OPTIMIZATION OF THIN LAYER CHROMATOGRAPHY METHODS FOR SEPARATION AND IDENTIFICATION OF ANTIDEPRESSANTS IN THEIR MIXTURE

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1 OPTIMIZATION OF THIN LAYER CHROMATOGRAPHY METHODS FOR SEPARATION AND IDENTIFICATION OF ANTIDEPRESSANTS IN THEIR MIXTURE PLONASLUOKSNĖS CHROMATOGRAFIJOS METODIKOS OPTIMIZAVIMAS ANTIDEPRESANTŲ MIŠINIO SKIRSTYMUI IR IDENTIFIKAVIMUI Daiva Kazlauskienė 1, Guoda Kiliuvienė 1, Palma Nenortienė 1, Giedrė Kasparavičienė 2, Ieva Matukaitytė 1 Lietuvos sveikatos mokslų universiteto Medicinos akademijos Farmacijos fakulteto Analizinės ir toksikologinės chemijos katedra 2 Lietuvos sveikatos mokslų universiteto Medicinos akademijos Farmacijos fakulteto Vaistų technologijos ir socialinės farmacijos katedra 1 Lithuanian University of Health Sciences, Medical Academy, Faculty of Pharmacy, Department of Analytical and Toxycological Chemistry 2 Lithuanian University of Health Sciences, Medical Academy, Faculty of Pharmacy, Department of Drug Technology and Social Pharmacy SANTRAUKA Reikšminiai žodžiai: antidepresantai, plonasluoksnė chromatografija, apsinuodijimas, toksikologinė analizė. Atliekant toksikologinę analizę, tikslinga naudoti tokią analitinę sistemą, kuri galėtų greitai ir tiksliai identifikuoti kelis vaistinius preparatus vienu metu. Šio darbo tikslas buvo sukurti ir validuoti plonasluoksnės chromatografijos metodiką, tinkamą išskirstyti antidepresantų mišinio (amitriptilino hidrochloridas, paroksetino hidrochloridas, sertralino hidrochloridas, fluvoksamino maleatas ir bušpirono hidrochloridas) komponentus ir juos identifikuoti. Sistema validuota įvertinant jautrumą, duomenų pasikartojamumą, atsparumą sąlygų pasikeitimui bei specifiškumą. Tyrimo metu sukurtos tirpiklių sistemos, kurios gerai atskiria mišinio komponentus acetonitrilas, metanolis, 25 proc. vandeninis amoniako tirpalas (85:10:5); acetonitrilas, metanolis, 25 proc. vandeninis amoniako tirpalas (75:20:5); dichlormetanas, 1,4-dioksanas, 25 proc. vandeninis amoniako tirpalas (50:45:5); dichlormetanas, 1,4-dioksanas, 25 proc. vandeninis amoniako tirpalas (42:55:3); trichlormetanas, 1,4-dioksanas, 25 proc. vandeninis amoniako tirpalas (25:70:5); trichlormetanas, 1,4 dioksanas, 25 proc. vandeninis amoniako tirpalas (60:36:4). Nustatyta tinkamiausia tiriamų junginių (sertralino, amitriptilino, paroksetino, bušpirono ir fluvoksamino) mišinio skirstymo tirpiklių sistema acetonitrilas, metanolis, 25 proc. vandeninis amoniako tirpalas (85:10:5). Naudojant šią tirpiklių sistemą, tiriamų junginių R f vidutinės vertės skiriasi labiausiai. Atlikta jos validacija ir nustatyta, kad tiriamų junginių vidutinės R f vertės pakartojamumo santykinis standartinis nuokrypis (SSN, proc.) svyravo nuo 0,6 iki 1,8 proc. ir neviršijo leistinos 5 proc. paklaidos. Metodikos jautrumas nustatytas vertinant mišinio dėmių intensyvumą ant chromatografinės plokštelės. Bušpirono aptikimo riba 0,0012 µg, sertralino 0,0008 µg, amitriptilino 0,0004 µg, fluvoksamino 0,0004 µg, paroksetino 0,0008 µg. Rezultatų atsparumas sąlygų pokyčiui nustatyta, kad didinant ar mažinant tirpiklių acetonitrilo ir metanolio kiekius ne daugiau kaip dviem mililitrais, tiriamų junginių vidutinės Rf vertės statistiškai reikšmingai nepakinta. ABSTRACT Key words: antidepressants, thin layer chromatography, poisoning, toxicological analysis. By conducting the toxicological analysis it is meaningful to determine the analytical system that could identify simultaneously several medicinal preparations quickly and precisely. The purpose of this work was to create and validate the method of thin-layer chromatography that would be suitable to separate the components of antidepressant mixture (amitriptyline hydrochloride, paroxetine hydrochloride, sertraline hydrochloride, fluvoxamine maleate and buspirone hydrochloride) and to identify them. The system was validated with regard to the sensitivity, repetition of data, resistance and particularity. The solvent systems with potential of high separation of components in their mixture were created: acetonitrile, methanol, ammonia solution 25 percent (85:10:5); acetonitrile, methanol, ammonia solution 25 percent (75:20:5); dichlormethane, Daiva Kazlauskienė Lietuvos sveikatos mokslų universiteto Farmacijos fakultetas Eivenių g. 4, Kaunas daiva.kazlauskiene@lsmuni.lt teorija ir praktika T. 21 (Nr. 1), p. doi: /mtp

