Available online at http://www.urpjournals.com International Journal of Analytical and Bioanalytical Chemistry Universal Research Publications. All rights reserved ISSN-2231-5012 Original Article Gas Chromatography Method for the Determination of Non-Ethanol Volatile Compounds in Herbal Formulation JAGDISH MANWAR 1, KAKASAHEB MAHADIK* 1, ANANT PARADKAR 2, SANJAY PATIL 3, L.SATHIYANARAYANAN 1 and RAHUL MANMODE 4 1 Department of Pharmaceutical Chemistry, Poona College of Pharmacy, Bharati Vidyapeeth University, Pune-411 038, MS, India 2 Centre for Pharmaceutical Engineering Science, Institute of Pharmaceutical Innovation, University of Bradford, Bradford, West Yorkshire-BD7 1DP, UK 3 Department of Alcohol Technology, Vasantdada Sugar Institute, Pune-412 307, MS, India 4 Department of Chemistry, 1 University Ave., University of Massachusetts Lowell-01854, USA Tel.: +91-20-5436898; Fax: +91-20-25439383. Email: krmahadik@rediffmail.com Received 11 December 2012; accepted 18 January 2013 Abstract In this paper, we have reported a gas chromatographic method for the determination of non-ethanol volatile compounds like acetaldehyde, acetone, ethyl acetate, methanol, 2-propanol, diacetyl, 2-butanol, 1-propanol, 2,3-pentanedione, n-butyl acetate, isobutene, 1-butanol, isoamyl acetate, isoamyl alcohol, acetoin, n-hexanol, acetic acid, and furfural in herbal formulation. The formulation was centrifuged at 6000 rpm for 20 minutes and distilled off. Volume of 0.8 μl of distillate containing 1-pentanol (internal standard) was injected in to column in a gas chromatograph fitted with a flame ionization detector. Hydrogen gas was used as carrier gas. The chromatographic conditions set were injector s temperature 230 C, column temperature initial 50 C for 2 minute hold and then temperature raised by 5 C per minute up to 220 C, detector s temperature 240 C, carrier flow 1.2 ml/min, and split ratio 1:30. The separation of all compounds was completed within 15 minutes. The validation of method was carried out in terms of linearity and range and accuracy. The average percent recovery was range from 95.93 to 103.55 % w/v. Thus, the proposed method is simple, rapid and accurate and therefore it is suitable for routine analysis of all herbal formulations. Keywords: Gas Chromatography, Internal standard, Ethanol, Methanol, Herbal formulation 2013 Universal Research Publications. All rights reserved INTRODUCTION Herbal formulation contain more than 15-20 different herbs wholly or parts thereof. Herbal formulations like Asava s, Arishta s, and Kadha s have occupied an important place in the Indian System of Traditional Medicine (ISTM). Over the hundreds of years, these formulations are used as prophylactic as well as for the treatment of various diseases and disorders of mankind. According to ISTM, these formulations are prepared by cold or hot extraction process by subjecting to long slow fermentation. Alcohol generated (ethanol, 5-10%v/v) helps in extracting active principles from herbal crude drugs especially the water insoluble compounds 1. The alcohol produced in the formulation also acts as good appetizer for health 2. Owing to presence of alcohol producing yeast Saccharomyces cerevisiae, grapes (Vitis vinefera) or flowers of Woodfordia fruticosa are added as inoculums to induce fermentation process 3,4. Presence of other microorganism in the inoculums causes the production of number of nonethanol volatile (NEV) compounds 5. These compounds are produced by various fermentation pathways 6. Ethyl acetate, methanol, 1-propanol, isobutanol and isoamyl alcohol are some important NEV compounds produced in formulations are ranges from 10 to 600 mg/l. The toxicity of these compounds is well known, and practically it is impossible to remove them from the product. International Conference on Harmonization (ICH) has used the term Residual solvents for all volatile solvents present in formulations. According to ICH, Residual solvents in pharmaceuticals are defined as organic volatile chemicals 12
