Synthetic test solutions

The ability of different control tests to mirror different types of adsorptive power is a primary consideration in the selection of the tests to be included in a multiple program. It must be kept clearly in rhind that when more than a single test is used, each additional test should be such as will catch deviations not detected by the other control tests in use. The selection can be based on a laboratory study in which a variety of synthetic test solutions are reacted with different batches of the grade of carbon under study. 

Thus far we have considered synthetic test solutions solely as a means for classifying finished product, and for providing trouble-free shipments. But synthetic test solutions can be of great utility in establishing and maintaining a proper activation environment. 

Testing and evaluation procedures, when established as part of the operating routine, must never be regarded as immutable or permanent. The true function of synthetic test solutions must be kept in mind at all times. Synthetic tests have no inborn worth instead they acquire utility to the extent that they mirror the needs of the markets being served. And as new processes and products enter the market place, some of them will call for activated carbons with new and different forms of usefulness. And some of these new needs will in turn call for appropriate new test procedures. 

Thus far the story has been a recital of successful experiences, but for future guidance it is well to mention one of the less fortunate ones. Activated carbon was used with apparent success in the initial manufacture of streptomycin, but at times the operation was marred by low recovery of streptomycin. This was traced to several factors, one of which was an uneven quality of the carbon delivered. Unfortunately, the nature of the unevenness could not be identified or measured by any of the synthetic tests solutions then in use and before suitable tests could be developed the manufacturers of streptomycin had turned to other methods of processing. The experience was unfortunate, not only because a large and valuable market was lost but also because the episode appeared to cause a waning of interest of research groups in exploring the potential use of activated carbon for the production of other antibiotics. 

A carbon-treated filtrate may have a different quality of color because of a change in pH. This may occur when a carbon that contains appreciable acid or alkali is used to decolorize a liquid containing indicator-type colored bodies. Such behavior requires experimental precautions. One method is to test the pH of each filtrate and adjust any deviation to the original pH. In the case of synthetic test solutions, these should be buffered to the natural pH of the dissolved dye. It is to be noted that the buffer can affect the adsorbability of the dye and the adsorption may not be the same from buffered as from unbuffered solutions. 

To qualify for use, synthetic test solutions should contain an adsorbable substance appropriate for the type of carbon and the... 

The adsorption characteristics of many dyes used in synthetic test solutions will vary from one batch to another. Therefore, when tests are to be correlated over a period of time, it is important to procure an ample supply of a selected batch of each dye, sufficient to last for the duration of the study. When several laboratories participate in a joint study, all should use reagents from an identical supply. 

When several tests are used to control the quality of activated carbon production and shipments, each test should be chosen to catch deviations and mutations not detected by other control tests in use. The selection of tests can be based on a laboratory study in which a number of batches of the same carbon are tested with various synthetic test solutions. 

It is to be emphasized that the data given for Carbon W in Table 14 5 and the deductions as to suitable control tests apply only to that particular grade of carbon. Another grade, particularly one made by a different process, would furnish other assortments of adsorptive power. A corollary is that specifications for the purchase of a certain grade of carbon should not be used automatically for the purchase of a different grade. Furthermore, if and when a switch to another carbon is being considered the decision should rest on a comparative performance with the solution to be purified. Carbons must never be substituted for one another on the basis of synthetic test solutions in an industrial application. 

Sample Composition of synthetic test solution used for azeotropic distillation Volume of test solution used for azeotropic distillation, ml Acrylonitrile added, pg (X) Weight of acrylonitrile in test solution, pg Recovery of acrylonitrile in first two fractions obtained by azeotropic distillation Y X 100/X, % w/v... 

In this study, a factorial experiment was set up to evaluate the effects of four variables at two levels on extraction efficiencies by using bonded-phase isolation techniques and a 27-component synthetic test mixture. The compounds studied and the respective mass ions used for quantitation are given in the box. The compounds in the mix vary greatly in water solubility and volatility and, in general, represent a wide class of organic compounds typical of those present in environmental samples. To maximize solute recoveries, the procedure was... 

Chromosorb T shows the direct correlation of capacity with the oc-tanol-water partition coefficient expected of hydrophobic adsorbents (6). Its overall affinity for hydrophobic water contaminants is similar to that of Amberlite XAD-8 (Rohm and Haas), but it has additional affinity for humic acid and for water-soluble, cationic, aromatic dyes. Chromosorb T is more easily cleaned than the XAD resins, and it is more inert, contributing essentially no contaminants to eluates. Table IV illustrates the adsorption and recovery of a series of hydrophobic test solutes at 50 ppb in 8 L of synthetic hard water on a 50-mL bed of Chromosorb T. 

