JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1,

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1 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, FOOD COMPOSITION AND ADDITIVES Determintion of Acesulfme nd Sucrlose in Orl Electrolyte Mintennce Solution y Liquid Chromtogrphy PAUL JOHNS nd LOBAT DOWLATI Aott Lortories, Ross Products Division, 3300 Stelzer Rd, Columus, OH A method ws developed for the direct, simultneous determintion of cesulfme nd sucrlose in orl electrolyte mintennce solution (OEMS). Anlyte seprtion nd quntittion were chieved y grdient reversed-phse liquid chromtogrphy (LC) nd UV sornce t 192 nm, respectively. Detection t second wvelength, 214 nm, ws used to check sucrlose pek purity; 20 L OEMS ws injected without preprtion or dilution. System linerity ws demonstrted s 192 nm pek re versus nlyte concentrtion t % OEMS sweetener fortifiction (r > 0.999, nd ll residuls <0.5%, for oth cesulfme nd sucrlose). Spike recoveries for OEMS smples prepred t 3 spiking levels (80, 100, nd 120% sweetener fortifiction) rnged from to 102.0% for cesulfme, nd from 97.9 to 102.3% for sucrlose. In second ssessment of method ccurcy, the sme spiked OEMS smples were tested y 2 lterntive methods: cesulfme (LC/UV t 230 nm) nd sucrlose (nion exchnge pulsed mperometric detection). Results for the lterntive cesulfme method were within 1.2%, nd for the lterntive sucrlose method within 6.0%, of the corresponding results otined y the 192 nm method. Repetility nd intermedite precision RSD vlues were <1% for cesulfme nd <3% for sucrlose. The limits of quntittion were 1.6 nd 32 mg/l for cesulfme potssium nd sucrlose, respectively. Despite the wek UV sorptivity of sucrlose nd the consequent smll size of its LC pek, no evidence ws found for sucrlose interference in ny of the commercil OEMS flvors. Anumer of similrities exist etween cesulfme potssium nd sucrlose. Both re non-nutritive, high intensity (200 nd 600 sucrose, respectively), sweetening gents (1, 2). Both re very solule in wter (270 nd 283 g/l t 20 C), nd queous solutions of ech (ph > 3) re light-, shelf-, nd psteuriztion-stle (1 3). Both were pproved for use y the U.S. Food nd Drug Administrtion in Received April 12, Accepted y JL June 20, Corresponding uthor s e-mil: pul.johns@rossnutrition.com. nonlcoholic everges in 1998, oth re ssigned n llowle dily intke (ADI) of 0 15 mg/kg/dy, nd oth re used t ppm levels in flvored orl electrolyte mintennce solutions (4 7). However, prt from these mny similrities, their UV sorptivities differ drmticlly, y virtue of structurl differences etween the cesulfme nd sucrlose molecules. Wheres cesulfme is reltively strong sorer of UV light ( > t 227 nm), sucrlose is very wek sorer ( < 130 t 192 nm; 8). The UV insensitivity of sucrlose is n importnt considertion in the identifiction nd/or development of nlyticl methods for its determintion. Accordingly, lthough UV sornce-sed methods for cesulfme determintion use vriety of detection wvelengths 200, 206, 214, 230, nd 254 nm such methods for sucrlose determintion re restricted to wvelengths of 200 nm, nd even t 200 nm sucrlose injection of 1600 g (versus 20 g cesulfme) is required to give sizle pek (9 14). With these fctors in mind, we developed liquid chromtogrphic (LC)/UV method for the direct nd simultneous determintion of cesulfme nd sucrlose in orl electrolyte mintennce solution (OEMS). Reversed-phse chromtogrphy nd ph 3.1 phosphte uffer cetonitrile elunt system (with reltively little sornce in the low UV rnge) re used for nlyte seprtion. Given the hydrophoicity enhncement of sucrlose (versus sucrose) fforded y its chlorine sustitutions (15), nd given the need for effective column rinsing etween injections, step grdient of 15 80% is specified. The quntittion wvelength is 192 nm. Although this selection is well short of optiml for cesulfme detection, it enles mximum sucrlose response without significntly compromising the ccurcy of the cesulfme determintion. In view of the wek sucrlose signl t 192 nm (OEMS sucrlose pek res pproximte 90 mau-s), the method specifies the simultneous use of second detection wvelength, 214 nm, to check sucrlose pek purity. The presence of sizle 214 nm pek t the sucrlose retention time signifies n interference nd positive is in the sucrlose pek re. A 20 L injection is used, ecuse this volume of OEMS delivers pproximtely 2000 g sucrlose nd therey complies with the criterion mentioned ove. Two externl stndrd solutions, whose nlyte concentrtions rcket the OEMS sweetener fortifiction level, re used to clirte the system. As shown y the experimentl dt documented elow, this pproch provides ccurte, precise, nd selective

