Hand-held water fluoride analysis: An accessible caries prevention tool for dental professionals.

This study sought to compare the relative accuracy of a commercially available hand-held water fluoride analysis unit with a standard laboratory bench-top fluoride-specific electrode/millivoltmeter apparatus, with the goal of identifying possible practical applications of the hand-held unit for preventive dentistry. The units analyzed identical gravimetrically prepared fluoride solutions ranging from 0.1 to 4.0 ppm. The average difference between the measurements from the hand-held unit and the nominal values of the fluoride solutions was 0.011 ppm (SD = 0.068), and the average difference between the hand-held unit's measurements and the bench-top unit's measurements was 0.030 ppm (SD = 0.115). T-test analysis demonstrated no statistical difference between measurements from the hand-held unit with either the nominal values of the fluoride solutions or the bench-top unit's measurements. Results indicate that the hand-held water fluoride analysis unit has an appropriate level of accuracy for the measurement of fluoride levels in drinking water samples by dental professionals.

Nanoparticle-induced potentiometric biosensing of NADH at copper ion-selective electrodes.

We demonstrate the first example of using potentiometry at ion-selective electrodes (ISEs) for probing in real-time monitoring of biometallization processes. A copper ISE is used for real-time monitoring of the NADH-mediated reduction of copper in the presence of gold nanoparticle seeds. Such potentiometric detection of NADH is not susceptible to surface fouling common with analogous amperometric measurements of this co-factor. Biosensing of ethanol is illustrated in the presence of alcohol dehydrogenase and NAD(+), along with potentiometric detection of the NADH product at the copper ISE. The concept can be readily expanded to the monitoring of various biometallization processes in connection to different enzymatic transformations and ISE, and used for ultrasensitive detection of bioaffinity interactions in connection to common enzyme tags.

Naproxen ion-selective electrode and its application to pharmaceutical analysis.

An ion-selective membrane electrode was prepared based on ion-pair complex of naproxen with methyltrioctylammonium. Its basic analytical parameters such as: slope characteristics, measuring range, detection limit, response time, life time were determined. The electrode showed Nernstian response from the 10(-1) to 10(-4) mol l(-1) concentration range and 5.5-8.5 pH range, low limit of detection 5 x 10(-5) mol l(-1) and short response time--20s. Selectivity was good over a number of organic and inorganic anions. The electrode was applied for the determination of naproxen tablets in aqueous solutions by the calibration curve method and standard addition method.

Polymeric membrane ion-selective electrode for determination of bismuth (III) in pharmaceutical substances.

A PVC-based membrane of tridecylmethylammonium chloride reveals a Nernstian potentiometric response (with slope of 55 mV/decade and a correlation coefficient of 0.99) for complex of bismuth (III) with ethylenediaminetetraacetate-anion [Bi(EDTA)](-) over a wide concentration range (1 x 10(-1) to 3 x 10(-5) mol/l). The potential of this electrode is independent of pH in the range of 4.0-11.0. It has a fast response time of about 30 s and was used for a period of 3 months with good reproducibility. The detection limit of this membrane electrode was 1 x 10(-5) M. This sensor exhibits a very good selectivity for [Bi(EDTA)] over a wide variety of complex metal ions with ethylenediaminetetraacetic acid. The proposed electrode has been used in the direct potentiometric monitoring of bismuth (III) in stomach anti-acids.

[Ion-selective electrodes with a liquid membrane for determining N-butylscopolammonium bromide]. / Electrozi ion-selectivi cu membrana lichida pentru determinarea bromurii de N-butilscopolamoniu.

Two ion-selective electrodes with liquid membrane for N-butylscopolamonium bromide are described, with N-butylscopolamonium tetraphenylborate (I) and N-butylscopolamonium reineckate (II), respectively, solved in benzylic alcohol as electroactive material. These electrodes have a linear response in the concentration range of 10(-2)-10(-6) M N-butylscopolamonium bromide, with the detection limit of 10(-7) M for both electrodes. These electrodes were used with good results for quantitative assay by direct potentiometry of injectable solutions of N-butylscopolamonium bromide.

Characterization of a new ion selective electrode for ionized magnesium in whole blood, plasma, serum, and aqueous samples.

