Chloridometer

Abstract: An araperometric titration method for Cl was suitable for reproducible analysis of equimolar Cl. Br and I in all possible combinations in the range 0.125 to 2.50 millimolar (mM). A solid state Br specific ion electrode exhibited a reproducible Nernstian response to Br over the range 0.005 to 1 mM, with minimal Cl interference. Bromide and Cl added to a lysimeter and a field were quantitatively recovered by estimation of (Cl + Br) amperometrically and Br potentiometrically.

Abstract: C fibrosis (CF) is one of the most common inherited diseases in Caucasian people. It is caused by mutations in both the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a transmembrane glycoprotein.1 One of the main consequences of mutations in the CFTR gene is a dysfunction of ion channels resulting in elevated sweat chloride concentrations, pancreatic insufficiency, and progressive lung disease.2 Sweat testing is a general term referring to the quantitative, or qualitative analysis of sweat to determine the electrolyte concentration, conductivity, or osmolarity for confirmation of a CF diagnosis, and despite the development of genetic testing, analysis of sweat chloride concentration remains the laboratory gold standard for the diagnosis of CF.3 The cut-off chloride value of 60 mEq/L is considered frankly abnormal. It is possible to make diagnosis of CF even with a chloride value 60 mmol/L), and a positive result on gene mutation analysis, plus clinical symptoms, and a positive family history of CF. Informed consent was obtained for all study subjects, and ethical clearance was obtained from the research committee of the Medical Research Centre, Hamad Medical Corporation, Doha, Qatar before enrolling participants in the study. Each patient was tested by QPIT on the right forearm, and by the Macroduct sweat collection system, and chloride and sweat conductivity determination on the left forearm on the same day. All tests were carried out by experienced personnel by following the guidelines of the National Committee for Clinical Laboratory Standards at Hamad Medical Corporation, Qatar, from May 2007 to February 2008. The QPIT was performed with measurements of sweat weight, and chloride concentrations. Sweat specimens were collected concurrently from the right arm by first cleaning the skin with water, then applying a 2-inch-square salt-free gauze pad soaked with 0.5% pilocarpine solution, and covered with a 33-mm-diameter metal electrode. After a 4-minute pause, the skin was rinsed with water and dried thoroughly, reweighed gauze was then applied over the stimulated area, and covered with a Parafilm. After 30 minutes the Parafilm was lifted, the gauze removed with forceps, and then rapidly reweighed in an analytical balance before the electrolytes were eluted with water. A minimum sweat weight of 50 mg was required for analysis. Chloride concentrations were analyzed with a digital Jenway chloridometer (Jenway Ltd, Essex, UK), colorimetric titration method. On the left arm, sweat simulation was achieved by pilocarpine iontophoresis from disposable gel discs, 2.5 cm in diameter that were fitted into circular recessed stainless steel electrodes. Current was applied with a controlled rate-of-change to avoid patient discomfort, and collection was facilitated by a disposable plastic device that provided a shallow concave surface designed to cover precisely the circular skin area previously stimulated. A small amount of a water-soluble dye (10 μL) on the concave surface of the disk allowed easy visualization of the sweat collected. The amount of sweat was sufficient when the capillary was filled (approximately 30 minutes). Both sweat conductivity and chloride concentration was then measured using a Sweat-Chek conductivity analyzer, and a Sherwood colorimeter (Sherwood Scientific Ltd, Cambridge, UK)). Descriptive statistics (mean, median, and standard deviation) were calculated and the associations between

Abstract: A micromethod for the analysis for chloride, based on the chemical precipitation of silver chloride by radial diffusion through agar gel containing silver nitrate, is described. The method is simple to run, requires little or no instrumentation, and requires only 10 mul of sample. Results by coulometric titration (Buchler Cotlove Chloridometer) correlated well for serum (r = 0.961), urine (r = 0.997), cerebrospinal fluid (r = 0.991), and sweat (r = 0.998). Other halide ions or protein do not interfere. Precision studies gave a within-day reproducibility (CV) of 1.3% and a day-to-day variability of 2.1% for a serum sample averaging 115 mmol/liter.