Determination of calcium in organometallic compounds by atomic absorption spectroscopy

A simple and relatively rapid procedure for the estimation of calcium in organometallic compounds is described. The oxygen filled flask for decomposition of the organic sample and AAS determination of the metal in aqueous medium without any effect of the organic portion of the molecule or solvent is recommended. The results of calcium determination in a lubricant obtained by different combustion procedures and different final determinations are also compared.     

Determinations of traces of calcium in phosphoric acid and its salts by atomic-absorption spectrometry

A method for the determination of traces of calcium by atomic-absorption spectrometry after extraction into an organic solvent, has been investigated for the determination of traces of calcium in phosphoric acid and its salts. Calcium is extracted as the hydroxy-quinolate complex, the extract is introduced into the flame, and the calcium atomic-absorption is measured. The effects of pH, concentration of reagent, and diverse ions on the calcium extraction were investigated.     

空气—乙炔火焰原子吸收法测定钙所用的有机增效剂及其应用

分别考察了9种有机试剂对火焰原子吸收法测定水中钙的影响。结果表明,Triton X—100、CTMAB和抗坏血酸对测定有明显的增敏作用。其中抗坏血酸体系不仅使灵敏度提高约一倍,且抗干扰能力也最强,是一种较好的增效剂。该体系可用于测定天然水中钙的含量,方法灵敏、简便、快速,结果令人满意。     

原子吸收法测定血清中的无机磷和钙

本文叙述了用原子吸收法测定同一个少量血清样品中的无机磷和钙。血清用高氨酸沉淀蛋白后,加过量钼酸铵。在pH0.4～1.6范围内,用乙酸丁酯萃取生成的微量磷钼酸,与过量的钼酸铵分离。水相测钙,有机相用稀氨水反萃后测钼,间接分析磷。     

Microdetermination of calcium in organic compounds

A sensitive method for microdetermination of calcium in organic compounds is described. The combustion in an oxygen stream or oxygen flask with electrical ignition of the sample in porcelain crucible was found advisable. Carbon dioxide has to be expelled and the erroneous effect of phosphate eliminated by adsorption on an anion exchanger prior to the spectrophotometric determination of calcium with glyoxal bis (2-hydroxyanil).     

Study on microwave induced plasma atomic absorption spectrometry (MIP-AAS) for the determination of calcium in axial viewing mode

A low-power surface-wave plasma device (surfatron) is employed as an atomizer for microwave induced plasma atomic absorption spectrometry (MIP-AAS) and a desolvation-condensation apparatus has been used to remove the solvent in the aerosol. An axial viewing absorption technique is adopted for the determination of calcium. The matrix effect on its determination has been investigated in detail. Some enhancing effects are observed on the calcium absorbance in the presence of organic additives. A possible mechanism for this enhancement is discussed.     

Evaluation of a New Method for the Determination of Elements in Vegetable Foods and Feeds by Atomic Absorption Spectroscopy with Sampling of Carbonaceous Slurry

Abstract

The new method, proposed in a preceeding paper for the determination of elements in plant material by flame atomic absorption spectroscopy (FAAS) with liquid sampling of carbonaceous slurry, was tested on other kinds of organic material such as vegetable foods and feeds. Results are reported for the determination of calcium, magnesium, potassium, iron, manganese, zinc and copper in these materials. Also, the analytical results relative to the determination of cadmium by graphite-tube furnace atomic absorption spectroscopy (GTFAAS) for two matrices are given. In all cases accuracy and precision of the analytical procedure were ascertained.     

Analysis of biogenic carbonates by inductively coupled plasma-mass spectrometry (ICP-MS). Flow injection on-line solid-phase preconcentration for trace element determination in fish otoliths

