Determination of alkaline earth metals by ion-exchange chromatography with spectrophotometric detection

Zenki, Michio

doi:10.1021/ac00230a010

Cited by 31 publications

(14 citation statements)

References 19 publications

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“…In such a scenario, the indicator anion could be added to the mobile phase either pre-or postcolumn and the concentration of the resultant complex monitored spectrophotometrically. While such an approach has been documented in the literature (7,8), and is indeed capable of a high degree of a selectivity between the analytes and interferants, in this study the sensitivity to both Ca2+ and Mg2+ was found to be insufficient to produce adequate precision. It was observed that pH was a major stumbling block in developing an assay that was sensitive for both Mg2+ and Ca2+.…”

Section: Resultsmentioning

confidence: 69%

Determination of alkaline-earth metals in samples containing a large excess of alkali by ion chromatography

Jenke¹

1987

Anal. Chem.

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The presence of a IO-fold excess of alkall metals In pharmaceutical samples represents a SnuaUon In whlch most avaWable Mea-and polymer-based exchange columns for Ion chromatography could not effectively separate these Interferants hwn slkaRneearth andytes. However, a heartattlng process that lnvolvc#i auhnnated sw#chlng of klentkal tandem columns 80 as to direct the Interferants to waste and the analytes to the detectkn system can be used to elLnlnate the problem. When coupled with regenerant flowtontrolled eluent suppresslon/conductlvlty detection, the methodology Is characterlzed by excellent performance. Area response Is linear In the range of 10-120 mg/L for Mg2+ and 20-200 mg/L for Ca2+. Accuracies for flve pharmaceutlcal matrkes routinely fell In the range of 100 f 2% recovery. For over 120 samples analyzed, mean and medlan preclslons were 0.84% and 0.45% for Mg2+ and 0.59% and 0.46% for Ca2+. Afler more than 1200 Injectlono, the system Is stlll capable of meeting rigorous suitablllty crlterla for chromatographlc performance and caHbraiion sultabltlty. Instrumental response Is constant over perlods of operatlon In excess of 48 h. Total analysls thne Is 9 mln.A large number of pharmaceutical products contain calcium and magnesium. These elements are present either as the counterion for anions, which act as preservatives, buffers, and diluents, or as electrolyte balance mediators. While ion chromatography represents a potentially viable approach for quantitating these ions in pharmaceutical samples, its universal application to these products is limited by the nature of the product's matrix. An overwhelming majority of solutions containing the alkaline earths also contain Na+ (or less commonly K+). The nature of these samples is such that the concentration of the alkali metals is an order of magnitude (or more) greater than that of the alkaline-earth analytes. The net result of this concentration mismatch is that under typical elution conditions the alkali metals cause chromatographic interference, especially with the Mg2+ peak, on most commercially available columns packed with either silica-or polymer-based resins. Even though the alkalis have little or no affinity for the resin under these conditions, the duration of what is essentially the void response is sufficiently large that complete resolution between this peak and the Mg2+ response is not achieved (for example, Figure 1). Even in situations where the overlap is relatively small, accurate integration of the Mg2+ response is hampered and analytical accuracy and precision suffer. Given the limited selectivity of these resins for Mg2+, there is little the analyst can do to improve the chromatographic behavior. While mobile-phase modification may improve the difference in apparent retention times between the alkalis and Mg2+, absolute resolution remains nearly constant as the increase in retention difference is nullified by an increasing peak width.Another way of handling the coelution problem would be to remove the alkalis from the sample before they ...

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Section: Resultsmentioning

confidence: 69%

Determination of alkaline-earth metals in samples containing a large excess of alkali by ion chromatography

Jenke¹

1987

Anal. Chem.

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“…Preliminary batchwise experiments revealed that CPN and its metal complexes were not adsorbed on the cation exchangers, 12 whereas neutral or cationic complexes, such as 1,10-phenanthroline-Fe 2+ derivatives, were adsorbed strongly. As they suggested, 14,15 the species that were adsorbed on the ion exchanger were positively charged and converted into a complex of a higher ligand number.…”

Section: Resultsmentioning

confidence: 99%

“…Although CPN reacts with Ca 2+ to form a blue complex over a wide pH range of 2 -12, 9 it is preferable to undergo the reaction under a weakly acidic solution because of growing background absorbance. [9][10][11][12] The influence of the pH on the complexation reaction was studied in the range of 3.5 -6.0 using appropriate mixing of 0.05 M acetic acid and a sodium acetate solution. The maximum complex formation was achieved for pH values ranging from 4.5 to 5.5.…”