2 80 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, 2003 Tle 1. Linerity s pek re versus concentrtion Stndrd curve ttriute Acesulfme potssium Sucrlose Dt points 5 5 Rnge, s % of OEMS trget Slope, mau-s-l/mg Y-intercept, mau-s Correltion coefficient Residul sum of squres, mg/l Residul, predicted concentrtion % of ctul concentrtion 80% of OEMS trget 0.1% +0.1% 80% of OEMS trget 0.1% +0.1% 80% of OEMS trget +0.2% 0.3% 80% of OEMS trget +0.4% +0.2% 80% of OEMS trget 0.3% +0.0% OEMS = orl electrolyte mintennce solution. determintion of cesulfme nd sucrlose in orl electrolyte mintennce solution. METHOD Apprtus nd Mterils () LC system. Equipped with inry grdient pump, solvent degsser, 20 L injection cpility, utosmpler, column oven set t 30 C, diode rry detector (DAD) set t 192 nd 214 nm, nd dt processing cpility. () LC column. Anlyticl column; YMC ODS-AQ, mm, 3 m, 120 Å. Regents All regents re of nlyticl purity unless otherwise stted. The wter used ws Milli-Q Plus grde (Millipore, Bedford, MA) or equivlent. () Solvents nd regents. Acetonitrile (LC grde), o-phosphoric cid, nd potssium phosphte monosic (crystls). () Stndrd. Acesulfme potssium (MW 201.2) from the Europen Phrmcopoei (Strsourg, Frnce) nd sucrlose (MW ) from the U.S. Phrmcopei (Rockville, MD). (c) Stndrd working solutions. Prepre stndrd working solution H y ccurtely weighing mg cesulfme potssium nd mg sucrlose into 500 ml volumetric flsk. Dissolve the stndrds in c 400 ml wter, nd dilute to volume with wter. Prepre stndrd working solution L y diluting 25.0 ml stndrd working solution H to 50 ml with wter. Stndrd working solution concentrtions should rnge from 60 to 128 mg/l for cesulfme potssium, nd from 68 to 144 mg/l for sucrlose. (d) 0.02M KH 2 PO 4. Dissolve 2.72 g potssium phosphte monosic in 950 ml wter, nd dilute to 1000 ml with wter. (e) Moile phse. (A) 850 ml 0.02M KH 2 PO ml cetonitrile; djust ph to 3.1 with o-phosphoric cid. (B) 200 ml wter ml cetonitrile. Degs solutions. Test Mterils OEMS (Pedilyte, Aott Lortories, Ross Products Division) were otined from locl grocery stores. Smple Preprtion OEMS were tested s is, without preprtion or dilution. LC Anlysis The LC conditions for the rtificil sweetener nlysis re s follows: column, YMC ODS-AQ; moile phses, (A) 0.02M KH 2 PO 4 cetonitrile ( , v/v), ph 3.1 with H 3 PO 4 ; (B) wter cetonitrile ( , v/v); grdient progrm, (B) 0% (0 2.0 min), (B) 12% ( min), (B) 100% ( min), (B) 0% ( min); run time, 30 min; column oven temperture, 30 C; detector, DAD; injection volume, 20 L. The detection wvelength selected for Tle 2. Accurcy s spike recovery Recovery, % of stndrd ddition Spiking level Acesulfme, % Sucrlose, % 80% of OEMS trget (n = 6) % of OEMS trget (n = 6) % of OEMS trget (n = 6) Recovery verge (n = 18) Stndrds were dded to unsweetened OEMS.

