Sample reduction

Fig. 1. Sample reduction of an ester group to the corresponding primary alcohol (CASREACT) (87) s(carboxyhc or carboxylate)/fg.rct (s) (primary...

Sample reduction in successive stages—primaiy to secondaiy, secondary to tertiary etc.—can be fulfilled using automatic sampling equipment while observing design principles of statistical sampling. Alternatively, sample quantity reduction may be carried out in a lab-oratoiy. 

Their physical properties (maximum particle size, mass, etc) are specified in the analytical procedure. Sampling covers sampling (in the narrow sense) and sample reduction. 

Samples of natural water should either be analysed immediately or be stored (not for a very long time) at a decreased temperature to suppress microbial processes. For the determination of nitrate and nitrite it is useful to conserve the samples by addition of 1 ml chloroform or 0.1% phenylmercuric acetate per Utre. To prevent oxidation of sulphide and some other substances in water samples, reductants are added [5, 147]. If the distribution of a species between the f ree ionic form and various complexes is to be studied, as is of ten the case, care must be taken not to shift the equiUbrium by adding substances that would enter into side reactions with the studied species. 

Fig. 4. Separated metal fractions from different grain size classes during sample reduction (by operators metal >5 cm from mixed sample metal > 1 cm from split < 1 cm metal from 1 cm to 2 mm from BA split <2 mm metal <2 mm).

Fig. 7. Differential heat of reoxidation and selectivity for oxidative dehydrogenation of butane on V2Ov y -AFO, samples. For the 2.9 V/nm2 sample, the selectivity was calculated for the detected gaseous products, (a) 8.2 V/nm2 sample, reaction at 400°C (b) 2.9 V/ntn2 sample, reaction at 480°C (c) 8.2 V/nm2 sample, reduction by CO at 530°C, butane reaction at 400°C and (d) 2.9 V/nm2 sample, reduction by CO at 400°C, butane reaction at 480°C. (a) and (b) are from Ref. 50 (c) and (d) and from P. J., Andersen, Ph D. thesis, Northwestern University, 1992.

Bangladesh Manikganj District Singair Thana 26 samples Reductive dissolution of Fe (oxy)(hydr)oxides — < 1 -240 Mohammad et al. (2003)... 

Bangladesh Sonargaon thana 35 samples Reductive dissolution of natural materials 6.53-7.59 30—750 (0.7 p.m filtered) Anawar et al. (2003), 115... 

USA Lake Coeur d Alene, Idaho 12 samples Reductive dissolution — 40-350 (0.2 pm filtered) Harrington, Fendorf and Rosenzweig (1998)... 

Sample reduction process whereby a sample is reduced in particle size by crushing or grinding without significant change (ASTM D-2013). 

Sample Reduction temperature (°C) Reduction time 00 Fitting technique ... 

Sample Reduction temperature (°C) Reduction time GO Liii-edge shift (eV) Normalized Lm-edge area Normalized Lu-edge area // Number of unfilled d states per atom11... 

Well-accepted method for sample reduction that is highly suitable for free-flowing powders. Used to produce samples with a minimum volume of 5 mL. 

Used for sample reduction with the advantages of low price and lack of moving parts. 

Sampling systems for multiple-stage sample reduction incorporating components such as crushing units, interstage feeders, reject handling, and others range up to several hundred thousand dollars in cost. A requirement would be rarely encountered in fine-powder applications. 

Application of the oxo reaction at 100—110° for 20 minutes to tri-O-acetyl-l,2-anhydro-D-glucopyranose (Brigl s anhydride) (73), followed by acetylation, gave, in over 80% yield, 1,3,4,5,7-penta-O-acetyl-2,6-anhydro-D-gli/cero-D-gttlo-heptitol (74), identical with an authentic sample. Reduction of the minor component [presumed to be the aldehydo precursor of (74)] with sodium borohydride, followed by acetylation, afforded the acetylated heptitol (74). 

In all cases, step changes (iii and v) showed that the sample re-oxidation by O2 (v) is much faster than the sample reduction by CO (iii). 

Kaye, B.H. Efficient sample reduction of powders by means of a riffler sampler. Soc. Chem. Ind. Monogr. 1964, 18, 159-163. 

There are several important reasons to include sample preparation in modem liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods. These include the elimination of matrix components from the sample reduction of ion suppression and, sometimes, improved sample utilization. 

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