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1 BAÜ Fen Bil Ens. Derg. (2001).3.1 OLIVE OIL ANALYSIS BY FLO INJECTION Constntinos A. Georgiou URL: E-mil: Phone: Fx: Chemistry Lbortory, Agriculturl University of Athens, 75 Ier odos, Athens , Greece ABSTRACT Automted nlyticl methods were developed for the qulity control of olive oil, including the determintion of cidity, peroxide vlue (PV), iodine vlue (IV), 2-thiobrbituric cid recting substnces (TBARS), iodine vlue (IV) nd nisidine vlue (AV). The developed flow injection methods exhibit the following dvntges: high nlysis rtes ( h -1 ); full utomtion tht results in incresed precision nd ccurcy; low cost; low solvent consumption nd elimintion of chlorinted solvents, tht renders the developed methods environmentl friendly; low smple consumption ( ml per nlysis); good greement with time consuming officil methods; nd protection of regents from light nd tmospheric oxygen. INTRODUCTION Flow injection (FI) is esily pplied in utomtion of wet chemistries tht do not involve orgnic solvents. However, when smples nd/or regents re not wter soluble specil considertion should be given to suitble pumping systems 1, refrctive index 2, 20

2 density nd viscosity 3 grdients formed during the dispersion of the smple in the orgnic solvent crrier strem. Also bsorptiondesorption processes t the tube wlls of the FI mnifold, known to ffect the shpe of FI peks 4, re distinct when using orgnic solvents. FI methods concerning the nlysis of non queous smples, especilly edible oils re scrce 5. In our lbortory we develop flow injection utomted methods for the qulity ssessment of olive oil. The developed methods re bsed on homemde nlysers, providing utomted dt cquisition nd control. Regents in orgnic solvents re continuously pumped by peristltic pump through PTFE microtubes of 0.8 mm inner dimeter (coils). Micro-quntities of olive oil smples re utomticlly injected in the flow using chromtogrphy injection vlve. Smples re mixed with the regents nd incubted while flowing through mixing chmber or mixing coil to the spectrophotometer. For methods bsed on slow rections, prllel flow injection (PA-FI) multichnnel nlyser bsed on strem selection vlve (SSV) nd ten incubtion coils hs been developed. hile stored smples re incubted, new smples re injected nd mixed with the regents. Then, incubted smples re spirted in the spectrophotometer by flow reversl. After mesurement, smples re driven to wste. Automted methods hve been developed for the determintion of cidity, peroxide vlue (PV), 2-thiobrbituric cid recting substnces (TBARS), iodine vlue (IV) nd nisidine vlue (AV). Acidity nd peroxide vlue correlte well with olive oil sensory chrcteristics. Therefore, olive oil pricing is bsed on the determintion of these two prmeters. Hydrolytic nd oxidtive rncidity re the processes tht crete free ftty cids nd ftty cid peroxides. Advnced oxidtive rncidity cretes secondry oxidtion products tht re mostly low moleculr weight ldehydes. These secondry oxidtion products re determined by the 2- thiobrbituric cid vlue nd the nisidine vlue. Secondry oxidtion products re usully determined in thermlly stressed oils, nd oils tht hve been stored for long time. Iodine vlue is used for the detection of olive oil dultertion with inexpensive seed oils. 21

3 EXPERIMENTAL Anlyser construction nd opertion The FI nlysers developed re depicted in Figures 1-5. Detils concerning their construction re given elsewhere Here, the opertion of the prllel flow injection nlyser used in the determintion of PV, IV nd TBARS will be briefly discussed. The opertion (timing sequence) of the nlyser is shown in Figure 6. Briefly, the following steps re involved: 1. Injected smples pss through the detector nd then re diverted by the strem selection vlve to the incubtion coils. During this cycle the pump opertes in the forwrd direction to lod ll ten incubtion coils for the first time. 2. After ll coils re loded, the pump reverses the flow nd the first stored smple tht hs been incubted for ten minutes is spirted to the detector for mesurement. 3. The pump chnges the flow to forwrd direction nd the mesured smple is wshed out, while the injector lods the next (eleventh) smple. ml/min KOH 4. IV MC D b Figure 1. Flow injection nlyzer developed for the determintion of olive oil cidity. KOH: M KOH nd M phenolphthlein in n-propnol; IV: injection vlve; MC: 1.1 ml Plexigls mixing chmber; D: spectrophotometer, λ=562 nm; : wste; : digitl control signls; nd b: nlog dt. 22

