Ground MIP Particles

The traditional method for preparing MIPs yields a porous monolith that is ground and sieved into a fine powder. It is important to note that the capacity and selectivity of an MIP monolith are independent of the particle size. This is because the particles 

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MIPs selective for phenylalanine anilide have been evaluated as stationary phases in TLC [58], Glass backing plates were coated with mixtures of finely ground MIP particles and binders. The plates showed a preferential retardation of the enantiomer used as the print molecule (Fig. 17.13). The R[ values of both enantiomers on non-imprinted polymers were higher than those observed on the... 

MIP particles in CEC. Other groups have attempted to remove the need for problematic retaining frits by first packing the column with ground MIP particles and subsequently polymerizing polyacrylamides [30] or silicates [31] around these particles so they will not be eluted from the column. 

MIP are often generated as simple bulk polymers to be ground into fine particles, which are subsequently sieved and sedimented - admittedly a time-consuming process, which requires large amounts of solvents. The loss of fine polymer particles in the sedimentation procedure is also not negligible. The result usually is a polymer powder with particle sizes of a relative broad size distribution. After the template has been extracted, this material can be packed into LC-columns [17,29,30], CE-capillaries, or be used directly in the batch mode. 

In a different approach, Lin et al. have used particles derived from a ground MI-bulk polymer and mixed with a polyacryl amide gel for chiral separation. Using a polymer imprinted with L-phenylalanine, D-phenylalanine could be separated from the template with a separation factor of 1.45 [35]. Although the combination of MIP with capillary electrochromatography is still not widely used, the ability to separate enantiomers in nanoliter samples promises interesting developments for the future. 

Due to their specific molecular recognition properties, MIPs have found their main application in analytical chemistry. As outlined in the introduction, the common preparation method of MIPs as bulk polymers, which are subsequently crushed, ground and sieved to obtain particles, is not well adapted to achieve a high separation performance. Thus, the preparation of monolithic MIPs seemed particularly attractive for separation science due to the permeability properties, the easy in situ preparation and the absence of retaining frits. On the other hand, the use of the monolith format is still limited and the strategy of MIP monolith preparation has been little developed in recent years. 

The MIP was synthesised in methanol using a TRIM HEMA reporter ratio of 86 5.19 0.119, ground and wet sieved in water. Particles sized to 45-106 /rM were washed in a Soxhlet apparatus using a 7 3 v/v mixture of H20 MeOH for a minimum of 24 h, then with pure MeOH for at least 24 h. 

Shaping the MIPs. The use intended for the MIP will determine its shape. The most widely used technique consists of preparing a bulk polymer which is then ground and graded. The particles obtained (Fig. 12(1)) can then be used in various applications [68,102,103]. 

Although the majority of MIA assays reported have employed traditional noncova-lent vinyl/acrylate-based MIPs, fabricated in organic solvents as macroporous monoliths then ground and sieved into useful particles, there have been many innovations in both the composition of MIPs and their macromorphology ... 

Fine (<1 pm) particles Haupt et al. in their several assay designs for 2,4-D [23,51,52], have employed a 2,4-D-imprinted MIP prepared as amonolith and ground in the traditional manner, but utilized not the intermediate-sized ( 25 pm) particles as commonly done, but the finest particles. The fine particles had the same selectivity characteristics as larger particles, but the incubation times were reduced due to shorter diffusion distances, and handling was easier since the particles remained longer in suspension so could be pipetted more accurately. 

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