Polycrystalline and monocrystalline antimony, iridium and palladium as electrode material for pH-sensing electrodes.

Different ways of making pH-sensing electrodes from monocrystalline or polycrystalline antimony, iridium and palladium have been investigated. Monocrystalline antimony and iridium are superior to the polycrystalline elements with respect to reproducibility between electrodes and stability of the electrode potential over long periods of time. No good palladium/palladium oxide electrode could be obtained by electrochemical oxidation and the thermal preparation method could not take advantage of the properties of the monocrystalline palladium. Therefore, only polycrystalline palladium was used to study this type of electrodes. The different electrodes were compared with respect to the manner of preparation, the pH-response (reproducibility and time response) and the effect that different complexing ligands present in the measuring solutions may have on the electrode response. Also, the redox-response of the electrodes and the effect of different oxygen pressures on the electrode potentials were studied. The monocrystalline antimony electrodes have the best reproducibility and long-term stability but also respond to complexing ligands and to variations in the oxygen pressure. Monocrystalline iridium electrodes can be obtained by continuously cycling the potential between -0.25 and +1.25 V (SCE) in 0.5M sulphuric acid. They do not respond to the complexing ligands tested, and have fairly good long-term stability, but the reproducibility between electrodes is inferior to that of the monocrystalline antimony electrodes. Polycrystalline antimony and iridium electrodes were inferior to the monocrystalline ones. The properties of the palladium electrodes were similar to those of the iridium ones.

Effects of some complex-forming ligands on the potential of antimony pH-sensors.

The E vs. pH relationship for oriented monocrystalline antimony electrodes was studied in various ionic media, containing no buffer or one of several common buffer substances, and the stability of the electrode potential with time was investigated. Several makes of commercially available polycrystalline antimony electrodes were also studied. The results indicate that tris(hydroxymethyl)aminomethane may be used for calibration of antimony electrodes, but most other commonly used buffer substances, e.g., orthophosphate, yield erroneous results. Monocrystalline antimony electrodes are preferable to polycrystalline ones, especially when measurements are made in unstirred solutions. The long-term stability of monocrystalline electrodes is superior to that of polycrystalline ones.

Psychological correlates of sexual abuse in adolescent girls in chemical dependency treatment.

A study involving 597 adolescent girls in treatment for substance abuse between 1984 and 1986 at nine inpatient facilities in five states reveals a strikingly high prevalence of sexual abuse victimization. Over one-third (35.2%) of the girls acknowledged such a history. In an additional 9.7% of the cases, the primary counselor reported such a history for the patient, although she had denied it, at least at intake. Within this multiproblem, highly stressed population, the sexual abuse victim appears to show slightly different and often more serious psychopathology: a greater incidence of suicidal ideation and attempts, symptoms of agitation, and a sense of shame.

Continuous pH monitoring with monocrystalline antimony electrodes: toxicity considerations from studies on heparinized human plasma.

Monocrystalline antimony electrodes can be used as pH sensors for continuous monitoring in vivo. The electric potential of the electrodes stems from a corrosion reaction in which antimony metal dissolution constitutes the anodic reaction. In this study the amount of antimony which leaves a monocrystalline antimony sensor, when monitoring pH in thermostatically controlled sterile human heparinized plasma, was determined by neutron activation analyses. From these results the toxicity hazard of using such electrodes in vivo is assessed. It is concluded that the amount of antimony released from a monocrystalline pH sensor, when used in a biological medium, is small compared with the amount of antimony accepted for administration as a medical therapeutic. Thus it should be safe from the toxicological point of view to use monocrystalline antimony electrodes for in vivo pH monitoring.

Arterial pH monitoring with monocrystalline antimony sensors. A study of sensitivity for PO2 variations.

Monocrystalline antimony catheter electrodes were studied intra-arterially in non-heparinized dogs. The sensitivity for variations in arterial PO2 (PaO2) was evaluated for this kind of metal-metal oxide pH sensor. The influence of PaO2 compensation on a previous pH sensitivity estimate was calculated. When the mV signal from the antimony sensor, after compensation for pH and temperature variations, was expressed as a function of log10 PaO2, a non-linear relation was found for the PaO2 range studied, 2.9-50 kPa. After calculations this range was divided into a lower and a higher sub-range. A first-order linear approximation was applied for these subranges. The sensitivity for oxygen was 70 mV/log10 PaO2 in the range 2.9kPa less than PaO2 less than 10 kPa, and 20.7 mV/log10 PaO2 in the range 10 kPA less than PaO2 less than 50 kPa. The non-logarithmic sensitivity for intra-arterial oxygen is contradictory to results from in vitro studies in test solutions. The present study indicates that the monocrystalline antimony pH sensor has a sensitivity for PaO2 variations which is closely correlated to the haemoglobin-oxygen dissociation function. When compensation for PaO2 variations was performed on an earlier evaluated study over a wide pH range but limited PaO2 range, the pH sensitivity previously found was not influenced.