The aragonite deposits within the ear bones (otoliths) of teleost fish retain a chemical signal reflecting the life history of fish (similar to rings of trees) and the nature of fish habitats. Otoliths dissolved in acid solutions contain high concentrations of calcium and a variety of proteins. Elimination of matrix salts and organic interferences during preconcentration is essential for accurate determination of trace elements in otolith solutions by inductively coupled plasma-quadrupole mass spectrometry. An iminodiacetate-based chelating resin (Toyopearl AF-Chelate 650 M) has been used for on-line preconcentration and matrix separation for the determination of 31 transition and rare elements. Successful preconcentration of the elements was achieved at pH 5 by on-line buffering, except Mn which required pH 8.8. Sample solutions were loaded on to the column for 1 min at 3.2 mL min(-1), and then eluted directly into the mass spectrometer with 4% v/v nitric acid. This procedure enabled up to 25-fold preconcentration with successful removal of the calcium matrix. The effect of heat-assisted oxidation with concentrated nitric acid was investigated to eliminate the organic matrix. It was found that heating to dryness after dissolution and further mineralization with the acid significantly improved the retention of the transition elements. The method was validated by analysis of a certified reference material produced from saggittal otoliths of emperor snapper ( Lutjanus sebae), and then applied to the determination of trace metal concentrations in juvenile bluefin tuna ( Thunnus thynnus) from the Western Pacific Ocean.     

Über die verteilung von metall-8-oxychinolin-verbindungen zwischen wasser und organischen lösungsmitteln : Mitt. photometrische bestimmung des magnesiums nach extraktion seines oxinates mit chloroform bei gegenwart von aminen

Under normal conditions, magnesium oxinate does not dissolve in non-polar organic solvents. In the presence of 2% butyl amine, however, magnesium can be extracted quantitatively in the pH range 10.5–13.6 by a 0.1% oxine-chloroform solution (concentration range 0.05–10γ Mg/ml), and can be determined photometrically by measurement of the extinction at 380 mμ. This reaction has been elaborated to a specific method of determination for small quantities of magnesium in the presence of the most important other elements. Furthermore, determination of magnesium can be combined quite simply with a photometric determination of slight iron content, also as the oxinate. The practical application of the method is demonstrated by determination of magnesium and iron in several calcium minerals, aluminium alloys and a zinc alloy.     

Three‐phase hollow‐fiber microextraction combined with ion‐pair high‐performance liquid chromatography for the simultaneous determination of five components of compound α‐ketoacid tablets in human urine

The determination of α‐ketoacid concentration is demanded to evaluate the absorption and metabolic behavior of compound α‐ketoacid tablets taken by chronic kidney disease patients. To eliminate the interference of endogenous substance of urine and enrich the analytes, a three‐phase hollow‐fiber liquid‐phase microextraction combined with ion‐pair high‐performance liquid chromatography method was established for the determination of d ,l ‐α‐hydroxymethionine calcium, d ,l ‐α‐ketoisoleucine calcium, α‐ketovaline calcium, α‐ketoleucine calcium, and α‐ketophenylalanine calcium of compound α‐ketoacid tablets in human urine samples. The extraction parameters, such as organic solvent, pH of donor phase and acceptor phase, stirring rate, and extraction time were optimized. Under the optimal conditions, the obtained enrichment factors were up to 11‐, 110‐, 198‐, 202‐, and 50‐fold, respectively. The calibration curves for these analytes were linear over the range of 0.1–10 mg/L for α‐ketovaline calcium, d ,l ‐α‐ketoisoleucine calcium, and α‐ketoleucine calcium, 0.5–10 mg/L for d ,l ‐α‐hydroxymethionine calcium, and α‐ketophenylalanine calcium with r > 0.99. The relative standard deviations (n = 5) were less than 6.27% and the LODs were 100.7, 10.0, 5.8, 7.8, and 8.6 μg/L (based on S/N = 3), respectively. Good recoveries from spiked urine samples (92–118%) were obtained. The proposed method demonstrated excellent sample clean‐up and analytes enrichment to determine the five components in human urine.     

Simultaneous determination of total and free calcium in milk by flow injection

A fast and reliable procedure for the determination of total and free calcium in milk is described. The method is based on the flow injection (Fl) technique. Total calcium is determined by atomic absorption spectrometry (AAS) (422.7 nm) and free calcium by spectrophotometry (580 nm). Interference in the determination of free calcium is eliminated by using a dialyser, which also separates the total and free calcium. Interference from phosphates in milk in the determination of total calcium by AAS is overcome by using a dinitrogen oxide-acetylene flame with the necessary suppression with K+. With 30-microliters samples the Fl system covers a standard working range of 100-1500 mg dm-3 of Ca2+. The system is suitable for the simultaneous determination of total calcium (relative standard deviation less than 1.30% for 1300-1500 mg dm-3 of total calcium) and free calcium (relative standard deviation less than 0.85% for 120-170 mg dm-3 of free calcium) in milk at a sampling frequency of about 60 samples h-1. The results obtained agree reasonably well with results from the AAS method.     

