Matching Fluid Research Articles

A lamp light-emitting diode-induced fluorescence detector for capillary electrophoresis

A light-emitting diode-induced fluorescence detector (LED-FD) for capillary electrophoresis was constructed and evaluated. A lamp LED with an enhanced emission spectrum and a band pass filter was used as the excitation light source. Refractive index matching fluid (RIMF) was used in the detection cell to reduce scattering light and the noise level. The limit of detection (LOD) for fluorescein was 1.5 nM (SNR = 3). The system exhibited linear responses in the range of 1 × 10 −8 to 5 × 10 −6 M ( R = 0.999). Application of the lamp LED-FD for the analysis of FITC-labeled ephedra herb extract by capillary electrophoresis was demonstrated.

Effective High-Density Wellbore Cleaning Fluids: Brine-Based and Solids-Free

Summary Displacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water-wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing, and cement liners. In many situations, the negative differential pressure cannot be tolerated, and the risk of failure at the liner top, etc., is increased—especially, if the wellbore has not been pressure-integrity tested. Additionally, with increasing rig/spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates. To overcome the density limitation of these cleaning fluids, conventional techniques, such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (e.g., water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is used. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency. Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology. This paper describes the field applications of new brine-based, high-density, solids-free cleaning fluids in balanced-displacements in deepwater and offshore shelf wells. The new high-density fluids were based on new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, a maximum pumping pressure of more than 9,000 psi was expected for conventional water-based displacement but was reduced to a little more than 3,000 psi with the new design. High-density cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and used successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

Development of a Microfabricated Optical Bend Loss Sensor for Distributive Pressure Measurement

A flexible high-resolution sensor capable of measuring the distribution of pressure beneath the foot via a microfabricated optical waveguide system is presented. The uniqueness of the system is in its batch fabrication process, which involves a microfabrication molding technique with polydimethylsiloxane (PDMS) as the optical medium. The sensor manufacturing technique is described in detail, the optical performance of the waveguides is quantified and the effect of using a matching fluid to improve fiber-coupling efficiency is demonstrated. Mechanical loading tests were performed on a 4 x 4 array with a 2-mm spacing between sensing elements. Loading displacement curves were obtained using a 0 to 0.4 mm triangle loading profile. A force of 0.28 N applied to one of the sensing elements produced a displacement of a 0.325 mm and 39% change in the output light intensity. Multiple loadings were conducted to demonstrate the repeatability of the sensor. A force image algorithm with a two-layer neural network system was used to identify four load magnitudes and four different shaped applicators. All four shapes were successfully identified with the neural network.

A glycerol assisted light-emitting diode-induced fluorescence detector for capillary flow systems

A glycerol assisted light-emitting diode (LED)-induced fluorescence detector (IF) for capillary flow systems was constructed and evaluated. A blue LED was used as the excitation source, and optical fibers (OF) were used to transmit the excitation light and collect the fluorescence. A commercial available 5-port manifold was used as detection cell, where the capillary tube and the OF were fixed into the manifold. The precision of the holes on the manifold ensured a self-alignment of optical path. A refractive index matching fluid (RIMF)-glycerol was used to eliminate the interfaces between the OF and the LED, as well as between the fused silica capillary and the transmitting/collecting fiber. The enhancement of excitation light led to 2.8-folds improvement on the signal-to-noise ratio. The use of RIMF also eliminates focusing effect of the capillary wall and reduces both the excitation light directed to the detection cell and background signal, resulting in reduction in the fluorescence intensity and noise level. The intensity was reduced to 47–63% for laser and 60–77% for LED, respectively, for capillaries with i.d. from 50 to 250 μm; while the noise level was reduced to 1/3 when RIMF was used for both laser and LED on the tested capillaries. About 5.6-fold enhancement in signal-to-noise ratio was obtained in total. The detection limit of the LED-IF for fluorescein isothiocyanate (FITC) was 4 nM. Application of the LED-IF for the analysis of FITC-labeled amino acids by electrophoresis was demonstrated.

