Automated cartridge exchanger

M Hedenmo, BM Eriksson. On-line solid-phase extraction with automated cartridge exchange for liquid chromatographic determination of lipophilic antioxidants in plasma. J Chromatogr 692 161—166, 1995. 

The automation of the use of disposable cartridges for solid-liquid extraction connected directly with a liquid chromatograph poses major techical problems which are, however, lessened by robotics. Although several partly automatic systems have been described [23-26], there is only one really completely automated system, which was reported recently [27]. It is an automated cartridge exchange module combined with a low-cost purge pump, a solvent selec-... 

Solid-phase extraction seems to be more suitable for multiresidue cleanup. This procedure has become the method of choice for isolation and/or cleanup of -lactam antibiotics from biological matrices, because it requires low solvent consumption, it is generally less time-consuming and labor-intensive, and offers a variety of alternative approaches that allow better extraction of the more hydrophilic -lactam antibiotics such as ampicillin. It is usually performed using reversed-phase Ci8 (69-71, 80-83, 90, 92-94, 99, 107, 112-116, 121-125) or Cg (103), anion-exchange (95, 124), and polar diol (95) or alumina (101, 113) sorbents. In recent applications, some workers demonstrated the potential of online solid-phase extraction in the determination of monobasic penicillins in bovine muscle tissues using a reversed-phase Cis 5 m cartridge and an automated... 

O. V. Olesen and B. Poulsen, On-hne fuhy automated determination of clozapine and desmethylclozapine in human serum by sohd-phase extraction on exchangeable cartridges and hquid chromatography using a methanol buffer mobile phase on unmodified silica , J. Chromatogr. 622 39-46 (1993). 

Solid-phase extraction (SPE) is a method of sample preparation that concen-Irates and purifies analytes from solution by sorption onto a disposable solid-phase cartridge, followed by elution of the analyte with a solvent appropriate for instrumental analysis. The mechanisms of retention include reversed phase, normal phase, and ion exchange. Traditionally, sample preparation consisted of sample dissolution, purification, and extraction that was carried out with liquid-liquid extraction. The disadvantages with liquid-liquid extraction include the use of large volumes of organic solvent, cumbersome glassware, and cost. Furthermore, liquid-liquid extraction often creates emulsions with aqueous samples that are difficult to extract, and liquid-liquid extraction is not easily automated. These difficulties are overcome with solid-phase extraction. Thus, solid-phase extraction was invented in the mid-1970s as an alternative approach to liquid-liquid extraction. 

In principle, there are no major differences between solid-phase extraction and liquid-liquid extraction, but SPE can avoid or reduce some of the disadvantages of liquid-liquid extraction. Thus, SPE can handle small samples and very dilute solutions, it overcomes the formation of emulsions, and can be easily automated. Furthermore, the sorbents that are commonly used are commercially available as cartridges. These sorbents are alumina, silica gel, reversed-phase silica gel, and various ion-exchange resins. It is also possible to pack different adsorbents in layers inside the same cartridge to give a sandwich-type extraction column. 

The use of two different phases can extend the range of compounds extracted. Three types are used, mixed mode, layered, and stacked phases. In the mixed mode, two different types of chemically bonded phases are mixed together in the cartridge. An example is a mixture of C8 and cation exchange particles. In the layered mode, the two different phases are packed, one on top of the other. Stacked phases use two cartridges in series to provide enhanced, separations. The first two modes are more readily adapted to automation since only a single cartridge is used. 

Hiemstra, M. and de Kok, A., Determination of A-methylcarbamate pesticides in environmental water samples using automated online trace enrichment with exchangeable cartridges and high-performance liquid chromatography, J. Chromatogr., 667, 155-166, 1994. 

Rainwater Automated rainwater collectors have been used in combination with IC for the determination of low-level concentrations of dissolved inorganic anions or cations. Due to the clean nature of the sample, online preconcentration of the analytes can be readily achieved using short ion exchange preconcentrator cartridges onto which large sample volumes can be loaded, prior to elution onto the appropriate separator ion exchange column. This approach is used for the ultratrace analysis of rainwater samples. 

A single multiresidue method was developed to determine 109 priority compoimds listed in the 76/464/EEC Coimcil Directive on Pollution of the EU [49]. For trapping analytes, automated off-line SPE with a polymeric sorbent "Oasis" 60 mg cartridge, was optimized. A multianalyte method for the confirmation and quantitation of 16 selected sulfonylurea, imidazolinone, and sulfonamide herbicides in surface water has been proposed [50]. This method is based on analyte extraction with a polymeric material (RP-102) and extract cleanup with a strong anion exchanger (SAX) cartridge stacked on... 

Solid—liquid extraction Can clean up complex specimens (plasma—serum), can preconcentrate analyte, can be used in multiple modes (ion exchange, hydrophobic, etc.), potential for automation—multiplex in multiwell format Individual solid-phase cartridges are expensive, not all potential interferents are removed, analyte preconcentration may require evaporation—reconstitution step Plasma and urine benadamustine and metabolites by LC—MS/MS [4]... 

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