Column packing methods evaluation

EPA. 1986b. Gas chromatography/mass spectrometry for semivolatile organics packed column technique. Method 8250. In Test methods for evaluating solid waste. Washington, DC U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1-30. 

One of the popular methods for evaluating effective diffusivities in heterogeneous catalysts is based on gas chromatography. A carrier gas, usually helium, which is not adsorbed, is passed continuously through a column packed with catalyst. A pulse of a diffusing component is injected into the inlet stream and the effluent pulse recorded. The main advantages of this transient method are its applicability to particles of arbitrary shapes, and that experiments can be carried out at elevated temperatures and pressures. Haynes [1] has given a comprehensive review of this method. 

In order to develop monographs for new drugs the EP, USP, and JP require validation data and analytical results for production batches of drug substance or drug product that are consistent with ICH guidelines. The EP has adopted a policy of transparency with respect to validation data this means that key aspects of the validation may be published or made available upon request. Key data may include the brands of column packing materials that have been evaluated or the names of the related compounds for which the method has been validated. Such a policy allows users to better understand the scope and limitations of particular methods. 

Modes of HPLC other than GPC can be used to evaluate polymer mixtures, copolymer composition, and to analyze additives. As indicated in Fig. 8 and in Secs. II.A and II.D, for this work a number of changes are made to the system, especially the type of column and detection methods. The mechanism of separation is no longer exclusion, in which no adsorptive interaction between the sample components and the column packing material is tolerable. Instead, there is deliberate adsorptive interaction between the samples and the column packing in order to achieve separations based on differences in chemical composition of the sample components, independent of molecular size. Sec. III.C. 

Danckwerts et al. (D6, R4, R5) recently used the absorption of COz in carbonate-bicarbonate buffer solutions containing arsenate as a catalyst in the study of absorption in packed column. The C02 undergoes a pseudo first-order reaction and the reaction rate constant is well defined. Consequently this reaction could prove to be a useful method for determining mass-transfer rates and evaluating the reliability of analytical approaches proposed for the prediction of mass transfer with simultaneous chemical reaction in gas-liquid dispersions. 

The silanophilic character of 16 reversed-phase high-performance liquid chromatographic columns was evaluated with dimethyl diphenycyclam, a cyclic tetraza macrocycle [101]. The method is rapid, does not require the removal of packing material, and uses a water-miscible solvent. The results demonstrate two points first, cyclic tetraza macrocycles offer substantial benefits over currently used silanophilic agents second, the method can easily differentiate the performance of various columns in terms of their relative hydrophobic and silanophilic contributions to absolute retention. 

The optimized operating conditions for each analytical method including the detector system of choice are reported in Table II. The reported columns and operating conditions yield satisfactory peak shapes and resolution of all the potential interferents evaluated for HCCP and HCBD. Two potential interferents—tetrachloro-l,2-difluoroethane and 1,2-dichloroethane— could not be separated from 1,2-DCP with conventional packed columns. Tetrachloro-l,2-difluoroethane, a compound with physical properties similar to 1,2-DCP, is not likely to be found with... 

---