Development of highly sensitive cadmium iondashselective electrodes by titration method and its application to cadmium ion determination in industrial waste water.
Characteristics of cadmium iondashselective electrode made cadmium sulphide (CdS)-silver sulphide (Ag(2)S) mixture were studied. CdS-Ag(2)S mixtures were obtained by gas/solid-phase reaction between silver-cadmium mixed powder and hydrogen sulphide gas (dry method) and by ionic reaction between cadmium-silver mixed ions and sulphide ion (wet method). As a result, it was found that the CdS-Ag(2)S mixture had to be made in the condition of excess existence of sulfur and had better regulate the excess sulfur quantity minimum, for the CdS-Ag(2)S pressed membrane gave a good Nernstian response against the cadmium ion concentration change. As the best way, CdS-Ag(2)S mixture was obtained by adding sulphide ion solution to 5 mol% cadmium ion and 95 mol% silver ion mixed solution while measuring silver sulphide (Ag(2)S) electrode potential as an indicator electrode. According to the reaction was stopped when the potential variation from the initial potential in the sulphide ion solution reached at 87-116 mV which the sulphide ion concentration became 10(-3) - 10(-4) of the initial concentration, the cadmium ion membrane pressed diameter of 8 mm and thickness of 2 mm showed a Nernstian response from 10(-8) to 10(-1) M of cadmium ion concentration. Furthermore, aiming to its application for industrial waste water, masking buffer for interfering metal ions such as lead ion (Pb(2+)) and copper ion (Cu(2+)), which were possibly coexisted and to adjust total ionic strength and pH of sample was developed. The present Cd(2+) iondashselective electrode was applied to the determination of Cd(2+) in the industrial waste water. The good regression line with correlation factor of 0.984 was obtained compared with the conventional atomic absorption spectroscopy.
Analytical study of a cadmium ion-selective ceramic membrane electrode
ZusammenfassungDie Membran wurde durch Pressen von Cd-, Ag und Cu(I)-sulfid bei 200–500°C und 3–7 t/cm2 hergestellt. Die beste Ansprechempfindlichkeit ergab sich bei einem Gehalt von <30% Cu2S und >5% CdS. Die Nernstsche Gleichung war gültig im Bereich von 10−1−10−6 M, der analytische Bereich war 10−1−10−7 M. Die Potentiale konnten mehr als 6 Monate auf einem konstanten Wert gehalten werden. Sie entsprachen dem Nernstschen Faktor, 2,303·R·T/2 F, im Temperaturbereich von 0–95°C. Erhebliche Störungen werden durch Ag+-, Cu2+-, Fe3+-, Hg2+-, S2− und J−-Ionen verursacht. Jedoch verursachen etwa 10–100fache Mengen von Pb2+- und Br−-Ionen sowie mehr als 1000fache Mengen von Alkali-, Erdalkali-, Zn2+-, Al3+-, Ni2+-, Co2+-, Mn2+-, ClO4−- und NO3−-Ionen keine Störungen.SummaryA cadmium ion-selective membrane electrode has been developed by applying a hot-pressing method. The membrane contains cadmium sulphide, silver sulphide, and copper(I)-sulphide.The best response was obtained with a membrane containing less than 30% of copper(I) sulphide and more than 5% of cadmium sulphide. The Nernstian slope was secured over an activity range of 10−1 to 10−6 M, and potentiometric analysis could be carried out over a concentration range of 10−1-10−7 M. The potentials were maintained at constant values over more than 6 months. Also, the potentials satisfied the Nernst's factor 2.303 RT/2F at the temperature range between 0 and 95°C. Among the common ions, silver, copper(II), iron(III), mercury(II), sulphide, and iodide ions interfered seriously. However, about 10–100 times of lead and bromide ions and more than 1000 times of alkali metal, alkaline earth metal, zinc, aluminium, nickel, cobalt, manganese(II), perchlorate, and nitrate ions did not interfere at all.
Perceived job importance and job performance satisfaction of selected clinical nutrition management responsibilities.
A nationwide survey of clinical nutrition managers was conducted to assess perceived importance of selected job responsibilities and perceived performance satisfaction of those job responsibilities. A questionnaire was developed to achieve the study objectives, validated by an expert panel, and pilot-tested prior to data collection. All members of the American Dietetic Association's Clinical Nutrition Management dietetic practice group (N=1,668) were asked to rate the importance of selected job responsibilities and their satisfaction with those responsibilities using Likert-type scales with descriptions. Results revealed that clinical nutrition managers perceived all job responsibilities listed in the questionnaire to be important (ie, the mean score of each responsibility was >3.0 of a 4.0 scale). Respondents rated regulatory-related job responsibilities as most important and were most satisfied with their performance of these responsibilities. Following regulatory-related responsibilities, clinical nutrition managers perceived patient satisfaction and staff retention to be more important than other responsibilities. In general, clinical nutrition managers were more satisfied with their job performance for job responsibilities that they ranked as more important.