有机试剂对锶火焰原子吸收光谱分析的增感机理

研究了火焰原子吸收光谱法中甲醇、甲醛、甲酸等6种有机试剂对元素Sr的增感行为,发现甲酸效果最佳。在选定的相对最佳条件下,增感效果高达70%。研究表明,甲酸所产生的增感效应主要在于其与Sr形成甲酸锶,改变了常规原子化机理,提高了火焰原子化效率。这一机理同样适用于甲酸存在下Ca、Ba等元素的火焰原子化。实验表明,甲酸对这两种碱土元素的增感效果分别达到54%和55%。甲酸对Sr的增感应用于高纯BaCO3中Sr含量测定,回收率达到100%～106%。     

有机钙作用下褐煤SO2、NO析出及燃烧特性

在管式炉上研究了醋酸调制白云石产物、醋酸钙、丙酸钙等有机钙作用下龙口褐煤燃烧时SO₂、NO的析出特性,并在热分析系统上考察了相应的燃烧特性。合适的工况条件下有机钙能有效抑制SO₂、NO的析出。在973~1 273 K下,有机钙均能有效抑制SO₂的析出,而当温度继续升高,除醋酸钙外,其他有机钙抑制效果下降。在973~1 173 K时,有机钙促进了NO的析出,而当温度高于1 173 K时,醋酸钙和丙酸钙的抑制效果明显。随着钙硫比的增加,有机钙对SO₂、NO抑制效果普遍增强,而醋酸调制白云石产物在钙硫比为2.0~2.5时却促进NO的析出。当钙硫比为2.0时,褐煤着火性能明显提高,着火点降低10~33 K,但其燃尽时间稍有延长。     

Conversion of Ca2+ salt of an organic compound to its Li+ salt to simplify the fast atom bombardment mass spectrum

The FAB mass spectrum of the Ca(2+) salt of RK-682 (1, MW 368), a potent protein tyrosine phosphatase inhibitor, shows a complex pattern due to Ca(2+) adduct ions with multimers of 1 and their decomposition ions. Addition of LiCl greatly simplified the FAB mass spectrum, providing a prominent Li(+) adduct ion of 1 at m/z 381 [M+2Li-H](+). The addition of LiCl also greatly simplified the FAB mass spectrum of calcium pantothenate. This approach may be generally useful for molecular weight determination of multivalent metal salts of organic compounds, or organic compounds that can form Li salts, by FAB mass spectrometry.     

Determination of barium and strontium peroxides (active oxygen) in igniters in small-arms tracer ammunition

A method is proposed for the determination of barium and strontium peroxides (active oxygen) in igniters in small-arms tracer ammunition. The sample is treated with dilute hydrochloric acid (1 + 9) which dissolves the magnesium powder almost instantaneously and then dissolves the barium or strontium peroxides within 10-30 min. The solution is then filtered to remove the organic substances (calcium resinate, "Parlon". Toluidine Red toner, and zinc stearate) and the peroxide is determined by means of the colour of the titanium-peroxide complex. It is shown that igniter mixes and igniters used in small-arms tracer ammunition deteriorate on storage.     

高效液相色谱法测定菌群降解纤维素产物中的糖、有机酸和醇

采用硫酸除钙和调节pH的样品预处理方法,利用高效液相色谱对菌群降解纤维素发酵液中的糖、有机酸和醇3类物质进行分析,待测组分与培养基成分能够得到有效分离。从菌群降解纤维素发酵液中检出纤维二糖、葡萄糖、乙醇、丁醇、甘油、乙酸与丁酸并进行了定量分析,7种组分的检出限范围为0.10~2.00 mg/L,线性相关系数均大于0.9996,线性范围为0.020~1.000 g/L,回收率为85.41%~115.60%,相对标准偏差(RSD)为0.22%~4.62%(n=6)。该方法准确可靠,可实现对菌群降解纤维素发酵液中糖、醇和有机酸的同时准确测定。     

