Base deactivation

A., Gauvrit,). Y., Lanteri, P., Veuthey, J. L. Simplification of a chromatographic test methodology for evaluation of base deactivated supports. Chromatographia 2002, 56, 665-671. 

Chepkwony, H., Vanderriest, I., Nguyo, ]., Roets, E., and Hoogmartens, J., Separation of erythromycin and related substances on base-deactivated re-versed-phase silica gel columns, /. Chromatogr. A, 870 (1 2), 227, 2000. 

Imazalil, OPP, and TBZ residues were determined using an HPLC system, consisting of a ternary HPLC pump attached to 250 X 4.6-mm-ID Hichrom RPB 5-/tm column with a 10 X 3.2-mm-ID guard cartridge column. The packing material of both columns was base-deactivated silica, fully endcapped with a bonded phase of Cg/C]8. The mobile phase was methanol/water at a flow rate of 1 ml/min at ambient temperature. Imazalil in the eluate was detected with UV detector at 204 nm a fluorescence detector was used to monitor OPP (excitation 285 nm, emission 350 nm) and TBZ (excitation 296 nm, emission 350 nm) (47). 

Chromatographic system (see Chromatography, in the general procedure (621) The liquid chromatography is equipped with a 305-nm detector and a 4.6 mm x 15-cm column that contains 5-/tm base-deactivated packing L7. The flow-rate is about 1.2 ml/min. The chromatograph is programmed as follows ... 

Organic bases Pyridine Separated on a base-deactivated C-18 or C-8 reverse phase column and detected by UV at 254 nm... 

Chromatographic column a stainless steel column, 0.25 m long and 4.6 mm internal diameter, packed with base-deactivated octadecylsilyl silica for chromatography R (5 pm particles). The column is maintained at a temperature of 40°C. 

A decision was also needed about the stationary phase to be chosen for the generic methods. Because we wanted to keep the run times as short as possible (within reason) the latest generation of base deactivated phases were investigated. These gave an excellent performance and were particularly resistant to peak tailing effects. The... 

After converting A -Phth-protected amines into the corresponding 2-(pyrrolidinocarbon-yl)benzamide derivative, Dieckmann reactions, ester hydrolysis, and transesterfication can be carried out. This strategy of pyrrolidine-based deactivation of phthaloyl-protected anoines followed by reclosure of the phthaloyl group has successfully been applied in the synthesis of (3-lactam antibiotics.P l... 

One approach to solving the problem of residual silanol interactions has involved improvements in the synthetic procedures for the production of hydrocarbonaceous stationary phases. One synthetic approach for the elimination of residual silanol groups involves the reaction of the bonded phase with a small silylating reagent such as trimethylchlorosilane which is presumed to have easier access to silanol groups than bulkier, long-chained chlorosilanes. An alternative, synthetic approach involves surface polymerization of the stationary phase, which is believed to reduce the accessibility of surface silanol groups to polar analytes in the mobile phase. Stationary phases produced by the former method are often referred to as end-capped and stationary phases produced by the latter method are sometimes called base-deactivated. ... 

Adsorption or chemisorption on column packing or on different hardware components. Increase mobile phase strength add competing base (for basic compounds) or use base-deactivated packing ensure no reactive groups are present use inert tubing and flow-path components, e.g., PEEK. 

Irreversible adsorption on active-sites (less than 90% yield) For basic compounds use end-capped, base-deactivated, sterically protected, high coverage, or polymeric reversed-phase for acidic compounds use endcapped or pol3mieric packing acidify mobile phase. 

Major improvements in hydrocarbon oxidation activity and overall thermal durability were achieved through the use of more palladium-rich formulations as lead disappeared from the fuel supply. Palladium is highly prone to lead-based deactivation. The dramatic increase in palladium in the late 1990s caused a significant supply-demand imbalance in the PGM markets in 2000, driving up palladium prices tenfold. The recent effort to reduce requirements for palladium without affecting hydrocarbon performance restored the market balance. 

Bogusz, M. Erkens, M. Maier, R.D. Schroder, I. Applicability of reversed-phase base-deactivated columns for systematic toxicological analysis. J.Liq.Chromatogr., 1992,15,127-150 [simultaneousbral-lobarbital, diphenhydramine, fluphenazine, imipramine, pentobarbital, salicylamide, secobarbital, thiopental, thioridazine]... 

Guard column 20 mm long C18 base-deactivated siUca (BDS) (Keystone)... 

Column 250 x 4.6 5 pm Zorbax Rx-C8 base deactivated octylsilane (Mac-Mod Analsdiical) Mobile phase MeCN 10 mM KH2PO4 adjusted to pH 4.0 with 1 M KOH 23 77 Flow rate 1... 

Inorganic oxide layers can be adjusted to a defined activity level by exposure to a defined gas phase in an enclosed chamber. This is best performed after sample application in a developing chamber that allows both conditioning and development of the layer in the same chamber (e.g. a twin trough chamber). Alternatively, separate conditioning and development chambers can be used. Atmospheres of different constant relative humidity can be obtained by exposure to the vapor phase in equilibrium with solutions of concentrated sulfuric acid or saturated solutions of various salts [100]. In the same way, acid or base deactivation is carried out by exposure to concentrated ammonia or hydrochloric acid fumes. 

BDS Base Deactivated Silica, (not activated = suitable for bases)... 

---