Potassium, flame photometric determination

Berges, D., G. Schmitt et al. (1959). The effects of helenien and vitamin A on the primary sight process. III. A flame photometric determination of the potassium and sodium content of the retina (German). Z. Biol. Ill 220-227. 

Empirical Modeling of the Effects of Interference on the Flame Photometric Determination of Potassium and Sodium in Water... 

In the following text it shall be demonstrated that possible interferences on the flame photometric determination of potassium and sodium in water can be described and eliminated by empirical mathematical modeling. 

The measured results and the standard deviations of the replicates for the flame photometric determinations of potassium and sodium are presented in Tab. 10-5. The following steps of testing and mathematical modeling correspond to the steps described more detailed in Section 3.3. 

Tab. 10-5. Measured results and standard deviations of replicates for the flame photometric determination of potassium and sodium (in pg mLT1)...

The effects of interference on the flame photometric determination of potassium can be described by the discussed model with only a slight error (Fig. 10-1 a). The effects of interference on the flame photometric determination of sodium are greater, as the model equation 10-16 shows. Also in this case the deviations of the calculated sodium concentrations from the true values are relatively small (Fig. 10-1 b). The comparison... 

K4. Kingsley, G. R., and Schaffert, R. R., Micro-flame photometric determination of sodium, potassium, and calcium in serum with organic solvents. J. Biol. Chem. 206, 807-815 (1954). 

Z. Fang, J. M. Harris, J. RdiiCka, and E. H. Hansen, Simultaneous Flame Photometric Determination of Lithium, Sodium, Potassium and Calcium by Flow Injection Analysis with Gradient Scanning Standard Addition. Anal. Chem., 57 (1985) 1457. 

The procedure for the determination of the alkalis (NaaO, K2O, and Li20) is effectively identical for all classes of material in that 0.25 g of sample is decomposed with hydrofluoric acid together with dilute nitric and sulfuric acids in a platinum dish on a sand bath. The residue is dissolved in dilute nitric acid and alkalis determined directly on the solution by flame photometry or flame atomic absorption spectroscopy (FAAS) in emission mode. Cesium and aluminum sulfate buffers are added to aliquots for the flame photometric determination of sodium and potassium. 

Several instrument manufacturers supply flame photometers designed specifically for the determination of sodium, potassium, lithium, and sometimes calcium in blood serum, urine, and other biological fluids. Single-channel and multichannel (two to four channels) instruments are available for these determinations. In the multichannel instruments, each channel can be used to determine a separate element without an internal standard, or one of the channels can be reserved for an internal standard such as lithium. The ratios of the signals from the other channels to the signal of the lithium channel are then taken to compensate for flame noise and noise from fluctuations in reagent flow rate. Flame photometers such as these have been coupled with flow injection systems to automate the sample-introduction process (see Section 33B-3). Typical precisions for flow-injection-analysis-based flame photometric determinations of lithium, sodium, and potassium in serum are on the order of a few percent or less. Automated flow injection procedures require l/KIO the amount of sample and 1/10 the time of batch procedures. -... 

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. 

Potassium is analyzed in chemicals that are used in the fertilizer industry and in finished fertilizers by flame photometric methods (44) or volumetric sodium tertraphenylboron methods (45) as approved by the AO AC. Gravimetric determination of potassium as IC PtClknown as the Lindo-Gladding method (46), and the wet-digestion determination of potassium (47) have been declared surplus methods by the AO AC. Other methods used for control purposes and special analyses include atomic absorption spectrophotometry, inductively coupled plasma (icp) emission spectrophotometry, and a radiometric method based on measuring the radioactivity of the minute amount of the isotope present in all potassium compounds (48). 

Analytical Procedures. The extracts from exposure pads, hand rinses, and apple leaves were evaporated to dryness in the 40-45°C water bath, and the carbaryl residues were determined by the procedure of Maitlen and McDonough (4). In this procedure, the residues were hydrolyzed with methanolic potassium hydroxide to 1-naphthol which was then converted to the mesylate derivative by reaction with methanesulfonyl chloride. The carbaryl mesylate was quantitated with a Hewlett Packard Model 5840A gas chromatograph (GLC) equipped with a flame photometric detector operated in the sulfur mode. The GLC column was a 122 cm x 4.0 mm I.D. glass column packed with Chromosorb G (HP) coated with 5% OV 101. The column was operated at a temperature of 205°C with a nitrogen flow rate of 60 ml/min. 

In a standard official metho d [53,54], potassium is determined in plant material by first digesting the sample with 60% perchloric acid 70% mlm nitric acid 1 3 v/v followed by extraction of the residue with 2 M hydrochloric acid or by dry combustion at 500 °C followed by extraction with 6 M hydrochloric acid. Potassium in the extracts is determined flame-photometrically. There is no significant interference from other elements. See also Sects. 7.34.1 and 7.34.7. 

Finally, the flame photometric methods for determination of sodium and potassium have been adapted to the device. In this case, after the addition of lithium as internal standard, the electrolytes are dialyzed into the recipient stream, which is then pumped into an atomizer-burner of more or less conventional design. A colorimeter has been designed to allow for simultaneous recording of sodium and potassium, utilizing a two-channel recorder as optional equipment. This arrangement would tend to conserve sample. Without the dual recorder, the recorder supplied as part of the basic instrument is used, and the specimens are sampled once for sodium and once for potassium. 

Water-soluble potassium (expressed as K2O) can be determined by manual or automated flame photometric and tetraphenylboron titration methods for all types of fertilizer samples. Atomic absorption can be used for samples below 5% K2O to maintain the highest degree of precision and accuracy. (Note Tetraphenylboron method for potassium is being used less often because of safety issues associated with formaldehyde.) Methods using ICP-OES for high concentration of potassium are currently being developed. Note Potentiometric measurements can be used to determine potassium in fertilizers but are not official approved methods and do not meet the accuracy and precision requirements as current methods. 

Among atomic emission spectrometry (AES) methods, the classic flame photometric technique is still favored for determination of sodium and potassium in foods. 

The first detector to be used for SFA was a photometer, and photometric determinations still form the vast majority of current methods. Other detectors in common use are UV spectrophotometers, used primarily for pharmaceutical compovmds and for bitterness in beer flame photometers, for potassium and sodium determination fluorimeters, used primarily for measuring low levels of determinants in the presence of interferences, such as the determination of histamine in blood, and vitamins in food extracts and ion-selective electrode and pH detectors. In principle, almost any detector with flow-through capability can be used with SFA systems, and determinations based on densitometry, thermometry, and luminescence have been published, among others. 

Hald, P. M. (1951). Determination of sodium and potassium ions with flame photometric method. In Medical research. Vol. IV 79. 

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