Single Drop Microextraction SDME

The ultimate in miniaturization of LLE uses a single drop of immiscible liquid. The seminal work on this approach to LLE (Jeannot 1996, 1997) was based on earlier work (Liu 1995) on partitioning of gas molecules into liquid 

While not thus far exploited for LLE, it is interesting to note experiments (Bogan 2002, 2004) in which charged droplets ( 0.27 xL) are produced from a piezo-electric atomizer and are levitated in the electric field of a modified quadrupole ion trap (Section 6.4.5) operated at atmospheric pressure. Thus far the main analytical application of this technique (Bogan 2004) has involved wall-free preparation of micrometer-sized sample spots for fmol detection limits of proteins by MALDI-MS, but extension to LLE in such levitated droplets is a possibility. 

1c Dispersive Liquid-Liquid Micro extraction (DLLE) 

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To enhance extraction efficiency in the SME system (also called single-drop microextraction [SDME]), He and Lee developed a procedure termed liquid-phase microextraction (LPME),89 which, in its static mode, resembles the SME system. 

Saraji and Bakhshi [197] performed a trace analysis of phenolic compounds in water by coupling single-drop microextraction (SDME) with in-syringe derivatization of the analytes and GC-MS analysis. The analytes were extracted from a 3 mL sample solution using 2.5 pL of hexyl acetate. After extraction, derivatization was carried out in syringe barrel using 0.5 pL of N,0-bis(trimethylsilyl)acetamide. In order to investigate the applicability of the proposed SDME method in real-sample analysis, they have performed... 

LPME or single-drop microextraction (SDME) involves extraction of organic contaminants from an aqueous donor solution into a microdrop (typically 1 jjlL) of an organic acceptor solvent suspended from the tip of a microsyringe. After extracting for a preset period of time, the microdrop is retracted back into the microsyringe and transferred to a gas chromatograph for further analysis [114]. Various types of pesticides have been extracted by LPME from water samples for determination by GC [115-121]. Recently, an automated d)mamic liquid-liquid-liquid microextraction (D-LLLME) system was developed for the extraction of phenoxy acid herbicides from environmental waters and their determination by LC [122]. 

Another injection technique, showing high similarity to SPME is called single drop microextraction (SDME). It this technique a drop of solvent is suspended at the end of a microsyringe needle in the headspace phase over the sample solution. A drop has a higher surface than the fiber in SPME, but instability of the drop is a factor that should be taken into account, to ensure reproducibility of the results. The main advantage of this technique is that it is less expensive than SPME. The main drawback is the higher detection limit for RS compared to SPME. ... 

Since the extraction medium is in tlie form of a single drop, this type of LPME has also been termed as single-drop microextraction (SDME). A microsyringe is commonly used in SDME and has two functions as a microseparatoiy funnel in the extraction step, and as device to further inject the analytes into GC or HPLC. The stability of the small drop is the key to achieve successful extraction recoveries the higher the size of the drop during long extraction times, the lower the obtained detection limits. 

Solvent Liquid/liquid extraction (LLE) Steam distillation/extraction (SDE) Solvent microextraction (SME) - SDME - LPME - DLLME Headspace-solvent-microextraction (HS-SME) - Headspace single-drop microextraction (HS-SDME) - Headspace liquid phase microextraction (HS-LPME) ... 

LLLME, (Hou and Lee 2003), liquid phase microextraction, LPME, (Tao et al. 2009), LLE-SPE tandem extraction (Alaejos et al. 2008) and headspace single-drop microextraction, HS-SDME, (Zhou and Ye 2008), have been reported for the extraction of aromatic amines from environmental water samples. 

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