Figures of Merit and Fundamental Processes in the Analysis of Ca from Liquid Samples Using an rf CCP Torch with Tubular and Ring Electrodes (original) (raw)
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Indian Journal of Clinical Biochemistry, 2013
To determine the concentration of ionized calcium (iCa) collected in lithium heparin and gel tubes and to correlate the measured iCa with calculated iCa. Anaerobic fasting blood samples were simultaneously collected from healthy laboratory workers in lithium-heparin and gel tubes. iCa, pH, total calcium (CaT), total protein and albumin were measured. Ionized Ca was calculated with albumin and globulin values using an appropriate formula. Mean iCa in gel tubes showed a positive constant bias of 0.08 mmol/L (p \ 0.001) when compared to lithium heparin results. The mean pH of blood taken in lithium heparin and gel tubes was non-significant (p = 0.3). Measured iCa poorly correlated with CaT (r = 0.2, p = 0.1) and calculated iCa (r = 0.2, p = 0.2). To evaluate the calcium status direct measurement of iCa must be done rather than using the formulae for iCa determination. In addition serum is recommended as the choice of sample for iCa determination in comparison to plasma samples.
A simplified protocol for measurement of Ca isotopes in biological samples
Journal of Analytical Atomic Spectrometry, 2014
We describe a chemical separation protocol of calcium from biological materials for isotopic measurement by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS). The method was tested using elution profiles along with HCl and HNO 3 acids only, on human urine, sheep serum and red blood cells (RBC), seawater and herbaceous plants. It allows the elimination of all interfering species (including K, Sr, Mg) and the remaining matrix (including Fe, P, Na and S) beyond required levels. In order to further test this protocol and better understand the Ca isotopic signatures of mammalian fluids and organs, we purified and analyzed a wide range of materials from sheep, i.e. serum, RBC, muscle, liver, kidneys, enamel, bone, urine and feces. The data show a wide range of variations, expressed as d, over 1& per amu, with a precision of 0.1& or better, spanning most of the variability reported so far. Red blood cells appeared to be heavier than serum by 0.3& per amu. This isotopic difference between serum and red blood cells was not taken into account in previous studies and it provides further information on Ca isotopic cycling in organisms. The Ca isotopic compositions of organs are correlated with concentrations, bone and RBC representing the two end-members, bone being Ca rich and 44 Cadepleted and RBC Ca poor and 44 Ca-enriched. The trend is compatible with a distillation process by which Ca is extruded from cells along with a kinetic fractionation process favoring lighter Ca isotopes.
LaboratoriumsMedizin, 2005
Plasma calcium exists in three forms: ionized, protein bound, and complexed with anions. Although all the forms are in equilibrium with each other, only the plasma ionized calcium has been reported to be physiologically active. Thus it is the preferred constituent for use in patient care. Despite this fact, the use of plasma total calcium concentration continues to be the predominant test for patient care in most hospitals mainly because of availability and ease of measurement. It has been documented that the use of total calcium is unreliable in cases where there is a change in the protein-calcium binding characteristics as in patients with hypergammaglobulinemia or a decrease/increase in pH. In an attempt to enhance the diagnostic accuracy of total calcium for these cases, several formulae have been developed for estimating ''corrected'' plasma total calcium. Although these formulae work reasonably well in normal healthy populations, they have been inadequate when applied for critically ill patients who are most prone to derangements in calcium metabolism. It has therefore been suggested that the measurement of the biologically active plasma ionized calcium be the routine rather than the exception. Ionized calcium however, has not gained widespread use for reasons that include the lack of familiarity by clinicians with the use of ionized calcium, problems historically associated with the measurement of ionized calcium, intricacies in the sample collection, and unavailability of ionized calcium measurement on the major clinical chemistry platforms. The advent of ionized calcium measurement as a standard feature in nearly all blood gas analyzers has enhanced its availability, especially in the critical care units. It is recommended that the use of ion
IOP Conference Series: Materials Science and Engineering
Spectrophotometric method for determination of Ca in aqueous solution using 1-(2pyridylazo)-2-naphthol (PAN) as colour reagent has been developed. The method was based on the formation of Ca-PAN complex at pH 12 and measuring absorbance at 550nm, with molar absorptivity of 1.70x10 4 L.mol-1 cm-1 , average recovery is 101.72 and precision (RSD) is better than ±2.8% indicating that the method is relatively sensitive, accurate and precise. The binary system of Ca(PAN)2 and conditional stability constant of 1.467x10 10 L 2 .mol-2 adherence of Beer's law over concentration range 0.08-2ppm. The method was applied for the determination of Ca in natural water, milk, yogurt, human serum, grip and tomato juice satisfactory. In presence of 1% tween 80 and composite masking agents of pH 11.5 the absorbance measurements were made at 540nm giving molar absorptivity of 2.7x10 4 L.mol-1 cm-1 , average recovery of 101.2 and precision (RSD) better than ±3% indicating that the Ca(PAN)2 system is sensitive, accurate, and precise. In addition it is considered to be simple, rapid and do not need heating or solvent extraction steps, moreover it can be applied successfully for the assay of Ca in various samples over concentration range of 0.0008-0.8ppm.
