1、Designation: E 2253 03Standard Method forEnthalpy Measurement Validation of Differential ScanningCalorimeters1This standard is issued under the fixed designation E 2253; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 standard provides procedures for validating enthal-pic measurements of differential scanning calorimeters (DSC)an
3、d analytical methods based upon the measurement of en-thalpy or heat by DSC. Performance parameters determinedinclude calorimetric repeatability (precision), detection limit,quantitation limit, linearity and bias. This method is applicableto both exothermic and endothermic events.1.2 Validation of a
4、pparatus performance and analyticalmethods is requested or required for quality initiatives or whereresults may be used for legal purposes.1.3 SI units are the standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility o
5、f 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:E 177 Practice for Use of the Terms Precision and Bias inASTM Test Methods2E 473 Terminology Relating to
6、 Thermal Analysis2E 967 Practice for Temperature Calibration of DifferentialScanning Calorimeters and Differential Thermal Analyz-ers2E 968 Practice for Heat Flow Calibration of DifferentialScanning Calorimeters2E 1142 Terminology Relating to Thermophysical Proper-ties2E 1860 Test Method for Elapsed
7、 Time Calibration of Ther-mal Analyzers2E 1970 Practice for Statistical Treatment of Thermoanalyti-cal Data2E 2161 Terminology Relating to Performance Validation inThermal Analysis22.2 Other Standard:United States Food and Drug Administration, Q2B Valida-tion of Analytical Procedures: Methodology, 6
8、2 FR27464, May 19, 199733. Terminology3.1 Technical terms used in this standard are defined inPractice E 177 and in Terminologies E 473, E 1142, andE 2161.4. Summary of Test Method4.1 Temperature and time are the primary independentparameters and heat flow is the primary dependent experimen-tal para
9、meter provided by DSC. Integration of heat flow, as afunction of time, yields enthalpy (heat).4.1.1 Time, measured by the DSC apparatus, shall conformto better than 0.1 % verified by Test Method E 1860 andreported.4.1.2 Heat flow, a measured value, is validated by itsintegration over time to obtain
10、the desired calorimetric (enthal-pic) information of interest. Determination and verification ofenthalpy is the primary scope of this test method.4.2 Calorimetric validation of a differential scanning calo-rimetric apparatus at a single temperature is performed usingthe indium metal melt as an analy
11、te.4.3 Validation of a DSC method based upon enthalpicmeasurement may be performed using the test specimen as theanalyte.4.4 The enthalpy of three (or more) specimens (nominallyrepresenting the maximum, midpoint and minimum of therange of the test method) are measured in triplicate (or more).A fourt
12、h blank specimen, containing no analyte, is alsomeasured in triplicate.NOTE 1Repeatability is determined by performing a sufficient num-ber of determinations to calculate statistically valid estimates of thestandard deviation or relative standard deviation of the measurement.4.4.1 Calorimetric linea
13、rity and bias are determined fromthe best-fit straight-line correlation of the results from mea-surements of the three (or more) specimens.1This test method is under the jurisdiction of ASTM Committee E37 on ThermalMeasurements and is the direct responsibility of Subcommittee E37.01 on ThermalAnalys
14、is Methods.Current edition approved Jan. 10, 2003. Published April 2003.2Annual Book of ASTM Standards, Vol 14.02.3Available from FDA, 5600 Fishers Lane, Rockville, MD 20857.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.4.2 Calor
15、imetric detection limit and quantitation limit aredetermined from the standard deviation of the blank determi-nation.4.4.3 Calorimetric repeatability is determined from the re-peatability measurement of the three (or more) specimens.5. Significance and Use5.1 This method may be used to determine and
16、 validate theperformance of a particular DSC apparatus.5.2 This method may be used to determine and validate theperformance of a particular method based upon a DSC enthal-pic measurement.5.3 This method may be used to determine the repeatabilityof a particular apparatus, operator or laboratory.5.4 T
17、his method may be used for specification and regula-tory compliance purposes.6. Apparatus6.1 Differential Scanning CalorimeterThe essential in-strumentation required to provide the minimum differentialscanning calorimetric capability for this method include:6.1.1 DSC Test Chamber, composed of:6.1.1.
