ASTM E1657-1998(2006) Standard Practice for Testing Variable-Wavelength Photometric Detectors Used in Liquid Chromatography《液相色谱用可变波长光度探测器试验的标准规程》.pdf
《ASTM E1657-1998(2006) Standard Practice for Testing Variable-Wavelength Photometric Detectors Used in Liquid Chromatography《液相色谱用可变波长光度探测器试验的标准规程》.pdf》由会员分享,可在线阅读,更多相关《ASTM E1657-1998(2006) Standard Practice for Testing Variable-Wavelength Photometric Detectors Used in Liquid Chromatography《液相色谱用可变波长光度探测器试验的标准规程》.pdf(8页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: E 1657 98 (Reapproved 2006)Standard Practice forTesting Variable-Wavelength Photometric Detectors Used inLiquid Chromatography1This standard is issued under the fixed designation E 1657; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the testing of the performance of avariable-wavelength photometric
3、detector (VWPD) used as thedetection component of a liquid-chromatographic (LC) systemoperating at one or more wavelengths in the range 190 to 800nm. Many of the measurements are made at 254 nm forconsistency with Practice E 685. Measurements at other wave-lengths are optional.1.2 This practice is i
4、ntended to describe the performance ofthe detector both independently of the chromatographic system(static conditions) and with flowing solvent (dynamic condi-tions).1.3 For general liquid chromatographic procedures, consultRefs (1-9).21.4 For general information concerning the principles, con-struc
5、tion, operation, and evaluation of liquid-chromatographydetectors, see Refs (10, 11) in addition to the sections devotedto detectors in Refs (1-7).1.5 The values stated in SI units are to be regarded asstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associat
6、ed with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E 685 Practice for Testing Fixed-Wavelength PhotometricDetect
7、ors Used in Liquid Chromatography3. Terminology3.1 Definitions:3.1.1 absorbance calibrationthe procedure that verifiesthat the absorbance scale is correct within 65%.3.1.2 driftthe average slope of the noise envelope ex-pressed in absorbance units per hour (AU/h) as measured overa period of 1 h.3.1.
8、3 dynamicunder conditions of a flow rate of 1.0mL/min.3.1.4 linear rangeof a VWPD, the range of concentrationsof a test substance in a test solvent over which the ratio ofresponse of the detector versus concentration of test substanceis constant to within 5 % as determined from the linearity plotspe
9、cified in 7.1.2 and illustrated in Fig. 1. The linear rangeshould be expressed as the ratio of the upper limit of linearityobtained from the plot to either a) the lower linear concentra-tion, or b) the minimum detectable concentration, if theminimum detectable concentration is greater than the lower
10、linear concentration.3.1.5 long-term noisethe maximum amplitude in AU forall random variations of the detector signal of frequenciesbetween 6 and 60 cycles per hour (0.1 and 1.0 cycles per min).3.1.5.1 DiscussionIt represents noise that can be mistakenfor a late-eluting peak. This noise corresponds
11、to the observednoise only and may not always be present.3.1.6 minimum detectability of a VWPD, that concentra-tion of a specific solute in a specific solvent that results in adetector response corresponding to twice the static short-termnoise.3.1.6.1 DiscussionThe static short-term noise is a mea-su
12、rement of peak-to-peak noise. A statistical approach to noisesuggests that a value of three times the rms (root-mean-square)noise would insure that any value outside this range would notbe noise with a confidence level of greater than 99 %. Sincepeak-to-peak noise is approximately five times the rms
13、 noise(12), the minimum detectability defined in this practice is amore conservative estimate.3.1.7 response time (speed of output) the detector, thetime required for the detector output to change from 10 % to90 % of the new equilibrium value when the composition ofthe mobile phase is changed in a s
14、tepwise manner, within thelinear range of the detector.3.1.7.1 DiscussionBecause the detector volume is verysmall and the transport rate is not diffusion dependent, theresponse time is generally fast enough to be unimportant. It is1This practice is under the jurisdiction of ASTM Committee E13 on Mol
15、ecularSpectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma-tography.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 1994. Last previous edition approved in 2001 as E 1657 98 (2001).2The boldface numbers in parentheses refer to the list of
16、 references at the end ofthis practice.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM Intern
17、ational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.generally comparable to the response time of the recorder anddependent on the response time of the detector electrometerand on the recorder amplifier. Factors that affect the observedresponse time include th
18、e true detector response time, elec-tronic filtering, and system band-broadening.3.1.8 short-term noisethe maximum amplitude, peak topeak, in AU for all random variations of the detector signal ofa frequency greater than one cycle per minute.3.1.8.1 DiscussionIt determines the smallest signal de-tec
19、table by a VWPD, limits the precision attainable in quanti-tation of trace-level samples, and sets the lower limit onlinearity. This noise corresponds to the observed noise only.3.1.9 staticunder conditions of no flow.3.1.10 wavelength accuracythe deviation of the observedwavelength maximum from the
20、 maximum of a known testsubstance.3.1.11 wavelength precisiona measure of the ability of aVWPD to return to the same spectral position as measured bythe reproducibility of absorbance values when the detector isreset to a wavelength maximum of a known test substance.4. Significance and Use4.1 Althoug
21、h it is possible to observe and measure each ofthe several characteristics of a detector under different andunique conditions, it is the intent of this practice that acomplete set of detector specifications should be obtainedunder the same operating conditions. It should also be notedthat to complet
22、ely specify a detectors capability, its perfor-mance should be measured at several sets of conditions withinthe useful range of the detector. The terms and tests describedin this practice are sufficiently general that they may be usedregardless of the ultimate operating parameters.4.2 Linearity and
23、response time of the recorder or otherreadout device used should be such that they do not distort orotherwise interfere with the performance of the detector. Thisrequires adjusting the gain, damping, and calibration in accor-dance with the manufacturers directions. If additional elec-tronic filters
24、or amplifiers are used between the detector and thefinal readout device, their characteristics should also first beestablished.5. Noise and Drift5.1 Test ConditionsPure, degassed methanol4shall beused in the sample cell. Air or nitrogen shall be used in thereference cell if there is one. Nitrogen is
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