Published Online *** 2016 (
IMPROVEMENT OF CITRONELLA (Cymbopogon nardus L) OIL QUALITY BY APPLYING VARIOUS
CHELATING AGENTS
Pocut Nurul Alam, Husni Husin, Teku Muhammad Asnawi, Hesti Meilina, Adi Salamun Department of Chemical Engineering, Syiah Kuala University, Banda Aceh, Indonesia
Email: pnaanwar@gmail.com
Received Month Day, Year; Revised xxxx; Accepted xxxx
ABSTRACT
Indonesia is unquestionably one of the world’s top biodiversity rich countries, which produce forty of eighty essential oils being traded in the world market. One of the oils is citronella. In Indonesia, Lemon grass can be classified into two groups, namely Lemon or lemon grass (Cymbopogon
citratus) and Citronella or Lemon grass Citronella (Cymbopogon nardus L). This study aims toimprove the quality of Citronella oil by chelating process to decrease its metal content with chelating agents. Chelating process is a binding metal process by applying the chelating agent to form complex compounds among metal and chelating compounds. Chelating agents applied in this research were citric acid, oxalic acid, Na-EDTA and tartaric acid at varied concentration i.e 0.5%, 1%, 1.5% and 2%. The stirring time was varied at 15, 30, 45, 60, 75 and 90 minutes with the operation temperature of 25
oC. The research showed that addition of citric acid at the concentration of 2% could reduced Fe content in Citronella by 80%, tartaric acid at the concentration of 2%
decreased Fe by 83%, oxalic acid at a concentration of 2 % can decrease Fe at 53%, and Na-EDTA compounds can decrease Fe by 80%.
Keywords
Citronella oil, citric acid, oxalic acid, Na-EDTA and tartaric acid.
INTRODUCTION
Indonesia’s rich on biodiversity produces 40 kinds of essential oil containing plants out of 80 kinds of essential oils traded on the world market. One of the essential crop planted in Indonesia is citronella.
Citronella oil is an agribusiness sector commodity that has a potential and competitive in global markets.
However, lemongrass is not optimally well-cultured as an agribusiness commodity in Indonesia. Citronella (Cymbopogon nardus L) produce essential oil is best-known Citronellal Oil as its trade name, which still less attention among researchers (Anonymous, 1988).
In Indonesia, lemongrass is classified into two groups, namely: kitchen-used lemon grass (Cymbopogon citrates) and fragrance- lemongrass or citronella (Cymbopogon nardus L). Generally ones do not distinguish between citronella and lemongrass, although both types are easily distinguishable (Ginting, 2004). In Aceh, especially in Gayo Lues district, one of the areas in which traditionally produce citronella oil, but its products still have many deficiencies that need a continuous and sustainable improvement process to meets with standard quality criteria in order to increase its competitiveness in potential market.
Citronella oil processing technology in Gayo Lues still apply traditional technology approach without any purification treatment prior to being sold , so that unable to establish consistency in quality and economically not competitive products in commercial market.
Citronella oil produced by traditional farmers in Gayo Lues is still looks brown color and not transparent enough. The application of traditional technology which still utilized used-oil drums would affect contamination of ill-contained metal to citronella oil products. Therefore, in this study we would improve quality of citronella oil by incorporating a chelating agent in order to obtain product which meets the standard quality. That have been defined by the ratio of the chelating compound, concentration and different stirrer. The objective of this research is to improve the quality of citronella oil by reducing the levels metal contained in the oil produced citronella oil, evaluating the appropriate concentration of chelating agent, and speed and stirring time applied as well. From experimental results indicated that the quality of citronella oil produced would be improved with reducing metal concentration and brightness of citronella oil, therefore improving a higher citronella oil prices in Indonesia especially in Gayo Lues, Aceh.
RESEARCH METHODOLOGY MATERIALS AND EQUIPMENTS
Citronella oil used in this study obtained from traditional distillation produced Gayo Lues.
Chemicals and other materials used for analysis i.e, oxalic acid, Na-EDTA, tartaric acid, 0.1 N NaOH, KOH 0,5 N, KOH 0, 1 N, 0.4 N HCl, 96% ethanol, 90% ethanol, diethyl ether, anhydrous Na2SO4, PP indicators, distilled water, and filter paper.
Equipment’s used in chelating process and quality analysis i.e.: Erlenmeyer, glass beakers, measuring cups, burette, picnometer, gas stove, spatula, magnetic stirrer, stirrer, filters, scales, thermometer, stopwatch and refractometer. In chelating treatment process, oil weight and was determined by 20 grams for each experimental run, while the chelating agent weight and stirring time were varied as explained previously in experimental procedures.
RESEARCH METHODS
Chelating experimental work steps was done as follows:
As-received citronella oil distillates which produced by utilizing used-oil drums and chelating agents were prepared in various weight and concentrations, respectively, for each experimental run.