Continuous intra-arterial pH-monitoring using monocrystalline antimony as sensor. A study in non-heparinized dogs.

Continuous intra-arterial pH-monitoring was performed on anaesthetized and artificially ventilated dogs. The pH sensor consisted of monocrystalline antimony. The sensor was placed on the tip of a catheter, length approximately 35 cm and diameter 0.8 mm. No anticoagulation was undertaken. The pH range studied was 7.01-7.53, the pH being changed by infusion of sodium bicarbonate ro ammonium chloride. Arterial reference blood samples for in vitro blood gas analyses were taken under stable monitoring conditions and analysed with a minimal delay. The millivolt signal from the antimony sensor was found to be a linear function of the pH of the reference blood samples in the intra-arterial pH range studied. The sensitivities of the different antimony sensors were closely correlated but not identical. When the antimony sensor was used completely uncalibrated, the standard deviation of the registered potential corresponds to 0.06 pH units. After single point calibration a standard deviation of 0.03 pH units was obtained. These standard deviations include a suspected influence of minor changes in the partial pressure of oxygen during the experiments.

The oxygen sensitivity of a multipoint antimony electrode for tissue pH measurements. A study of the sensitivity for in vivo PO2 variations below 6 kPa.

Monocrystalline micro antimony electrodes in a multipoint arrangement as described by Lund et al. were placed on the skeletal muscle surface of the rabbit. Tissue oxygen levels were measured simultaneously with the MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode. The sensitivity for variations in tissue PO2 (PO2(t)) was evaluated for the antimony metal-metal oxide sensor. The sensitivity (delta E/delta log10 PO2)+/- SE was found to be 21.8 +/- 1.2 mV in the interval between 0.1 kPa and 1 kPa and 53 +/- 5 mV in the interval between 1 kPa and 6 kPa. These results are not consistent with the oxygen sensitivity of monocrystalline antimony described in vitro, but are in agreement with the findings of Nilsson & Edwall. A plausible explanation for the S-shaped oxygen sensitivity curve of antimony at oxygen levels below 10 kPa could be an interaction, at the electrode surface, between the dissolved oxygen and the oxygen bound to haemoglobin. If this is the case, the use of an antimony electrode would make possible the determination of the dissociation of oxyhaemoglobin in tissues.

Differential drug use patterns among sexually abused adolescent girls in treatment for chemical dependency.

A sample of 444 girls admitted to adolescent chemical dependency treatment was divided into four groups based on sexual abuse experiences. Girls who reported intrafamilial abuse, extrafamilial abuse, or both, were compared with nonvictims in terms of alcohol and drug use histories. Prevalence and frequency of alcohol, marijuana, and cocaine did not differ significantly among the groups. However, all sexual abuse victims were significantly more likely to regularly use stimulants, sedatives, tranquilizers, and hallucinogens. Sexual abuse victims also reported earlier onset of alcohol and drug use, more self-medication, and more use to escape family problems.

Continuous intra-arterial PO2 monitoring with a surface heparinized catheter electrode. A study of conformity in conventional blood gas analysis and of long-term electrode function in the non-heparinized dog.

Surface-heparinized catheter PO2 electrodes were used for continuous intra-arterial monitoring in non-heparinized dogs. During one-day experiments the read-out of the electrode monitoring unit was compared with that of conventional blood gas analysis. Furthermore, the electrodes were studied after long-term implantation. The intra-arterial PO2 electrodes have previously been reported to be linear in the gas phase, water phase and in heparinized blood. The present study demonstrates that the catheter electrodes remain linear after surface heparinization. As compared with the conventional blood gas analysis it was found that the desk analyser in the range PaO2 greater than 18 kPa underestimated the actual PaO2 as compared to the invasively monitored PaO2, but in the range below 7 kPa the desk analyser overestimated the PaO2. Surface-heparinized PO2 catheter electrodes were studied after up to 23 days of implantation. No coagulation phenomenon was found around the catheters, neither macroscopically nor by scanning electron microscopy. The electrical function withstood 7 days of implantation. After more extended periods the electrical leads were broken without any damage to the catheter itself. When compared with acutely implanted surface-heparinized electrodes, there was no difference in monitoring characteristics between the acutely implanted and the long-term implanted PO2 electrodes.