3D Imaging of particle motion during penetrometer testing

We present the results of direct observation of material rearrangement due to penetration of a solid rod (penetrometer) through a granular medium. Two different techniques and their advantages are discussed in this paper. We investigate the motion of material within the bulk around the rod. Transparent, polydisperse, and irregularly shaped silica particles immersed in index matching fluid are used for detailed imaging of the interior of a granular pile. Motion of material is observed by confocal microscopy from the bottom boundary up to 100 particle diameters in height. Image analysis indicates that rearrangements spread furthest not directly under the penetrometer but in a ring around the penetrometer. In addition, the direction of preformed stress chains in the material influences the particle rearrangements. Material compressed from one side exhibits anisotropic particle rearrangements under penetrometer testing. Laser sheet scanning allows for direct imaging of individual particle motion with greater accuracy, but works best for spherical particles only.

Two-Dimensional Radio Frequency Tomography

A new formalism for scalar tomographic inversion is developed for two-dimensional radio frequency tomography. A least squares minimization of the difference between predicted and measured data is performed in order to obtain the lossless permittivity distribution. The novelty of the method is twofold. First, a multifrequency near-field two-dimensional scattering forward problem is solved via Richmond's moment method. Second, the tomographic inversion is regularized using a roughness constraint on the model permittivity. The algorithm has been tested with synthetic data. The experimental setup for acquiring the relevant data in a real-world application (viz. in situ testing of lumber quality) is under development. It is anticipated that the algorithm will work equally well on the experimental data. In the tests, the relative lossless permittivity was determined from synthetic scattered multifrequency transverse magnetic data, which had been corrupted by additive Gaussian noise. The method was able to recover the location and magnitude of permittivity anomalies without immersing the target prism in a matching fluid

Adaptive-mesh-based algorithm for fluorescence molecular tomography using an analytical solution

Fluorescence molecular tomography (FMT) has become an important method for in-vivo imaging of small animals. It has been widely used for tumor genesis, cancer detection, metastasis, drug discovery, and gene therapy. In this study, an algorithm for FMT is proposed to obtain accurate and fast reconstruction by combining an adaptive mesh refinement technique and an analytical solution of diffusion equation. Numerical studies have been performed on a parallel plate FMT system with matching fluid. The reconstructions obtained show that the algorithm is efficient in computation time, and they also maintain image quality.

Compact 90° trench-based splitter for silicon-on-insulator rib waveguides

Compact silicon-on-insulator (SOI) rib waveguide 90 degrees splitters based on narrow, high-aspect ratio (~10:1) trenches are designed and experimentally demonstrated. The splitter area is only 11 mum x 11 mum. Splitter optical performance is investigated as a function of both trench width and refractive index of the trench fill material. We examine three trench fill materials, air (n=1.0), SU8 (n=1.57), and index matching fluid (n=1.733), and find good agreement between experimental measurement and three dimensional (3D) finite difference time domain (FDTD) simulation. A splitting ratio of 49/51 (reflection/transmission) is measured for an index fluid-filled trench 82nm wide.

Organic light-emitting device luminaire for illumination applications

The total light output of an organic light-emitting device (OLED) with a truncated square-pyramid luminaire is shown to be 1.8–2.1 times greater than the forward emission of an OLED without a luminaire. Luminaires increase the amount of outcoupled light by reducing waveguiding in the glass substrate, and they are made from 1.2-cm-thick acrylic and attached to the OLED glass substrate using index matching fluid. Based on experimental results and ray tracing models, the ratio of the OLED total emission to the OLED forward emission is found to be independent of luminaire taper angles between 30° and 80°.