Section: Optimization Of Chemical and Fi Variablesmentioning

confidence: 99%

“…The aim of the work described here was an attempt to regenerate and reuse the reagents in a circulatory FI system in order to develop a method for rapid and repetitive measurements. The spectrophotometric determination of Ca 2+ with chlorophosphonazo III (CPN) [9][10][11][12] was chosen to illustrate the application. After the spectrophotometric determination of Ca 2+ in a flow through-cell, the reagent stream was passed through a mini-column packed with a cation exchange resin for regeneration of the free CPN.…”

Section: Introductionmentioning

confidence: 99%

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Repetitive Determination of Calcium Ion and Regeneration of a Chromogenic Reagent Using Chlorophosphonazo III and an Ion Exchanger in a Circulatory Flow Injection System

2002

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The spectrophotometric determination of Ca 2+ with chlorophosphonazo III (CPN) has been carried out by a circulatory flow injection (FI) method. A cation-exchange mini-column for the on-line regeneration of the main reagent was incorporated in this FI system, allowing a repetitive determination of Ca 2+ . A solution of 4.0 × 10 -5 M CPN in a 0.05 M acetate buffer (pH 5.0) in a single reservoir (50 ml) was continuously circulated at a constant flow rate of 1.5 ml min -1 . Into the stream, an aliquot (20 µl) of a sample containing Ca 2+ was quickly injected by means of a 6-way valve. The complex formed was monitored spectrophotometrically at 670 nm in the flow system. Then, the stream passed through a cation-exchange column, which was introduced after the flow-through cell. A successful ligand-exchange reaction of Ca 2+ between the CPN reagent and a cation exchanger, as well as a simultaneous regeneration of the free reagent took place. The stream then returned to the reservoir. The regeneration and recycling of the CPN reagent allowed as many as 300 repetitive determinations of 2.5 mg l -1 Ca 2+ solutions with the same 50 ml circulating solution.

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“…The direct spectrophotometric mode is used to measure absorbance after mixing color reagent on a post-column basis (Smith Abbreviations: AAS, atomic absorption spectrophotometry; ACS, American Chemical Society; EDT A, ethylenediaminetetraacetic acid; HPLC, high performance liquid chromatography; IC, ion chromatography; ICP-AES, inductively coupled plasma-atomic emission spectrophotometry; NIST, National Institute of Standards and Technology; SCIC, single column ion chromatography; SIC, suppressed ion chromatography; SRM, standard reference material; TBAOH, tetrabutylammonium hydroxide; UV, ultraviolet. and Fritz, 1988;Fritz and Story, 1974;Arguello and Fritz, 1977) or mixing the color reagent with eluent (Zenki, 1981). The indirect spectrophotometric mode is used to measure absorbance after mixing a radiation-absorbing species in the eluent while the cations are nonabsorbing.…”

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confidence: 99%

Simultaneous Determination of Total Sodium, Potassium, Magnesium, and Calcium in Plant Tissues Using Acid Digestion and Ion Chromatography

Goyal

Rains

1993

Agronomy Journal

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Sodium, K, Mg, and Ca in plant tissue were measured by single column ion chromatography (SCIC) as an alternative to traditional methods such as atomic absorption spectrophotometry (AAS) or inductively coupled plasma–atomic emission spectrophotometry (ICPAES). Interference of the NH4 peak on the Na peak in SCIC was eliminated by removal of NH4 ions by drying the nitric‐perchloric acid plant digest at 350 °C. Cations were separated using an IC‐Pack CM/D column with 0.1 mM EDTA + 3 mM HNO3 as eluent. Inclusion of 10% (v/v, = 1.89 M) acetonitrile in the eluent shortened the retention time of divalent cations by 22% compared with the time without acetonitrile. The Na, K, Mg, and Ca content of plant samples analyzed with this technique agreed closely with certified values provided by the National Institute of Standards and Technology (NIST). The lower limit of detection of SCIC for Na, K, Mg, and Ca were 0.05, 0.2, 0.025, and 0.05 mg L−1, respectively, using a 100‐μL sample. The response of peak areas as a function of solute concentration was linear up to 10 mg L−1 of each cation. The SCIC method was cheaper than AAS or ICP, and faster than AAS, mainly due to simultaneous analyses of all four cations. SCIC did not generate hazardous and toxic waste and thus did not require special disposal procedures.

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Determination of alkaline earth metals by ion-exchange chromatography with spectrophotometric detection

Cited by 31 publications

References 19 publications

Determination of alkaline-earth metals in samples containing a large excess of alkali by ion chromatography

Determination of alkaline-earth metals in samples containing a large excess of alkali by ion chromatography

Repetitive Determination of Calcium Ion and Regeneration of a Chromogenic Reagent Using Chlorophosphonazo III and an Ion Exchanger in a Circulatory Flow Injection System

Simultaneous Determination of Total Sodium, Potassium, Magnesium, and Calcium in Plant Tissues Using Acid Digestion and Ion Chromatography

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