Effect of pentaerythritol and organic tin with calcium/zinc stearates on the stabilization of poly(vinyl chloride)

The stabilization effect of calcium and zinc stearates (CaSt₂/ZnSt₂) combined with pentaerythritol (PeE) and organic tin on poly(vinyl chloride) was investigated. The results show that the addition of calcium/zinc stearates combined with PeE and organic tin can improve thermal and colour stability of poly(vinyl chloride) in both static and dynamic tests. Mechanisms for improving stability of PVC are also discussed. The increase of stabilizing effectiveness of calcium/zinc stearates is ascribed to the synergistic effect between CaSt₂/ZnSt₂ and PeE and the interaction between organic tin and double bonds formed during the degradation of PVC. There is no synergistic action between organic tin and PeE or organic tin and calcium/zinc stearates.     

Spectrophotometric study of the reactions of arsenazo III with alkaline-earth metals

Arsenazo III is used as a spectrophotometric reagent for alkaline-earth metals. The molar absorptivities of the calcium, strontium and barium complexes at 650 nm are 4.40 x 10(4), 4.00 x 10(4) and 3.65 x 10(4) l.mole(-1).cm(-1) respectively. The interference of magnesium is eliminated at pH 5-6. The use of sodium sulphate as masking agent permits the determination of small amounts of calcium, strontium and magnesium in the presence of barium. The alkaline-earth ions can be determined in the presence of each other at pH 4.2 at the 2-10 mug level. Some organic solvents such as dioxan, acetone and ethanol increase the sensitivity and selectivity in acidic medium. The stability constants have been measured and the structure of the complexes is discussed.     

Determination of Rosuvastatin in Pharmaceutical Formulations by Capillary Zone Electrophoresis

A capillary zone electrophoretic method with diode array detection was developed and validated for the determination of rosuvastatin calcium in pharmaceutical formulations. Using fused-silica capillary (i.d. 50.0 μm, total length 48.5 cm and effective length 40.0 cm), the influence of the buffer composition, buffer pH and buffer concentration, as well as organic modifier, applied voltage, capillary temperature and injection time were investigated to optimize the method. Optimum results were obtained with 50.0 mM borate buffer at pH 9.5, capillary temperature 30 °C and applied voltage 25 kV. The samples were injected hydrodynamically for 5 s at 50 mbar. Detection wavelength was set at 243 nm. Diflunisal was used as internal standard. The migration times of rosuvastatin calcium and diflunisal were 3.20 ± 0.01 and 4.20 ± 0.02. The total time of analysis was <6 min. The method was validated for rosuvastatin calcium determination in pharmaceutical formulations through following performance parameters: stability, linearity, sensitivity, precision, accuracy, recovery, selectivity, robustness and ruggedness. The linear calibration range was 3.00–200.00 μg mL^?1 and the limits of detection and quantification were 1.00 and 3.00 μg mL^?1 with RSD of 4.38 and 3.09%. The proposed method was applied for the determination of rosuvastatin calcium in its pharmaceutical formulation.     

Determination of calcium stearate in polyolefin samples by gas chromatographic technique after performing dispersive liquid-liquid microextraction.

In this study, a gas chromatographic method is presented for the determination of calcium stearate after its conversion to stearic acid in a polymeric matrix. A solution of hydrochloric acid in 2-propanol is used as an extracting solvent of calcium stearate and its converter to stearic acid. For stearic acid preconcentration before its injection to a separation system, a recently presented extraction method, dispersive liquid-liquid microextraction, using carbon tetrachloride as an extracting solvent is used. Finally, 1 microL of the organic phase collected at the bottom of a conical test tube after centrifuging is injected into a gas chromatograph (GC) for quantification. This method has a relatively broad linear dynamic range (50 - 2000 mg/L) with a limit of detection (LOD) of 15 mg/L for stearic acid in solution. The LOD of the proposed method in a polymeric sample using 10 mg of polymer is 60 ppm as calcium stearate. Some effective parameters, such as the time and temperature of heating, the concentration of hydrochloric acid and the volume of distilled water, were studied.