Cartridge column format

Lately, chromatography using laboratory-made open columns for cleanup is being replaced by the increasingly popular SPE, where cartridges ( columns ) in ready-to-use format are employed, resulting in an improved batch-to-batch reproducibility. 

The first MISPE protocol reported in the literature [18] involved the use of an imprinted dispersion polymer in a column format, for the selective enrichment of pentamidine (1) in urine. In this case the high selectivity of the polymer allowed the analyte to be detected directly in the eluate without the need for any further chromatographic separation (entry A in Tables 15.1 and 15.2). In view of the high selectivity of MIPs, this is a viable approach that brings the benefits of shorter analysis times and simpler instrumentation. In most cases, however, MISPE has been used prior to a chromatographic separation step. The MIP has been applied in a batch-wise extraction [23] or in columns or cartridges [20-22,24-26,33]. 

Fig. 2 (A) Extrelut column for LLE (B) SPE cartridge (C) SPE cartridge, disk format (D) 96-well extraction plate and (E) SPME device.

The optimum use of SPE procedures requires investigation of different stationary phases, their masses, the volume of conditioning, sample load, wash, elution solvents, and the sample size. These variables are readily studied in column format. But it is costly or inconvenierit to use only a fraction of the 96 wells to perform all the studies. Hence, modular well plates have been developed that have small removable plastic SPE cartridges that fit tightly in the 96-hole base plate, and only a portion needs to be used to develop a method. 

The most common and diverse approach to cleanup (and extraction of water samples) in pesticide residue analysis is SPE. Over the last 20 years, improvements and diversifications in SPE formats, sorbent types, and apparatus have made SPE a widely used approach for a variety of applications, including the analysis of pesticide residues. SPE cartridges or disks can be likened to low-resolution HPLC columns in that similar stationary and mobile phases are used. A typical particle size in SPE is 40 pm, and the plastic cartridges are generally packed with 0.1-1 g of sorbent in plastic tubes. The choice of reversed-phase, normal-phase, and ion-exchange media in SPE is very diverse, and Table 2 lists some of the more popular SPE applications for the cleanup of pesticides. 

Format Stainless steel column Plastic cartridge... 

Flexible formats. Because they do not swell, silica gels can be packed into a variety of flow-through formats such as HPLC columns, flash cartridges and well plates. 

After the optimization of these conditions, by adding an azide to the input stream it was possible to synthesize a range of substituted triazoles in a heterogeneously catalysed three-component reaction (Scheme 18). After the CFC, the stream was passed through a column containing a resin-immobilized copper-based catalyst, which was used in a previous work by the same authors to successfully catalyze the formation of triazoles from alkynes and azides [44]. An immobilized thiourea-containing cartridge was subsequently used to remove any leached Cu catalyst. In a similar way as for the alkynes production, the series of resins was used to purify the product. 

It is interesting to mention that occasionally one may use batch MIP extraction instead of the MISPE, i.e., instead of the column or cartridge format, even with real samples [40]. 

SPE sorbents are commercially available in three formats contained within cartridges, in columns fashioned like syringe barrels, or in disks... 

The use of SPE cartridges allows a considerable simplification of the work-up procedures, avoiding liquid-liquid extractions and tedious chromatographic columns. Moreover, parallel processing is possible, because prepacked 48- and 96-well format plates with different sorbent fillings are commercially available. 

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