Supercritical fluid extraction as a use-ful method for pesticides determination

Abstract

Despite attractive features (rapid extractions, small solvent volumes, non-toxicity of CO 2 , potential of selectivity depending on the fluid density, relatively clear and concentrated ex t ra c t s , p o s s i ble coupling with ch romatography and automation), the use of SFE in routine analytical ap p l i c ations is a rather slow process. Indeed, t h e major drawback of this recent technique is the large number of parameters to control and optimize, which results in time re q u i red for developing a new method. In add i t i o n , t h e extraction conditions are strongly dependent on the matrix to be extracted, so that parameters need to be adjusted for every new application. D e t e rm i n ation of pesticides remains a ch a l l e n ge fo r mainly three reasons: the wide variety of physicochemical properties and chemical structures of pesticides, the many possible matrices that should be investigated, and the trace c o n c e n t rations at wh i ch pesticides are usually pre s e n t . Recent papers reviewed environmental applications of SFE [1,2], especially with regards to the extraction of the main classes of pesticides [3][4][5]. As SFE perfo rmances are strongly dependent on the nature of the sample, this article will consider the matrices that have been submitted to SFE for pesticides determination. Principle of SFEA fluid is in its supercritical state when both its pressure and temperature are above their critical value (when only one c ritical value is at t a i n e d, the fluid is said subcri t i c a l ) . Supercritical fluids possess unique properties, intermediate between gas and liquids properties [6][7][8][9][10]. In particular, their high diffusivity allows for rapid extractions. In addition, the fluid density may be precisely adjusted, by a correct choice of both pressure and temperature.The key parts of an SFE system are the high-pressure pump wh i ch delive rs the fl u i d, and the re s t rictor wh i ch maintains the pressure inside the system. Extraction is performed inside a high-pressure cell (containing the sample), maintained at the correct temperature. The fluid may simply fill the cell (static mode), or continuously flow through the vessel (dynamic mode). The extracted solutes are entrained by the supercritical fluid flow out of the cell; their collection is usually achieved as the fluid is depressurized by passing through the restrictor. The collected solutes are further analyzed using gas or liquid chromatography. Also, a few recent studies report the use of enzyme immunoassay as a rapid screening process [5,11,12]. Alternatively, the SFE system may be coupled on-line with chromatographic systems, gas chromatography (GC), liquid chromatography (LC), or supercritical fluid chromatography (SFC), by means of an interface [5,8]. For example, the coupling of SFE and SFC e n abled the determ i n ation of thiolcarbamate herbicides (molinate and thiobencarb) from spiked soil samples (with organic content from 1.75 to 12.9%) [13]. Obviously, such a system seems very attractive when traces of pest...

Supercritical Carbon Dioxide Extraction of Essential Oils from Perovskia atriplicifolia Benth.

“…Carbon dioxide is an excellent extraction medium for nonpolar species such as alkenes and terpenes. It is also reasonably good for moderately polar species, including polycyclic aromatic hydrocarbons (PAHs), aldehydes, esters, alcohols, and fats, but it is less useful for polar components (15)(16)(17)(18)(19). The extraction of polar mol- ecules requires addition of a modifier, most commonly methanol or ethanol (20)(21)(22).…”

Microwave extraction of organochlorine pesticides from soils

“…The analysis of pesticides in soils involves an extraction step, which can be performed in different ways. For the isolation of pesticides from soil samples, various extraction procedures have been proposed such us shakeflask, Soxhlet [1], ultrasonic solvent extraction [2], supercritical fluid extraction (SFE) [3], pressurized liquid extraction (PLE) [4] and microwave extraction (MAE) [5]. The employment of analytical-scale microwave-assisted extraction (MAE) has many advantages over other classical extraction techniques (Soxhlet, sonication or shakeflask extraction) like reduction of extraction time, reduction of solvent consumption, possibility of running multiple samples etc.…”

GC–MS determination of organochlorine pesticides in medicinal plants harvested in Brazil

“…In general, the analytical method involves the following stages: sampling, sample preparation, extraction, detection and data analysis, where the sample preparation could be considered a critical step. The official multiresidue pesticide methods recommend extraction of the pesticides with organic solvents, 8 clean-up by column chromatography 4,9,10 or gel permeation chromatography 8,11 and quantification by capillary GC-MS. [12][13][14] Since the recommended extraction procedure requires large quantities of toxic solvents, other extraction procedures have been reported, including, solid-phase extraction, 9,10,15,16 supercritical fluid extraction 17 and microwave assisted extraction coupled to solid phase microextraction. 18 With relation to current Brazilian legislation, which regulates the registration of phytopharmaceuticals, the determination of pesticides has not been included in the purity assay of herbal plants.…”