4 C 1 N I ml/min L 1 IV L 2 D SS V C 2 CH 3COOH L 3 b C 10 Figure 2. Automted multichnnel Prllel Flow Injection nlyser for the determintion of olive oil peroxide vlue. NI: 1.0 % w/v NI in n-propnol; CH 3 COOH: 43.2 % v/v cetic cid in n- propnol; L 1, L 2 nd L 3, 10, 70 nd 60 cm coils respectively; IV: injection vlve; D: spectrophotometer, λ=360 nm; SSV: ten position strem selection vlve; C 1 -C 10 : 100 cm incubtion coils; : wste, : digitl control signls; nd b: nlog dt. 4. Next smple (eleventh) is injected nd driven through the detector to the incubtion coil. 5. Steps from 2 to 4 re repeted until ll smples re nlyzed. The time required for storing single smple in the incubtion coil vries between 30 nd 60 s. According to the incubtion time required for ech determintion, the number of incubtion chnnels cn be vried from 7 to 10. During the TBARS determintion, ll ten incubtion 23

5 ml/min C 1 Hnus L 1 L D SSV C 2 IV b C 10 Figure 3. Automted prllel flow injection multichnnel nlyzer developed for the determintion of olive oil iodine vlue. Hnus: M IBr in cetic cid; L 1, L 2 : 10 nd 70 cm coils, respectively; IV: injection vlve; D: Spectrophotometer, λ=392 nm; SSV: ten position strem selection vlve; C 1 -C 10 : 100 cm incubtion coils; : wste; : digitl control signls; b: nlog dt. B ml/mi C1 C2 IB TBA 1.9 IV L1 SSV L2 D CCl3COOH 1.9 C10 b Figure 4. Lbortory-mde prllel flow injection nlyser for the determintion of 2-thiobrbituric cid recting substnces in olive oil. TBA: M 2- thiobrbituric cid in n-propnol; CCl 3 COOH: 0.10 M in n-propnol; L 1 nd L 2 : 50 cm coils; IV: injection vlve; D: spectrophotometer, λ=532 nm; SSV: ten position strem selection vlve; C 1 -C 10 : 110 cm incubtion coils; B: wter bth, 95±1 o C; IB: ice bth; : wste, : digitl control signls; nd b: nlog dt. 24

6 coils re filled with olive oil smples during 5 min. Then, to minimize regent consumption, the peristltic pump stops for 25 min to fcilitte n incubtion time of 30 min. The use of the PA-FI nlyser overcomes the one 'smple t time' disdvntge of the FI technique permitting incubtion times up to 30 min while the smpling rte is more thn 20 smples per hour. ml/min p- nisidine 1.9 L 1 IV L 2 D CH 3 COOH 0.7 b Figure 5. Automted two line flow injection nlyser for the determintion of olive oil nisidine vlue. p- nisidine: M p- nisidine in propnol-2; CH 3 COOH: glcil cetic cid, L 1 nd L 2, 100 nd 50 cm coils respectively; IV: injection vlve; D: photometer, λ=350 nm; : wste, : digitl control signls; nd b: nlog dt. 25

7 S 1.0 BT LT FT A SSV: turn h h P : bck forwrd IV: lod inject lod t(s) Figure 6. Timing sequence of the Prllel Flow Injection nlyser. Recording obtined by injecting n olive oil of 40 peroxide vlue. BT: bck time, 14 s; LT: lod-wsh time, 18 s; FT: forwrd time, 17 s; ST: stop time, 11 s; SSV: strem selection vlve; P: pump; nd IV: injection vlve. 26

8 1.2 A pr 0.9 Absorbnce 0.6 b c 0.3 d e f g h i j k t (s) Figure 7. FI titrtion peks. Stndrds of ) 0.100, b) 0.150, c) 0.277, d) 0.400, e) 0.800, f) 1.00, g) 2.00, h) 3.00, i) 6.00, j) 8.00 nd k) 10.0 cidity degrees. Pek widths mesured : ) 16.5, b) 31.7, c) 42.6, d) 48.7, e) 60.9, f) 64.4, g) 75.4, h) 81.1, i) 91.9, j) 97,0 nd k) 101 s respectively. Pek widths were clculted t the A pr =1.000 bsorbnce level. RESULTS AND DISCUSSION Determintion of olive oil cidity by flow injection titrimetry 6 The homemde FI nlyser shown in Figure 1 ws used. The nlyser is bsed on single line mnifold using the FI titrtion technique. Olive oil smples re injected nd dispersed in the titrnt (mixed phenolphthlein, KOH solution) while flowing through mixing chmber (MC). The bsorbnce of the rection 27

