Chloride Cl-

• Major extracellular anion. • Chloride concentration in ECF is about 103 mmol/L, intracellular fluids of RBCs is 45 to 54 mmol/

• Chloride ions are almost completely absorbed from the intestinal tract., • passively reabsorbed, along with Na+, in the proximal tubules

maintenance of blood volume maintenance osmotic pressure maintenance anion-cation balance in the ECF (electric neutrality)

excreted in the urine and sweat.

• The earliest methods for determining Cl− in biological fluids • A protein free sample is titrated with mercuric nitrate solution in the presence of diphenylcarbazone as an indicator • Free Hg2 + combines with Cl− to form soluble mercuric chloride (HgCl2). • Excess Hg2 + reacts with diphenylcarbazone to form a blue-violet color complex

• Chloride most often is measured in serum or plasma, urine and sweat • Serum chloride is stable, gross hemolysis does not affect plasma chloride concentrations • Erythrocyte concentration of Cl− is approximately half of that in plasma. • Very little Cl− is protein bound, change in posture or stasis, or the use of tourniquets, has little effect on its plasma concentration

• Generally chloride is determined using methods including: ISE Mercurimetric titration, Spectrophotometry, Coulometric-amperometric titration Colorimetry

• Based on the reaction of Cl− with mercuric thiocyanate • Chloride ions react with undissociated mercuric thiocyanate to form undissociated mercuric chloride and free thiocyanate ions. • In the presence of perchloric acid, thiocyanate reacts with ferric ions forming ferric thiocyanate • Ferrric thiocyanate [Fe(SCN)3] is a reddish colored compound that absorb light at 480nm • High concentrations of globulins in the serum interfere in these methods through turbidity

• Based on the generation of Ag+ from a silver electrode at a constant rate and on the reaction of Ag+ with Cl− in the sample to form insoluble silver chloride (AgCl) • Excess Ag+ in the mixture triggers shutdown of the Ag+ generation system • A device records elapsed time between the start and stop of Ag+ generation. • The time interval is proportional to the amount of Cl− in the sample,

• In clinical analyzers tri-n-octylpropylammonium chloride decanol, are used to construct Cl− selective electrodes • These electrodes have been reported to suffer from membrane instability and lot-to-lot inconsistency in selectivity

plasma or serum = 98- 107 mmol/L Urine( 24h) = 110-250 mmol/L varies with diet

• Hypochlorinaemia is associated with respiratory acidosis • Hyperchlorinaemia occurs in dehydration prolonged diarrhea and overtreatment with normal saline • Hyperchlorinamia may also be seen in respiratory alkalosis

Used to confirm diagnosis of cystic fibrosis (CF), conducted in conjunction with newborn screening

• Used to confirm diagnosis of cystic fibrosis (CF), conducted in conjunction with newborn screening • Sweat test involves sweat stimulation, sweat collection and qualitative or quantitative analysis • Qualitatively sweat chloride concentration is determined (positive or negative results are obtained) • Quantitatively sweat chloride concentration is determined using colorimetric titration with chloridometer and ISE • Sweat is collected onto preweighed gauze pad, filter paper, macroduct coils • Infants, greater or equal to 60mmol/L is indicative of CF

sweat stimulation, sweat collection and qualitative or quantitative analysis