Home>ASTM Standards>ASTM E685-93(R2021) pdf free download

ASTM E685-93(R2021) pdf free download

ASTM E685-93(R2021) pdf free download.Standard Practice for Testing Fixed-Wavelength Photometric Detectors Used in Liquid Chromatography
1. Scope
1.1 This practice is intended to serve as a guide for the testing of the performance of a photometric detector (PD) used as the detection component of a liquid-chromatographic (LC) system operating at one or more fixed wavelengths in the range 210 nm to 800 nm. Measurements are made at 254 nm, if possible, and are optional at other wavelengths. 1.2 This practice is intended to describe the performance of the detector both independently ofthe chromatographic system (static conditions) and with flowing solvent (dynamic condi- tions). 1.3 For general liquid chromatographic procedures, consult Refs (1-9). 2 1.4 For general information concerning the principles, construction, operation, and evaluation of liquid- chromatography detectors, see Refs (10 and 11) in addition to the sections devoted to detectors in Refs (1-7). 1.5 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.6 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions: 3.1.1 absorbance calibration, n—the procedure that verifies that the absorbance scale is correct within 65 %. 3.1.2 drift, n—the average slope of the noise envelope expressed in absorbance units per hour (AU/h) as measured over a period of 1 h. 3.1.3 dynamic, n—under conditions of a flow rate of 1.0 mL/min. 3.1.4 linear range, n—ofa PD, the range of concentrations of a test substance in a mobile phase over which the response ofthe detector is constant to within 5 % as determined from the linearity plot specified below and illustrated in Fig. 1. The linear range should be expressed as the ratio of the highest concentration to the minimum detectable concentration or the lowest linear concentration, whichever is greatest. 3.1.5 long-term noise, n—the maximum amplitude in AU for all random variations of the detector signal of frequencies between 6 cycles per hour and 60 cycles per hour (0.1 cycles per min and 1.0 cycles per min). Discussion—It represents noise that can be mistaken for a late-eluting peak. This noise corresponds to the observed noise only and may not always be present. 3.1.6 minimum detectability, n—ofa PD, that concentration ofa specific solute in a specific solvent that results in a detector response corresponding to twice the static short-term noise.3.1.7 response time (speed of output), n—the detector, the time required for the detector output to change from 10 to 90 % of the new equilibrium value when the composition of the mobile phase is changed in a stepwise manner, within the linear range of the detector. Discussion—Because the detector volume is very small and the transport rate is not diffusion dependent, the response time is generally fast enough to be unimportant. It is generally comparable to the response time of the recorder and dependent on the response time of the detector electrometer and on the recorder amplifier. Factors that affect the observed response time include the true detector response time, elec- tronic filtering, and system band-broadening. 3.1.8 short-term noise, n—the maximum amplitude, peak to peak, in AU for all random variations of the detector signal of a frequency greater than one cycle per minute. Discussion—It determines the smallest signal detect- able by a PD, limits the precision attainable in quantitation of trace-level samples, and sets the lower limit on linearity. This noise corresponds to the observed noise only. 3.1.9 static, n—under conditions of no flow.

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