Determination by flame photometry

See the section on Sodium . The characteristic spectral line for lithium lies at a wavelength of 671 nm. 

In the case of lithium levels around or below 1 mg/1, concentration is 

Since calcium ions in concentrations greater than 1000 mg/1 have the effect of raising emissions, ethanol extraction must be used for waters of this type (investigation of the sample following concentration). 

See the section on Sodium 3.3.2. The following items are required in addition  

Dissolve 10 g barium chloride, BaCl2 2 H2O, reagent purity, in 100 ml 

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Figure 14-9 also shows a flowchart for analysis of wet and dry precipitation. The process involves weight determinations, followed by pH and conductivity measurements, and finally chemical analysis for anions and cations. The pH measurements are made with a well-calibrated pH meter, with extreme care taken to avoid contaminating the sample. The metal ions Ca, Mg, Na, and are determined by flame photometry, which involves absorption of radiation by metal ions in a hot flame. Ammorda and the anions Cl, S04 , NO3 , and P04 are measured by automated colorimetric techniques. 

All the alkali metals have characteristic flame colorations due to the ready excitation of the outermost electron, and this is the basis of their analytical determination by flame photometry or atomic absorption spectroscopy. The colours and principal emission (or absorption) wavelengths, X, are given below but it should be noted that these lines do not all refer to the same transition for example, the Na D-line doublet at 589.0, 589.6 nm arises from the 3s — 3p transition in Na atoms formed by reduction of Na+ in the flame, whereas the red line for lithium is associated with the short-lived species LiOH. 

The phenomenon of ion exchange has been confirmed by chemical analysis Films were exposed to potassium chloride solutions of increasing pH, ashed and their potassium content determined by flame photometry. It was found that the potassium content of the films increased as the pH of the solutions rose until saturation was reached at a value which corresponded to that of the change-over in the mechanism of conduction. It was concluded that the change-over in the mechanism of conduction corresponded to the point at which the exchange capacity of the film had reached its limit. 

The ratio, Nj/N0, can therefore be calculated. For the relatively easily excited alkali metal sodium, it is 9.9 x 10 6 at 2000 °K and 5.9 x 10 4 at 3000 °K this latter temperature is about the highest commonly obtained with flames used for atomic absorption or emission work. Hence, only about 1(T3 % of the sodium atoms are excited at 2000 ° and 6 x 1(F2 % at 3000°. For an element such as zinc,Nf/N0 is 5.4 x 10"10 at 3000 and so only 5 x 10"8% is excited. In spite of the small fraction excited, good sensitivities can be obtained for many elements by flame photometry if a high temperature flame is used, because the difference between zero and a small but finite number is measured. For example, seventy elements can be determined by flame photometry using the nitrous oxide-acetylene flame 1H. 

Potassium and sodium are determined by flame photometry (see Method 5.2 Measurement of potassium and sodium by flame photometry ). 

The content of aluminum in the reaction solution was determined at 50 p.p.m., the content of sodium at 100 p.p.m. Up to 95% conversion, the metal content in solution did not change, but at the end of the esterification about 50% of the aluminum had separated as an insoluble substance, and only 10% of the original concentration of the alkali still existed in solution. After removing the remaining alcohol and brightening the plasticizer with adsorbents, the content of the two metals lies with 0.07 p.p.m. sodium and 0.1 aluminum at the limit of detectability. The sodium was determined by flame photometry the determination of aluminum is discussed later. 

An official method has been published for the determination of nickel in 1M ammonium nitrate extracts of potassium from soil [178]. The level of potassium in the extract is determined by flame photometry. Inductively coupled plasma atomic emission spectrometry (Sect. 2.55) and stable isotope dilution (Sect. 2.55) have been applied to the determination of potassium in multi-metal analyses. 

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-... 

Flow-injection analysis is a versatile technique to evaluate the performance of a detector system. CHEMFETs may have an advantage over ISEs because of their small size and fast response times. We have tested our K+-sensitive CHEMFETs in a wall-jet cell with a platinum (pseudo-)reference electrode. One CHEMFET was contineously exposed to 0.1 M NaCl and the other to a carrier stream of 0.1 M NaCl in which various KC1 concentrations in 0.1 M NaCl were injected. The linear response of 56 mV per decade was observed for concentrations of KC1 above 5 x 10"5 M (Figure 9). When we used this FIA cell (Figure 10) for determination of K+ activities in human serum and urine samples, excellent correlations between our results and activities determined by flame photometry were obtained (Figure 11). 

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. 

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). 

A study has been performed in which a single piece of 1200 EW Nafion was successively placed in the H ", Na" ", Cs+, Mg2" ", and Ca2+ forms analyses were performed for each counterion after desorption (7). No difference could be found, within 1% relative error, in the measured number of exchange sites for each counterion form. This result agrees with an infrared study of the conversion of hydrogen ion forms of Nafion samples of various equivalent weights into univalent and divalent metal ion forms (8). The degree of replacement of hydrogen ion was measured to be 99-100% in all cases. However, Roche and co-workers (9) estimated the extent of conversion of a H" "-form of Nafion to the Na" "-form to be only 77%, as determined by flame photometry. No... 

For simultaneous determinations and /or speciation, different separation/ concentration steps can be implemented in the same manifold, as in, e.g., the determination of nitrogen, phosphorus and potassium in fertilisers [314]. The sample was inserted and passed successively through a dialysis unit and a gas diffusion unit to a flow cell for the spectrophotometric determination of phosphate. The dialysed potassium ions and the diffused gaseous ammonia were collected in specific streams and determined by flame photometry and potentiometry, respectively. 

Sodium and potassium content in polyethers is determined by flame photometry from aqueous solutions of polyethers disaggregated before, or directly from solutions of polyethers in ethanol. The determinations are based on calibration curves made with solutions having known amounts of sodium and potassium ions. The maximum content of Na and K ions in polyethers was around a maximum of 5-10 ppm. In the polyether polyols used for prepolymer manufacture, the maximum limit for Na and K content is accepted as a maximum of 2 ppm in order to avoid the trimerisation and gelation of the prepolymer during storage. 

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. 

Within the separated liquid phases, Si02 and Al203 were analyzed according to conventional chemical methods. Na20 was determined by flame photometry. Crystalline reaction products were identified by Debye-Scherrer diagrams the composition of the mixtures was determined by comparison with diagrams of test samples. 

The instructions given in the section on sodium determination by flame photometry (3.3.2.1) should be applied analogously. 

The precipitate is dissolved in acetone and used for determination by flame photometry (see also detection by atomic absorption. Section 3.3.4.2). The tetraphenylborate anion does not interfere with flame emission (I. Rubeska). 

Measure a quantity of the sample containing exactly 200 mg of K+ on the basis of the potassium content of the sample previously determined by flame photometry. If the potassium content of the water is so low that 10 litres of water contain less than 200 mg of K+, measure off 10 litres of the water sample with known potassium content and add the missing proportion of... 

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