3.Working standards:Mixed working standards for sodium and potassium are
prepared as follows:
(a) Sodium/potassium (110/2 mEq/L): This standard is prepared by
mixing 11 ml of stock sodium and 2 ml of stock potassium standards
in 87 ml distilled water. Thefinal 100 ml mixture contains 110 mEq of
sodium and 2 mEq of potassium.
(b) Sodium/potassium (140/4 mEq/L):To prepare the standard, take 14 ml
of stock sodium and 4 ml of stock potassium standards in aflask, and add
82 ml distilled water to makefinal volume to 100 ml.
(c) Sodium/potassium (170/8 mEq/L):Take 17 ml of stock sodium and
8 ml of stock potassium standards in aflask, and add 75 ml distilled
water to prepare standard.
36.5 Procedure
- Theflame photometer is switched on, and appropriatefilter is selected with the
help offilter selector wheel. - Put the air compressor on, and adjust air pressure between 0.4 and 0.6 kg/cm^2.
- Introduce glass-distilled water through atomizer.
- Then open the gas cylinder; theflame is ignited after removing the trapper at the
rear of theflame photometer. Adjust it so thatflame is divided intofine sharp
cones. - Make zero adjustment by introducing distilled water.
- Aspirate mixed Na+and K+standard (110/2 mEq/L), and adjust knob meant for
sodium to digits 110 and by knob meant for potassium to digit 2. - Introduce standard 140/4 mEq/L. The digital display will show exact reading if
standards are correct. - Then aspirate third standard 170/8 mEq/L for sodium and potassium, and adjust
reading. - Now introduce the diluted test serum sample, and record readings for sodium and
potassium.
36.6 Clinical Significance...............................
Normal sodium levels in serum are 135–145 mmol/L, while serum potassium level is
3.5–5.0 mmol/L. Increase in sodium concentration more than 145 mmol/L is called
hypernatremia. Hypernatremia is caused by hyperactivity of adrenal cortex, loss of
water due to dehydration, high administration of sodium salts, and steroid therapy.
The decrease in serum sodium levels (<135 mmol/L) is called hyponatremia. It may
occur due to prolonged vomiting, diarrhea, severe polyuria, diuretic medication, and
metabolic acidosis.
36.6 Clinical Significance 149