18、1 Furnace(s), to provide uniform controlled heating orcooling of a specimen and reference to a constant temperatureor at a constant rate within the applicable temperature range ofthe test method.6.1.1.2 Temperature Sensor, to provide an indication of thespecimen temperature to readability required.6
19、.1.1.3 Differential Sensor, to detect a heat flow differencebetween the specimen and reference.6.1.1.4 A means of sustaining a test chamber environmentof an inert purge gas at a rate of 10 to 50 mL/min 6 10 %.NOTE 2Typically, 99+ % pure nitrogen (or other inert gas, such asargon or helium) is employ
20、ed when oxidation in air is a concern. Unlessthe effects of moisture are to be studied, the use of a dry purge gas isrecommended, especially for operation at subambient temperatures.6.1.2 Temperature Controller, capable of executing a spe-cific temperature program by operating the furnace(s) between
21、selected temperature limits at a rate of temperature changeconstant to 6 1 % or at an isothermal temperature constant to6 0.5C.6.1.3 Recording Device, capable of recording and display-ing the heat flow (DSC) curve as a function of time andtemperature.6.1.4 Containers, (pans, crucibles, vials, lids,
22、closures,seals, etc.) that are inert to the specimen and referencematerials and that are of suitable structural shape and integrityto contain the specimen and reference in accordance with thespecific requirements of the test method.6.2 Balance, of 100 mg or greater capacity to weighspecimens and con
23、tainers to 6 1 g.NOTE 3A balance of this high precision is required so that weighingimprecision is not part of the overall method imprecision.7. Reagents and Materials7.1 Indium Metal, 99.99+ % purity, preferably a certifiedreference material for which the melting temperature andenthalpy of fusion a
24、re known.8. Calibration and Standardization8.1 After turning the power on, allow the instrument toequilibrate for at least one hour prior to any measurements.8.2 Perform any cleaning and calibration procedures de-scribed by the manufacturer in the apparatus OperatorsManual.8.3 If not previously esta
25、blished, perform temperature andheat flow calibrations according to Practices E 967 and E 968respectively, using the same purge gas, purge gas flow rate andheating rate (here 10C/min) to be used for validation experi-ments.8.4 If not previously established, obtain the instrumentselapsed time conform
26、ance using Test Method E 1860.9. Procedure for Determining Calorimetric Repeatability,Detection Limit, Quantitation Limit, Linearity, andBias9.1 This process involves characterizing, in triplicate, ablank and three (or more) test specimens taken to represent thelow, medium and high extremes of the r
27、ange over whichperformance is to be validated.NOTE 4The details of this procedure are written using indium as ananalyte. For validation of an enthalpic method, test specimens represent-ing the range of that method shall be used, and steps 9.2 to 9.7 replacedwith the enthalpic method procedure.9.2 Pr
28、epare three (or more) indium test specimens coveringthe enthalpy or mass range of the tests. Nominal mass valuesmight be 1, 10, and 20 mg. Measure the mass of each of thesespecimens to the nearest 1 g and record as Mmin, Mmid, andMmax. Enclose each test specimen within clean specimencontainers and l
29、ids. Also prepare a blank specimen thatcontains no analyte but otherwise is similar to the specimensprepared above.NOTE 5Most thermoanalytical methods cover 1.5 to 2 decades ofrange. The mass values selected should be approximately equally distrib-uted over the anticipated range. Other masses and ma
30、ss ranges may beused but shall be reported.9.3 Load the largest specimen into the instrument chamber,purge the chamber with dry nitrogen (or other inert gas) at aflow rate of 10 to 50 mL/min 6 10 % throughout theexperiment. An empty sample specimen container is loaded inthe reference position.9.4 Er
31、ase any thermal history in the test specimen byheating the specimen to 180C, then cool at 5C/min to 120C.The thermal curve need not be recorded.9.5 Equilibrate at 120C for one minute.9.6 Heat the test specimen at 10C/min through the indiummelting transition to 180C and record the thermal curve.NOTE
32、6Other heating rates may be used but shall be reported.9.7 Cool the test specimen to 120C at 5C/min, then cool toambient temperature at any convenient rate. The thermal curveneed not be recorded.9.8 Construct a baseline for the melting endotherm byselecting a point on the curve immediately before an
33、d anotherimmediately after the endotherm. Record the temperatures ofthese two points as T1and T2. Construct a linear baselinebetween the two points (see Fig. 1).E22530329.9 Integrate, as a function of time, the heat flow describedby the constructed baseline and the melting endotherm. Recordthis valu
34、e as enthalpy (DQmax(1), in mJ).9.10 Repeat steps 9.3 through 9.9 for the medium mass testspecimen from step 9.2. Use the same integration limits (T1andT2) determined in step 9.8. Record this value as enthalpy(DQmid(1) , in mJ).NOTE 7Loading and unloading of the specimen is required todetermine anal