9 mixture is continuously monitored t 562 nm, the λ mx of the bsic form of the indictor. The resulting negtive bsorbnce peks indicte the trnsition bse (red)-cid (colorless)- bse (red) of the indictor. The nlysis rte chieved by the FI method is smples per hour. The nlyticl rnge is % cidity degrees (AD, % w/w free ftty cid content expressed s oleic cid). Typicl FI peks cquired during the determintion of cidity determintion re shown in Figure 7. Results obtined by the proposed FI method compre well with those obtined through the officil Europen Community titrimetric method ( % reltive difference for the nlysis of 32 olive oil smples). Advntges of the proposed FI method in comprison to the officil one re depicted in Tble 1. Determintion of olive oil peroxide vlue by flow injection prllel multichnnel nlysis 7 The PA-FI multichnnel nlyser shown in Figure 2 ws used. The developed method is bsed on monitoring, t 360 nm, the bsorbnce of iodine liberted by olive oil peroxides. Olive oil smples re injected in NI strem nd cidified by merging with n CH 3 COOH strem. As the two regents used re incomptible, seprte flow lines re used for ech regent. An nlysis rte of 100 smples per hour is chieved while ech smple is incubted for 5 min. ith the proposed nlyser design the drwbck of one smple t time is overcome s 7 smples reside simultneously in the nlyser, resulting in high nlysis rtes. The nlyticl rnge is peroxide vlue (PV, meq O 2 /kg oil). Results obtined by the proposed method compre well with those obtined by the officil Europen Community titrimetric method (0-5.6% reltive difference for the nlysis of 27 olive oil smples). Other dvntges of the proposed PA-FI method in comprison with the officil one re shown in Tble 1. Determintion of olive oil iodine vlue by flow injection prllel multichnnel nlysis 8 The home-mde prllel flow injection multichnnel nlyser shown in Figure 3 ws used. Olive oil smples re diluted 1:50 in n-propnol nd injected in n cetic cid Hnus strem. Using the developed PA-FI nlyser, n nlysis rte of 60 smples 28

10 per hour is chieved while smples re incubted for 10 min. The IBr bsorbnce in the crrier strem is continuously monitored t 392 nm. Injected smples consume IBr resulting in two negtive bsorbnce peks (Figure 8) for ech smple, corresponding to the first nd second pss through the spectrophotometer. The nlyticl rnge is iodine vlue (IV, g I 2 /100 g oil) nd results obtined by the proposed method compre well with those obtined by the Assocition of Officil Anlyticl Chemists Hnus titrimetric method ( % reltive difference for the nlysis of 25 olive oil smples). Tble 1 highlights the merits of the proposed method in comprison to the officil method. Determintion of 2-thiobrbituric cid recting substnces by flow injection prllel multichnnel nlysis 9 Mlondildehyde (MDA) is one of the secondry oxidtion products of polyunsturted ftty cids. Quntittion of MDA is bsed on rection with 2-thiobrbituric cid (TBA) tht is not specific. As other oxidtion products rect with TBA, the term 2- thiobrbituric cid recting substnces (TBARS) hs been coined. The nlyser developed for the TBARS determintion is depicted in Figure 4. Olive oil is injected in TBA strem nd then is cidified by merging with CCl 3 COOH strem in mixing coil. The resulting mixture is diverted through the SSV to the first incubtion coil. All ten incubtion coils tht re immersed in wter-bth t 96 o C re loded in 5 min. Then the flow is stopped for 25 minutes. After smple incubtion, the flow strts, the rection mixture is cooled by pssing through n ice-bth nd subsequently mesured in the spectrophotometer t 532 nm. The developed method chieves n nlysis rte of 20 smples per hour, while smples re incubted for 30 min. The nlyticl rnge is (4-110) 10-4 M MDA nd the proposed method compres well with mnul method (reltive difference 0-5.6% for the nlysis of 30 olive oil smples). The comprison of the proposed PA-FI method nd the mnul method is presented in Tble 1. 29

