Teflon Capillary Research Articles

On-column catalysis of hydratization equilibria during liquid chromatographic analysis of acetaldehyde and formaldehyde

The aldehydes were separated by reversed phase chromatography on a polymer-based support. Acid catalysis on the column was needed to obtain sufficiently fast equilibrium between acetaldehyde and its hydrate. Deuterium labeled acetaldehyde (D3) yielded complete separation from the nonlabeled compound, probably due to a difference in hydratization. Fluorescent products were obtained by reaction between the aldehydes and a mixture of ammonia and dimedone (5.5-dimethyl-1.3-cyclohexanedione). The fluorescence was detected at 460 nm after excitation at 390 nm. A reaction time of 42 seconds at 90°C in a knitted teflon capillary produced detection limits of 0.5 and 1 ng for acetaldehyde and formeldehyde, respectively. A method for preparation of a stable reagent with low background fluorescence is described.

EFFECT of DIFFERENT TUBE MATERIALS ON the STEADY SHEAR TUBE FLOW of SEMI‐SOLID FOODS

ABSTRACTThe effect of different tube materials was studied using galvanized steel, PVC, teflon and glass capillaries on tomato paste, apple sauce, ketchup and mustard as typical semi‐solid food materials. In the shear rate range of 10 to 1000 s−1 studied apple sauce and mustard showed the most pronounced effect which was wall material and shear rate dependent.

Integrated air sampling technique using a glass syringe

Abstract A simple, inexpensive integrated sampling method using a glass syringe has been developed for air pollution measurements. The syringe is mounted vertically so that the weight of the plunger provides a constant suction to a Teflon capillary of 20–500 cm length. Uniformity and reproducibility of sampling rate are easily attained with most commercial syringes. Sampling duration from 5 to 60 minutes can be predetermined from the dimensions of the capillary using the Hagen‐Poiseuille equation. The method was tested both indoors and outdoors and found to be useful for routine air sampling.

Capillary zone electrophoresis: Effect of physical parameters on separation efficiency and quantitation

AbstractSeparation efficiency in capillary zone electrophoresis was examined as a function of capillary length and diameter as well as solute concentration for a borosilicate glass capillary/phosphate buffer system. Electroosmotic flow coefficients in borosilicate, fused silica, and teflon capillaries were measured over the useful operating pH range of 3–8 at constant applied power (0.333 W). Sample introduction by a simple, low‐dispersion electromigration method was found to be a reliable procedure for solute quantitation.

An HF-Resistant Sample Introduction System for the Inductively Coupled Plasma

A sample introduction system constructed of materials completely resistant to HF was developed for analysis of HF-containing samples. A machined graphite injector tube, polytetrafluoroethylene (PTFE) spray chamber, and cross flow nebulizer containing PTFE capillaries were employed. The arrangement is completely compatible with commercial ICP systems and can be interchanged readily. The nebulizer efficiency and memory effect were studied and compared with a conventional system. Analysis of silicon in commercial HF acid was performed.

Modification and optimization of a 50 MHz inductively coupled argon plasma with special reference to analyses using organic solvents

The torch and nebulizer of an existing argon ICP system were modified and the system was (re-) optimized for aqueous and organic liquids. The paper describes the design considerations and construction of (1) a new, streamlined torch including a torch base used in this study, where a demountable rather than a prealigned version of the torch was preferred; (2) a cross-flow pneumatic nebulizer with adjustable teflon capillaries including a spray chamber with flow spoiler, concentric aerosol pick-up tube, and “U” tube with unequal legs to smooth the flow of wasted liquid to the drain. The (re)-optimization of the ICP system for analysis of aqueous solutions with inorganic matter or with both inorganic and organic matter is discussed in the light of earlier work in this laboratory regarding the selection of “compromise conditions” and the choice of representative spectral lines and measurement criteria for establishing such compromise conditions. In this context the authors consider the concepts of norm temperature and “hard” and “soft” lines, as well as recent results of measurements of spatial distributions in ICPs. The authors further describe experiments aimed at the optimization of the operating conditions of an “organic ICP” using methyl isobutyl ketone (MIBK) as organic solvent. Trends of net line and background signals and signal-to-background ratios with the ICP parameters (power; outer, intermediate and carrier gas flow; observation height; liquid feed rate) are reported, and a rational choice of compromise conditions for the ICP is argued. Performance characteristics of the modified ICP system, such as detection limits, precision and interference level, achieved under compromise conditions, have been communicated in a previous report [ Spectrochim. Acta 36B, 1031 (1981)] to demonstrate the capabilities of the system for analysis of aqueous solutions. Detection limits in MIBK and oil diluted in MIBK are reported in the present work as an illustration of the performance of the system when used for organic liquid analysis.

