Interpretation of the New Edition of Three Chromatographic Instruments

The General Administration of Quality Supervision, Inspection and Quarantine recently issued an announcement that the new editions of the "Liquid Chromatograph," "Ion Chromatograph," and "Gel Chromatograph" metrological verification protocols were formally released. The three new procedures will be implemented from August 14 this year. After the implementation, the three old procedures will be replaced respectively.

He Yajuan of the National Physical and Chemical Measurement Technical Committee introduced that the application of chromatographs covers industrial and mining production, environmental protection, food safety, medical care, and scientific research. In order to measure the accuracy and reliability of the instrument, the instrument itself must first measure accurately, which is inseparable from the measurement verification. The metrological verification procedures for liquid chromatographs have been more than a decade old since the last revision; the verification protocols for ion chromatographs and gel chromatographs have not been revised for 20 years since implementation. With the development of science, the instrument science is continuously advancing, and the detector using the latest detection principle has been continuously developed and applied. The detection range of the chromatograph has been continuously expanded, and the detection accuracy has been continuously improved. It has become an imminent task to perform more accurate, comprehensive, and scientific measurement verification on these scientific instruments to ensure accurate measurement of their own values.

According to reports, this revision proposes metrological verification requirements for new equipment that has emerged and been widely used in recent years. For example, in liquid chromatographs, evaporative light detectors are new types of detectors that have been widely used in recent years. Especially in China's Pharmacopoeia, the method of detection of antibiotics as evaporative light scattering method, the evaporative light detector is widely used in the pharmaceutical and drug testing industry. When the old “Liquid Chromatograph” metrological verification protocol was established, there was no mature condition to incorporate the verification content of the evaporative light scattering detector into the protocol. An important part of the new protocol was to increase the verification content of the evaporative light scattering detector. In the revision of the "Ion Chromatograph" verification protocol, the relevant contents of UV-visible detectors and electrochemical detectors were intentionally added. It is with the continuous development of these detectors that the detection range of the ion chromatograph can only detect some ions with high ion intensity at the beginning, and it can also detect I-, CN-, CrO4-, organic acids, sugars, etc. Weak ions.

The old regulations were implemented for nearly 20 years, and many technical indicators have not been adapted to the current development of the instrument. Adjusting the relevant technical indicators has become an important part of the revision of this regulation. For example, with the development of science and technology, the signal stability and sensitivity of the differential detector and ultraviolet detector of the gel chromatography are greatly improved, and the technical indicators of the detector baseline in the original verification protocol have greatly lag behind the actual level. The revised verification protocol has relevantly revised the detection results of the detector baseline to make these technical indicators more in line with the requirements of the new international standards.

The main standard devices for chromatographic analyzers are various reference materials. The selection of different standard materials may affect the efficiency and accuracy of the verification work. The revision also regulates the use of certified reference materials. In the 2002 edition of the "Liquid Chromatograph" verification protocol, the standard substance used for fluorescence detector verification was quinine sulfate/perchloric acid aqueous solution. Due to various reasons, signals such as unsatisfactory signals often appear during the verification, which results in the inability of the verification to proceed smoothly. This revision will change it to naphthalene/methanol solution, which avoids the above-mentioned problems and improves the efficiency of the verification. In the 1993 version of the “Gel Chromatograph” verification protocol, the reference material was only specified as “narrow distributed polyphenylene. Ethylene Standards," but such regulations have led to the inability to perform characterization on gel chromatographs that use water as a mobile item. The revised protocol supplements the provisions of the reference substance by adding dextran reference material so that the verification protocol can be used for gel chromatographs that characterize organic flow terms and water flow terms.