Determination Of Metal Cations Research Articles

Quantitative determination of metal cations chemisorbed by polycaproamide fabrics

Studies were conducted to develop a method of quantitative determination of metal cations chemisorbed by fabrics made of polycaproamide fibres. A complexonometric method was selected to determine the cation content. Complexonometric methods, which are highly accurate, approaching the accuracy of gravimetric methods, require much less time for execution. A single method is proposed for determining the amount of different metal cations chemisorbed by synthetic materials. The reproducibility of the results is good.

Natural Cyclodextrins as Efficient Boosters of the Chemiluminescence of Luminol and Isoluminol: Exploration of Potential Applications

The chemiluminescent oxidation of luminol (LUM) and isoluminol (ISOL) is notably enhanced, both in intensity and duration, in the presence of natural cyclodextrins (alpha-, beta-, gamma-CD). The experiments have considered some of the most widespread applications of these compounds: the determination of metal cations and the revealing of bloodstains by oxidation with hydrogen peroxide in alkaline solution in the presence of Co(II), Fe(III), human hemoglobin, and blood, in order to explore potential applications. The largest enhancement in the emitted intensity occurs for the reaction of LUM with Co(II) in the presence of beta-CD. The use of the more soluble gamma-CD permits to expand the range of concentration and obtain more intense emission, although soluble derivatives of the beta-CD (methyl, hydroxypropyl-beta-CD, and a soluble cross-linked epichlorhydrin polymer) do not improve the chemiluminescence (CL) yield. In the case of hemoglobin and diluted human blood, the CDs aid in producing more light but only at high concentration of CDs, with a more lasting luminescence, up to three times longer. The changes in CL when glucose is used instead, much lower than with any of the CDs, imply that the cyclic structure of these oligosaccharides plays a key factor in the boosting of the emission. The results are explained in terms of the binding between the luminescent intermediate of the reaction, 3-aminophthalate (3-AP) and the CD, rather than to the luminescent reactant itself. The association constants obtained by steady-state fluorescence by assuming 1:1 stoichiometries reveal that the most stable association occurs between beta-CD and the intermediate, in accordance with the trend in the chemiluminescence. The topology of the complex deduced via ROESY experiments confirms a shallow inclusion of the double-charged intermediate by the primary rim of the CD, which accounts for the low stability of the complexes.

Separation and determination of metal cations in milk and dairy products by CE

To prevent casein adsorption and improve between-run repeatability, a CE procedure is developed for cation analysis in milk using a modified imidazole/alpha-hydroxyisobutyric acid (HIBA) BGE system to operate at pH 6 to match the pH of milk and elevate imidazole concentration to enhance its buffer action. The procedure is shown to produce a fast, economic and efficient method for cation separation in milk with only simple dilution. Upon direct hydrodynamic injection of diluted milk sample at 8 cm for 30 s in an uncoated column with a BGE consisting of 10 mM imidazole, 10 mM HIBA and 10% methanol at pH 6.0 under +18 kV, baseline separation was achieved for K(+), Na(+), Ca(2+), Mg(2+), Mn(2+), Cd(2+), Co(2+), Ni(2+)and Zn(2+). Agreeable results at 95% confidence level were obtained using CE and inductively coupled plasma-atomic emission spectrometry (ICP-AES) for milk samples after protein removal. Baseline-resolved peaks for essential minerals were obtained for fresh and non-refrigerated reconstituted milks. Long-term stability was demonstrated by repeated determinations without rinsing and improvement in repeatability was shown by rinsing with 60 mM SDS in BGE. Information on metal speciation useful for nutritional assessment was obtained from CE to complement the ICP methods.

Compact Design for a Square Wave Excitation Contactless Conductivity Detector: Determination of Metal Cations in Environmental Water Samples

A compact and inexpensive contactless conductivity detection (CCD) based on a square wave excitation voltage, was implemented by integrating the function generator, detective cell, and detective circuit on a printed circuit board with a size of 100 mm length and 50 mm width, and it exhibited excellent sensitivity at the optimal frequency of 198 kHz. The separation for 13 metal ions was demonstrated by optimizing some most significant concentration factors, such as the concentration of 2‐(N‐morpholino) ethanesulfonic acid/DL‐histidine (MES/His), cetyltrimethylammonium bromide (CTAB), and α‐hydroxyisobutyric acid (HIBA). Under the optimized condition of 15 mM MES/His, 0.02 mM CTAB, and 0.5 mM HIBA, the detection limits were in the range of 0.9∼5 µM for K+, Ba2+, Ca2+, Na+, Mg2+, Mn2+, and Li+; 7∼25 µM for Pb2+, Cd2+, Zn2+, Co2+, Cu2+, and Ni2+. This CCD was further used to determine the metal cations in the real samples, such as tap water and low pH galvanic bath rinse water, and the results demonstrated that this CCD system was feasible for analysis of ions in an environmental sample.

