

WinScan for compliance with 21 CFR 

Part 11, U.S. Food and Drug 

Administration and Good Laboratory 

Practice (GLP) standards. 

Applications for which the AR-2000 

have been used include PET or single 

photon emission computed tomography 

(SPECT) radiopharmaceutical QC and 

synthesis process control (compounds 

labeled with 18 

F, 11 

C, 99m 

TC, 111 

In, etc.); 

pharmaceutical metabolite analysis for 

beta-, gamma-, or positron-labeled 

products; radiotracer toxicology studies 

with 14 C-labeled organic compounds and 

agrochemicals; biosynthesis studies 

involving complex lipids, phospholipids, 

and glycolipids; radiochemical purity 

quality assurance (QA) analyses for 

tracer or metabolism studies; 

radiolabeled reporter gene or enzyme 

assays; quantitative radiolabeled 

biochemical separations (programmable 

scanning and quick change magnetic 

collimators can be used for optimization 

of resolution and sensitivity); and study 

of constitutive expression of 

25-D 3 -1alpha-hydroxylase in a 

transformed proximal tubule cell line: 

evidence for direct regulation of 

vitamin D metabolism by calcium (7). 

Raytest GITA 

The GITA gamma isotope TLC 

analyzer (Figure 7) is an X-Y scanner 

controlled by a personal computer (PC) 

Figure 5. Determination of radiochemical 

purity for the 90 Y-based drug Zevalin on multiple 

TLC strips simultaneously 

(courtesy of PerkinElmer). 



Figure 6. AR-2000 TLC imaging scanner 

(courtesy of Bioscan Inc.). 

for automatic measurement, data 

evaluation, and report printing. It scans 

along one trace from start to front and 

then goes to the next preprogrammed 

trace position and scans that trace with 

individual nuclide settings. The 

V-shaped bismuth germanate (BGO-V) 

crystal scintillation probe detector, 

mounted in tungsten shielding, can be 

automatically energy calibrated using a 

137 Cs standard, and many energy 

windows can be preprogrammed for 

various nuclides. Collimators of 3 mm 

(stainless steel) and 5–20 mm (tungsten) 

size are available to optimize resolution 

and sensitivity for gamma detection in 

different energy ranges (0–60, 60–150, 

150–250, 250–450, and >450 keV) 

depending on the radioactive compound. 

Up to 80 sample traces can be 

programmed in terms of location, scan 

speed, etc., in both directions on two 20 

� 20 cm plates. Specifications include 

energy 0–2000 keV, activity 

10–100 000 Bq, sensitivity 20 Bq for 

99m Tc, resolution 2 mm for 99m Tc, linearity 

10 5 , and decay correction. A single 

chromatogram can be displayed live on 

the screen of a connected PC, and 

multiple traces can be displayed in 3 

dimensions. Peak integration can be 

performed manually or automatically, 

and measurement and data handling are 

digital (single event counting). A typical 

scan of a TLC zone containing a gamma 

radiolabeled compound is shown in 

Figure 8. Beta/positron detection can be 

made using an optional Geiger-Mueller 

(GM) detector ( 3 

H is not detected). 

Raytest miniGITA Star 

The miniGITA Star (Figure 9) is a 

scanner for gamma and beta/positron 

radiation from TLC zones that is similar 

to the GITA. The major differences are 

that the scan area is 5 � 20 cm and only 

one trace can be made at a time in the X 

direction. The BGO-V crystal has a 3 � 

25 mm entry window and is 25 mm high, 

and the tungsten shielding has an outside 

diameter of 70 mm. 

Raytest RITA Star 

The RITA Star beta radiation TLC 

analyzer (Figure 10) has a position 

sensitive proportional gas flow counter 

detector with an active length of 200 mm 

and active width of 20, 15, 10, 3, or 

1 mm controllable by exchange of the 

diaphragm. The sensing element is gold 

plated for easy cleaning and long life. 