2 1,4-dioxane, ammonia solution 25 percent (50:45:5); dichlormethane, 1,4-dioxane, ammonia solution 25 percent (42:55:3); trichlormethane, 1,4-dioxane, ammonia solution 25 percent (25:70:5); trichlormethane, 1,4-dioxane, ammonia solution 25 percent (60:36:4). One of the most suitable solvent systems for separation of the analyzed mixture (sertraline, amitriptyline, paroxetine, buspirone, fluvoxamine) was determined acetonitrile, methanol, ammonia solution 25 percent (85:10:5). When this solvent system was used, the average R f values of the analyzed compounds differed the most. Validation was conducted the relative standard deviation (RSD, percent) of the average R f value of the analyzed compounds varied from 0,6 to 1,8 percent and did not exceed the permissible error of 5 percent. The sensitivity of methodology was determined by assessing the intensity of the mixture s spots on the chromatographic plate. The detection limit of buspirone was 0,0012 µg; sertraline 0,0008 µg; amitriptyline 0,0004 µg; fluvoxamine 0,0004 µg; paroxetine 0,0008 µg. The resistance of results to the changed conditions it was determined that when the amounts of the solvents acetonitrile and methanol were increased or decreased to two milliliters, the average R f values of the analyzed compounds did not change statistically significantly. INTRODUCTION A big part of the intoxication cases recorded in Lithuania is caused by incorrectly used dosage of the medication, interaction of medication or deliberate overdose. According to the data of the territorial institutions of public health in ,1 percent of all the examined intoxication cases consisted of intoxication of children (under 18) with medicaments, alcohol, gas/carbon monoxide, alcohol with other substances, etc. [1 6]. The majority of intoxication cases consists of the intoxication with psychotropic medicine (in ,8 percent), medicine affecting autoimmune nervous system (in percent) and antiepileptic, sedative, antispasmodic medicine (in ,2 percent) [6 9]. According to the statistical data of the comparative analysis of the intoxication cases in , the cases of deliberate intoxication with medicaments have been predominant for several years already 59,3 percent [1, 3, 9]. It is important to have a possibility to determine the lethal preparation and to provide as urgent aid as possible in order to avoid death. By conducting the toxicological analysis it is meaningful to determine the analytical system that could identify simultaneously several medicinal preparations quickly, simply and without big financial losses [10 13]. The purpose of this work was to create and validate the method of thin-layer chromatography that would be suitable to distribute the components of antidepressant mixture (amitriptyline hydrochloride, paroxetine hydrochloride, sertraline hydrochloride, fluvoxamine maleate and buspirone hydrochloride) and to identify them. The system was validated with regard to the sensitivity, repetition of data, resistance and particularity [14 16]. The methods of thin-layer chromatography were created, which are suitable to distribute and identify the components of the antidepressant mixture (amitriptyline hydrochloride, paroxetine hydrochloride, sertraline hydrochloride, fluvoxamine maleate and buspirone hydrochloride) and which are used for toxicological analyses, in case of various acute intoxication cases and in the laboratories of forensic expertise in order to determine the substance that has caused the lethal intoxication. MATERIALS AND METHODS The chromatographic plates (silica gel 60 F 254; Merck, Germany), dimensions cm and cm covered by silica gel sorption mass were used. The glass chambers with lids, glass capillaries, volume 1 5 μl and 10 μl, were used for chromatography. The following solvents were used: methanol, ammonia solution 25 percent, trichlormethane, ethanol, ethyl acetate, cyclohexane, ethane acid, acetone, acetonitrile, 2-propanol, trifluoracetic acid, dichlormethane, 1,4-dioxane, benzene, petrol ether, isopenthyl alcohol, diethyl ether, octane, methane acid, N,N dimethylaniline, nitrobenzene and hexane [14,17 20]. In order to develop the chromatographic plates the following developers were used: ninhydrin, Mandelin reagent, Dragendorff reagent (modified according to Mounier). The standard solutions of amitriptyline, fluvoxamine, paroxetine, buspirone and sertraline are made by dissolving the standard substances in methanol (concentration 0,2 mg/ml) [14, 15, 21 23]. RESULTS AND DISCUSSIONS The data were collected and analyzed using Microsoft Office Excel 2007 and statistical data program SPSS 19. In order to substantiate the suitability of the optimized methodology of solvents the validation was carried out and the following parameters were assessed: repetition of results, sensitivity of methodology and resistance of methodology to the changed conditions [10 13, 15 17, 24, 25]. The repetition of the inhibition index during the research was calculated using twenty repetitions of analyses on the same day and in the same conditions (solvents, concentration, saturation of chamber). The used system of solvents acetonitrile, methanol, ammonia solution 25 percent (85:10:5). The relative standard deviation RSD (percent) of the repetition of the inhibition index differed sufficiently with regard to all the compounds. The smallest RSD was in case of buspirone (0,9 percent), while the biggest in the case of paroxetine (1,8 percent). According to the calculated R f results of all the analyzed compounds, the RSD of the inhibition index does not exceed the required 5 percent, thus the conclusion is made that the repetion 12 teorija ir praktika T. 21 (Nr. 1)