Determination of calcium in Urine and serum by atomic absorption spectrophotometry (AAS)
Clinical Chemistry
The determination of calcium in biologic fluids by atomic absorption spectrophotometry is interfered with by the presence of protein, cations, and those anions that form complexes with calcium. Such interference was overcome when lanthanum was included in a 1:50 dilution of serum or urine. Recovery of calcium added to calciumfree serum was 100%. The S.D. based on double-blind duplicates was 0.22 mg./lOO ml. Excellent statistical agreement was found between the test method and each of the 2 reference methods.
Time-dependent variation of ionized calcium in serum samples
Biochemia Medica
Introduction: The aim of this study was to compare ionized calcium (iCa) concentrations in arterial heparinized blood and venous serum and to investigate time-dependent variation of iCa in serum samples centrifuged and analysed at different times. Materials and methods: Ionized calcium was measured (N = 25) in arterial blood within 20 min after puncture, and in serum within 10 min after centrifugation conducted 30 min after sampling. Effect of time between sampling and centrifugation was examined in three tubes (N = 30) centrifuged 15, 30 and 60 min after sampling, and analysed within 10 min. Effect of time between centrifugation and analysis was investigated in three tubes (N = 31) centrifuged 30 min after sampling and analysed: 0-10, 30-40 and 90-100 min after centrifugation. Ionized calcium was measured on the Siemens RapidLab 348EX analysers. Statistical significance was tested using Wilcoxon test and ANOVA analysis. Clinical significance was judged against reference change valu...
Biological fluids monitoring is one of the important tools in prevention of diseases. Mineral elements in these media are essential factors to collaborate biological monitoring, disease conditions of humans, and maintenance of good health. These minerals are usually measured in laboratories using complicated and expensive techniques as ion chromatography (IC), atomic absorption spectroscopy (AAS), and inductive coupled plasma (ICP). The current work tries to validate alternative simpler and cheaper methods for the measurement of calcium (Ca 2+) and magnesium (Mg 2+) in the biological medium. Therefore, we had optimized EDTA titration, flame-atomic emission spectroscopy (FAES), and ion-selective electrode (ISE) to measure biological calcium. In addition, EDTA titra-tion and ISE used to measure magnesium in biological samples. In fact, we are the first who totally validated cheapest analytical methods for the analyses of these cations in biological fluids. The influence of standard calibration curve on method imprecision and inaccuracy was examined using external and internal quality control materials. In general, the recoveries of the optimized methods were sufficiently good [92–103%]. Good stable re-producibility was registered especially with the lowest values of the relative standard deviation (RSD) of the ISE. Besides, good readabilities expressed as the limits of quantitation (LOQs) for Ca 2+ measurements using FAES, ISE, and EDTA were (2.1–3.0 mg/L), (3.1–6.1 mg/L), and (3.9–7.7 mg/L), respectively. In addition, the LOQs for Mg 2+ measurements using ISE and EDTA were (1.2–4.5 mg/L) and (2.0–5.7 mg/L), respectively. Difference (%) of the reproducibility of the measurements in 5 days and the uncertainty was in the following range: FAES (just for Ca 2+) ISE EDTA. The validated methods showed acceptable correlations (0.9734–0.9990). They provided rapid, less tedious, practical and more accurate alternatives for the quantification of those bivalent cations in human fluids. Consequently, this research supports the implementation of cheap techniques and provides accurate analytical methods for the measurements of biological calcium and magnesium.
Talanta, 2012
Tungsten coil atomic emission spectrometry (WCAES) is employed for the determination of calcium in juice, mineral and coconut water samples. A sample aliquot of 20 mL is placed directly on the coil and a constant-voltage power source is used to dry and atomize the sample, as well as to promote Ca atomic emission. Analytical signals are resolved and detected using a Czerny-Turner spectrometer and a charge coupled device detector. Some experimental parameters such as coil position related to the spectrometer entrance slit and integration time are critically evaluated. A heating program with relatively constant drying temperatures is used in all measurements. An in situ digestion procedure is used to partially decompose organic matrices and improve WCAES precision and accuracy. By adding an oxidizing mixture to the sample and including a digestion step in the heating cycle, no statistical difference was observed between WCAES and ICP OES results for Ca in juice and coconut water samples. Mineral water samples were simply diluted with 1% v v À 1 HNO 3 before analysis and no significant interference was observed for concomitants such as Na and K. Despite severe positive interference caused by Mg, good agreement was obtained between WCAES and ICP OES results for Ca in several mineral water samples. Limits of detection and quantification obtained were 0.02 and 0.07 mg L À 1 , respectively. The method precision, calculated as the relative standard deviation for 10 consecutive measurements of a 2.5 mg L À 1 Ca solution, is 3.8%.
Impedance of Results Using Lithium Heparin to Plain Tubes for Ionized Calcium
The study was conducted to evaluate the differences in results obtained for assays of ionized calcium (iCa+2) by plain and heparinised blood sample and observe for any errors in values done by ion selective electrode (ISE) method and to determine which of the collection methods could be ideal and reliable. 49 samples of heparinised and 31 plain blood samples were analyzed at lab services, Apollo Reach hospital, Karimnagar, Telangana state for iCa+2 by ISE method using radiometer analyzer and the differences in data were documented statistically by calculating the mean and SD. The results of the study showed statistically significant difference in values of iCa+2 when blood was collected in plain tube (4.7±0.2) and with heparinised collection (4.4±0.3). It appears in the study that plain tube collection for the assay is ideal.