that are used or produced in the manufacture of drug substances or excipients, or in the preparation of drug products. These solvents are not completely removed by practical manufacturing techniques, but we can ensure the safety of products by checking their levels in final products. ICH has recommended the permissible amount of such compounds in pharmaceutical formulations for the safety of the human being or patient. Based on the possible risk to the human health, ICH has classified these compounds (solvents) into three main classes like Class 1 (solvents to be avoided), Class 2 (solvents to be limited) and Class 3 (solvent with low toxicity) 7. Gas chromatography is a rapid method for the determination of volatile compounds in herbal formulations. Recently, one gas chromatography method is reported for the analysis of two NEV compounds in herbal formulation using nitrogen as a carrier gas 8. In this paper, we have reported a new gas chromatographic method for the determination 18 NEV compounds in herbal formulations. In our method, hydrogen was used as carrier gas which gives good resolution and provides more rapid separation than nitrogen gas. It is less expensive than nitrogen and also acts as fuel for flame ionization detector. 1-Pentanol was used as internal standard because it does not produce in herbal formulations. Internal standard was used to improve the precision of analysis. MATERIALS AND METHODS Instrumentation and chromatographic conditions A Hewlett Packard 6890 plus gas chromatographic system with flame ionization detector was coupled with computer programmer. A Stabilwax-DA column (60m 0.25µm ID) was used for chromatographic separation. Initial column temperature was 50 C for 2 minutes and then was raised up to 220 C by 5 C/min. Injector and detector temperature was set at 230 C and 240 C, respectively. Split ratio was adjusted to 1:30 and flow rate of carrier hydrogen gas was 1.2 ml/min. Hydrogen and air provided to the detector was at a rate of 30 and 300 ml/min, respectively. Sample size injected was 0.8 µl using 1 µl syringe (Model 1B7, SGE Scientific Ltd., Melbourn). Chemicals and reagents All the chemicals and solvents used in work were of analytical grade, and purchased from Merck s Chemicals Ltd. Tripled distilled water was prepared in laboratory and filteredthroughmilli-qsystem(millipore,bedford,ma, USA). Collection of marketed formulation Three different brands of herbal formulation i.e. Shwasonil (The Ayurvedic Arkashala Ltd.), Ashwagandharishtha (Baidyanath) and Saraswatarishtha (Sandu) were procured from local Ayurvedic Pharmacy Shop in India. Internal Standard Stock Solution About 500 ml of internal standard solution was prepared by diluting 1-Pentanol with distilled water to get final concentration 800 mg/l. The solution was stopper and stored at 4 C. Preparation of standard mixture Different marketed formulations were initially analyzed for NEV compounds by gas chromatographic method reported for analysis of wine 9. The amounts of compounds in samples were taken as average reference for preparing standard mixture in tripled distilled water. The compounds which were absent in the samples, their amount taken was 200 mg/l. Acetic acid which is less sensitive, for which the amount taken was 400 mg/l. Ethanol 200 mg/l was also added in mixture to confirm its retention time and resolution. According to reference results, standard mixture of various compounds was prepared by adding known amount of compounds in 15-20 ml of distilled water in 100 ml volumetric flask and final volume was made up with distilled