3 of the results satisfies the set requirements and that such a separation methodology is suitable for distribution of mixture and identification of compounds by the method of thin-layer chromatography [15, 17, 24, 26, 27]. In order to determine the sensitivity of the methodology, the tests were carried out by dripping 1 10 µl of each analyzed compound in methanol of standard solutions and the solution of their mixture on the chromatographic plate. The sensitivity of methodology was assessed according to the intensity of spots under ultraviolet (UV) light and spray of the Dragendorff reagent (modified according to Mounier). The received results allowed calculating the minimal detection limit of solutions of the standard analyzed compounds. Moreover, the intensity of spots was assessed and the minimal detection limit of the analyzed compounds was calculated when they are present in the mixture [18, 26, 28]. According to the research results of the sensitivity of methodology, which were received using the system of solvents: acetonitrile, methanol, ammonia solution 25 percent (85:10:5), the minimal detection limit of the spot of standard buspirone solution is 0,0006 µg (only when UV light is used, because the Dragendorff reagent does not cause the spot to appear); minimal detection limit of the spot of standard sertraline solution is 0,0006 µg (only when the Dragendorff reagent is sprayed, because the UV light does not cause the spot to appear); the minimal detection limit of amitriptyline is 0,0002 µg under effect of both developers; the minimal detection limit of fluvoxamine is 0,0002 µg under UV light; the minimal detection limit of paroxetine is 0,0014 µg under UV light, and 0,0004 µg when the Dragendorff reagent is sprayed. The research results of intensity of spots of the mixture of analyzed compounds are the following: buspirone is 0,0012 µg under UV light; sertraline is 0,0008 µg when the Dragendorff reagent is sprayed; amitriptyline 0,0004 µg appears when the Dragendorff reagent is sprayed an when UV light of certain length of wave (λ nm) is used; fluvoxamine 0,0004 µg appears under UV light; the detection limit of paroxetine is 0,0008 µg when the Dragendorff reagent is sprayed and 0,0014 µg under UV light. To generalize the received results: the detection limit of the analyzed compounds in the standard solutions is 0,0006 µg, although paroxetine is visible only when the Dragendorff reagent is sprayed in case of such amount. In order to detect paroxetine on the chromatographic plate under UV light, the minimal 0,0014 µg concentration is needed, where its intensity is not very high either. The minimal amount necessary to distribute and identify the analyzed compounds in the mixture is 0,0014 µg. In order to justify the resistance of methodology to the changed conditions the amounts of solvents of the validated system (acetonitrile, methanol, ammonia solution 25 percent 85:10:5) was changed to the following amounts: 85,5:9,5:5; 86:9:5; 86,5:8,5:5; 87:8:5; 84,5:10,5:5; 84:11:5; 83,5:11,5:5; 83:12:5. The graphical variability of the analyzed compounds when the amount of the solvent is changed is shown in the figure 1. When the content ratio of solvents in the system acetonitrile, methanol, ammonia solution 25 percent (85:10:5) is changed by reducing or decreasing it up to 2 milliliters (ml) acetonitrile or methanol, the R f values of the analyzed compounds do not change statistically significantly. Fig. 1. Graphical illustration of the changing Rf values of the analyzed compounds when the amounts of solvents is changed teorija ir praktika T. 21 (Nr. 1) 13