Polished Silver Solid Amalgam Electrode: Further Characterization and Applications in Voltammetric Measurements

Polished silver solid amalgam electrode (p‐AgSAE) appears to be a good alternative to hanging mercury drop electrode (HMDE). The present work focuses on analysis of the electrode material and of the working electrode surface. It has been demonstrated that this electrode can be successfully used in inorganic electrochemical measurements for determination of metal cations, nitrates, and thiocyanates, etc.

Determination of metal cations in microchip electrophoresis using on‐chip complexation and sample stacking

Determination of metal cations in microchip electrophoresis using on‐chip complexation and sample stacking

Ion chromatographic separation of alkali metals in organic solvents

Ion-exchange chromatography is a common method for the separation and determination of metal cations. Although much research has been done on improving various aspects of this technique, the use of non-aqueous eluents has received little attention. The effect of organic solvents on the retention of alkali-metal cations on a macroporous polystyrene-divinylbenzene resin was studied. The retention of alkali cations increases as the organic content in the eluent increases for most organic solvents. Methanol was an exception with a maximum retention occurring at an eluent composition of methanol-water (75:25). Since organic solvents do not solvate these cations in the same manner as water, increases in the separation factors and changes in elution order are observed. Several separations that are not possible with aqueous eluents will be shown. The effect of crown ethers in the mobile phase was also investigated. In most solvent 18-crown-6 (18C6) altered the retention of all cations. In some cases 18C6 changed elution order or improved peak shape. Separations with an organic eluent and 18C6 modifier will also be shown.

Determination of metal cations by capillary electrophoresis effect of background carrier and completing agents

The determination of trace metals in aqueous samples can be readily accomplished by capillary electrophoresis (CE) via indirect absorbance detection. Methods for simultaneously determining alkali, alkaline earth and transition metal ions and Group IB, IIB and IVA metals ions were developed. Imidazole, benzylamine, ephedrine or pyridine was used as the carrier buffer and the background absorbance provider. Glycolic acid, α-hydroxy-isobutyric acid or succinic acid was used as the complexing agent. The elements determined were Li, Na, K, Cs, Mg, Ca, Sr, Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ag, Al and Pb. All ions could be separated in less than 15 min. In most instances reported here, more than a dozen ions could be separated in 5–10 min. All peaks were well separated and baseline resolved ( i.e., no peaks overlapped), except Ag and Al, which required a separate and additional analysis. The detection limit was in the range 0.02 (Na)−208 ppb (Cr) with the electrokinetic injection mode (10 kV, 5 s). The reproducibility was 1% for the migration time and better than 5% for the peak height for most metal ions. The calibration graphs were linear for most ions in the concentration range 10 −5−10 −3 M ( R 2 = 0.9995−0.9999) using the hydrodynamic injection mode. Concentrations lower than 10 −5 M can be determined using the electrokinetic injection mode, but the calibration graph is not linear. The methods developed here are well suited for determining metal ions in a variety of real samples.

A look at contemporary ion chromatography

The principles and historical development of ion-exchange chromatography are discussed briefly. Modern ion chromatography includes ion-exchange, ion-pair, ion-exclusion and the chromatography of ion—organic complexes. Each is explained briefly. The major detection systems for ion chromatography are outlined: conductivity (suppressed and non-suppressed), direct and indirect spectrophotometry, spectrophotometry with a post-column reactor, electrochemical, and differential refractometry. The question of isocratic vs. gradient elution is examined briefly. Recent studies on the selectivity of ion-exchange resins are presented. Several examples are given of recent separation methods from the author's laboratory. These include the separation of weak acids by ion-exclusion chromatography, the use of additional ion-exchange columns to enhance the detection of carbonic acid by conductivity, and the determination of metal cations by complexation and subsequent chromatographic separation.

Determination of metal cations by Fielddesorption Massspectrometry in biological tissues and fluids

Determination of metal cations by Fielddesorption Massspectrometry in biological tissues and fluids