Diffuse optical tomography and spectroscopy of breast cancer and fetal brain

Diffuse optical techniques utilize light in the near infrared spectral range to measure tissue physiology noninvasively. Based on these measurements, either average bulk optical properties or three-dimensional spatial maps of tissue properties such as total hemoglobin concentration, blood oxygen saturation and scattering can be obtained using model-based reconstruction algorithms. In this thesis, diffuse optical techniques were applied for in vivo breast cancer imaging and transabdominal fetal brain oxygenation monitoring. For clinical in vivo breast cancer imaging, diffuse optical tomography technique and related instrumentation were developed. The clinical diffuse optical tomography instrument utilized near infrared light sources of multiple wavelengths, and multiple source-detector positions in a parallel plate geometry. Transmission continuous-wave measurements by a lens-coupled CCD camera and remission frequency-domain measurements by fiber-coupled detector channels were performed simultaneously. Human subject measurements were carried out in the prone position. The breast was softly compressed and the space adjacent to the breast was filled with a matching fluid with similar optical properties to that of the breast. A nonlinear conjugate gradient inverse algorithm with a priori spectral constraints was utilized to reconstruct three-dimensional endogeneous optical and physiological breast properties. Bulk physiological properties were quantified for 52 healthy subjects in the parallel-plate transmission geometry. Three-dimensional images of the breast were reconstructed for 21 subjects with breast carcinomas. Tumor contrast with respect to normal tissue was found in total hemoglobin concentration and scattering coefficient. An optical index combining total hemoglobin concentration and scattering coefficient shows the tumor contrast to be 2–3 times larger compared to the healthy tissue. Tumor contrast and tumor volume changes during neoadjuvant chemotherapy were tracked for one subject and compared to the dynamic contrast-enhanced magnetic resonance imaging (MRI). Our measurement revealed tumor shrinkage during the course of chemotherapy, in reasonable agreement with magnetic resonance images of the same subject. Finally, the feasibility of measuring blood flow of breast tumors using optical methods was demonstrated for seven subjects. In a qualitatively different set of experiments, the feasibility of transabdominal fetal brain oxygenation monitoring was demonstrated on pregnant ewes with induced transient fetal hypoxia. Preliminary noninvasive clinical measurements before and after human Cesarean sections were discussed, identifying future directions. Overall, this research has translated diffuse optical tomography techniques into a clinical research environment.

Improvements to a new equation of state for pure components

In a recent work [Fluid Phase Equilib. 194–197 (2002) 401], Kedge and Trebble presented a non-cubic equation of state (EOS) including a near-critical correction term. The evaluation of that equation was limited initially to matching fluid properties of methane. In this work, we investigate the impact of incorporating a Carnahan–Starling (CS) repulsive term [J. Chem. Phys. 51 (2) (1969) 635] into the non-cubic equation. The CS term improves the fit of the critical isotherm and it is shown to improve the fit of the entire PVT space. Anomalies in the fit of temperature dependence in the EOS parameters in the near-critical region are also reduced. We also demonstrate in this work how the new correction term serves to flatten the top of the vapor–liquid coexistence curve. The new term is compared to the exponential term in Soave’s modification of the BWR equation (SBWR) [Ind. Eng. Chem. Res. 34 (1995) 3981] which achieves a similar effect in a slightly different way.

A mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interaction

Restricted accessMoreSectionsView PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail Cite this article Xing J. T., Price W. G. and Chen Y. G. 2003A mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interactionProc. R. Soc. Lond. A.4592399–2430http://doi.org/10.1098/rspa.2002.1110SectionRestricted accessA mixed finite–element finite–difference method for nonlinear fluid–structure interaction dynamics. I. Fluid–rigid structure interaction J. T. Xing J. T. Xing Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author , W. G. Price W. G. Price Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author and Y. G. Chen Y. G. Chen Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author J. T. Xing J. T. Xing Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author , W. G. Price W. G. Price Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author and Y. G. Chen Y. G. Chen Ship Science, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK Google Scholar Find this author on PubMed Search for more papers by this author Published:08 October 2003https://doi.org/10.1098/rspa.2002.1110AbstractA mixed finite–element finite–difference numerical method is developed to calculate nonlinear fluid–solid interaction problems. In this study, the structure is assumed to be rigid with large motion and the fluid flow is governed by nonlinear, viscous or non–viscous, field equations with nonlinear boundary conditions applied to the free surface and fluid–solid interaction interfaces. A moving coordinate system fixed at a point in the structure is used to describe the fluid flow, and for numerical analysis purposes, an arbitrary Lagrangian–Eulerian mesh system is constructed relative to this moving system. This provides a convenient method of overcoming the difficulties of matching fluid meshes with large solid motion. Nonlinear numerical equations describing nonlinear fluid–solid interaction dynamics are derived through a numerical discretization scheme of study. A coupling iteration process is used to solve these numerical equations. A selection of numerical examples illustrates the developed mathematical model and through numerical simulations it is shown that the proposed approach is practical and useful. Previous ArticleNext Article VIEW FULL TEXT DOWNLOAD PDF FiguresRelatedReferencesDetailsCited by (2019) Bibliography Fluid-Solid Interaction Dynamics, 10.1016/B978-0-12-819352-5.00029-X, (627-649), . Abou-Dina M and Ghaleb A (2016) Multiple wave scattering by submerged obstacles in an infinite channel of finite depth. I. Streamlines, European Journal of Mechanics - B/Fluids, 10.1016/j.euromechflu.2016.04.005, 59, (37-51), Online publication date: 1-Sep-2016. Wei K and Yuan W (2013) Seismic Analysis of Deep Water Pile Foundation Based on Three-Dimensional Potential-Based Fluid Elements, Journal of Construction Engineering, 10.1155/2013/874180, 2013, (1-10), Online publication date: 11-Apr-2013. Liao K and Hu C (2012) A coupled FDM–FEM method for free surface flow interaction with thin elastic plate, Journal of Marine Science and Technology, 10.1007/s00773-012-0191-0, 18:1, (1-11), Online publication date: 1-Mar-2013. Li Y, Li Z and Wu Q (2017) Experiment and Calculation Method of the Dynamic Response of Deep Water Bridge in Earthquake, Latin American Journal of Solids and Structures, 10.1590/1679-78253872, 14:13, (2518-2533) This Issue08 October 2003Volume 459Issue 2038 Article InformationDOI:https://doi.org/10.1098/rspa.2002.1110Published by:Royal SocietyPrint ISSN:1364-5021Online ISSN:1471-2946History: Published online08/10/2003Published in print08/10/2003 License: Citations and impact KeywordsALE numerical modelnonlinear free surface wavesfluid–rigid structure interactionspartitioned solution procedurenonlinear dynamics

Surface-reflection elimination in polarization imaging of superficial tissue.

A major drawback in polarization gating of light backscattered from tissue is that surface reflections dominate the image. An optically flat plate and matching fluid applied to the tissue surface, combined with off-axis detection, were previously used to address this problem. This approach is often inappropriate or inconvenient for practical use and more importantly can affect the tissue's optical properties. A method is demonstrated that combines images obtained with linearly and circularly polarized light to produce a polarization-gated image that is free from surface reflections and does not require optically flat plates or matching fluid.

EXPERIMENTAL STUDY ON GENERATION AND DISSIPATION MECHAMISIMS OF TURBULENCE INCIDE AND IN THE VICINITY OF POROUS MEDIA

A measuring method of fluid motion inside and in the vicinity of porous media made of silicon spheres is presented. Sodium iodide solution is used as the refraction index matching fluid. In order to capture pictures, a CCD camera and YAG laser are used. The velocity datum are obtained by analyzing the pictures using the superresolution PIV method. Some experimental results on the velocity field and turbulence kinematic energy are presented. Structure of the flow filed inside and in the vicinity of the porous media is discussed. Moreover generation and dissipation mechanisms of the turbulence are discussed.

Ultrasound transducer assembly incorporating acoustic mirror

An ultrasound transducer assembly includes an acoustic mirror, an ultrasound transducer positioned to direct a scanned ultrasound beam at the acoustic mirror, wherein the scanned ultrasound beam is reflected by the acoustic mirror to form a reflected ultrasound beam, and an actuating device for moving the acoustic mirror relative to the scanned ultrasound beam so that the reflected ultrasound beam scans a three-dimensional volume. An ultrasound matching fluid may be disposed between the ultrasound transducer and the acoustic mirror. The actuating device may be configured for rotating the acoustic mirror, translating the acoustic mirror or rotating and translating the acoustic mirror. The acoustic mirror may have a single acoustically-reflecting surface of may be a polygon having a plurality of acoustically-reflective surfaces.

