The relative standard deviations (RSDs) of the retention time for intra-day (n = 5) and inter-day (n = 3) runs and between columns (n = 3) are less than 0.39%, 1.22% and 3.87%, respectively. This novel type of fluoro-functionalized stationary phase represents a great application potential in organic fluorides separation field.We describe the design and performance evaluation of a portable gas chromatograph suitable for the analysis of volatile organic and odorous compounds at trace levels. The system comprises a carbon nanotube sponge preconcentrator, an electronic pressure control (EPC) unit, a temperature-programmable column module, and a fast-response photoionization detector. A built-in tablet computer controls instrumental parameters and chromatogram display functions. The compact GC with dimensions of 35 cm (l) × 26 cm (w) × 15 cm (h) is self-contained, weighing less than 5 kg without a battery pack, and uses no auxiliary compressed gases. Our design has three main advantages over conventional portable GCs recharging configuration of ambient air as the carrier gas using a miniature diaphragm pump, precise control of column flow by the built-in canister and EPC system, and rapid thermal desorption of the preconcentrator facilitated by intrinsic resistivity of the carbon nanotube sponge. A 30 m, 0.28 mm I.D. capillary column operated at a head pressure of 14 psi provided a peak capacity of 55 for a 10 min isothermal analysis. The temperature-programmability feature could decrease the analysis time of less than 5 min for vapor mixture of benzene, toluene, ethylbenzene, and o-xylene. More than a 100-fold increase in sensitivity by preconcentrating a sample adsorption volume of 90 mL resulted in improved detection limits of 0.13 (benzene), 0.20 (toluene), 0.23 (ethylbenzene), and 0.28 (o-xylene) ppb (v/v). Our instrument displayed good stability and reproducibility of retention times ( less then 0.14% RSD) and intensities ( less then 4.5% RSD) for continuous measurements using the preconcentrator over 10 h. Thus, continuous and on-site determinations of trace volatile organic compounds in air samples with this instrument appear feasible.Polychlorinated dibenzo-p-dioxins and furans are environmentally persistent and highly toxic compounds. 136 chlorinated dioxins and furan congeners contain at least four chlorine atoms and pose a complex separation challenge in environmental and biological matrixes. The complexity arises from the dioxin and furan molecules with substitutions at positions 2, 3, 7, and 8, which are toxicologically relevant but are not easily separated from the other non-/less toxic congeners. Many regulatory methods require the use of two columns with different polarities or selectivity for dioxin analysis. The most common confirmation column pair is a (5% phenyl)-methylpolysiloxane and a (biscyanopropyl-/ cyanopropylphenyl)-methylpolysiloxane. These phases are required in USEPA-1613 for 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran specificity. However, other column phases, such as the Rxi-17SilMS and the Rtx-Dioxin2, offer alternatives to the traditional column pairing and provide a similar or better separation of 2,3,7,8-substituted congeners. This study compares four columns for dioxin analysis the Rtx-Dioxin2, Rxi-17SilMS, Rxi-5SilMS, and Rtx-2330. All columns used in this study are capable of meeting the requirements for dioxin analysis required by USEPA-1613. However, the Rtx-Dioxin2 demonstrated improved selectivity for a wider range of dioxin compounds than the Rxi-5SilMS. The Rtx-Dioxin2 is capable of resolving 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran from common interferants better than the Rxi-5SilMS and can be used as a confirmation column with either the Rtx-2330 or Rxi-17SilMS.The high cost of protein A resins drives the biopharmaceutical industry to maximize its lifetime, which is limited by several processes, usually referred to as resin aging. In this work, two model based strategies are presented, aiming to control and improve the resin lifetime. The first approach, purely statistical, enables qualitative monitoring of the column state and prediction of column performance indicators (e.g. yield, purity and dynamic binding capacity) from chromatographic on-line data (e.g. UV signal). The second one, referred to as hybrid modeling, is based on a lumped kinetic model, which includes two aging parameters fitted on several resin cycling experimental campaigns with varying cleaning procedures (CP). The first aging parameter accounts for binding capacity deterioration (caused by ligand degradation, leaching, and pore occlusion), while the second accounts for a decreased mass transfer rate (mainly caused by fouling). The hybrid model provides important insights into the prevailing aging mechanism as a function of the different CPs. In addition, it can be applied to model based CP optimization and yield forecasting with the capability of state estimation corrections based on on-line process information. Both approaches show promising results, which could help to significantly extend the resin lifetime. https://www.selleckchem.com/products/amg-900.html This comes along with increased understanding, reduced experimental effort, decreased cost of goods, and improved process robustness.Fixed dose combination (FDC) of tenofovir disoproxil fumarate (TDF) and lamivudine (3TC) is one of the most preferred FDC for the treatment of acquired immunodeficiency syndrome (AIDS)/human immunodeficiency virus (HIV) infection. To the best of authors' knowledge there are no reported methods for chiral purity estimation of both drugs simultaneously from a FDC. The current study was focused on the development of a single chiral method uisng supercritical fluid chromatography (SFC) for separation of stereoisomers of TDF and 3TC combination employing design of experiment (DoE) approach. Method development was planned in three steps by using different experimental designs for each step. I-optimal, Taguchi orthogonal array and face-centred central composite designs (CCD) were employed for primary parameter selection, secondary parameter screening and final method optimization, respectively. All six stereoisomers were separated in a 10 minute run on Chiralpak IA column with carbon di-oxide /methanol (containing 0.