ABSTRACT
Calcium, phosphate and buffering capacity were measured in children's (n=43) unstimulated saliva between September 1990 and June 1991 inclusive. Saliva samples were collected in the afternoon, once a month, on 10 consecutive occasions. Buffering capacity was assessed immediately after sample collection using the Dentobuff strip method. The remainder of the saliva sample was then stored at -18 degrees C and, after thawing, total calcium and inorganic phosphate were measured. The intra-individual variation of buffering capacity over time was statistically significant (Friedman two-way ANOVA, p < 0.001). The intra-individual variability of salivary calcium was also statistically significant (repeated-measures ANOVA, p < 0.001). However, no evidence of a statistically significant variation in phosphate was observed. It is concluded that a combination of flow-rate fluctuation over time and the methods used to assess salivary constituents might have contributed to this variability.
Subject(s)
Calcium/analysis , Phosphates/analysis , Saliva/chemistry , Adolescent , Analysis of Variance , Buffers , Child , Female , Follow-Up Studies , Humans , Male , Reagent Strips , Saliva/metabolism , Saliva/physiology , Seasons , Secretory Rate , SpectrophotometryABSTRACT
The complexing ability of a range of 19 symmetrical, unsymmetrical and bridged calix[4]arene derivatives having ester, ketone, amide, amine and thioether functionalities were determined by the picrate extraction method. On incorporating these calix[4]arene derivatives as neutral carrier ionophores in sodium-selective poly (vinyl chloride) membrane electrodes the performance was assessed on the basis of the sensitivity and selectivity over the alkali, alkaline earth metals and hydrogen and ammonium ions. The temperature dependence, response times and lifetimes were also determined. Four ionophores in particular gave excellent sensitivity and selectivity and lifetimes of > 200 days. These electrodes were then tested without additional lipophilic additives and one ionophore was incorporated into poly (vinyl chloride) membrane electrodes with plasticizing solvents of varying polarity.
ABSTRACT
Four lipophilic sulphur and/or nitrogen containing calixarene derivatives have been tested as ionophores in Ag(I)-selective poly (vinyl chloride) membrane electrodes. All gave acceptable linear responses with one giving a response of 50 mV/dec in the Ag(I) ion activity range 10(-4)-10(-1)M and high selectivity towards other transition metals and sodium and potassium ions. This ionophore was also tested as a membrane coated glassy-carbon electrode where the sensitivity and selectivity of the conventional membrane electrode was found to be repeated. The latter electrode was then used in potentiometric titrations of halide ions with silver nitrate.
ABSTRACT
An automated routine method was developed for the determination of trace metals using a flow injection system into a direct current plasma spectrometer. The characteristic emission in the 'Spectra- Metrics' three-electrode jet is channelled through an echelle grating to the detector of the instrument. The emission signal is continuously recorded, and, after digitalization, calculated and recorded by a Touchstone software package and interface card. The software has facilities for recording peaks, generating calibration curves, calculating and printing results, enhancing line sensitivities, monitoring signal response and for filter noise, recalibration, background correction, status monitoring and general diagnostics. Up to 70 elements can be determined both in aqueous and non-aqueous media.
ABSTRACT
The reaction between hydrogen peroxide and a mixture of cyanocuprate(I) species at pH 11.2 is selectively catalysed by traces of osmium. With potentiometric or amperometric monitoring, osmium concentrations up to 1 ng ml can be determined, with a lowest determinable concentration of 0.03 ng ml . In the presence of luminol a Landolt-type reaction proceeds and visual or instrumental monitoring of the chemiluminescence can be used. A large number of other cations can be tolerated. The kinetics, mechanism, rate constants and Arrhenius parameters have been investigated.
ABSTRACT
The reaction between peroxodisulphate and bromide has been utilized for the catalytic determination of 0-1 ppm of copper in dissolved samples. The kinetics and mechanism of the uncatalysed and catalysed reaction have been studied, and the most important kinetic parameters determined. Under the experimental conditions described, the determination can be carried out in the presence of large numbers of other ions with an error less than 5%.
ABSTRACT
For the emission flame photometric determination of strontium and barium in the presence of interfering ions such as phosphate, sulphate, arsenate and oxalate, calibration or simple standard addition methods cannot be used. Greatly reduced errors can be achieved by dividing the sample solution into four equal parts and adding to each certain known amounts of two metal ions. One of these is identical to the determinand (e.g., strontium or barium) the other has similar characteristics to it (e.g., calcium). The amounts of these metals are chosen so that the total (molar) concentration of these should be identical in all solutions, but the ratio of the concentrations of the two metals should be different. The emission of the determinand metal must be measured, and a standard addition plot produced. The amount of determinand present in the sample can be obtained from the intersection of the emission vs. concentration line with the concentration axis.
ABSTRACT
Phosphate ions decrease the flame emission of calcium, but this effect can be partly offset by adding a second metal which partly displaces calcium from the non-excitable species. For the determination of phosphate the sample solution is divided into four equal parts; to each of these, various amounts of calcium and barium ions are added such that the total (molar) concentration of the metals is constant. Plotting the intensity measured at 630 nm vs. the calcium content of the solution gives a straight line, the slope of which depends on the concentration of phosphate ions present. The method is suitable for rapid determination of phosphate. Accuracy and precision are within the usual limits characteristic of flame photometric methods.
ABSTRACT
The reaction between peroxidisulphate and iodide, modified by the addition of thiosulphate to show the Landolt effect, has been used for the determination of copper and iron in the range 1-100 mug ml , based on the catalytic effect of these ions. The procedure is rapid and simple, and the errors are less than 10%. The interference from iron in the determination of copper may be overcome by the addition of a masking reagent such as fluoride.
ABSTRACT
The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere.
ABSTRACT
The principles of various methods of differential spectrophotometry are briefly discussed. Practical problems connected with the measurements are presented and analytical applications so far available are reviewed.
ABSTRACT
A rapid method is described for the simultaneous determination of 2,4-tolylene diamine and 2,4-tolylene diurea by infrared spectroscopy. The method is satisfactory for the diurea determination but gives rather large errors in the diamine determination.
