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Specific Electrolytes (Chloride, Calcium, Magnesium, Phosphate)
Clinical Chemistry 2 (MDT 3122L)
Our Lady of Fatima University
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Week 5 CC Specific Electrolytes Cl−, Ca2+, Mg2+, PO 4 −
Chloride (Cl−) Chloride is the major extracellular anion. Involved in maintaining osmolality, blood volume, and electric
neutrality. Disorders are similar to sodium.
Determination of Chloride - Pseudohypochloremia – dilutional effect to serum chloride due to marked hemolysis.
Serum or plasma may be used, with lithium heparin being the anticoagulant of choice. 24-hour collection is most preferred for urine specimen.
METHODOLOGY: ISEs, amperometric-coulometric titration, mercurimetric titration, and colorimetry.
Schales and Schales method – mercuric titration. Utilizes; Diphenylcarbazone = indicator; HgCl 2 = end product.
Spectrophotometric methods a. Mercuric thiocyanate (Whitehorn Titration Method) – reddish complex b. Ferric perchlorate – colored complex
Amperometric-coulometric titration – Cotlove chloridometer
Ion-selective electrodes – most commonly used method.
- utilizes an ion-exchange membrane (tri-n- octylpropylammonium chloride decanol)
REFERENCE RANGE: 98 – 107 mmol/L
Calcium (Ca2+) Calcium is exclusively present in the plasma. It is in volved in blood coagulation, enzyme activity, excitability of skeletal and cardiac muscle – ergo, maintenance of blood pressure.
Regulated by 3 hormones: Parathyroid hormone, vitamin D, and calcitonin. Calcium distribution: 99% in hydroxyapatite in bone. 1% in blood and other ECF. 45% = Free form / iCa 40% = Protein bound 15% = bound to anions (HCO 3 – , citrate, and lactate)
Determination of Calcium For iCa, samples must be collected anaerobically to prevent loss of CO 2.
PARAMETERS HYPOCHLOREMIA HYPERCHOREMIA
Cl− serum levels
<98 mmol/L >107 mmol/L
PARAMETERS HYPOCALCEMIA HYPERCALCEMIA
Ca2+ serum levels <1 mmol/L (7. mg/dL)
>2 mmol/L (10. mg/dL) Symptoms Neuromuscular symptoms – irritability, parasthesia, cramps, tetany, and seizures; cardiac irregularities – arrythmia, heartblock.
Neurological symptoms – weariness, weakness, depression, lethargy and coma; GI symptoms - constipation, nausea, vomiting, anorexia, and peptic ulcer disease; Renal symptoms - nephrolithiasis and nephrocalcinosis.
Treatment Oral and parenteral Ca2+ therapy, administration of vitamin D.
Estrogen replacement, parathyroidectomy, salt and water intake, and bisphosphonates.
The preferred specimen for total Ca2+ determinations is either serum or lithium heparin plasma. Timed urine collection for urinalysis of Ca2+ and must be acidified with 6 mol/L HCl, with approximately 1 mL of the acid added for each 100 mL of urine.
METHODOLOGY: ISE, AAS, FEP, titration, colorimetric, and precipitation.
1. Precipitation and Redox Titration a. Clark Collip Precipitation – end product: oxalic acid (purple) b. Ferro Ham Chloranilic Acid Precipitation – end product: chloranilic acid (purple)
- Colorimetric Method a. Ortho-cresolphthalein complexone (CPC) dye
- Arsenazo III
EDTA Titration Method – Bachra, Dower, and Sobel.
Ion-selective electrode – Liquid membrane
REFERENCE RANGE:
Total Calcium—Serum, Plasma Child, <12y 2–2 mmol/L (8–10 mg/dL) Adult 2–2 mmol/L (8–10 mg/dL)
Ionized Calcium—Serum Child 1–1 mmol/L (4–5 mg/dL) Adult 1–1 mmol/L (4–5 mg/dL)
Magnesium (Mg2+) Magnesium is the second most abundant intracellular cation. An essential cofactor of more than 300 enzymes, including those important in glycolysis; transcellular ion transport; neuromuscular transmission; synthesis of carbohydrates, proteins, lipids, and nucleic acids; and the release of and response to certain hormones.
PARAMETERS HYPOMAGNESEMIA HYPERMAGNESEMIA
Mg2+ serum levels
<1 mEq/L >2 mEq/L
Symptoms Acute renal failure, malnutrition, malabsorption syndrome, chronic alcoholism, severe diarrhea.
Diabetic coma, Addison’s disease, chronic renal failure, increased intake of antacids, enemas, and cathartics. Treatment Oral magnesium lactate, magnesium oxide, or magnesium chloride.
Hemodialysis, IV diuretics, and supportive therapy.
Determination of Magnesium Pseudohypermagnesemia – due to hemolysis.
Oxalate, citrate, and ethylenediaminetetraacetic acid (EDTA) anticoagulants are unacceptable because they will bind with Mg2+. Serum or lithium heparin plasma is more preferrable. A 24-hour urine sample is preferred for analysis because of a diurnal variation in excretion.
METHODOLOGY: Colorimetric, Dye-Lake, and AAS – reference method. 1. Colorimetric Method a. Calmagite method: (+) reddish-violet complex @ 532 nm b. Formazen dye method: (+) colored complex @ 660 nm c. Magnesium thymol blue method: (+) colored Complex
REFERENCE RANGE:
Serum, colorimetric 0 – 1 mmol/L (1 – 2. mmol/L)
Phosphate (PO 4 – ) Phosphates are found everywhere in cells; inversely related to calcium. They consist the genetic material DNA and RNA through complex phosphodiesters; acts as coenzymes as asters of phosphoric or pyrophosphoric acid. Probably the most important function of phosphates lies with its biochemical energy form, ATP. PARAMETERS HYPOPHOSPHATEMIA HYPERPHOSPHATEMIA PO 4 – serum levels
<2 mg/dL >4 mg/dL
Regulated through hormones: PTH: decreases phosphate renal excretion.
Specific Electrolytes (Chloride, Calcium, Magnesium, Phosphate)
Course: Clinical Chemistry 2 (MDT 3122L)
University: Our Lady of Fatima University