Initial analysis of as-received citronella oil was conducted according to ISO 1995.
The amount of 20 grams of citronella oil was weighed, then also weighed up the amount of chelating agent (Citric Acid, Oxalic Acid, Na-EDTA and tartaric acid) with a varied ratios of 0.5%; 1%, 1.5% and 2% to citronella oil weight to prepare a reaction mixtures. The reaction mixture was continuously stirred at a moderate pace with a magnetic stirrer for 15, 30, 45 and 60 minutes at temperature of 60 ℃. After completing chelating process, the reaction mixture was then filtered out by using filter paper to obtain purified citronella oil. As-treated citronella oil was then ready to be analyzed and tested referred to ISO 1995.
RESULTS AND DISCUSSION 1. Effect of chelating agent concentration on Density
Density is one of the important criteria in determining the purity and quality of citronella oil. Density is defined as the ratio of oil weight to water in a mixture on a equal volume basis of water to oil. (Gunther,
Density values which obtained from experimental tests is quite various, as can be seen in Fig.1. Fig.1 shows that the addition of various concentration of chelating agent resulted the density values still meet allowed the standard range. Density values of citronella oil produced corresponds to the addition of citric acid at various concentrations i.e: 0.5% = 0.9308; 1% = 0.8928; 1.5% = 0.8912; 2% = 0.8852. Meanwhile the addition of tartaric acid density values obtained at a concentration i.e: 0.5% = 0.8864; 1% = 0.8912; 1.5% = 0.8904; 2% = 0.8832, and the addition of oxalic acid density values obtained at a concentration i.e: 0.5% = 0.8916; 1% = 0.8928; 1.5% = 0.9152; 2% = 0.9340, the addition of Na-EDTA density values obtained at a concentration i.e.: 0.5% = 0.8842; 1% = 0.8892; 1.5% = 0.9364; 2% = 0.8872. Refer to the results of this research, density values of as-produced citronella oil obtained meets in the range allowed by Indonesia National Standards SNI 1995, ranging from 0880-0922.
Fig.1. Correlation of chelating agent concentration on Citronella Oil Density
2. Effect of chelating agent concentration on refractive index
The basic principles of use of refractometer as follows: if light radiation penetrates to two different kinds of media which has different densities, then refraction occurs due to different density of the media. The refractive index of essential oil is closely correlated with constituents contained in the essential oil produced. Similar to density, the constituents of essential oil would also affect its refractive index. In this study, we use refractometer to determine the refractive index of citronella oil samples.
There are several factors that would affect density of a component i.e: type and amount of functional groups, the number and position of double bonds, the amount of carbon and other atoms.
The type and number of functional groups contained of a component could affect its density value.
If the number of functional groups on a component more than one type of component, the value of the weight is more than one. The number and position of double bonds may affect the value of the density of a component. The density would increase with increasing the number of double bonds (Isnina, 2009).
Fig.2. Correlation of chelating agent concentration on Citronella Oil Refractive Index
In Fig.2 shows refractive index of citronella oil obtained after the addition of citric acid as chelating agent at a concentration i.e.: of 0.5% = 1,473; 1% = 1,471; 1.5% = 1.470; 2% = 1,468. The refractive index obtained in the addition of tartaric acid as chelating agent with a concentration of 0.5% = 1,469; 1% = 1.470; 1.5% = 1.470; 2% = 1,467. While refractive index on the addition of oxalic acid as chelating agent with a concentration of 0.5% = 1,471; 1% = 1,471; 1.5% = 1,473; 2% = 1,468, and the addition of Na-EDTA at various concentration as chelating agent, refractive index obtained i.e.: 0.5% = 1,468; 1% = 1,469; 1.5% = 1,474; 2% = 1,468. For all samples prepared with various types of chelating agents and concentration, the refractive indexes obtained still meet Indonesia National Standard SNI, ranging 1466-1475. Refractive index of a material is one of parameters to determine materials purity. Level of
influenced by the presence of water in oil. The more the water content in oil, the lower the refractive index. It due to the nature of water which is easily to refract light. Therefore, the essential oil with higher refractive index is better in quality than that of the lower.
1. Citronella Oil Solubility in alcohol
Essential oils are soluble in alcohol and rarely soluble in water, Due to its solubility in alcohol, thus essential oils produced is contained oxygenated terpene components. This fact is consistent with the Guenther, 1987, that the solubility of oil in alcohol is determined by the type of chemical components contained in oil. In general, essential oils containing oxygenated terpene compound is more soluble than that containing terpene compounds. It can be concluded that the smaller the solution of essential oils in alcohol, the better the quality of essential oils. In Table 4.1, there can be seen that with increasing chelating agent concentrations, there is not affects its solubility in alcohols.
