Ion concentration measurements

Hydrogen-ion concentration measurements cannot distinguish between a bis-hydroxy species and a mono-oxy species because the equilibrium 2 OH — 02 + H20... 

Table 1. Comparison of metal ions concentrations measured by 1C and certified values [22].

Table 13.2 shows the concentrations of Cu2+ in tap water and lake water determined by the MPA-Gly-Gly-His modified electrode and compared with those of inductively coupled plasma mass spectrometry (ICP-MS). The measured concentration of Cu2+ in tap water when dilutions were accounted for using the MPA-Gly-Gly-His modified electrode was 0.55 +0.08 pM (95% confidence interval). This value is much lower than the copper concentration measured by ICP-MS of 1.70+0.15 pM (95% confidence interval). The peptide-modified electrode measures free Cu2+ or weakly bound copper complexes rather than the total metal-ion concentration measured by ICP-MS. Hence the use of peptides has the ability to measure metal-ion bioavailability for specific species. The results are consistent with others who have also shown that the labile fraction of copper is much less than the total copper [7]. 

The pH of potassium permanganate solution cannot be tested using universal indicator solution because the colour of the potassium permanganate solution interferes. However, the pH can be determined using a pH electrode since the colour of the solution does not affect the H(aq) ion concentration measurement. 

The reason the hydroxide ion concentration measures the concentration of protons released is that when water acts as an acid, i.e., a proton releasing species, it produces a hydroxide ion for every proton released. When water acts as a base, it forms one H30 for every proton consumed. The hydronium ion concentration, abbreviated as [H" ], is a measure of the proton consumption of water. 

Positive-ion concentrations measured with 2 X 10 atoms cm of metal added to 034 C2H4/O.O4 C HJ2.0 O2/4.O N2 flame (from Addecott and Nutt )... 

Indicalors and test-papers. 2. Hydrogen-ion concentration—Measurement. I. Title. 

Calculate the 95% and 99% confidence limits of the mean for the nitrate ion concentration measurements in Table 2.1. 

Thus, by the end of the nineteenth century the electromotive force from high resistance sources could be measured with a relatively high precision. The introduction of the glass membrane electrode for the hydrogen-ion concentration measurement presented a challenge and a test of instrument capabilities. The State of the Art (1905) for the measurement of membrane potentials had been described by Max Cremer in the paper entitled (14.) ... 

A three-dimensional modular setup for a miniaturized analysis system for flowing streams is presented The system uses silicon micromachined pumps and flow manifolds in combination with electrochemical sensors or optical detection Applications range from simple ion concentration measurements with ISFETs to a multi-step chemical analysis of phosphate Miniaturization of the flow systems leads to a substantial reduction in reagent consumption... 

The pH scale from 0 to 14 covers all the hydrogen ion concentrations (Table 2.1) found in dilute aqueous solutions and biological systems. Pure water has a pH of 7 which is considered to be neutrality. When pH < 7, the solution is acidic and when pH > 7, the solution is basic or alkaline. Because of the logarithmic function a change of one pH unit represents a tenfold difference in hydrogen ion concentration. Measurements of pH can be easily performed using a pH-meter. 

Ion concentration measurements with ion sensitive field effect transistors (ISFETs)... 

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