Calcium flame photometry

Calcium, strontium and barium produce characteristic flame colours like the Group 1 cations (calcium, orange strontium, red barium, green) and flame photometry can be used for their estimation. All give insoluble carbonates in neutral solution. 

Presence of aluminium and calcium. The quantity of aluminium in vaccines containing aluminium hydroxide or aluminium phosphate as an adjuvant is limited to 1.25 mg per dose and it is nsnally estimated compleximetrically. The qnantity of calcium is limited to 1.3 mg per dose and is usually estimated by flame photometry. 

Polarography has also been applied to the determination of potassium in seawater [535]. The sample (1 ml) is heated to 70 °C and treated with 0.1 M sodium tetraphenylborate (1 ml). The precipitated potassium tetraphenylborate is filtered off, washed with 1% acetic acid, and dissolved in 5 ml acetone. This solution is treated with 3 ml 0.1 M thallium nitrate and 1.25 ml 2M sodium hydroxide, and the precipitate of thallium tetraphenylborate is filtered off. The filtrate is made up to 25 ml, and after de-aeration with nitrogen, unconsumed thallium is determined polarographically. There is no interference from 60 mg sodium, 0.2 mg calcium or magnesium, 20 pg barium, or 2.5 pg strontium. Standard eviations at concentrations of 375, 750, and 1125 pg potassium per ml were 26.4, 26.9, and 30.5, respectively. Results agreed with those obtained by flame photometry. 

Calcium Adsorption on Chelex-100 resin, desorbed with hydrochloric acid Flame photometry at 622 nm [167]... 

Flame photometry is the name given to the technique that measures the intensity of the light emitted by analyte atoms in a flame. It is the oldest of all the atomic techniques. It is not highly applicable because of the low temperature of the flame. Only a handful of elements can be measured with this technique, including sodium, potassium, lithium, calcium, strontium, and barium. The technique was formerly used... 

The results obtained with ISEs have been compared several times with those of other methods. When the determination of calcium using the Orion SS-20 analyser was tested, it was found that the results in heparinized whole blood and serum were sufficiently precise and subject to negligible interference from K and Mg ([82]), but that it is necessary to correct for the sodium error, as the ionic strength is adjusted with a sodium salt [82], and that a systematic error appears in the presence of colloids and cells due to complexa-tion and variations in the liquid-junction potential [76]. Determination of sodium and potassium with ISEs is comparable with flame photometric estimation [39, 113, 116] or is even more precise [165], but the values obtained with ISEs in serum are somewhat higher than those from flame photometry and most others methods [3, 25, 27, 113, 116]. This phenomenon is called pseudohyponatremia. It is caused by the fact that the samples are not diluted in ISE measurement, whereas in other methods dilution occurs before and during the measurement. On dilution, part of the water in serum is replaced by lipids and partially soluble serum proteins in samples with abnormally increased level of lipids and/or proteins. 

Flame Photometry, Atomic Absorption, and Neutron Activation. Comparatively few substances amenable to measurement by these techniques are used therapeutically chief among those that are being sodium, potassium, lithium, calcium, magnesium, zinc, copper, and iron, for all of which one or other of the techniques is the method of choice. 

Complexometric titration with EDTA is the usual winery procedure for determining calcium (4, 6, 22, 113), but atomic absorption spectrophotometry (51,53,112) and flame photometry and a rapid micro method based on oxalate precipitation (114) have been used successfully. 

Conditioning of the manganese oxide suspension with each cation was conducted in a thermostatted cell (25° 0.05°C.) described previously (13). Analyses of residual lithium, potassium, sodium, calcium, and barium were obtained by standard flame photometry techniques on a Beckman DU-2 spectrophotometer with flame attachment. Analyses of copper, nickel, and cobalt were conducted on a Sargent Model XR recording polarograph. Samples for analysis were removed upon equilibration of the system, the solid centrifuged off and analytical concentrations determined from calibration curves. In contrast to Morgan and Stumm (10) who report fairly rapid equilibration, final attainment of equilibrium at constant pH, for example, upon addition of metal ions was often very slow, in some cases of the order of several hours. 

Major and minor elements in coal, having concentrations easily detectable by most modem analytical techniques, can be determined by a number of acceptable procedures. Various approaches, combining a. number of specific procedures, are frequently referenced in the literature. For example, the presently accepted procedure (ASTM D-2795) determines silicon, aluminum, iron, titanium, and phosphorus colorimetrically, calcium and magnesium chelatometrically, and sodium and potassium by flame photometry. This standard test method was withdrawn in 2001 but is still used in some laboratories. 

In Table 3 uncertainty components are summarized including the magnitude and method of evaluation for the end-point determination of glucose, urea and calcium, along with potassium determination by flame photometry. Unknown samples consisted of sera-type materials, gravimetrically prepared under well-con-... 

In environmental analysis, flame photometry is most widely used for the determination of potassium, which emits at 766.5 nm. It is also often used for the determination of sodium at 589.0 nm, although spectral interference problems (see Chapter 3) then may be encountered in the presence of excess calcium because of emission from calcium-containing polyatomic species. Molecular species are more likely to be found in cooler flames than in hotter flames. Some instruments use single, interchangeable filters, while others have three or more filters, for example for the determinations of potassium, sodium and lithium,... 