For measurement of low energy betas 

from 3 H, the counting tube is used open 

(without any window) and is placed as 

close as possible to the radioactive TLC 

zone. Therefore, the detector rests on the 

surface of the layer in order to close the 

counting chamber and reduce gas 

leakage, and the gold-plated tungsten 

counting wire can be accurately aligned 

for optimum results. The entrance 

window is closed for 14 

C and other beta 

emitting nuclides. The counting tube is 

automatically moved to measure traces 

of multiple chromatograms on a layer. 

2D thin-layer chromatograms are 

measured by assembling individual 

one-dimensional traces. Data collection, 

analysis, and documentation meet GLP 

requirements. Two 20 � 20 cm plates can 

be measured at once. 

The RITA Star is designed for 

maximum sensitivity for low energy 

emitting nuclides such as 3 

H, 14 

C, 35 

S, 33 

P, 

and 32 P. Sensitivity and resolution values 

are 100 dpm/peak and 0.5 mm for 3 H, 

and 10 dpm/peak and 1 mm for 14 

C, 

respectively, and the dynamic range is 

10 6 . Background is 80 cpm/200 mm. 

Position deviations of the counting tube 

are less than 0.5 mm over the 200 mm 

length. The counting gas is 90% Ar and 

10% methane (P10 gas) with a 

0.5–1 L/min flow rate. 

Gamma and positron emitting 

nuclides such as 125 

I, 99m 

Tc, and 18 

F are 

detected more sensitively using the 

GITA or miniGITA Star. 

Raytest MARITA Star 

The MARITA Star (Figure 11) is an 

automatic single-trace instrument for 

measurement of one 5 � 20 cm TLC 

plate. The same position sensitive 

Figure 7. GITA gamma TLC scanner 

(courtesy of Raytest). 



Figure 8. Scan of a thin-layer chromatogram containing a 99m Tc-labeled compound obtained using a 

GITA with gamma detector (courtesy of Raytest). 

proportional counter detector is used as 

for the RITA Star, and the resolution, 

sensitivity, and background specifications 

are the same. 

Applications 

TLRC with the described techniques 

and modern instruments can be used, 

among other applications, for animal, 

human, and plant metabolism analysis; 

biodistribution studies; toxicology 

studies; separation, detection, and 

quantification of separated radioactive 

zones of all compound classes; and 

radiopharmaceutical synthesis, QC, and 

purity, efficacy, and stability 

determinations. The phosphor imaging 

and in situ scanning instruments are 

highly automated and have significant 

advantages in terms of simplicity, speed, 

accuracy, precision, and sensitivity 

compared to traditional film 

autoradiography or scraping followed by 

LSC. The in situ scanner methods are 

direct analyses that minimize technician 

radiation exposure and do not require 

disposal of contaminated screens or 

liquid waste. 

The following are a selection of 

references reporting studies using the 

TLRC methods described above: 

3�-sulfonylesters of 2.5�-anhydro- 

1-(2-deoxy-beta-D-threo-pentofuranosyl) 

thymine as precursors for the synthesis 

of 

18 

F-fluorothymidine (FLT; 8); 

molecular cloning and biochemical 

characterization of a serine threonine 

prorein kinase, PknL, from 

Mycobacterium tuberculosis (9); 

preparation, QC, and biodistribution of 

67 

Ga-DOTA (tetraazacyclododecanetetraacetic 

acid)-anti-CD20 (CD 20 is a 

nonglycosylated phosphoprotein expressed 

on the surface of mature B-cells; 10); 

synthesis and biodistribution of 

99m 

Tc-glucoheptonoate-guanine (11); 

preparation, QC, and stability of 

99m 14 

Tc-cefuroxime axetil (12); C-benzyl 

acetate as a radiotracer for measurement 

of glial metabolism in rat brain (13); 