11 Absorbnce A 1. 4 B 1. 2 C 1. 0 D E Determintion of olive oil nisidine vlue by flow injection 10 T Figure 8. FI peks obtined during iodine vlue determintion. Stndrds of (A,1) 23, (B,2) 44.5, (C,3) 67.5, (D,4) 89.5 nd (E,5) IV. (A-E) Reversed flow nd (1-5) Forwrd flow. Bck time: 18s; Lod-wsh time: 18 s; Forwrd time: 25 s. The homemde nlyser used for the determintion of olive oil nisidine vlue is depicted in Figure 5. The method developed is bsed on monitoring the rection product of p-nisidine nd the ldehydic secondry oxidtion products from olive oil. As p- nisidine is not comptible with cetic cid when using propnol-2 solvent, two flow lines were used for premixing the regents while flowing through 100 cm coil. The bsorbnce is continuously monitored t 350 nm. The nlysis rte chieved is 80 smples per hour. Results obtined compre well with those obtined through the officil method ( % reltive difference for the nlysis of 28 olive oil smples). The comprison of the proposed FI method nd the mnul method is presented in Tble 1. 30

12 CONCLUSIONS The developed flow injection methods exhibit severl dvntges. They re fst chieving nlysis rtes of h -1. Full utomtion results in incresed precision nd ccurcy. The nlysis cost is low, since smll quntities of orgnic solvents re consumed. The low orgnic solvent consumption nd the elimintion of chlorinted solvents render developed methods environmentl friendly. Good greement with time consuming officil methods is ccomplished. The PA-FI nlyser developed llows utomtion of methods tht require long incubtion time without loss of smpling rte. Tble 1 presents the dvntges of the developed methods over the officil ones. ACKNOLEDGMENTS This work ws prtilly finnced by the Agriculturl University of Athens reserch fund nd the Greek Stte Scholrship Foundtion. 31

13 Tble 1. Comprison of the developed flow injection methods with the officil methods 1. Acidity Anlysis time Solvent consumption Olive oil consumption FI method s 3-7 ml n-propnol ml E.C. b method 2. Peroxide vlue min 50 ml ethnol, 50 ml ethyl ether g FI method 43 s 3.4 ml n-propnol, 3 ml cetic cid 0.02 ml E.C. b method 3. Iodine vlue min 10 ml chloroform, 15 ml cetic cid g FI method 60 s 3.1 ml cetic cid ml AOAC c method 4. TBARS 30 min 25 ml cetic cid, 10 ml chloroform 0.25 g FI method 3 min 1.7 ml n-propnol, 0.2 ml trichlorocetic 0.04 ml cid mnul >45 min 6 ml cetic cid, 4 ml CCl 4, 5 ml method d trichlorocetic cid 5. p-nisidine vlue 0.05 ml 45 s 1.4 ml propnol-2, 0.4 ml cetic cid 0.04 ml 10 min 25 ml isooctne, 1ml cetic cid 0.5 g Anlysis time nd therefore n-propnol consumption depend on smple concentrtion. b Europen Communities. c Assocition of Officil Anlyticl Chemists. d P.G. Ke nd A.D. oyewod, Anl. Chim. Act 106, (1979). e IUPAC method

14 REFERENCES [1] C.A. Georgiou nd M.A. Kouppris, Anlyst, 113, (1988). Abstrct: [2] R.A. Lech, J. Ruzick nd J.M. Hrris, Anl. Chem., 55, (1983). [3] D. Betteridge,.C. Cheng, E.L. Dgless, P. Dvid, T.B. God, D.R. Dens, D.A. Newton nd T.B. Pierce, Anlyst, 108, (1983). [4] S.S. Vives, M.J.M. Hernndez, J.L.M. Herrer nd G.R. Rmos, Anl. Chim. Act, 268, (1992). [5] N.S. Thomidis, nd C.A. Georgiou, Anl. Chim. Act, Lb. Autom. Inf. Mnge., 34, (1999). Abstrct: [6] P.G. Nouros, C.A. Georgiou, nd M.G. Polissiou, Anl. Chim. Act, 351, (1997). Abstrct: Simplified presenttion: [7] P.G. Nouros, C.A. Georgiou, nd M.G. Polissiou, Anl. Chim. Act, 389, (1999). Abstrct: Simplified presenttion: [8] N.S. Thomidis, nd C.A. Georgiou, Anl. Chim. Act, Anl. Chim. Act, 405, (2000). Abstrct: Simplified presenttion: [9] P.G. Nouros, C. A. Georgiou, nd M.G. Polissiou, Anl. Chim. Act, 417, (2000). Abstrct: Simplified presenttion: [10] N.S. Thomidis, E. Lbrine nd C.A. Georgiou, in preprtion. Simplified presenttion: 33

JUMO MIDAS C18 SW. OEM seawater pressure transmitter. Applications. Brief description. Customer benefits. Special features. Approvals/approval marks

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