water (See Table 1). Preparation of standard mixture containing 10% v/v ethanol To study the effect of ethanol concentration (10% v/v) on retention time and peak characteristics of NEV compounds, a standard mixture containing all NEV compounds plus 1- pentanol was prepared in the similar way. In this case, ethanol concentration taken was 10% v/v. System suitability parameters Checking of system suitability is the integral part in the analysis by gas chromatography. They are used to verify that resolution and reproducibility of system are adequate for the analysis to be done 10. Various parameters for each were determined by injecting three replicates of standard mixture. The chromatograms were recorded and their parameters like Retention time, Resolution, Capacity factor, Peak asymmetry, and Theoretical plates were measured. Sample preparation Marketed preparation (150 ml) was centrifuged at 6000 rpm for 20 minutes. About 100 ml of supernatant liquid was distilled off and 70 ml of distillate was collected. To the distillate, about 20 ml of internal standard solution of 1-Pentanol (800 mg/l) was added and final volume of made up to 100 ml with distilled water. Standardization of method Four standard mixtures were used for the standardization of method. Each of the four standard solutions was diluted three times. The dilutions for each standard were injected and a relative response factor (RRF) for compound in dilutions was calculated. For the given standard compound, an average RRF for dilutions of that standard was taken. The dilutions which produced RRF closer to the average was retained for standardization and other dilutions for that were discarded. This method of selection of average dilutions corresponding to the four standards were each injected once for initial standardization of method and each injected once on the consequent days. Relative response factor (RRF) = (Ac x Cis M )/(Ais M x Cc) Where, Ac = Area of target analyte in standard mixture Cis M = Concentration of internal standard in standard mixture Cc = Area of target analyte in standard mixture Ais M = Area of internal standard in standard mixture Analysis of standard and sample solutions Volume 0.8 L of solution was injected and chromatograms were recorded and amount of each NEV compounds present in sample solution (mg/l) was calculated from following formula. Concentrations of analyte in sample = (As x Cis M )/(Ais S x RRF) 13
Where, As = Area of target analyte in sample Cis M = Concentration of internal standard in standard mixture Ais S = Area of the internal standard in sample RRF = Relative response factor Validation of method Accuracy Accuracy of the method was ascertained in five replicate by standard addition method. Known amounts of NEV compounds were added to pre-analyzed distillate of sample (marketed formulation) and their corresponding concentrations in the sample were calculated. Linearity and range Linearity and range of the method was checked by injecting three standard solutions (containing ethanol) of known concentration prepared separately in triplicate. The regression equation for each compound was set up on the basis of peak area. has increased with the use of internal standard 1-pentanol, which elutes with retention time of 10.28 min. The retention times of each compound including ethanol and 1- pentanol (internal standard) are given in Table 1. All the compounds showed good resolution at the given chromatographic conditions. Among all 20 compounds including ethanol and 1-pentanol, 16 are eluted in order of their increase in molecular weights and boiling points; but 4 compounds viz. ethyl acetate, 2-propanol, n- butyl acetate and acetic acid are eluted irrespective of their molecular weight and boiling point. Figure-1: Chromatograms of standard mixtures.