Potassium determination

The probe was selective for potassium determination no significant fluorescence signal was observed with other metals. However, Na+ andLi+ induced a hypsochromic shift of the absorbance maximum in the NIR dye in free solution. Although the NIR dye offered some selectivity for potassium in analysis, the selectivity was enhanced further by the polymer matrix. Furthermore, the sensitivity of the probe to KOH and KCI was almost identical. This may indicate that the sensor response was not influenced by a pH change or the presence of anions. The fluorescence response of the immobilized NIR dye with KOH and KCI is shown in Figure 7.11. 

Renai function impairment Perform periodic BUN and serum potassium determinations to check kidney function, especially in patients with suspected or confirmed renal insufficiency and in elderly or diabetic patients diabetic patients with nephropathy are especially prone to develop hyperkalemia. 

Note that turbidity measurement plays an important role in many types of routine chemical analyses (e.g. nephelometric determination of water quality, the evaluation of the concentration of barium and sulphate, or potassium determination with sodium tetraphenylbo-rate in water analysis, and determination of seric proteins). Also, the characterization of turbidity measurements is very important when evaluating some sources of uncertainty in gravimetry used in valid chemical metrology [5],... 

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-... 

Note that overall measurement uncertainty did not exceed 6% for glucose and potassium determinations. For Ca the overall measurement uncertainty did not exceed 2.5% and for urea 13%. These values closely agree with measurement uncertainties reported for dif-... 

Although ionization of sodium is negligible and potassium small in an air—propane flame, some ionization is experienced in the recommended hotter air—acetylene flame. Ionization should be suppressed by the incorporation of excess potassium or cesium (for sodium determinations) or excess sodium or cesium (for potassium determinations), at concentrations of 1000/igml-1 or greater, in the form of chlorides or nitrates, in both sample and standard solutions. Cesium is the more effective but more expensive ionization suppressant. Extent of ionization is inversely related to analyte concentration with errors due to incomplete suppression thus being greater at low concentrations. As it is difficult to obtain alkali metal salts free from traces of other alkali metals, possible contamination must be considered, especially at low analyte levels. Use of a branched capillary for introduction of ionization buffer has been advocated for flame spectrometry to... 

An adult contains about 3 g of potassium. The plasma level is maintained within narrow limits by the kidney which can efficiently conserve or excrete potassium according to need. Abnormally low plasma levels cause muscle irritability and weakness together with potentially dangerous cardiac arrhythmias. Similar changes can also occur with abnormally high plasma potassium levels, thus making potassium determination one of the more important investigations in clinical medicine. 

Fig. 13. (a) The cross section and chemistry of the Seralyzer reagent strip (Miles Ditignostic, Inc.) for serum potassium determination, (b) Comparison of strip and gravimetric analyses for potassium. 

Sodium and Potassium. Sodium and potassium can be determined by either atomic emission or absorption. Large concentrations of sodium can interfere with the potassium determination in either of these methods. Excess sodium can be added to both the potassium standards and samples to minimize any variations in the samples. Proper positioning of the flame helps reduce sodium interference in atomic absorption. 

Flo. 1. A control chart showing the results of serum potassium determinations performed daily on the same control serum (previously determined mean value, 4.40 mEq/liter). The warning and action limits are set at 2 SD and 3 SD, respectively. 

Fiq. 5. The effect on the coefficient of variation of continuous performance of serum potassium determinations carried out by one technician and assessed on the basis of duplicate determinations, performed in batches of six pairs of analyses [redrawn from Robinson (R6)]. 

Table 14. Thermodynamic parameters for the complex formation of macrotetrolide compounds with sodium and potassium determined by microcalorimetry and relaxation methods at 298 °K (Table from Ref.315,))... 

Despite its low concentration in the ECF, potassium determines the resting membrane potential of cells. Changes in plasma potassium concentration means that excitable cells, such as nerve and muscle, may respond differently to stimuli. In particular, because the heart is largely muscle and nerve, loo high or uk> low a plasma potassium concentration may have life-threatening consequences. 