Sodium is still often determined by flame photometry, measuring the emission intensity of the doublet at around 589 nm, but care is necessary to make sure that excess calcium does not cause spectral interference (from molecular emission). This is unlikely to be a problem if AES is used, with a narrow spectral band-pass, and the intensity of emission at 589.0 nm from an air-acetylene flame is measured. However, at low determinant concentrations it is then advisable to add 2-5 mg ml 1 potassium or caesium as an ionization buffer. This is even more true if a nitrous oxide-acetylene flame is used for FES, although its use is rarely justified in environmental analyses because the additional sensitivity gained is rarely necessary. 

Urine and serum samples are analyzed for uric acid (Uricaquant-method), creatinine (Jaffe reaction), sodium and potassium (flame photometry), calcium and magnesium (atom absorption method), and chloride (argentometry) as well as for osmolality. 

The development of fast and accurate procedures for the determination of calcium in biological materials represents one of the important early achievements of atomic absorption spectroscopy. The diflBculties encountered with calcium in emission flame photometry are well known (Dll, L6, S6, SIO), but spectral interferences and extreme dependency on flame temperature, serious obstacles in emission, are either nonexistent or of lower importance in absorption. Chemical interferences, however. 

D14. Dinnin, J. I., Releasing effects in flame photometry. Determination of calcium. Anal. Chem. 32, 1475-1480 (1960). 

Spector, J., Mutual interferences in elimination of calcium interference in flame photometry. And. Chem. 27, 1452-1455 (1955). 

The concentration of sodium ions was determined by flame photometry. Analysis of nickel, calcium, and magnesium ion concentration was carried out by atomic absorption spectrophotometry (Pye Unicam 8800, United Kingdom). The concentration of sulfate ions was determined by titration with barium chloride (BaCl2) solution in the presence of rhodizonate as indicator. Chloride ions were determined using ion-selective electrodes (manufacmred by Radelkis, Hungary). 

The general viability of low-temperature flame photometry depends on two factors. First, the alkali and alkaline earth metals of analytical interest (sodium, potassium, lithium, cesium, rubidium, magnesium, calcium, strontium, and barium) reach their excited states at relatively lower temperatures than do most other elements. Second, the emission wavelengths offer enough resolution such that optical filtering can be accomplished at a relatively low cost. 

Figure 1 represents four examples of the evaluation of measurement uncertainty for potassium, calcium, magnesium and glucose using flame photometry, atomic absorption spectrometry and molecular spectrometry (Mg determination with Titan Yellow and glucose determination with glucose oxidase). For the sake of simplicity in Fig. 1, the component of uncertain-... 

Fig 1 Measurement uncertainty components for the determination of potassium by flame photometry (SI), calcium by atomic absorption spectrometry (S2), magnesium by molecular spectrophotometry (55), glucose by molecular spectrophotometry (S4)... 

In modem laboratories sodium and potassium are almost exclusively determined by flame photometry and it seems likely that the same will shortly become true of calcium and magnesium and possibly of iron, copper, chromium, manganese, cobalt, lead, and zinc. 

The normal range of plasma or serum calcium concentration varies slightly with the method of estimation. The ranges are 9.0-11.4 mg/100 ml by the classic oxalate precipitation method (Kl) 9.6-11.2 by flame photometry (M4) and 9.0-10.5 by chelation with EDTA in the presence on an indicator (author s observations). For the purpose of this article, it will be assumed that the normal calcium concentration in plasma is... 

Dobbins, J.T. Jr Elution column preparation of leaf samples for flame photometry. II. Determination of calcium in tobacco J. Assoc. Off. Agr. Chem. 46 (1963) 418-424. 

Another advantage (or disadvantage, depending on the problem at hand) of many electrochemical methods is that they respond to the activity of a chemical species rather than to the concentration. An example where this may be of importance is the calcium level in serum. Ion-selective electrodes respond to free, aquated Ca ions, whereas the usual clinical method for serum calcium is flame photometry, which measures the total calcium present including a large amount tied up as protein-bound calcium. The more important physiological parameter, the measure of the effective level of calcium actually available for participation in various enzymatic... 

The titre of the sodium and potassium composition was carried out in emission flame photometry and for calcium in atomic absorption. By means of this method we determined the total quantity of sodium, potassium and calcium to be compared with the result obtained by the electrodes (ISE) both at 37 C and 25 C the electrodes have been previously standardized with pure sodium, potassium and calcium chloride solutions. 

The standardization solutions adopted reduce the error deriving from the activity coefficient and the presence of the liquid junction potential supplying results on samples of normal blood (for content of total proteins, cholesterol, triglycerides and plasma water) or its serum or plasma in agreement with those determined for sodium and potassium through indirect methods (for example, flame photometry or ISE dil) otherwise through comparison methods for pH and ionized calcium (already existing commercial instrumentation). 

There are also test methods (ASTM, 2011k,w) for the analysis of coal (and coke) ash which cover the determination of nine major constituents of ash silicon dioxide, aluminum oxide, ferric oxide, titanium dioxide, phosphorous pentoxide, calcium oxide, magnesium oxide, sodium oxide, and potassium oxide (ASTM, 2011k) by a combination of spectrophotometric techniques, chelatometric techniques, and flame photometry. Determination of these same constituents, including manganese dioxide, can be achieved by atomic absorption (ASTM, 2011w). 

Metallic cations in milk and dairy products (including sodium, potassium, calcium, and heavy metal contamination) may be measured by flame photometry (Na, K ) or atomic adsorption spectrometry (AAS) (other elements) in which the sample is atomized in the gas flame and the adsorption is measured at the characteristic wavelength of each element. 

Calcium in wet-oxidized samples is determined by AAS. In principle, it can be measured by flame photometry but the lower sensitivity of instruments for the calcium flame limits the usefulness of this method. 

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