定价： 116元 / 折扣价： 99 元

General Utility—The molecular mass (MM) and molecular mass distribution (MMD) are fundamental characteristics of a synthetic polymer that result from the polymerization process. The MM and MMD is useful for a wide variety of correlations for fundamental studies, processing and product applications. For example, it is possible to compare the observed MMD to predictions from an assumed kinetic or mechanistic model for the polymerization reaction. Differences between the values will allow alteration of the model or experimental design. Similarly, it is possible the strength, the melt flow rate, and other properties of a polymer are dependent on the MM and MMD. Determination of the MM and MMD are used for quality control of polymers and as specification in the commerce of polymers.Limitations—If the MMD is too wide, it is possible that the assumption of the constancy of the intensity scale calibration is in serious error.1.1 This test method covers the determination of molecular mass (MM) averages and the distribution of molecular masses for linear atactic polystyrene of narrow molecular mass distribution (MMD) ranging in molecular masses from 2000 g/mol to 35 000 g/mol by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). This test method is not absolute and requires the use of biopolymers for the calibration of the mass axis. The relative calibration of the intensity axis is assumed to be constant for a narrow MMD. Generally, this is viewed as correct if the measured polydispersity is less than 1.2 for the molecular mass range given above.1.2 The values stated in SI units are to be regarded as the standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.Note 1—There is no known ISO equivalent to this standard.

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定价： 116元 / 折扣价： 99 元

This practice may be used as part of a bioassay program for workers potentially exposed to nuclear material by measuring 237Np, 232Th and 235U and 238U in their urine samples. ICP-MS has been used to analyze for many actinides in high-level radioactive wastes (1) , in soils (2) as well as uranium in urine (Test Method C1379). 237Np and 239Pu analysis by ICP-MS in bioassay samples has also been reported (3). Several days counting times are required for alpha-particle analysis of 237Np, 232Th and 235U and 238U whereas ICP-MS requires only four minutes per sample. Alpha-particle counting methods for neptunium may also require the use of 239Pu as a radiotracer for determination of chemical yield. ICP-MS sensitivity limits and isobaric interferences preclude accurate determination of 239Pu, 241Am and 234U at levels present in the urine samples. 234U may be estimated from the 235U: 238U ratio by inference.1.1 This practice covers the separation and preconcentration of neptunium-237 (237Np), thorium-232 (232Th), uranium-235 (235U) and uranium-238 (238U) from urine followed by quantitation using ICP-MS. 1.2 This practice can be used to support routine bioassay programs. The minimum detectable concentrations (MDC) for this method, taking the preconcentration factor into account, are approximately 1E-2Bq for 237Np (0.38ng), 2E-6Bq for 232Th (0.50ng), 4E-5Bq for 235U (0.50ng) and 6E-6Bq for 238U (0.48ng). 1.3 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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定价： 193元 / 折扣价： 165 元

定价： 193元 / 折扣价： 165 元

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本标准适用于生产、销售的葱姜中农药残留测定 本标准可测定的农药品种见附录A

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本标准适用于生产、销售的花生、大豆中农药残留测定 本标准可测定的农药品种见附录A

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本标准适用于生产，销售的蔬菜，水果中农药残留测定 本标准可测定的农药品种见附录A

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定价： 636元

定价： 600元