In the early studies of ammonium fixation there was much uncertainty as to the amount of fixed ammonium present in untreated soils. The capacity of the soil for fixing ammonium could be determined readily by the methods already mentioned, but such techniques furnished no information on the amount of fixed ammonium present initially. Since surface soils usually fixed less ammonium than did subsoils, it seemed likely that this was because the surface soils already contained fixed ammonium, and also potassium. Determination of naturally-occurring fixed ammonium was difficult because it was not known if the Kjeldahl method for total nitrogen actually accounted for all of the fixed... 

The results for the sums of squares within and between the laboratories based on the potassium determinations in Table 2.13 are given in Table 2.14. This representation of data is called an ANOVA table. 

Table 2.14 Results of a one-way analysis of variance for the potassium determinations as in Table 2.13.

The value for f=5.02 is greater than the tabulated one f (1 - a = 0.95 /j = 3 /2 = 8) = 4.07 (see Table A.4). The test is therefore significant, that is, the differences between the laboratories cannot be considered to be different at random. The potassium determinations of at least one laboratory deviate systematically from each other. 

Potassium hydroxide potassium determination N-(1-Naphthyl) ethylenediamine dihydrochloride potassium fluoride mfg. 

The high stability of the flame source, when compared to arc or spark excitation, was recognized as the key to the construction of simple instruments for the determination of easily excited elements, such as the alkali metals. Thus the first flame photometer produced in the U.S. in 1945 by Barnes used filters rather than a prism or grating, and used a modified Meeker burner as the flame excitation source. The instrument was especially useful for sodium and potassium determinations and was also soon utilized for calcium and magnesium analyses despite the handicap of poor detection limits. 

Other releasing agents have been used in other cases. Copper has been used as a releasing agent for noble metals and barium has been used for sodium and potassium determinations in the presence of aluminum and iron. 

Potentiometry The favored ISE for potassium determination uses valinomycin, an ion carrier of natural origin, in its ion-selective membrane. In undiluted samples an estimate of the concentration in the water phase is made, whereas in highly diluted samples the results reflect the concentration of the total sample. In hyperlipemia and hyperproteinemia or in hypoproteinemia, the results from undiluted samples will differ from diluted samples to the same extent as described above for sodium. As the relative reference interval of potassium is much larger than that of sodium (the upper limit of the reference interval of potassium differs from the lower limit by 50%, and in the case of sodium by 7%), the effects are clinically less meaningful. 

Water-Soluble Potassium Determinations - Method 12 (Used for Water-Soluble Potassium Fertilizers)... 

Sodium, potassium, calcium, ammonium, fluoride, chloride, and nitrate determinations and measurement of pH are among the applications of ISEs in foodstuffs analysis. Sodium and potassium determinations are two of the assays most easily performed using ISEs. 

In clinical chemistry the determination of sodium, potassium, and calcium is well standardized. In the past decades flame photometry has been reputed to be the mediod of choice in the analysis of biological samples. The advantages of this procedure are a short requirement of time and materials for sample preparation, short duration of the analytical procedure, and the possibility of automation. The procedure became improved due to the application of lithium as internal standard. Excellent precision and accuracy could be obtained in sodium and potassium determination. In calcium determination inaccuracy occurs due to the matrix. It is of disadvantage that only the determination of total calcium and not the differentiation between free and protein bound calcium is possible. Furthermore special equipment (flame photometer) is necessary. 

Treatment of hypokalemia should usually be instituted gradually to prevent overload. Oral potassium chloride is the treatment of choice usually given in an enteric-coated formulation [24]. Intravenous potassium chloride may be used for emergency treatment and in particular when managing serious arrhythmias or shock after myocardial infarction. Such infusion should not exceed 30 mmol/hr of KCl and should be monitored by frequent electrocardiogram recording and plasma potassium determinations at least every 4 hr. 

Fig. 1, Effect of reference electrode on potassium determination. Single measurements in NaCl or KCl with reference electrode (glass micropipet with 5 y m tip) against a 3 M KCl agar bridge 2 mm in diameter, upper lines, and with liquid ion-exchanger electrode against the reference electrode, lower lines. The reference electrode was filled with a solution of 3 M lithium acetate with or without addition of agar 2 g/100 ml.

Fig. 4. Effect of sodium on potassium determination. Single measurements with ion-exchanger microelectrode in pure solutions and mixtures of NaCl and KCl.

Effect of Bound or Structured Water, 16, 69 Effect of Sodium on Potassium Determination, 82 Electrodes... 

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