AUTOMATED SYNTHESIS OF 11C-LABELLED RADIOPHARMACEUTICALS

Abstract This article describes a method by which about a hundred mCi of different radiopharmaceuticals (imipramine, chlorpromazine, nicotine or methionine) may be prepared in 30–35 min with no irradiation risk to the operators. All operations (preparation of precursor, methylation of the monodesmethyl derivative, purification and sterilisation of the end product) are carried out in a closed shielded hood. The passage of fluids from one reaction tube to another through flexible teflon capillaries is controlled by electrovalves and purification is achieved by HPLC. The end products are chromatographically pure, sterile and apyrogenic. Their specific radioactivity at the time of use averages 500 mCi/μmol (maximum 1.0 Ci/μmol).

Automated synthesis of 11C-labelled radiopharmaceuticals: Imipramine, chlorpromazine, nicotine and methionine

This article describes a method by which about a hundred mCi of different radiopharmaceuticals (imipramine, chlorpromazine, nicotine or methionine) may be prepared in 30–35 min with no irradiation risk to the operators. All operations (preparation of precursor, methylation of the monodesmethyl derivative, purification and sterilisation of the end product) are carried out in a closed shielded hood. The passage of fluids from one reaction tube to another through flexible teflon capillaries is controlled by electrovalves and purification is achieved by HPLC. The end products are chromatographically pure, sterile and apyrogenic. Their specific radioactivity at the time of use averages 500 mCi/μmol (maximum 1.0 Ci/μmol).

The Tuned Pipeline - A Link between Small Accelerators and Nuclear Medical Needs

Short-lived radioactive gases are produced in thick high pressure gas targets for ultimate use as medical imaging agents. Small Teflon capillaries have been used to span the 500 m distance between a Van de Graaff accelerator and a nuclear medicine department. Theoretical calculations model the gas flow through these capillaries for the tuned condition of highest specific activity at 1 atmosphere output pressure. These results compare favorably with experimental data and provide the foundation for a pipeline to a new hospital facility 3000 m away.

Pure Oxygen Fixed Film Reactor

The aerobic media trickling filter is compared with other biological processes. It is feasible and functions under organic loadings higher than activated sludge and trickling filter plants. The process is applicable for domestic sewage. Nitrification occurred at combined low organic and hydraulic loadings. Oxygen application rates in this process were comparable to the oxygen activated sludge process. The sludge yield coefficients were approximately the value reported for the high-rate trickling filter, however, the process had higher design organic loadings. A reactor was constructed containing Teflon capillaries pressurized with pure oxygen. With flow outside the Teflon tubings, they became covered with a biological film. Oxygen was provided by diffusion through the walls of the tubing. The device provides more than 90% BOD removal at high organic loadings.

Etude polarographique de l'antimoine(III) et (V) dans le fluorure d'hydrogène anhydre et dans ses mélanges avec l'eau

The electrochemical behaviour of Sb(III) and Sb(V) in water–HF mixtures (2.5 to 50% HF) and in anhydrous HF is described. A Teflon capillary dropping mercury electrode is proposed for polarographie investigations in these fluorinated media. It is shown, by classical or puise polarography, that Sb(III) can be reduced to Sb(0), as in acidic non-fluorinated media. The electrochemical reaction becomes reversible by addition of Cl−, Br− or I−. Sb(V) is not electroactive in the various HF-media, except when it is introduced as the SbCl5. In this case, the two polarographie waves of Sb(V) disappear with time because of SbF6− formation. Analytical applications to the determination of Sb(III) in water–HF and in anhydrous HF are discussed.

Field evaluation of gossyplure, the synthetic sex pheromone of Pectinophora gossypiella (saund.) (Lepidoptera, Gelechiidae) in Malawi