Fiber-loop ring-down spectroscopy

Pulsed, visible and near-infrared laser light is coupled into an optical fiber, which is wound into a loop using a fiber splice connector. The light pulses traveling through the fiber-loop are detected using a photomultiplier detector. It is found that once the light is coupled into the fiber it experiences very little loss and the light pulses do a large number of round trips before their intensity is below the detection threshold. Measurements of the loss-per-pass and of the ring-down time allow for characterization of the different loss mechanisms of the light pulses in the fiber and splice connector. This method resembles “cavity ring-down absorption spectroscopy” and is well suited to characterize low-loss processes in fiber optic transmission independent from power fluctuations of the light source. It is demonstrated that by measuring the ring-down times one can accurately determine the absolute transmission of an optical fiber and of the fiber connector. In addition it is demonstrated that the technique is useful as an absorption spectroscopic technique of very small sample volumes. A solution of an organic dye was placed between the fiber ends instead of the usual index matching fluid, and an absorption spectrum of 7×10−15 mol of the dye 1,1′-diethyl-4,4′-dicarbocyanine iodide in 7×10−12 L of dimethylsulfoxide was recorded.

Modelling of layered resonators for ultrasonic separation

The potential of ultrasonic techniques for the separation and concentration of particles within a fluid has been investigated in some detail in recent years. Devices for effecting such separation typically consist of a piezoceramic transducer driving into a matching layer, fluid layer and reflector layer. This paper uses an equivalent-circuit transducer model, coupled with acoustic impedance transfer relationships to model such cells with regards to both their electrical characteristics and the strength of the resonance produced under different conditions. The model is compared with experimental results from two different cells and is shown to match experimental values well in terms of electrical characteristics and separator performance. The effects of matching layer thickness are also examined using the model. The importance of the adhesive bonding layer is demonstrated, and it is shown that the model can predict the effects of such a layer. The model is also used to demonstrate the effects of coincident resonances in cell layers and to examine the pressure distribution across cells at key frequencies.

A comparison of oral fluid collection devices for use in the surveillance of virus diseases in children

Three oral fluid collection devices (OraSure, Omni-SAL and Oracol) were compared in terms of the quality of oral fluid collected by each device for antibody testing and their acceptability to participants. Participants (143 children aged 3.5–5 y from North Hertfordshire, UK, who had recently received DTaP and MMR vaccination) were randomised to use one of the three types of collection device. Oral fluid was collected by a parent who completed a short questionaire recording information on ease of use and willingness to use the device again. A matching serum sample was collected by a nurse. Oral fluid samples were screened for total IgG and IgM by ELISA and for rubella specific IgG and parvovirus specific IgG by radioimmunoassay. Serum samples were screened for rubella specific IgG and parvovirus B19 specific IgG by ELISA. 87.4% (125) of participants provided a matching oral fluid and serum sample. Of these, 100% (125) and 10.4% (13) had serum IgG specific for rubella and parvovirus B19, respectively. The Oracol device provided oral fluid samples with the highest geometric mean titres of total IgG and IgM and with rubella specific IgG results which correlated most closely with those of matching sera. A higher proportion of parents found the Oracol and OraSure devices easier to use than the Omni-SAL ( P<0.001) and the proportion who would not take another test was higher for the Omni-SAL than for the Oracol or Orasure. Oral fluid samples collected by each of the devices gave qualitative results acceptable for surveillance and epidemiological studies of rubella and parvovirus B19. The highest quality oral fluid sample for antibody testing in terms of total IgG and IgM concentration and rubella specific IgG concentration was collected by the Oracol. The acceptability to participants of both the Oracol and OraSure was high. As the cheapest device available, the Oracol is the preferred oral fluid collection device for studies involving children in the UK. Public Health (2001) 115, 201–207.

