Potassium, in serum

FIGURE 5-17 Flow injection potentiometric determination of potassium in serum. (Reproduced with permission from reference 47.)... 

The most important application of the valinomycin macroelectrode is for the determination of potassium in serum [9, 126,141,174] and in whole blood [45, 71, 224]. This electrode with a polymeric membrane is a component of most automatic instruments for analysis of electrolytes in the serum. It has also been used for monitoring the K level during heart surgery [168]. The valinomycin ISE is also useful for determination of Rb [33]. 

Carter RJ, Mather A, Dawson CD, Turner WE, Neese JW, Bayse DD (1980) The development of a CDC reference method for determining sodium and potassium in serum. 

Kumar A et al (1988) Chromogenic ionophore-based methods for spectrophotometric assay of sodium and potassium in serum and plasma. Clin Chem 34 1709-1712... 

Berry MN, Mazzachi RD, Pejakovic M, Peake MJ. Enzymatic determination of potassium in serum. 

Rimura S, Asari S, Hayashi S, et al. New enzymatic method with tryptophanase for determining potassium in serum. Clin Chem 1992 38 44-7. 

The activity coefficient of sodium ion in normal human serum has been estimated, using ion-selective electrodes, to be 0.780 0.001, and in serum water to be 0.747 (serum contains about 96% water by volume). Standard solutions of sodium chloride and potassium chloride are usually used to calibrate electrodes for the determination of sodium and potassium in serum. Concentrations of 1.0, 10.0, and 100.0 mmol/L can be prepared with respective activities of 0.965, 9.03, and... 

M. E. MeyerhofF and P. M. Kovach, An Ion Selective Electrode/Flow Injection Analysis Experiment. Determination of Potassium in Serum. J. Chem. Educ., 60 (1983) 766. 

Gramlich, J.W., Machlan, LA.. Brietic, K.A., Kelly, W.R. (1982). Thermal ionisation isotope dilution mass spectrometry as a definitive method for the determination of potassium in serum. Clin. Chem. 28, 1309-1313. 

Sodium and potassium in serum are determined in the clinical laboratory by atomic-emission spectroscopy, using an instrument designed specifically for this purpose [5]. Two filter monochromators isolate the sodium and potassium emission lines. A lithium internal standard is used, and the ratios of the Na/Li and K/Li signals are read out on two separate meters. The internal standard compensates for minor fluctuations in flame temperature, aspiration rate, and so forth. A cool flame, such as air-propane, is used to minimize ionization. Typically, the serum sample and standards are diluted 1 200 with a 100 ppm Li solution and aspirated directly. The instrument can be adjusted to read directly in meq/1 for sodium and potassium by adjusting the gain while aspirating appropriate standards. 

You need to determine potassium in serum samples by FA AS. What will you add to correct for ionization interference in the determination ... 

Potassium in serum or urine may be determined by FAES, absorption spectrometry, or potentiometry... 

Some of the advantages of this type of sensor were already anticipated in one of the earliest FIA applications, namely, the joint determination of sodium and potassium in serum. Important parameter include the angle at which the carrier impinges on the active surface, the electrode placement angle, the immersion depth and surface area, the flow rates, and the cell void volume. 

The normal concentration of potassium in serum is in the range of 3.5-5.0 mEq/L (3.5-5.0 mmol/L). 4 As stated in Chapters 1 and 3, potassium levels must be maintained within a narrow range to avoid the electrical disruptions that occur when the concentration of potassium is too high or too low. Potassium levels are regulated primarily through reabsorption and excretion in the kidneys. 

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. -... 

Potassium is found largely in the intracellular compartment, the concentration in extracellular fluid being only 5% of that within the cells. Studies with have indicated a constant exchange of potassium between intra- and extracellular phases. However, concentration of potassium in serum does not necessarily reflect concentration within the cells. In normal subjects, the average concentration of potassium in serum was found to be 4.18 meq. per liter by Elliott and Holley. Deane and Smith, using found the concentration of intracellular potassium to range from 96 to 125 meq. per liter with a mean of 112 meq. 

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