Determination of chloride in blood serum, plasma, or other biologic fluids by a new rapid precision method.

NEW, RAPID, SENSITIVE, AND ACCURATE method for determination of chloride was recently developed and described (1) which eliminates many difficulties inhereiit in other procedures. This method, called the precision null-point potentiometric method, can be applied for accurate determinations of chloride over a wide concentration range, as low as 10 M. and as high as necessary if the sample can be diluted to at least 0.1 NI. Therefore, it is possible to take a small volume of biologic specimen, such as 0.1 ml. of blood serum, spinal fluid, urine, etc., and dilute a thousand times. This provides a sample volume easily handled by ordinary macro technics. Many methods have been used previously for the determination of chloride in biologic specimens, but most either lack sensitivity, accuracy, or speed or use the relatively inconvenient micro technics. The most generally used methods employ the titration procedure with potentiometric, amperometric, or visual color end point detection. Many of the reported methods are based on Clark’s (2) original work and use dissimilar electrodes for potentiometric end point detection. The disadvantages of this system are the necessity of lengthy and frequent electrode preparation, relatively long equilibration time after each added increment of titrant, and relatively low sensitivity unless the determination is conducted on the rather inconvenient micro scale, which requires special apparatus. A new instrument for the determination of chloride in small quan-