(1) acetaldehyde, (2) acetone, (3) ethyl acetate, (4) methanol, (5) 2-propanol, (6) ethanol, (7) diacetyl, (8) 2-butanol, (9) 1- propanol, (10) 2,3-pentanedione, (11) n-butyl acetate, (12) isobutanol, (13) 1-butanol, (14) isoamyl acetate, (15) isoamyl alcohol, (16) 1-pentanol, (17) acetoin, (18) 1-hexanol, (19) acetic acid, (20) furfural. RESULTS AND DISCUSSION In this work, we have reported a new gas chromatography method for the analysis of NEV compounds in herbal formulation. From the typical chromatograms of standard mixture, it is clear that 18 NEV compounds can be separated within 15 min (Figure-1). Percentage of accuracy Figure-2: Chromatograms of marketed herbal formulations (a) Shwasonil (b) Ashwagandharishtha, (c) Saraswatarishtha. (1) acetaldehyde, (3) ethyl acetate, (4) methanol, (6) ethanol, (9) 1-propanol, (12) isobutanol, (15) isoamyl alcohol, (16) 1- pentanol (internal standard), (17) acetoin. Calibration equation for each compound was established using standard mixture of known concentration. Linearity study shows good coefficient of regression (r 2 ) with ranges from 0.9917 for furfural to 0.9992 for isoamyl acetate. The straight line calibration curve for each compound indicates the method is sensitive and depends on response to flame ionization detector. The obtained data of linearity study for eight standard solutions for each compound is shown in Table 2. The lowest sensitivity was shown by acetic acid, whereas highest sensitivity was shown by acetone. Three marketed herbal formulations like Shwasonil, Ashwagandharishtha and Saraswatarishtha were analyzed. All the formulations showed presence of fewer NEV compounds within the ICH permissible limit. Acetaldehyde, ethyl acetate, methanol and amyl alcohol were present in all formulations. The results of marketed 14
TABLE-1: Results of System Suitability Parameters Parameters a Compounds Amount in std. mixture (mg/l) b R t R c K d e W 0.1% N e Acetaldehyde 130 3.57-16.85 1.18 164293 Acetone 109 4.07 12.90 19.55 1.24 156502 Ethyl acetate 205 4.57 11.33 21.82 1.14 170382 Methanol 129 4.67 2.27 22.36 1.14 130316 2-propanol 103 4.98 5.65 23.91 1.21 138310 Ethanol 222 5.11 2.31 24.57 1.29 153047 Diacetyl 144 5.77 11.55 27.78 1.34 188253 2-butanol 113 6.43 12.40 31.26 1.25 235758 1-propanol 102 6.69 4.54 32.43 1.31 214083 2,3-pentadione 238 7.10 7.87 34.49 1.25 402803 n-butyl acetate 130 7.27 4.05 35.38 1.13 565410 Isobutanol 101 7.71 8.51 37.52 1.18 257187 1-Butanol 101 8.11 7.39 40.17 0.96 465609 Isoamyl acetate 102 8.59 10.71 42.00 1.19 650189 Isoamyl alcohol 203 9.60 23.15 47.03 0.95 744831 1-pentanol 215 10.28 15.18 50.40 1.26 851242 Acetoin 125 11.13 9.98 53.21 1.58 126145 1-hexanol 120 11.78 6.65 57.90 1.83 471754 Acetic acid 360 13.53 23.94 66.63 1.67 490881 Furfural 130 14.02 5.27 69.08 2.08 255608 a The given values are the mean of three replicates of injections. b Rt, Retention time in min. c R, Resolution. d K, Capacity factor. e W 0.1%, Asymmetry at 10% of full peak height. f N, Theoretical plates. TABLE-2: STATISTICAL DATA OF LINEARITY AND RANGE Compounds Range (mg/l) Slope Intercept Regression (n = 8) LOD(mg/L) LOQ (mg/l) Acetaldehyde 32.50-260 7.30 10-3 4.8635 0.9985 6.03 18.27 Acetone 27.25-218 5.04 10-3 0.1851 0.9967 12.71 8.53 Ethyl acetate 51.25-411 7.33 10-3 0.0933 0.9984 16.38 49.65 Methanol 32.25-259 5.02 10-3 1.1700 0.9989 8.56 25.95 2-propanol 25.75-207 4.84 10-3 0.4686 0.9966 12.15 36.84 Ethanol 55.50-444 4.09 10-3 1.4642 0.9992 12.15 36.84 Diacetyl 36-288 5.55 10-2 8.8894 0.9951 13.86 42.00 2-Butanol 28.28-226 3.96 10-3 -3.0451 0.9977 9.78 29.65 1-Propanol 25.50-205 3.54 10-3 1.0671 0.9963 12.47 37.79 2,3-Pentadione 59.50-476 3.04 10-3 -10.1505 0.9987 6.85 20.77 n-butyl acetate 32.50-260 2.92 10-3 3.3043 0.9971 13.03 39.51 Isobutanol 25.25-203 3.05 10-3 4.1075 0.9960 