3 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, Tle 3. Accurcy s intermethod comprison Recovery, % vs lterntive method Spiking level Acesulfme Sucrlose 80% of OEMS trget concentrtion (n = 3) % of OEMS trget concentrtion (n = 3) % of OEMS trget concentrtion (n = 3) Alterntive method for cesulfme = reversed-phse LC with UV detection t 230 nm; lterntive method for sucrlose = nion exchnge LC with pulsed mperometric detection. OEMS = orl electrolyte mintennce solution. cesulfme nd sucrlose quntittion ws 192 nm, nd for sucrlose pek purity ssessment ws 214 nm. Method Vlidtion Vlidtion experiments were performed to evlute the qulity of the dt nd to ensure reliility of the method. Method linerity, ccurcy, precision, sensitivity, nd selectivity were evluted, long with limits of detection nd quntittion, in series of experiments. Results nd Discussion System linerity ws ssessed s 192 nm pek re versus nlyte concentrtion for series of 5 stndrd solutions prepred to contin oth cesulfme potssium nd sucrlose t levels tht were 80, 90, 100, 110, nd 120% of the OEMS fortifiction (Tle 1). The correltion coefficients for these plots were (cesulfme potssium) nd (sucrlose). The sttisticl residul, s regression concentrtion % devition from ctul concentrtion, ws lso clculted for ech of the 5 stndrd solutions. None of these residuls (for cesulfme potssium or sucrlose) exceeded 0.4%. These dt demonstrte the existence of strong positive correltion etween pek re nd nlyte concentrtion over the rnge of interest (i.e., % of the expected OEMS concentrtion). The ccurcy of the method ws ssessed y spike recovery experimenttion (Tle 2) nd intermethod comprisons (Tle 3). In the former, nlyte concentrtions were determined in unsweetened (nd unflvored) OEMS, which ws spiked with oth cesulfme potssium nd sucrlose. Three spiking levels were prepred (80, 100, nd 120% of OEMS fortifiction), nd ech spiking level ws prepred in triplicte. The spike recovery verges (n = 3) rnged from to 101.5%. In second ssessment of ccurcy, these sme 9 spiked smples (3 spiking levels 3 preprtions) were tested y n lternte vlidted method for cesulfme determintion, nd y n lterntive vlidted method for sucrlose. The lterntive cesulfme method lso used reversed-phse LC (with different column, temperture, nd injection volume), ut specified UV detection wvelength, 230 nm, which is much closer to cesulfme s UV mximum (227 nm). No cesulfme concentrtion determined y the lterntive method differed y >1.2% from the concentrtion determined y the primry method. The lterntive sucrlose method used nion exchnge LC with pulsed mperometric detection. The sucrlose concentrtions determined y the lterntive method were 0 6% lower (2.6% lower, on verge) thn those mesured y the primry method. (Note: the primry method results more closely pproximted the true concentrtions thn did the lterntive method results.) These ssessments demonstrted the ility Tle 4. Repetility s RSD Tle 5. Intermedite precision s RSD RSD for triplicte determintion RSD (3 determintions 2 dys) Spiking level Acesulfme, % Sucrlose, % Spiking level Acesulfme, % Sucrlose, % 80% of OEMS trget (n = 6) % of OEMS trget (n = 6) % of OEMS trget (n = 6) % of OEMS trget (n = 6) % of OEMS trget (n = 6) % of OEMS trget (n = 6) RSD = reltive stndrd devition. OEMS = orl electrolyte mintennce solution. RSD = reltive stndrd devition. OEMS = orl electrolyte mintennce solution.

4 82 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, 2003 Figure 1. Liquid chromtogrms of (A) stndrd working solution, (B) unflvored nd unsweetened OEMS, (C) fruit flvor OEMS, (D) grpe flvor OEMS, nd (E) ulegum flvor OEMS. The pek identities re (1) cesulfme nd (2) sucrlose. Chromtogrphic conditions re descried in the text.

5 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, Tle 6. Detection sensitivity t selected wvelengths Tle 7. UV sornce t 192 nm (versus wter) Sensitivity s pek re/concentrtion Asornce wvelength, nm Acesulfme Sucrlose < Comprison of sucrose nd sucrlose At 1.00 g/l in wter At 1.00 mole/l in wter Sucrose AU 58.9 AU Sucrlose AU 129 AU Sensitivity vlues re expressed s mau-s/ M (i.e., pek re/concentrtion). of the primry method to ccurtely quntify cesulfme nd sucrlose in OEMS. Method precision ws chrcterized y testing the sme set of 9 spiked smples in single nlysis on single instrument (repetility, Tle 4), nd in 2 nlyses conducted on 2 different dys nd on 2 different instruments (intermedite precision, Tle 5). As expected (Figure 1), the cesulfme determintion ws more precise [no reltive stndrd devition (RSD) exceeded 0.9%] thn the sucrlose determintion (RSD = %); nonetheless, the method ws cple of reltively precise quntittion of oth nlytes. The poorer precision ssocited with the sucrlose determintion is lrgely ttriutle to method sensitivity considertions, given tht the 192 nm (molr) response for cesulfme is nerly 9 times tht of sucrlose (Tle 6). Although higher wvelengths re much etter suited for cesulfme detection, sucrlose s very wek UV sorptivity dictted the choice of 192 nm s the optimum UV wvelength for the single signl determintion of oth sweeteners. Although the chlorine functions on the sucrlose molecule significntly enhnced its hydrophoicity nd reversed-phse column retention versus sucrose (Figure 2), the 2-fold increse in 192 nm sorptivity (i.e., sucrlose versus sucrose, Tle 7) hd little prcticl impct. The limiting sensitivity of sucrlose ws further illustrted y n exmintion of the limits of method detection nd quntittion (Tle 8). Even t 192 nm, with n undiluted 20 L OEMS injection, the Figure 2. LC column retention nd UV detector response for 27 g sucrlose (2) injection re compred with those for 27 g sucrose (0) injection. Chromtogrphic conditions re descried in the text.

