INFLUENCE OF PRESSURE AND TIME ON EXTRACTION PROCESS USING SUPERCRITICAL CO2

The supercritical fluid extraction (SFE) by carbon dioxide (CO2) of Salvia officinalis L. was investigated. SFE by CO2 was performed at different pressure (80, 100, 150, 200 and 300 bar) and constant temperature of 40oC (all other extraction conditions, such are flow rate, particle diameter of Salvia officinalis, extraction time were kept constant. The GC – MS method was used for determination of qualitative and quantitative composition of obtained extracts and essential oils.


Introduction
The extraction by gases under pressure has been more and more used, representing a good alternative to the classic extraction procedures.
The advantages of the supercritical fluid extraction (SFE) technique are well known by now and it is often regarded as an alternative to the traditional methods.CO 2 is most widely used in SFE because it is simple to use, inexpensive, nonflammable, nontoxic, chemically stable, shows great affinity to volatile (liphopilic) compounds and can be easily and completely removed from any extracts.With critical point at 31.3ºC and 72.8 bar, carbon dioxide can be used at temperatures and pressures which are relatively safe, convenient and particularly appropriate for extraction of a range of more volatile and/or heat -labile compounds [1], [3], [4].Supercritical fluid extraction is widely used in natural products, foods and flavors, pharmaceuticals, nutraceuticals, polymers, chemicals, and parts cleaning industries.
Natural materials contain various extractable fractions.Among these, essential oils are particularly relevant since they represent the basic material for many foods, cosmetics, and pharmaceutical preparations.
Several studies have been devoted to the extraction of essential oils and of related products by supercritical CO 2 , as reviewed by Stahl et [5], [6], [7].Much work has recently been done on the composition of Salvia officinalis essential oil obtained by traditional techniques [1], [2], [3].
In this paper, the influence of extraction time, as well as of carbon dioxide pressure in SFE of Salvia officinalis by carbon dioxide is described.

Plant Materials
For this experiments Salvia officinalis from Berkovici, near Trebinje gathered 2006 was used.The mean particle radius (r) were d=0.3157 mm.After the grinding using sieve sets (Erweva Apparatebau GmbH, Germany), the mean particle radius was calculated as r=100/Σ(m i/ Q m ), where mi is the fraction (%) after sieving, and Q m is the mean aperture diameter of two adjacent sieves.

Chemicals
Commercial carbon dioxide (99% purity, Tehno -gas, Novi Sad, Serbia) as the extracting agent was used.All other chemicals were of analytical reagent grade.

Results and Discussion
The supercritical fluid extraction (SFE) by carbon dioxide (CO 2 ) of Salvia officinalis L. was investigated.SFE by CO 2 was performed at different pressure (80, 100, 150, 200 and 300 bar) and constant temperature of 40ºC (all other extraction conditions, such are flow rate, particle diameter of Salvia officinallis, extraction time were the same) The extract yields and essential oils yield are given for different pressures in Table 1.By increasing the pressure from 80 to 300 bar at 40ºC increasing extract yields and decreasing the essential oil content in the total extract.In the first 2.5 hours of extraction by supercritical carbon dioxide, extract yield is the highest.Dependence extract yield on extraction time at pressure 80, 100, 150, 200 and 300bar can be shown by polinomial second order y = ax 2 + bx + c approximately (Eq. 1).Calculated values paramerters at investigated pressures, as well as values correlation coefficient r are given in Table 2.
The relative contents of the identified components of essential oil EO1 (p=80 bar), EO 2 (p=100 bar), EO 3 (p=150 bar), EO 4 The GC -MS method was used for determination of qualitative and quantitative composition (Table 3. and Table 4.).As an illustration GC chromatograms of Salvia officinallis extract and essential oil obtained by SFE -CO 2 method are shown in Fig. 2. and Fig. 3.

Conclusions
As expected from the studies on Salvia officinalis, the main compounds in essential oils were α -thujone, camphor, isoborneol, bornylacetate, phyllocladene.The main components in extract were camphor, isoborneol, γ -elemene, selina -3,7 (11)diene, phyllocladene.The composition of main compounds in essential oils is not largely influenced by extraction pressure.Indeed, chemycal analysis of sage oil at different pressure evidenced composition variations along the extraction process but it is not large.The composition of main compounds in extract at pressure p=80 bar is largely different from composition at other pressure.
In the first 2.5 hours of extraction , extract yield is the highest .
Eighteen compounds of essential oil EO4 were identified, representing 95.7482 % of the total eessential oil, and seventeen compounds of essential oil EO2 were identified representing 96.1645% of the total essential oil.The five most abundant compounds (α -thujone, camphor, isoborneol, bornylacetate, phyllocladene) represent 69.7164% of the essential oils.
Fourteen compounds of extract E3, E4 were identified, and thirteen compounds of extract E1, E2 and E5.The content of phyllocladene and camphor in extract E1 was considerably lower than in other extracts, and content of γ elemene and isoborneol was considerably higher than in other extract.

2. 4 .
Supercritical Fluid Extraction SFE-CO 2 was carried out with a laboratory -scale high -pressure extraction plant (NOVA -Swiss, Effretikon, Switzerland).The main parts and characteristics (manufacturer specification) of the plant were as follows: a diaphragmtype compressor (up to 1000 bar), extractor with an internal volume of 200 mL (Pmax =250 bar), and maximum CO 2 mass flow rate of approximately 5.7 kg/h.The mass of Salvia sample in extractor was 60g at the investigated value of pressure and at 40ºC, and the CO 2 flow rate was 97.72 dm 3 /h.Separotor conditions were 15 bar and 25ºC.
Now the influence of exctraction time on supercritical extraction of Salvia officinalis L at different pressure was investigated.Obtained results are shown on Fig. 1.
al. and by Reverchon et al.

Table 1 .
The results of the extraction of Salvia officinalis L. by supercritical carbon dioxide

Table 2 .
Parameters of Eq. 1 (coefficients a, b, c and correlation coefficient r) Fig. 1.Extract yield vs extraction time at different pressure

Table 3 .
Composition of essential oils of Salvia officinallis L.

Table 4 .
Composition of the CO 2 extracts of salvia officinallis