Cartridge systems, application

In the Automotive industry there is a trend towards complete automation of production lines. In the application of adhesives/sealants for gasketing, the principles of dispensing have normally been to use a pressure-time system, or alternatively a cartridge system with a robotic head. However, a faster system is to screen print an anaerobic on to the surface of a component. 

In Thermal spray processes the nature of the process was described here, applications to adhesion are presented. Thermal spray coatings for applications involving adhesion are in three general areas, metallic bond or anchor coating, ceramic bond coat, and sprayed polymer as the adhesive. In many cases, the surface modification by the deposition of a thermally sprayed coating is an alternative to environmentally hazardous methods. The thermal spray process is a dry process in which the effluent is collected in a dry cartridge system and usually recycled. 

Cartridge collectors perform very effectively in many different applications. Common applications of cartridge filter systems with pulse jet cleaning are comparable to baghouses described earlier. In addition to these applications, cartridge collectors can be used in any process where dust is generated and can be collected and ducted to a central location. 

These replaceable cartridges or packs are the most commonly used however, there are cartridges of wire mesh, sintered or porous metal which can be removed, cleaned, and replaced. Usually, the fine pores of the metal become progressively plugged and the cartridges lose capacity. They are often used for filtering hot fluids, or polymers with suspended particles, pharmaceuticals, and foods (liquids). In the case of polymers and other applications a special solvent and blow-back cleaning system may be employed. 

Some applications, however, cannot use the cartridge design, for example, when the operating environment is too hot for the seals. Another example is when minute leaks or the accumulation of traces of dirt at the lip seals cannot be tolerated (e.g., food processing machines). In these cases, bearings with specialized sealing and lubrication systems must be used. 

Metal-catalyzed cross-couplings are key transformations for carbon-carbon bond formation. The applicability of continuous-flow systems to this important reaction type has been shown by a Heck reaction carried out in a stainless steel microreactor system (Snyder et al. 2005). A solution of phenyliodide 5 and ethyl acrylate 6 was passed through a solid-phase cartridge reactor loaded with 10% palladium on charcoal (Scheme 2). The process was conducted with a residence time of 30 min at 130°C, giving the desired ethyl cinnamate 7 in 95% isolated yield. The batch process resulted in 100% conversion after 30 min at 140°C using a preconditioned catalyst. 

Sometimes orthogonal offline SPE steps were used prior to online SPE LC/MS/MS. These preparation steps were used to remove interference and concentrate samples. In an application to measure urinary N7-(benzo[a]pyren-6-yl)guanine (BP-6-N7Gua), a biomarker for exposure to polyaromatic hydrocarbons (PAHs), a two-step offline SPE was first performed using Sep-Pak C8 (Waters, Milford, Massachusetts) and Strata SCX (Phenomenex, Torrance, California) cartridges to obtain high sensitivity (Chen et al. 2005). The extracts were applied to an online reversed phase SPE LC/MS system. The lower limit of detection was 2.5 fmol/mL when 10 mL of urine was used. 

These systems have been used in many bioanalytical applications. A Prospekt system coupled with MS quantitated eserine N-oxide, a cholinesterase inhibitor, in human plasma for low level (4.5 mg) oral administration pharmacokinetic studies (Pruvost et al. 2000). After conditioning of the SPE cartridge (PLRP-S, Spark) with methanol (5 mL/min, 0.5 min) and water (5 mL/min, 0.5 min), a volume of 250 jj.L plasma plus internal standard was injected and washed (water, 1 mL/min, 3 min). The analytes were flushed out with 80 20 ammonium acetate (20 mM, pH 3.5 adjusted with formic acid) and acetonitrile (0.3 mL/min) and separated on a Zobax SB-CN column (150 x 2.1 mm inner diameter, 5 jim). A calibration range of 25 pg/mL to 12.5 ng/mL was achieved with a run time of 10.5 min. 

Because the instability of the N-oxide metabolite, which was subjected to decomposition during sample preparation (solvent evaporation during offline SPE), online SPE LC/MS became the method of choice for the application. Hsieh et al. (2004) built a system with two TFC cartridges and one analytical column, and another system with two TFC cartridges and two analytical columns for GLP quantitative bioanalysis of drug candidates. A Turbo C18 (50 x 1.0 mm, 5 /.mi, Cohesive Technologies), an Xterra MS C18 (30 x 2.0 mm, 2.5 /mi), and a guard column were used. Protein precipitation preceded injection. The cycle times for the two systems were 0.8 and 0.4 min. 

Online SPE LC/MS/MS is commonly used for bioanalytical applications in the pharmaceutical industry. Column switching systems and TFC systems are easy to build and control. Sophisticated commercial systems and SPE cartridges are readily available. Compared to offline sample preparation, the online approach can save time and labor. However, the development of online SPE bioanalytical assays remains analyte-dependent. Generic methods can be applied to many analytes. For extremely hydrophobic, hydrophilic, and ionic analytes at normal pH range and analytes with a variety of hydrophobicity and pKa values, analyte-specific methods must be developed. An understanding of the chemistry of the analytes and SPE is critical. 

---