Effects of commercial (pH approximately 3.5) and freshly prepared (pH approximately 6.5) lidocaine-adrenaline solutions on tissue pH.

Differences in the effects of commercially available, sodium bisulfite-containing (pH 3.5-4), and freshly prepared (pH 6.5) lidocaine-adrenaline solutions on tissue pH and tissue oxygenation were studied experimentally. In rabbits, a 5 x 5 cm area under the panniculum was infiltrated with 0.9% NaCl, plain lidocaine, plain adrenaline or one of the two lidocaine-adrenaline solutions. Tissue pH was measured continuously as well as intermittently in the infiltrated area with monocrystalline antimony needle electrodes. Infiltration of the tissue with the 4 ml volume of a test solution did not seem to induce any significant tissue injury. Tissue pH was decreased for 30 min following plain lidocaine and for 90 min or more following lidocaine-adrenaline infiltration. With the exception of the first few minutes, no significant differences in the effects on tissue pH between commercial and freshly prepared lidocaine-adrenaline solutions could be seen. Tissue hypoxia occurred only following infiltration with plain adrenaline. It may thus be concluded that in spite of the low pH and the O2-reducing properties of commercial lidocaine-adrenaline solutions, a rapid buffering occurs in the tissues. The use of commercial lidocaine-adrenaline solution for local infiltration thus seems as safe as that of freshly prepared lidocaine-adrenaline solutions.

Polarographic pO2 sensors with heparinized membranes for in vitro and continuous in vivo registration.

The membranes of the pO2 sensor in a conventional blood gas analyser and a commercially available catheter pO2 electrode were coated with a glutardialdehyde stabilized heparin layer. It was analysed whether or not the "non-thrombogenic" heparin surface could improve the accuracy of in vitro pO2 registration and continuous in vivo paO2 monitoring. The in vivo experiments were performed on anaesthetized and non-anticoagulated dogs. Two identical blood gas analysers were used, one furnished with a heparin coated pO2 membrane and the other with a standard pO2 membrane. In vitro pO2 determinations exhibited--when simultaneously analysing the same blood sample--identical mean values. For repeated pO2 determinations, however, the standard deviation was significantly lower on the analyser furnished with a heparinized membrane. The non-heparinized catheter pO2 electrode showed a marked deterioration in accuracy with time as compared with blood-gas analysis on reference blood samples. Falsely low paO2 values were presented. The heparinized catheter electrode monitored values in full agreement with those of the conventional blood gas analyser using standard membranes. It is concluded that the heparin surface on the oxygen diffusible membranes diminishes the variability of the diffusion characteristics both at contact with anticoagulated blood in vitro and during in vivo paO2 monitoring. The "non-thrombogenic" heparin surface prevents diffusion impeding clot formations when an arterial catheter pO2 sensor is used.

A multipoint micro antimony pH electrode for tissue surface measurements.

Based on monocrystalline antimony we have developed a multipoint tissue surface pH electrode. The six electrodes were produced by spark cutting from a large antimony single crystal. The electrodes were then cast in epoxy resin in a ring shaped structure which fitted around the MDO oxygen electrode. The antimony electrode was ground and polished to expose an undisturbed closely packed crystal plane of antimony to the measuring solution. Before and after monitoring periods standardization was performed in TRIS buffers of pH 6.72, 7.32 and 7.74 at 37 degrees C. Antimony electrode potential is influenced by oxygen. Therefore, mean tissue oxygen pressure was registered simultaneously with an MDO electrode. The oxygen sensitivity factor used in this study was 18mV/logpO2. The correction factor for the antimony electrode oxygen dependence, measured in vitro, seemed to be correct also for the in vivo state. This, however, needs further investigation. To illustrate the usefulness of the multipoint pH electrode seven normal state rabbits were studied, and thereafter four - one each in a hypoxic, hypocarbic, hypovolemic or hyperoxic situation. In the normal state tissue pH measured on a skeletal muscle surface varied from 7.0 to 7.4. In the case of tissue microcirculation shutdown (in the hypocarbic or the hypovolemic situations), the initial reaction was a scattering of the pH values, and then the development of tissue acidosis. Our conclusion is that the use of a multipoint pH sensor enables improved and more detailed monitoring of the tissue acid-base status.