A comparison of oral fluid collection devices for use in the surveillance of virus diseases in children

Three oral fluid collection devices (OraSure, Omni-SAL and Oracol) were compared in terms of the quality of oral fluid collected by each device for antibody testing and their acceptability to participants. Participants (143 children aged 3.5–5 y from North Hertfordshire, UK, who had recently received DTaP and MMR vaccination) were randomised to use one of the three types of collection device. Oral fluid was collected by a parent who completed a short questionaire recording information on ease of use and willingness to use the device again. A matching serum sample was collected by a nurse. Oral fluid samples were screened for total IgG and IgM by ELISA and for rubella specific IgG and parvovirus specific IgG by radioimmunoassay. Serum samples were screened for rubella specific IgG and parvovirus B19 specific IgG by ELISA. 87.4% (125) of participants provided a matching oral fluid and serum sample. Of these, 100% (125) and 10.4% (13) had serum IgG specific for rubella and parvovirus B19, respectively. The Oracol device provided oral fluid samples with the highest geometric mean titres of total IgG and IgM and with rubella specific IgG results which correlated most closely with those of matching sera. A higher proportion of parents found the Oracol and OraSure devices easier to use than the Omni-SAL ( P <0.001) and the proportion who would not take another test was higher for the Omni-SAL than for the Oracol or Orasure. Oral fluid samples collected by each of the devices gave qualitative results acceptable for surveillance and epidemiological studies of rubella and parvovirus B19. The highest quality oral fluid sample for antibody testing in terms of total IgG and IgM concentration and rubella specific IgG concentration was collected by the Oracol. The acceptability to participants of both the Oracol and OraSure was high. As the cheapest device available, the Oracol is the preferred oral fluid collection device for studies involving children in the UK. Public Health (2001) 115 , 201–207.

Extracellular adenosine levels and cellular energy metabolism in ischemically preconditioned rat heart.

Microdialysis and 31P-NMR spectroscopy were used to test opposing hypotheses that ischemic preconditioning inhibits adenine nucleotide degradation and purine efflux, or that preconditioning activates cardiovascular adenosine formation to provide enhanced cardioprotection. 31P-NMR spectra and matching interstitial fluid (ISF) or venous effluent samples were obtained from Langendorff perfused rat hearts. Control hearts (n = 9) underwent 30 min of global normothermic ischemia and 30 min reperfusion. Preconditioned hearts (n = 6) were subjected to a 5 min ischemic episode and 10 min reflow prior to 30 min ischemia and 30 min reperfusion. Effects of repetitive ischemia-reperfusion (3 x 5 min ischemic episodes) on adenosine levels and energy metabolism were also assessed (n = 8). Preconditioning improved post-ischemic recovery of heart rate x left ventricular developed pressure (71 +/- 5 vs 43 +/- 8%, P < 0.05) and end-diastolic pressure (14 +/- 3 vs 29 +/- 4 mmHg, P < 0.05) compared with control hearts, respectively. Preconditioning did not alter intracellular ATP, phosphocreatine (PCr), inorganic phosphate (Pi), H+ or free Mg2+ during global ischemia, but improved recoveries of PCr, Pi, and delta GATP on reperfusion. ISF adenosine increased more than 20-fold during 30 min ischemia. The 5 min preconditioning episode increased ISF adenosine 3-fold, and reduced ISF adenosine and inosine during subsequent prolonged ischemia by up to 75%. Venous purine levels during reperfusion were also reduced by preconditioning. Accumulation of adenosine in ISF and venous effluent during repetitive ischemia was progressively reduced despite comparable changes in substrate for adenosine formation via 5'-nucleotidase, (5'-AMP), and in allosteric modulators of this enzyme (Mg2+, H+, Pi, ADP, ATP). (i) Ischemic preconditioning reduces interstitial and vascular adenosine levels during ischemia-reperfusion, (ii) reduced ISF adenosine during ischemia is not due to reduced ischemic depletion of adenine nucleotides in preconditioned rat hearts, (iii) preconditioning may inhibit adenosine formation via 5'-nucleotidase in ischemic rat hearts, and (iv) improved functional recovery with preconditioning is unrelated to metabolic/bioenergetic changes during the ischemic insult, but may be related to improved post-ischemic recovery of [Pi] and delta GATP in this model.