Thermo Kit pH-Detect 500mL

Intended Use

The DRI® pH-Detect Test® is intended for the determination of urine pH.

Summary and Explanation of the Test

A urine drug of abuse testing program typically involves specimen collection, initial screening with an immunoassay, followed by a confirmation test, such as gas chromatography/mass spectrometry (GC/MS), for the positive samples. Many drug users will attempt to evade detection by adulterating the specimen in order to produce false negative results during the initial immunoassay screening. Adulteration methods include dilution with water, substitution with a drug free liquid, addition of readily available household materials (e.g., vinegar, baking soda, liquid drain opener, detergent, etc.) or tampering with certain chemicals (e.g., Urine-Aid, which contains glutaraldehyde).

Several methods have been used to detect urine adulteration. These methods include measuring the temperature, pH, specific gravity and creatinine concentration of the sample. Normal urine should have the following typical characteristics: temperature between 32.5-37.7°C or 90.5-99.8°F, pH within 4.7-7.8, specific gravity within a range of 1.003-1.035 and creatinine concentration of 80.0-200.0 mg/dL. If any of the urine parameters is outside the specified range, there should be reason to believe that the urine sample has been adulterated.

Urine pH®, as well as other markers of adulteration, are useful for indicating specimen validity for drugs of abuse testing. Most urine pH determination is performed with pH paper or by a pH meter.

pH-Detect Test is an end point colorimetric method which can be performed with automated clinical chemistry analyzers for urine pH measurement. The method is based on the property of acid-base indicator dyes, which produce color depending on the pH of the urine sample. The color change can be measured as an absorbance change spectrophotometrically. A linear two-point calibration curve can be established using the pH 3.0 and pH 11.0 calibrators.