At-line coupling is also a useful a

At-line coupling is also a useful approach that facilitates automation, and hence it is stated here for comparison as listed
in Table 1. The coupling approach is based on the injection of the pretreated sample solutions using an auto sampler combined with transport unit for liquid handling. As shown in Fig. 4B (IV), the sample solutions are collected in vials prior to the injection by an auto sampler. A well-defined volume of sample solutions can be aspirated into the sample loop of the auto sampler by a metering pump, and then injected into an analytical column after the valve is switched to position 2. The approach is suitable for current automated SP techniques in multi-well-plate formats, such as LLE [125], SPE [150] and SPME [151], which typically run on generic liquid handling robotic systems [152]. These automated
techniques are often coupled with LC in an offline mode, in which the obtained sample solutions have to be transferred from the liquid handing system to the LC autosampler manually by an operator. In an at-line mode, the automated transfer of sample solutions is performed using commercially available robotic systems (e.g., from
the company of CTC PAL or Gerstel) equipped with transport units for liquid handling (e.g., a robotic programmable arm). These automated systems could be fully under software control, consequently improving the precision and accuracy significantly.