18 

analysis of F-labeled synthesis 

products by radioactivity scanning, film 

autoradiography, and phosphor 

imaging (14); phosphor imaging 

analysis of short-lived radioactive 

metabolites from microdyalysis 

fractions (15); quantification of 

sphingomyelin-derived 32 P-ceramide in 

tissue and plasma from humans and mice 

with Niemann-Pick disease using a 

phosphor imaging system after TLC 

separation (16); investigation of 

(-)-deprenyl metabolism using 

reaction-displacement TLC with 2D 

position sensitive proportional counting 

scanning (PSPCS; 17); radioscanning 

quantitative characterization of 

insecticidal sugar esters of petunia (18); 

quantitative PSPCS for the analysis of 

neutral 14 C-lipids neosynthesized by the 

human sebaceous gland (19); 

quantitative assessment of microsomal 

tolbutamide hydroxylation by a 

TLC-phosphor imager technique (20); 

isolation and identification of 3 H- and 

14 

C-deramciclane in different biological 

matrixes such as plasma and urine by 

Figure 9. miniGITA Star beta radiation scanner 

with GM tube detector (courtesy of Raytest). 



Figure 10. RITA Star beta TLC scanner 


octadecylsilyl (C18) SPE, 

overpressurized layer chromatography 

(OPLC)-PSPCS, and mass 

spectrometry (21); fate of 

14 

C-diphenylamine in apples based on 

radioscanning (22); rapid assay for nitric 

oxide synthase by autoradiography and 

radiometric scanning of L- 14 

C-arginine 

Beckman Coulter, Inc. 

4300 N. Harbor Blvd 

PO Box 3100 

Fullerton, CA 92834-3100 

600-742-2345 

http://www.beckmancoulter.com 

Bioscan Inc. 

4590 MacArthur Blvd, N.W. 

Washington, DC 20007 

800-255-7226 

http://www.bioscan.com 

and -citrulline (23); adsorption and 

mobility of the fungicide metalaxyl in 

vineyard soils with 14 C detection by a 

Bio-Image analyzer (24); metabolism of 

the herbicide 2,4-dichlorophenoxyacetic 

acid (2,4-D) in laying hens and lactating 

goats with detection of radioactive zones 

by a radio-TLC scanner (25); 

degradation of the pesticide 

14 C-carfentrazone-ethyl under aerobic 

aquatic conditions with detection of 

radioactive zones using an imaging 

Figure 11. MARITA Star beta TLC scanner 


Contact Information 

Fujifilm Life Science USA 

419 West Ave 

Stamford, CT 06902 

886-902-3854 

http://www.fujifilmlifescienceusa.com 

PerkinElmer Inc. 

940 Winter St 

Waltham, MA 02451 

800-762-4000 

http://www.perkinelmer.com 

scanner (26); separation and assay of 

14 

C-labeled glyceryl trinitrate and its 

metabolites by OPLC-PSPCS (27); 

pharmacokinetics and metabolism of the 

novel muscarinic receptor against 

SNI-2011 (cevimeline) in rats and dogs 

with 2D-TLC and bioimaging 

analysis (28); and combinatorial 

enzymatic phosphor imaging assay for 

the high throughput screening of a new 

class of bacterial cell wall 

inhibitors (29). 

Raytest USA, Inc. 

515 Cornelius Harnett Dr 

Wilmington, NC 28401 

800-887-2666 

http://www.raytest.com 

—Joseph Sherma 

John D. & Frances H. Larkin 

Professor Emeritus 

Department of Chemistry 

Lafayette College 

shermaj@lafayette.edu 



References 

(1) Sherma, J. (2001) in Encyclopedia of Chromatography, J. Cazes (Ed.), Marcel Dekker, Inc., New York, NY, pp 572–576 

(2) Sherma, J. (2005) in Encyclopedia of Chromatography, 2nd Ed., J. Cazes (Ed.), Taylor & Francis, CRC Press, Boca Raton, FL, pp 1232–1240 

(3) Sherma, J. (2000) Inside Laboratory Management 4(10) 5–9 

(4) Sherma, J. (2008) J. AOAC Int. 91, 51A–58A 

(5) Klebovich, I. (2001) in Planar Chromatography, S.Z. Nyiredy (Ed.), Springer Scientific Publisher, Budapest, Hungary 

(6) Hazai, I., & Klebovich, I. (2003) in Handbook of Thin Layer Chromatography, 3rd Ed., J. Sherma & B. Fried (Eds), Marcel Dekker, Inc., New York, 

