A Sample Extraction

If the recovered material is insoluble in the aqueous recovery solution, and it is a solid, collect the crystals on a Buchner funnel. If they are not pure, you should recrystallize them. 

If the recovered material is insoluble in the aqueous recovery solution and it is a liquid, you can use your separatory funnel to separate the aqueous recovery solution from your liquid product. Then dry your liquid product and distill it if it is not clean. Or, you might just do a back-extraction as just described. This has the added advantage of getting out the small amount of liquid product that dissolves in the aqueous recovery solution and increases your yield. Remember to dry the back-extracted solution before you remove the organic solvent. Then distill your liquid compound if it is not clean. 

I think the only way I can bring this out is to use a typical example. This may ruin a few lab quizzes, but if it helps, it helps. 

Say you have to separate a mixture of benzoic acid (1), phenol (2), p-tolui-dine (4-Methylanaline) (3), and anisole (methoxybenzene) (4) by extraction. The numbers refer to the class of compound, as previously listed. We re assuming that none of the compounds react with any of the others and that you know we re using all four types as indicated. Phenol and 4-methylanaline are corrosive toxic poisons and if you get near these compounds in lab, be very careful. When they are used as an example on these pages, however, you are quite safe. Here s a sequence of tactics. 

Dissolve the mixture in ether. Ether is insoluble in the water solutions you will extract into. Ether happens to dissolve all four compounds. Aren t you lucky You bet It takes lots of hard work to come up with the typical student example.  

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Figure 2.16 Clirotnatograms of a pentane extract of a water sample containing 200 ppb of a naphtha fraction (a) sample extracted by using a continuous flow system, where a pressurized bottle was employed as the sample-delivery system (b) batch-extracted sample. Reprinted from Journal of Chromatography, A 330, J. Roeraade, Automated monitoring of organic Race components in water. I. Continuous flow exti action together with on-line capillary gas cliro-matography , pp. 263 - 274, copyrigth 1985, with permission from Elsevier Science.

A sensitive method has been developed to determine the aged residues of diflufenican in soil by GC/ECD. A sample extraction using 100% methanol with extended shake was performed. The extract was concentrated and purifled using a Cig SPE column. Further cleanup was effected by using a silica SPE column. The LOD for diflufenican in soil was 0.001 mgkg The recovery of diflufenican at fortiflcation levels from 0.02 to 0.2 mg kg in soil by this method was between 94 and 121%. ... 

Difficult matrix introduction (DMI) is another recently introduced way of automating trace analysis in complex and dirty matrices [101]. The technique may be used for both liquid and dirty solid samples. In DMI a sample extract or sample matrix (solid) is introduced directly into a microvial in the injector. Volatiles are desorbed directly... 

Fig. 2.54. High-performance liquid chromatography profile of a peppermint sample (gradient no.l), extracted with ethyl ether (a) and ethanol (b). Chromatographic profile of a sample extracted with ethanol (gradient no.2) (c). Detection at 320 nm. For peak identification see Table 2.55. Reprinted...

The progress of the reaction can be monitored by hydrolysis of a sample, extraction with ethyl acetate, and TLC [silica gel Macherey, Nagel Co. "Polygram Sil G/UV 254", petroleum ether/ethyl acetate/acetic acid 99 50 1, UV visualization, R, (2) = 0.40, R, (3) = 0.31 (yellow spot)]. 

Gas Analysis. Most of the analyses were carried out either on the average" sample taken during an experiment or on a sample extracted from the total gas sample. Some spot samples were also taken to investigate the variation in composition during an experiment. The gas analyses were carried out mainly using either gas chromatographic or infrared methods, but in some cases the... 

In this approach, residues from a sample extract were concentrated on a column in pure phosphate buffer and then eluted with a MeCN gradient. Fractions corresponding to each analyte of interest (1.5-ml fraction centered on the retention time) were collected and analyzed under different chromatographic conditions. 

Fig. 5.2 Dose-response curve for 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD) in the CALUX bioassay. The concentration (expressed as TCDD) can subsequently be determined by comparing the response obtained with a sample extract with the calibration...

Similar to GC instruments, HPLC instruments consist of an injection port, a separation column, a detector, and an instrument control/data acquisition computer. The use of liquid as a mobile phase influenced the design and construction materials of HPLC instrumentation elements. A sample extract or an aqueous sample is introduced into the separation column through an injection loop that can be programmed to receive various volumes of liquid (5 pi to 5 ml). 

Check each new batch of silica gel and alumina and maintain the results of the analyses on file for examination during EPA onsite evaluations. To accomplish this, combine 50 pL of the continuing calibration solution (CC3) with 950 pL of hexane. Process this solution through both columns in the same manner as a sample extract (Paragraphs 9.9.3 through 9.9.9). Concentrate the continuing calibration solution to a final volume of 50 pL. Proceed to Section 10. If the recovery of any of the analytes is less than 80% the batch of alumina or silica gel must not be used. 

Duplicate analysis of a sample extract solution - i.e. one sample has been taken through the analytical procedure up to the measurement step. At this point the extract solution is split into two portions and each portion measured. 

It is easily observable that each selection X and its associated y shown in Tables 5.2 or 5.3 correspond to a sample extracted from each type of population. In the current example we have 5 populations, which give the input reactant concentration, and 5 populations for the transformation degree of the reactant. In the tables, the first population associated to the input concentration corresponds to the experiment where the proposed concentration has the value 13.5 g/1. 

Several samples were obtained from the Sphinx were compared to a sample extracted from the Kephren Valley Temple. The mortars consist predominantly of gypsum with small quantities of lime and quartz. Table 1 gives a description of the sample origin. 

It is usually impossible to measure the size distribution of a bulk powder and so it is necessary to carry out measurements on a sample extracted from the bulk. This sample is itself frequently too large and has to be further sub-divided. 

Because SFE is a sample extraction-separation technique, it must precede other steps of the analytical process if the type and content of the species of interest in the extract are to be accurately determined. The analytical equipment required to develop the steps following extraction can either be coupled on-line to it or performed off-line. The way the extract should be treated with a view to identilying or quantifying the target analytes depends on its complexity and the type of information required. Thus, the analytes may require clean-up, individual separation or some other treatment prior to reaching the detector. 

Compared to HPLC, GC, TLC, GLC, and IC, CE offers (1) high resolution efficiency, (2) rapid separation speed, (3) simple sample pretreatment, (4) small consuming sample, and (5) short analysis time. No derivatiza-tion is needed as in GC or a sample extraction as in HPLC or IC. Addition of SDS (anionic surfactant) causes an increase in migration times of all organic acids. (Tang and Wu, 2007). 

The Road to Recovery—Back-Extraction A Sample Extraction Performing an Extraction or Washing Extraction Hints... 

All comparisons of the elemental composition of soil humates with aquatic humates must be viewed with caution. In recent years, the extraction methodology has changed rapidly. A soil sample extracted with base in the classical manner may have up to 20% carbohydrate and up to 10% ash, while a sample extracted with XAD resins may have less than 2% carbohydrate and 2% ash. To compare two samples extracted by two different methods would be akin to comparing apples and oranges. Fortunately, a body of literature is accumulating which reports the properties of humates extracted by a single, well-defined method. 

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