35、ytical repeatability. If only instrumental repeatability isbeing determined, the specimen may be left in place between determina-tions.9.11 Repeat steps 9.3 through 9.9 for the small mass testspecimen from step 9.2. Use the same integration limits (T1andT2) determined in step 9.8. Record this value
36、as enthalpy(DQmin(1), in mJ).9.12 Repeat steps 9.3 through 9.9 for the blank test speci-men from step 9.2. Use the same integration limits (T1and T2)determined in step 9.8 (see Fig. 2). Record this value asenthalpy (DQo(1), in mJ).NOTE 8Observe and record the sign of the value for DQo. It may beposi
37、tive or negative.FIG. 1 Integration of Large Indium Melting EndothermFIG. 2 Integration of BaselineE22530339.13 Repeat steps 9.5 through 9.9 two more times for thelarge mass specimen. Remove the specimen from the DSCsample chamber and reload it between each determination.Record these values as entha
38、lpy (DQmax(2) and DQmax(3), inmJ).9.14 Repeat steps 9.5 through 9.9 two more times for themedium mass specimen. Remove the specimen from the DSCsample chamber and reload it between each determination.Record these values as enthalpy (DQmid(2) and DQmid(3), inmJ).9.15 Repeat steps 9.5 through 9.9 two
39、more times for thelow mass specimen. Remove the specimen from the DSCsample chamber and reload it between each determination.Record these values as enthalpy (DQmin(2) and DQmin(3), inmJ).9.16 Repeat steps 9.5 through 9.9 two more times for theblank specimen. Remove the specimen from the DSC samplech
40、amber and reload it between each determination. Recordthese values as enthalpy (DQo(2) and DQo(3), in mJ).9.17 Calculate the mean (Q), standard deviation (s) andrelative standard deviation (RSD) for the enthalpy from thereplicate determinations made on each of the three massspecimens (see Practice E
41、 1970). Record these values as Qmax,Qmid, Qmin, smax, smid, smin, and RSDmax, RSDmid, and RSDmin,respectively. Calculate the mean and standard deviation for theenthalpy determination of the blank. Record these values as Qoand sorespectively.9.18 Using the standard deviation for the enthalpy of thebl
42、ank (so) from step 9.17, determine the instrument detectionlimit (DL) and quantitation limit (QL) as in calculations 10.2and 10.3. Report DL and QL.9.19 Calculate the pooled relative standard deviation for theenthalpy of fusion from the RSDmax, RSDmid, and RSDmin,obtained in step 9.17 (see Practice
43、E 1970). Report this valueas the Calorimetric Repeatability value (r).9.20 Using the three (or more) mass values from step 9.2 asthe independent (X) values and the three (or more) meanenthalpy values from step 9.17 as the dependent (Y) values,determine the least square best fit values for the slope
44、(m)inmJmg-1, and intercept (b) in mJ (see Practice E 1970).NOTE 9The units of mJ mg-1for slope are equivalent to the units ofJg-1.9.21 Calculate the Percent Linearity (L) of the enthalpy offusion data from the values in step 9.20 and the calculation of10.4.9.22 Compare the slope (mean enthalpy of fu
45、sion) from step9.20 to the accepted reference value for enthalpy of fusion asin calculation of 10.5 (see Practice E 968). Report this value asthe Calorimetric Bias (Bias) as a percentage.10. Calculations10.1 When performing these calculations, retain all avail-able decimal places in the measured val
46、ues and in intermediatecalculated values. The final result should be rounded to threesignificant figures.10.2 Detection Limit (DL) is given by:DL 5 3.3 so(1)where:DL = detection limit, mJ, andso= blank enthalpy standard deviation, mJ.NOTE 10To express the Detection Limit in terms of mass of analyte,
47、the value for DL may be divided by the slope value m from 9.20.10.3 Quantitation Limit (QL) is given by:QL 5 10 so(2)where:QL = quantitation limit, mJ.NOTE 11To express the Quantitation Limit in terms of mass of theanalyte, the value for QL may be divided by the slope value m from 9.20.10.4 Percent
48、Linearity (L) is given by:L 5F100 % 3 ? Largest dY ?!m 3 Mmax1 bG(3)where:L = linearity, %,m = slope, mJ mg-1, (from 9.20),b = intercept, mJ, (from 9.20),Mmax= mass of largest test specimen, mg, and|Largest dY| = absolute value of the largest deviation frombest fit straight line.10.5 Calorimetric Bi
49、as (Bias) is given by:Bias 5DHref2 m! 3 100 %DHref(4)where:DHref= accepted reference value for indium heat of fusion,28.58 mJ mg-1.411. Example Calculations11.1 For the example calculations described below, thefollowing experimental data is used:Mmax= 15.680 mg Qmax= 444.33 mJMmid= 8.000 mg Qmid= 233.33 mJMmin= 0.376 mg Qmin= 11.133 mJMo= 0.000 mg Qo= 0.0019093 mJnmax=3 smax= 6.4470 mJnmid=3 smid= 0.14012 mJnmin=3 smin= 0.089629 mJno=3 so= 0.0041285 mJwhere:n = number of replicate determinations.11.2 Example calculation for Detection Limit:DL 5 3.3 3 0.0041285
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