NY, pp 339–360 

(7) Bland, R., Walker, E.A., Hughes, S.V., Stewart, P.M., & Hewison, M. (1999) Endocrinology 140, 2027–2034 

(8) Windhorst, A.D., Klein, P.J., Eisenbarth, J., Oeser, T., Kruijer, P.S., & Eisenhut, M. (2008) Nucl. Med. Biol. 35, 413–423 

(9) Lakshminarayan, H., Narayanan, S., Bach, H., Sundaram, K.G.P., & Av-Gay, Y. (2008) Protein Expres. Purif. 58, 309–317 

(10) Jalilian, A.R., Mirsadeghi, L., Haji-Hosseini, R., & Khorrami, A. (2008) Radiochim. Acta 96, 167–174 

(11) Unak, P., Teksoz, S., Muftuler, F.Z.B., Medine, E.J., Acar, C., & Yurekli, Y. (2008) J. Radioanal. Nucl. Chem. 275, 379–385 

(12) Lambrecht, F.Y., Durkan, K., & Unak, P. (2008) J. Radioanal. Nucl. Chem. 275, 161–164 

(13) Monosaki, S., Hosoi, R., Sanuki, T., Todoroki, K., Yamaguchi, M., Gee, A., & Inoue, O. (2007) Nucl. Med. Biol. 34, 939–944 

(14) Kamarainen, E.L., Haaparanta, M., Siitari-Kauppi, M., Koivula, T., Lipponen, T., & Solin, O. (2006) Appl. Radiat. Isotopes 64, 1043–1047 

(15) Haaparanta, M., Gronroos, T., Eskola, O., & Solin, O. (2006) J. Chromatogr. A 1108, 136–139 

(16) He, X., Chen, F., Gatt, S., & Schuchman, E.H. (2001) Anal. Biochem. 293, 204–211 

(17) Kalasz, H., Lengyel, J., Szarvas, T., Morovjan, G., & Klebovich, I. (2003) J. Planar Chromatogr.-Mod. TLC 16, 381–385 

(18) Chortyk, O.T., Kays, S.J., & Teng, Q. (1997) J. Agric. Food Chem. 45, 270–275 

(19) Christelle, C., Vingler, P., Boyera, N., Galey, I., & Bernard, B.A. (1997) J. Planar Chromatogr.-Mod. TLC 10, 243–250 

(20) Ludwig, E., Wolfinger, H., & Ebner, T. (1998) J. Chromatogr. B 707, 347–350 

(21) Ludanyi, K., Vekey, K., Szunyog, J., Mincsovics, E., Karancsi, T., Ujszaszy, K., Nemes, K.B., & Klebovich, I. (1998) J. AOAC Int. 82, 231–238 

(22) Haesook, K.K., Roninson, R.A., & Wu, J. (1998) J. Agric. Food Chem. 46, 707–717 

(23) Kumar, V.B., Bernardo, A.E., Alshaher, M.M., Buddhiraju, M., Purushothaman, R., & Morley, J.E. (1999) Anal. Biochem. 269, 17–20 

(24) Andrades, M.S., Sanchez-Martin, M.J., & Sanchez-Camazano, M. (2001) J. Agric. Food Chem. 49, 2363–2369 

(25) Barnekow, D.E., Hamburg, A.W., Puvanesarajah, V., & Guo, M. (2001) J. Agric. Food Chem. 49, 156–163 

(26) Elmarakby, S.A., Suplee, D.M., & Cook, R. (2001) J. Agric. Food Chem. 49, 5285–5293 

(27) Klebovich, I., Morovjan, G., Hazai, I., & Mincsovics, E. (2002) J. Planar Chromatogr.-Mod. TLC 15, 404–409 

(28) Washio, T., Kohsaka, K., Arisawa, H., & Masunaga, H. (2003) Arzneim.-Forsch. Drug Res. 53, 26–33 

(29) El Zoeiby, A., Beaumont, M., Bubuc, E., Sanschagrin, F., Voyer, N., & Levesque, R.C. (2003) Bioorg. Med. Chem. 11, 1583–1592 

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