Drying samples, liquid solid

Miller and Hawthorne [416] have developed a chromatographic method that allows subcritical (hot/liquid) water to be used as a mobile phase for packed-column RPLC with solute detection by FID, UV or F also PHWE-LC-GC-FTD couplings are used. Before LC elution the extract is dried in a solid-phase trap to remove the water. In analogy to SFE-SFC, on-line coupled superheated water extraction-superheated water chromatography (SWE-SWC) has been proposed [417]. On-line sample extraction, clean-up and fractionation increases sensitivity, avoids contamination and minimises sources of error. 

Water in the sample when you don t have a lot of sample. Since solid drying agents can absorb lots of liquid, what can you do if you have a tiny amount of product to be dried Add some solvent that has a low boiling point. It must dissolve your product. Now you have a lot of liquid to dry, and if a little gets lost, it is not all product. Remove this solvent after you ve dried the solution. Be careful if the solvent is flammable. No flames ... 

The earliest applications for quantitative analysis of liquid samples and solid preparations entailed sample dissolution in an appropriate solvent. A number of moisture determinations in APIs and pharmaceutical preparations based on both reflectance and transmission measurements have been reported. Their results are comparable to those of the KF method. The high sensitivity provided by the NIR technique has fostered its use in the determination of moisture in freeze-dried pharmaceuticals. ° The noninvasive nature of NIR has been exploited in determination of moisture in sealed glass vials. " " ... 

Liquid Samples. Liquid samples such as plasma or milk are shell-frozen in the lyophilizer flasks using a mixture of crushed dry ice and 2-propanol. They are then dehydrated in the same way as the solid samples. The resulting material, which is brittle and spongy and easily broken up, is then pressed into cans and sealed. No preservative is added to the dried materials they can be stored indefinitely at room temperature. Approximately 2 liters of fresh milk can be dried and compressed into one can. 

Sample Requirement Compatible with high vacuum. Dry and conductive samples only Any sample type (including liquids, solids, powders, and insulators) plus dynamic reactions. 

In contrast, as shown in Figure 4.5, the Si/Ti ratio of the samples synthesized by the method A drastically increased during the period of crystal growth the solid samples in the induction period were obtained directly by drying the liquid at 100 °C... 

The porosity of a solid is most easily determined by the imbibition method. A sample of solid is dried, weighed while dry, then saturated with a wetting liquid (such as water or heptane), under vacuum. The accessible pore volume is calculated by a material balance ... 

The method of sample preparation to be used for a given analysis is governed by the nature and concentration of the analyte, the nature (solid or liquid) and type of matrix, the available sample amount, and also by the instrumental technique employed. Freeze-dried samples will require some form of digestion or dissolution in order to be analyzed by a classic atomic technique (i.e., using nebuliza-tion). Liquids might be analyzed by direct nebulization, but this is not always possible due to matrix interferences. Milk pretreatment may be necessary under such circumstances. 

Titratable Acidity (as Lactic Acid) Accurately weigh a portion of the finely ground dry sample or liquid equivalent to 10.0 g of total solids based on the value obtained under Loss on Drying (above), and transfer into a 500-mL conical flask. Add 100 mL of carbon dioxide-free water, and stir for 1 min. Allow to stand for 1 h at room temperature. Add 0.5 mL of phenolphthalein TS, and titrate with 0.1 A sodium hydroxide to a pink endpoint that persists for 30 s. Each milliliter of 0.1 A sodium hydroxide is equivalent to 9.008 mg of lactic acid. 

Feldman (FI6) explained the difference between the values for D-dried samples obtained with aqueous and other fluids. When the material is dried, the layers partially collapse, and some empty spaces remain between them. Water penetrates into this space, and the density obtained, after correction for CH and any other phases present, is that of the layers themselves. Organic liquids do not penetrate, and helium penetrates only slowly. The empty interlayer space is counted as part of the solid volume, with a consequent decrease in the measured density. 

Next we shall describe some of the objectives used in sample pre-treatment. The objective of these procedures is to reduce the volume of the samples. Portioning, evaporation concentration, chemical separation, absorption and so forth are techniques used alone or in an appropriate combination for liquid samples. Drying, sieving, pulverisation, mixing, reduction, ashing and so forth are techniques used alone or in an appropriate combination, for preparing samples of solids for measurement. 

Sample Preparation. Samples were prepared by exposing the silica gel, previously dried at 150 °C for 24 h, to either cyclohexane or pentane solutions containing selected amounts of the fluorophore. The solvent was carefully removed under vacuum when required. Complete probe adsorption of liquid-solid samples was verified with absorption spectroscopy. Less than 0.07% of the silica surface was typically covered by the probe. Immediately before data collection, dry samples were evacuated under vacuum at 125-130 °C for 30 min. The total dehydration procedure was sufficient to remove the physisorbed water while leaving the surface silanol functionality intact (12). Selected amounts of oxygen were introduced into a... 

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