4 The statistical data program SPSS 19 was used to carry out the linear regressive analysis, which shows the dependency of the dependent variable (analyzed compound) on the independent variable (acetonitrile or methanol). When the amount of acetonitrile increases, the R f values of the analyzed compounds also increase: buspirone 1,115; sertraline 0,423; amitriptyline 2,462; fluvoxamine 1,231; paroxetine 2,500. When the methanol s amount increases, the R f values decrease: buspirone 0,003; sertraline 0,013; amitriptyline 0,034; fluvoxamine 0,029; paroxetine 0,060. When the amount of acetonitrile is reduced, the R f values of the analyzed compounds also decrease: buspirone (-)1,500; sertraline (-)1,250; amitriptyline (-)3,000; fluvoxamine (-)2,250; paroxetine (-)2,750. When the methanol s amount decreases, the R f values also decrease: buspirone - 0,003; sertraline 0,059; amitriptyline 0,334; fluvoxamine 0,183; paroxetine 0,353. To summarize the received regressive equations, it is possible to conclude that the change of the amount of acetonitrile (its decreasing or increasing) has the biggest impact on the change of the R f values. The change of the amount of this solvent affects the least the change of sertraline s R f values, while paroxetine is affected the most. The increase or reduction of the methanol amount also affects the most the change of the R f value of paroxetine the most. COMPARISON OF SOLVENT SYSTEMS The figure 2 shows that when all the solvent systems are used, R f difference between the sertraline and amitriptyline is the least. When all the solvent systems are used, the R f values of paroxetine are the smallest and the most remote from other analyzed compounds. The most suitable solvent system to separate and identificate the compounds of the mixture (sertraline, amitriptyline, paroxetine, buspirone and fluvoxamine) was determined to be acetonitrile, methanol, ammonia solution 25 percent (85:10:5). When this solvent system is used, the average R f values of the analyzed compounds differed the most: buspirone 0,83; sertraline 0,76; amitriptyline 0,64; fluvoxamine 0,52; paroxetine 0,27. CONCLUSIONS 1. 6 thin-layer chromatographic methods (three solvent systems containing two different solvent content ratio) suitable for separation and identification the compounds of the mixture amitriptyline, paroxetine, sertraline, fluvoxamine and buspirone were developed: 1.1 Acetonitrile, methanol, ammonia solution 25 percent (85:10:5); 1.2. Acetonitrile, methanol, ammonia solution 25 percent (75:20:5); 1.3. Dichloromethane 1,4-dioxane, ammonia solution 25 percent (50:45:5); Fig. 2. R f differences of analyzed compounds of different solvent systems I solvent system acetonitrile, methanol, ammonia solution 25 percent (85:10:5); II solvent system acetonitrile, methanol, ammonia solution 25 percent (75:20:5); III solvent system - dichlormethane, 1,4-dioxane, ammonia solution 25 percent (50:45:5); IV solvent system dichlormethane, 1,4- dioxane, ammonia solution 25 percent (42:55:3); V solvent system trichlormethane, 1,4- dioxane, ammonia solution 25 percent (25:70:5); VI solvent system trichlormethane, 1,4 dioxane, ammonia solution 25 percent (60:36:4). 14 teorija ir praktika T. 21 (Nr. 1)

5 1.4. Dichloromethane 1,4-dioxane, ammonia solution 25 percent (42:55:3); 1.5. Trichloromethane 1,4-dioxane, ammonia solution 25 percent (25:70:5); 1.6. Trichloromethane: 1,4 dioxane, ammonia solution 25 percent (60:36:4). 2. One of the most suitable solvent systems for separation of the analyzed mixture was selected (acetonitrile: methanol: ammonia solution 25 percent 85:10:5) and its validation was conducted. In such a way the repetition of results, sensitivity of methodology and its resistance to the changed conditions was proved. 2.1 The relative standard deviation (RSD, percent) of the average Rf value of the analyzed compounds varied from 0,6 to 1,8 percent and did not exceed the permissible error of 5 percent. 2.2 The sensitivity of methodology was determined by assessing the intensity of the mixture s spots on the chromatographic plate. The detection limit of buspirone was 0,0012 µg; sertraline 0,0008 µg; amitriptyline 0,0004 µg; fluvoxamine 0,0004 µg; and paroxetine 0,0008 µg. 2.3 The resistance of results to the changed conditions it was determined that when the amounts of the solvents acetonitrile and methanol were increased or decreased mostly up to two milliliters, the average Rf values of the analyzed compounds did not change statistically significantly. REFERENCES 1. Anderson IB, Clark RF, Benowitz NL et all. Poisoning & drug overdose. In: Benowitz NL editor. Antidepressants, general (noncyclic). In: Benowitz NL editor. Antidepressants, tricyclic. 6th ed. New York: McGraw-Hill; 2012, Hiemke C, Härtter S. Pharmacokinetics of selective serotonin reuptake inhibitors. Pharmacology & Therapeutics 85(2000): Available from: 3. Hoffman RS, Nelson LS, Howland MA, et all. Goldfrank s manual of Toxicologic emergencies. In: Seratonin Reuptake Inhibitors and Atypical Antidepressants. In: Cyclic Antidepressants. 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