br Experimental br Results and discussion In the presented

Experimental
Results and discussion In the presented study four samples of double-coated pellets each in three batches with different thicknesses of the second coat, composed of Eudragit® RL, Kollidon® 25 and PEG 400, were prepared. The semipermeable second coat was expected to prevent the enzyme leaching of carriers into the solution in which pellets were immersed during the detection. Moreover, due to this coating an improvement in color intensity change was expected together with a more distinctive difference between the color of the test solution and the created yellow color of the pellets during the detection in the case when the enzyme is not inhibited. All of these parameters are essential for ensuring fast, accurate and distinct detection of the cholinesterase inhibitors within liquids. Besides this, carriers intended as a filler for detection tubes should be an approximate size of 1 mm and spherical in shape for an optimal Cy7.5 maleimide(non-sulfonated) sale of color change and easy filling into the detection tubes. Suitable carriers must also show a good mechanical resistance to enable filling the detection tubes. The results of physical parameters of the prepared samples are summarized in Table 2. The equivalent diameter ranged from 1.09 to 1.14 mm, which is within the required size distribution of 0.8–1.25 mm. A slight increase in size is probably caused by increasing the thickness of the second coat. To determine the precise appearance of the carriers, SEM photos of the sample E2.5 were taken according to the methodology in the Section 2.8. From Fig. 1 it is obvious that the double coating is uniformly spread over the pellet core and remains intact during the analysis, which is a vital attribute to prevent leaching of reagents from pellets to a liquid media. Sphericity and Hausner ratio are parameters characterizing flow properties of carriers, which are important for filling the detection tubes. Sphericity can range from 0 to 1, where the sphericity between 0.8–1.0 means a sufficiently spherical shape [28]. According to Ph. Eur. 9, Hausner ratio of 1.00–1.11 corresponds with an excellent flow character of particles. In both cases the tested samples achieved excellent results. Easy filling into detection tubes, occupying only a small volume by carrier particles, forming a compact layer and facilitating easier observation of the color transition could be expected for all the samples. Measured values of pycnometric density showed a slight decrease with the increasing thickness of the second coat. Eudragit® RL used for the preparation of the second layer is commonly intended for controlling the release of drugs by diffusion through the coating. This polymer enables preparing homogeneous coatings without pores and it can be supposed that the used gas did not penetrate inside the pellets during the measurement. Fig. 1 confirms the theory of creating the second coating without pores. Thus the mentioned slight decrease probably means that the density of the second coat was lower than the density of the core and the first coat. Interparticular porosity indicates the amount of air gaps between the individual pellets and correlates with the flow properties of the carriers. The lower the values are, the less space the pellets occupy and create a more compact layer when filled into the detection tubes facilitating an easier detection. Interparticular porosity was almost similar for all samples varying from 40.35% up to 41.17%.