Results from a novel ion selective electrode (ISE) for ionized magnesium (Mg2+) correlate well with atomic absorption spectroscopy on aqueous solutions containing from 0.1-3.0 mmol MgCl2/L. Day to day precision (coefficient of variation) of the electrode on protein-based controls is < 4%; aqueous-based controls < 6%. The new ISE is selective for Mg2+ with a selectivity constant for Ca2+ (KMgCa) of 8 x 10(-2). Adding pathophysiologic concentrations of Cd2+, Ca2+, Cu2+, Fe3+, K+, Na+, or Zn2+ to serum and aqueous solutions gave negligible to minimal changes in measured Mg2+. Ligand binding studies in aqueous solution indicate that pathophysiologic concentrations of different anions (e.g. heparin, lactate, bicarbonate, phosphate, acetate and sulfate) bind to Mg2+, effectively reducing its concentration in solution. Likewise, silicon (as either found in Vacuutainer tubes or as chlorosilane) failed to exert any significant effect on measured Mg2+. Addition of Intralipid (up to 500 mg/dL) gave negligible to minimal changes in Mg2+. Mg2+ measurements on whole blood, plasma, and serum for a given human subject's samples are virtually identical, at least within the reference range for Mg2+. Typically, Mg2+ is 71% of TMg, but varies from subject to subject; i.e. Mg2+ cannot be predicted from TMg. Clinical studies revealed that the Mg2+/TMg ratio could be remarkably consistent in sequential samples (e.g., throughout the course of coronary bypass surgery) taken from one patient, but that this ratio could differ dramatically from the ratio in sequential samples taken from another. Mg2+ is held within a narrow range (0.53-0.67 mmol/L) in normal, healthy subjects when compared to TMg (0.70-0.96 mmol/L).

Characterization, standardization and experiences with KONE ISE for Mg2+.

The principles of a fully automated potentiometric determination of ionized magnesium in human blood serum are presented. By incorporating a magnesium selective electrode, into a commercially available six channel electrolyte analyzer (Microlyte 6, KONE Instruments, Finland), determination of the biologically-active, ionized fraction of magnesium has been made possible. In this paper, the analytical performance of the measurement system is presented and determination of ionized magnesium in real patient samples is discussed with special attention to the significance of this new parameter.

Clinical findings on human blood with the KONE ISE for Mg2+.

Ionized magnesium was measured using a clinical analyzer MICROLYTE 6 (KONE, Finland). Total magnesium was measured colorimetrically. The influence of anion-ligands on Mg-ISE responses was investigated. Ionized magnesium (iMg) concentration changes with pH were made to observe the accuracy of results. The dependence of iMg and iCa on heparin (used as anticoagulant in plasma samples) was made. Less than 40 units per 1 ml of blood decreased the concentration of iMg and iCa less than 1.5%. The range of iMg and total Mg in serum and plasma of healthy and ill adults (short bowel syndrome, myocardial infarct) was investigated and compared to each other. In both illnesses, the concentration of ionized and/or total magnesium is significantly different from the range for healthy people. The range of iMg and total Mg as well as the percentage of iMg against total Mg seem to be specific for given illness. The range of iMg and total Mg in blood serum of healthy children was also investigated.

Standardizing and reporting results from Mg2+ ISEs, with some notes on sample handling.

Mg2+ by ion-selective electrode (ISE) is a direct measure of the reactivity of magnesium ions in plasma, which may be clinically and physiologically more relevant than the concentration of total magnesium. The Mg(2+)-ISE will build up an electric potential which exactly matches the chemical potential of Mg2+ in the sample. Chemical potential (= chemical work per unit of Mg2+) has no absolute value and is difficult to visualize. The results must be standardized, either to the magnesium concentration in a protein-free calibrator or to the concentration of total magnesium in plasma. The constant factor relationship will assure identical clinical discrimination, no matter how the Mg(2+)-ISE results are reported. The general opinion of a conference held in Orlando, Florida in March of 1993 was to define free Mg2+ in plasma as the concentration of magnesium in a saline standard with the same magnesium activity as the sample, and report it in SI units (mmol/L). The small differences in liquid junction potential and water concentration will provide a value for free Mg2+ in plasma of approximately 103% of the true concentration, or 96% of the true molality. Differences between plasma and interstitial fluid and Donnan equilibria across the vascular endothelium will effect the result, so sampling should take place with the patient at rest to assure a stable plasma volume. Since heparin binds magnesium, it is preferable to use serum or plasma with a minimum of heparin which has been titrated with magnesium. Binding of Mg2+ depends on pH, and pH of circulating plasma is not constant.(ABSTRACT TRUNCATED AT 250 WORDS)