6 84 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, 2003 Tle 8. Limits of detection nd quntittion Concentrtion, mg/l OEMS Acesulfme Sucrlose Detection limit (S/N = 3) Quntittion limit (S/N = 10) OEMS = orl electrolyte mintennce solution. Tle 10. Verifiction of sucrlose pek purity y pek height comprison Sucrlose pek height, mau Orl electrolyte mintennce solution 192 nm 214 nm Bulegum flvor Fruit flvor Grpe flvor Tle 9. Sensitivity s LOQ nd LOD % of expected nlyte concentrtion Acesulfme, % Sucrlose, % LOQ % of OEMS trget 2 32 LOD % of OEMS trget LOQ = limit of quntittion; LOD = limit of detection. OEMS = orl electrolyte mintennce solution. typicl sucrlose response ws still only 3 times the method quntittion limit (Tle 9). Becuse this fctor leves the sucrlose pek vulnerle to interference, second detection wvelength, 214 nm, is specified y the method to check sucrlose pek purity (Figure 3). The presence of sizle pek t the sucrlose retention time in the 214 nm plot signified interference, nd invlidted sucrlose quntittion. In this mnner, we showed the sence of ny such interference in ll flvors of OEMS; the 192:214 nm pek height rtio t the sucrlose retention time exceeded 68 in ech cse (Tle 10). On the sis of the experimentl dt documented ove, we conclude tht the descried method enles direct nd simultneous determintion of cesulfme nd sucrlose in OEMS. The method is ccurte, precise, nd selective, nd requires no preprtion or dilution of OEMS efore LC injection. Figure 3. Detil of liquid chromtogrm of grpe OEMS, showing superimposed plots of 192 nd 214 nm detection. Becuse the 192 nm response for sucrlose (2) is out 100 greter thn the 214 nm response, 192/214 nm dul wvelength detection ffords ssessment of sucrlose pek purity.

7 JOHNS & DOWLATI: JOURNAL OF AOAC INTERNATIONAL VOL. 86, NO. 1, References (1) von Rymon Lipinski, G-W. (1985) Food Chem. 16, (2) Quinln, M.E., & Jenner, M.R. (1990) J. Food Sci. 55, (3) Jenner, M.R., & Smithson, A. (1989) J. Food Sci. 54, (4) Federl Register (July 6, 1998) 63, (5) Federl Register (April 3, 1998) 63, (6) FAO/WHO Joint Expert Committee on Food Additives (2001) Acesulfme Potssium, INS 950, (7) FAO/WHO Joint Expert Committee on Food Additives (2001) Sucrlose, INS 955, (8) Myer, D.G., & Kemper, F.H. (1991) in Acesulfme-K, Mrcel Dekker, Inc., New York, NY (9) Lwrence, J.F., & Chronneu, C.F. (1988) J. Assoc. Off. Anl. Chem. 71, (10) Veerhdrro, M., Nryn, M.S., Kpur, O., & Sstry, C.S. (1987) J. Assoc. Off. Anl. Chem. 70, (11) Lin, Y.H., Chou, S.S., Sheu, F., & Shyu, Y.T. (2000) J. Chromtogr. Sci. 38, (12) Zho, R.R., & Johnson, B.P. (2000) J. Liq. Chromtogr. Rel. Technol. 23, (13) Frzier, R.A., Inns, E.L., Dossi, N., Ames, J.M., & Nursten, H.E. (2000) J. Chromtogr. A 876, (14) Chen, Q-C., Mou, S-F., Liu, K-N., Yng, Z-Y., & Ni, Z-M. (1997) J. Chromtogr. A 771, (15) Mthlouthi, M., & Hutteu, F. (1999) Food Chem. 64, 77 82