AbstractThe synthetic sex attractant of the pink bollworm of cotton, Pectinophora gossypiella (Saund.) (Lepidoptera, Gelechiidae), is a mixture of (Z, Z) and (Z, E)-7, 11-hexadecadien-l-ol acetate, referred to as gossyplure (Hummel et al., 1973). Field trials in the Lower Shire Valley, Malawi, have shown that of various mixtures tested, 55–60% of the (Z,Z) isomer in a mixture of the two acetates gives maximum field attraction. The catches of both pink bollworm males and males of the red bollworm of cotton, Diparopsis castanea Hmps., in pheromone traps are not affected by the release of mixtures of the pheromones of both species together. Dual-purpose sex pheromone traps may therefore be used to monitor both pest species at the same time. A simple omnidirectional flat disc trap is as efficient in trapping pink bollworm males as more complex designs. Release of gossyplure from a sealed 2·5 ml polyethylene vial or from a Zoecon beem-polyethylene vial is more efficient than from narrow-bore teflon capillary. Presence of the antioxidant 2,6-di-tert-butyl-P-cresol at 8·4% w/w gossyplure does not increase the attractive life of the pheromone in the field. Considerable numbers of the Angoumois grain moth Sitotroga cerealella (Ol.) (Tineidae), together with a new species of gelechiid, were occasionally caught by gossyplure lures in cotton fields. Catches of pink bollworm are not influenced by moonlight or trap colour but are significantly influenced by trap area. Maximum catches of males occur between midnight and 04.00 h in June and between 01.00 and 05.00 h in August.

Development of a reliable gas-jet transport system for use at the Oak Ridge isochronous cyclotron

In a previous paper transport yields of recoil nuclei produced in heavy-ion-induced reactions through capillaries were reported. These studies have now been extended to develop a reliable gas-jet-capillary transport system for use in conjunction with the heavy-ion beams available at the Oak Ridge isochronous cyclotron. Several additives to the helium gas were used and tested for their effectiveness to increase the transport efficiency. With water as the additive and a 10 m teflon capillary, i.d. of 1.3 mm, connecting the reaction and collection chambers an efficiency of ≈20% was measured. Under similar conditions an upper limit of ≤10 s was determined for the transport time. [However, with an annular Si(Au) α-detector it was possible to observe 162W, T 1 2 ≤0.25 s .] Also, the efficiency of the system was found to be remarkably constant; during a 7 h period it varied only by about 10%. Most of the tests and developments were made as part of experiments that had to do with short-lived nuclei. As part of this paper, therefore, we describe some of these experiments so as to illustrate the versatility and usefulness of the capillary transport system.

The measurement of the absolute transport efficiency for recoils from heavy ion reactions with He-JET systems

The complex problems involved in the transport of reaction recoils with He-jet systems have been investigated. The recoils 149,150,151Dy produced in the reactions 141Pr( 14N; 6, 5, 4n) were stopped in He gas and transported with the He flow through teflon, stainless steel, and glass capillaries. From the recoils knocked out of the target, 65% were transported through a 0.86 mm i.d. teflon capillary of 5 m length, 75% through a 2.25 m stainless steel capillary. The dependence of the transport efficiency on various parameters was investigated. The transport efficiency was increased by a small amount of carbon tetrachloride injected into the target chamber. In order to transport the reaction products from the high pressure region necessary to stop the recoils into a low pressure region where in future experiments an ion source can be operated, various glass-capillary-skimmer systems and also a double vacuum chamber evacuated by booster jet pumps have been tested. With the glass-capillary-skimmer system and using differential pumping with mechanical pumps only, about 30% of the recoils were brought into a region with a 3 × 10 3 times smaller pressure. Using two booster pumps and the double vacuum chamber with one 1.5 mm brass skimmer, 46% of all the recoils were introduced into the second vacuum chamber where the pressure is 10 6 times smaller than in the target chamber. The opening angle of the cone into which the recoils from the He-jet are emitted has been measured by radiograms to be 3°. The double vacuum chamber was put on high potential during the operation without the occurrence of a gas discharge.

Electrokinetic studies on fibrinogen. IV. The effect of thrombin and heparin on the fibrinogen-solid interfacial potential

Streaming-potential studies were done to evaluate the effect of heparin and also thrombin on the ζ-potential of fibrinogen solutions in contact with capillary surfaces. It is found that unclotted mixtures of thrombin and fibrinogen streamed through clean capillaries have ζ-potentials higher than the fibrinogen in the pH range of 5.5–8. Polymerizing mixtures have ζ-potentials slightly below those for fibrinogen. Heparin is found to increase the ζ-potential of fibrinogenated Teflon and Pyrex capillaries. It is demonstrated that the previous history of the capillary surface influences the extent of these increases. Higher ζ-potentials for mixtures of heparin and fibrinogen are obtained with clean surfaces than with coated capillaries at several pH values. The effect of increasing the heparin concentration in the mixtures streamed through clean capillaries for several fibrinogen concentration levels at pH 7.4 was investigated. It is observed that the ζ-potentials increase to a maximum and remain constant thereafter as the heparin concentration is increased. These results are discussed in terms of electrostatic interaction and a mass-action mechanism.