Table 1. Citronella oil solubility in ethanol 80%
Type Chelating
Solubility in ethanol 80%
Chelating Concentration
0.5% 1% 1.5% 2%
Citric Acid 1 : 2 1 : 2 1 : 2 1 : 2
Tartaric Acid 1 : 2 1 : 2 1 : 2 1 : 2
Oxalate Acid 1 : 2 1 : 2 1 : 2 1 : 2
Na-EDTA 1 : 2 1 : 2 1 : 2 1 : 2
Duration of stoking of citronella oil may also influenced and changed its solubility. It was due to the polymerization process occurred would decreased its solubility, therefore it necessary a higher alcohol concentration to dissolve.
2. Effect of Fe concentration
The high iron concentration in citronella oil would affect oil color becomes reddish brown. Iron ions dissolved in citronella oil is contaminated from distillation container made of iron that carried over during the distillation process. One of the chemical properties of citronella oil could be evaluated from its metal concentration, especially iron metal dissolved (Fe). Fe concentration contained in citronella oil was analyzed using Atomic Absorption Spectrophotometry (AAS). The principle of AAS analysis method is based on the adsorption of light by atoms of substances. The atoms would absorb light at specific wavelengths is depend
on the nature of elements. The absorption of radiation energy by atoms was measured and called as absorbance. The measurement of iron metal concentration of citronella oil prior to and after purification process was conducted by this methods. The difference of concentration analysis result was influenced by the type of chelating agent used, thus, ferrous metals concentrations in citronella oil can be seen in Fig.3.
Fig. 3. Fe concentration of citronella oil products at various chelating agents used.
In Fig. 3, it can be seen that the addition of chelating agents in citronella oil by variations of types and concentration on Fe concentration reduction. By the addition of citric acid to the citronella oil at a concentration of 2%, reduced Fe concentration in the citronella oil to 80% from 2,785 mg/ kg to 0.5649 mg/
kg. By the addition of tartaric acid concentration of 2%, Fe concentration reduced to 83% from 2,785 mg / kg to 0.4663 mg / kg. In the addition of oxalic acid at concentration of 0.5%, concentration of Fe in the oil reduced to 53% from 2,785 mg/ kg to 0.6392 mg/ kg. The addition of Na-EDTA on citronella oil by concentration of 0.5%, Fe concentration reduced to 80% from 2,785 mg/kg to 0.5556 mg/kg.
Chelating agents used in this study could reduce Fe concentration contained in citronella oil. By concentration variations applied results indicated that most appropriate chelating agent to reduce Fe concentration contained in citronella oil is tartaric acid at 2% concentration.
3. Gas Chromatography Mass Spectrophotometry Analysis
The chromatogram of GC-MS analysis results of the of citronella oil components contained in citronella plant shown in Fig.4.
Fig.4 Citronella
Oil Preliminary Analysis Chromatograma. Citronella oil analysis result by the addition of tartaric acid 2%
Fig.5 Chromatogram of Citronella oil with chelating agent tartaric acid 2%
From GC-MS analysis data there are 16 types of compounds found in citronella oils without using any chelating agent, as shown in Table 4.2.
Tabel 4.2 Citronella oil compositions
No. Komposisi Kimia Minyak Awal Minyak Dengan Penambahan Asam Tartarat 2%
1 Citronella 26.01 42.02
2 .beta.-Citronellol 11.96 16.27
3 Geraniol 15.87 18.94
4 Geranyl acetate 3.42 1.98
5 Citronellyl Acetate 2.7 1.84
6 Eugenol 1.47 1.23
7 Elemol 2.7 1.82
8 Limonene 6.5 3.92
Based on GC-MS composition analysis data of citronella oil on Table 4.2, it can be seen that the area of citronella and geraniol before the addition of chelating agent is 26.01% and 15.87%, respectively. The experimental results showed that by the addition of 2% of tartaric acid as chelating agent, some amount of Fe ion removed. It can be seen from percentage area of citronella and geraniol which amounted to 42.02% and 18.94%.
CONCLUSIONS
Based on the research results, it can be concluded as follows:1. Brownish red color of citronella oil by using oil-used drums for distillation process would contaminated citronella oil products by dissolved Fe ions originated from drum wall. The more the concentration of chelating agent used and extended adsorption time for Fe removal, the color is also increasingly clear.
2. The utilization of tartaric acid as chelating agent could remove 1.7972 ppm iron concentration, whereas Na-EDTA removed Fe content of 2.1429 ppm from initial concentration of 75.936 ppm content in citronella oil.
3. The concentration of citronella and geraniol prior to addition of a chelating i.e: 26.01% and 15.87, meanwhile after the addition of tartaric acid as chelating agent it concentration is 42.02% and 18.94%, respectively.