11.06 33.54 1-Butanol 25.25-203 4.41 10-3 0.9988 0.9947 14.82 44.93 Isoamyl acetate 25.50-204 2.93 10-3 -0.8836 0.9992 5.67 17.21 Isoamyl alcohol 50.75-406 2.79 10-3 0.0121 0.9982 17.54 53.16 1-pentanol 53.75-429 2.61 10-3 3.0448 0.9988 14.41 43.69 Acetoin 31.25-251 1.42 10-3 12.7224 0.9890 15.09 45.74 1-Hexanol 30-239 2.68 10-3 -0.8194 0.9969 13.44 40.74 Acetic acid 90-720 10.07 10-3 16.2065 0.9969 30.71 93.07 Furfural 32.50-260 2.65 10-2 10.3223 0.9917 16.46 49.90 formulations are given in Table 3 and chromatograms are shown in Figure 2. The recovery of method was determined for two preanalyzed marketed herbal formulation Shwasonil and Ashwagandharishtha. Average recovery of individual compound was ranged from 95.93 to 103.55% w/v. The precision of method is expressed in terms of percent standard deviation, and it was ranges from 2.5 for methanol to 0.013 for 1-butanol (Table 4). 15
TABLE-3: ANALYSIS OF MARKETED FORMULATIONS Formulation As per ICH Compound (mg/l) SH a AS b SR c Allowed limit d Class Acetaldehyde 49.67 37.84 70 NG f NG Acetone ND e ND ND 5000 3 Ethyl acetate 15.82 132.05 14.42 5000 3 Methanol 53.94 75.63 34.60 3000 2 2-Propanol ND ND ND 5000 3 Diacetyl ND ND ND NG NG 2-Butanol ND ND ND 5000 3 1-Propanol ND 22.39 61.52 5000 3 2,3-Pentadione ND ND ND NG NG n-butyl acetate ND ND ND 5000 3 Isobutanol ND 21.82 62.29 5000 3 1-Butanol ND ND ND 5000 3 Isoamyl acetate ND ND ND NG NG Isoamyl alcohol 14.59 111.06 108 5000 3 Acetoin ND ND 33.27 NG NG 1-Hexanol ND ND ND NG NG Acetic acid ND ND ND 5000 3 Furfural ND ND ND NG NG a SH, Shwasonil. b AS, Ashwagandharishtha, c SR, Saraswatarishtha. d Amount is acceptable per day. e ND, Not detected, f NG, Not given. TABLE-4: RECOVERY OF NON-ETHANOL VOLATILE COMPOUNDS FROM MARKETED FORMULATIONS Compound Std. compound Percent Recovery ± SD (n=5) added (mg/l) SH a AS b SR c Acetaldehyde 130 98.76 ± 2.44 100.14 ± 2.02 99.57 ± 1.95 Acetone 109 99.21 ± 2.48 100.60 ± 2.20 100.23 ± 1.90 Ethyl acetate 205 100.56 ± 0.71 99.86 ± 0.65 99.45 ± 2.21 Methanol 129 99.43 ± 2.05 99.91 ± 1.66 99.72 ± 1.82 2-propanol 103 100.03 ± 2.28 100.17 ± 3.60 100.12 ± 1.06 Diacetyl 144 96.98 ± 5.20 99.01 ± 2.64 98.88 ± 3.32 2-butanol 113 103.55 ± 1.01 100.12 ± 2.36 100.45 ± 2.02 1-propanol 102 99.70 ± 2.39 100.43 ± 2.95 100.14 ± 1.12 2,3-pentadione 238 97.68 ± 0.55 100.27 ± 0.65 99.17 ± 1.87 n-butyl acetate 130 99.90 ± 0.88 100.41 ± 1.29 99.91 ± 1.86 Isobutanol 101 99.33 ± 1.45 98.88 ± 4.21 98.91 ± 1.48 1-butanol 101 100.22 ± 2.30 99.98 ± 1.97 99.43 ± 1.78 Isoamyl acetate 102 100.39 ± 0.82 100.81 ± 2.53 99.17 ± 2.39 Isoamyl alcohol 203 99.75 ± 1.97 99.75 ± 0.71 98.82 ± 1.51 Acetoin 125 98.24 ± 3.70 98.84 ± 4.05 95.84 ± 4.40 1-hexanol 120 100.43 ± 2.51 100.21 ± 1.86 99.52 ± 0.78 Acetic acid 360 95.96 ± 8.50 97.72 ± 7.07 97.56 ± 2.45 Furfural 130 99.73 ± 2.56 99.38 ± 2.49 99.30 ± 1.82 a SH, Shwasonil, b AS, Ashwagandharishtha, c SR, Saraswatarishtha. CONCLUSION The gas chromatography method described here is simple, rapid and accurate and hence it could be useful for the routine analysis of non-ethanol volatile compounds without interference of each other in all liquid herbal formulations. Internal standard (1-pentanol) was used to improve the precision of quantitative analysis. REFERENCES 1. Ayurvedic Formulary of India, Department of Ayurveda, Yoga & Naturopathy, USANI, Siddha and Homeopathy, publisher, New Delhi: Ministry of Health and Family Planning, Government of India, Volume 1,1978. 2. Satoskar R., Bhandarkar S., Ainapure S.: Pharmacology and Pharmacotherapeutics, Mumbai Popular Prakashan, Mumbai; Volume 15, 1997, p.73-76. 3. Martini A., Ciani M., Scorzetti G, Direct enumeration and isolation of wine yeasts from grape surfaces, Am. J. Enol. Vitic, 1996, 47, 435-440. 16
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