In a method proposed by Booth et al. (141) for the determination of phylloquinone in various food types, extracted samples are subjected to silica solid-phase extraction followed, in the case of meat or milk samples, by further purification using reversed-phase solid-phase extraction or liquid-phase reduction extraction, respectively. The final test solution is analyzed by NARP-HPLC, and the fluorescent hydroquinone reduction products of phylloquinone and the internal standard are produced online using a postcolumn chemical reactor packed with zinc metal. 2, 3 -Dihydrophylloquinone, a synthetic analog of phylloquinone, is a suitable internal standard for the analysis of vegetable juice, whole milk, and spinach. Another synthetic analog, Ku23), is used for the analysis of bread and beef, because a contaminant in the test solution coelutes with dihydro-phylloquinone. 

Sprincl, L., Exner, J., Sterba 0., and Kopecek, J. New types of synthetic infusion solutions III. Elimination and retention of poly-[Af-(2-hydroxypropyl)methacrylamide] in a test organism. J. Biomed. Mater. Res. 10(6) 953-963. 1976. 

Inspection of the americium test data showed that the entire spike (about 8xlO 6M americium) dissolved in the presence of 0.1M HEDTA. Subsequent synthetic HLW test solutions having 0.1M HEDTA completely dissolved an 8xlO"4M americium spike (0.6 Ci 241Am/L), tnus confirming the strong effect of HEDTA on americium solubility. Citrate and hydroxyacetate also increased americium solubility. At 0.03M citrate, with <. 10 5M HEDTA,... 

The rotifer toxicity assay was performed with juveniles of B. calyciflorus hatched from cysts after 16-18 h of incubation at 25°C in synthetic freshwater (moderately hard U.S. Environmental Protection Agency medium)28 under continuous illumination (light source 3,000-4,000 lux). Test solutions were... 

The crustacean toxicity test to assess the mortality of T. platyurus was conducted by hatching these anostraca from cysts after 20-22 h of incubation at 25°C in the same synthetic freshwater used for rotifers and at the same illumination conditions. The test solutions in five concentrations (two-fold dilutions) with three replicates of 10 animals were poured in disposable multiwell test plates (1 mL per well). After 24 h in a 25 °C incubator in the dark, the number of dead crustaceans was recorded. 

The oxidation of S(IV) is a first order reaction with respect to S(IV) (2,3). This reaction is accelerated by the presence of metallic ions such as ferric and manganous ions which act as catalysts (4-8). Therefore, the effect of the metallic ions on the oxidation of S(IV) was investigated by using test solutions. Table I shows experimental conditions for the oxidation of S(IV) in test solutions. The pH values of synthetic rain water samples were adjusted between 3 and 6. S(IV) concentration in the test solutions was adjusted to 12.5 yM most of S(IV) existed as bisulfite at pH 3-6 (9). The rate of S(IV) oxidation was measured using ion chromatographic analysis. The pH of each test solution was adjusted by using a buffer. 

Zeeman and Butler (Zl) determined copper in wines. Following acid digestion and dry-ashing the samples were taken up in nitric acid and aspirated. None of the elements found in the ash, when tested individually, had any effect on copper absorption, but when synthetic ash solutions were investigated, containing a combination of the ash constituents, absorption depression occurred. This effect had to be compensated for in the calibrating solutions. 

Results obtained from denitration tests performed on a concentrated synthetic HAW solution (500 l/ton U) as proposed in the TBP process scheme (option 2), were comparable to those discussed above. The experiments were so far done on simulated HAW solutions. Active runs are scheduled for the second half of 1979. 

Before solvent extraction, the feed was treated with manganous nitrate and less than equivalent permanganate to convert plutonium to Pu(VI). Tests in miniature mixer-settlers with synthetic feed solution but not containing Cf showed acceptably small concentrations of actinides in the aqueous waste (1AW) and organic raffinate (1CW) streams, and also acceptable separation of plutonium from curium and americium. 

Table 1. Laboratory Tests of Am and Cm Recovery With Synthetic Feed Solution...

It is to be recognized that the data provided by these simplified procedures have limited significance. Their main value is that eluants and conditions of no value can be eliminated from further consideration. Conclusions reached from these simplified procedures —as to the best eluants and conditions—should be confirmed by a supplementary test using the full adsorption-desorption procedure on the substance to be processed. This is especially necessary when the preliminary studies employ a synthetically prepared solution these studies, do not fully reflect the behavior of a substance when present in industrial or biological preparations containing coadsorbates. 

Studies of the influence of activation procedures on the characteristics of the resulting activated carbon employ synthetic solutions in which a single adsorbable solute is dissolved in water. Some recent studies indicate that a test solution containing two or more adsorbable solutes will reveal properties not disclosed when only a single solute is present. 

Miscellaneous Tests with Synthetic Scaling Solutions. Figure 5 shows graphically the results obtained using the following synthetic hard waters, prepared from Melbourne tap water (ca. 40 p.p.m. of total dissolved solids). 

In Vitro Studies. A series of elastomers were soaked in a 37°C synthetic plasma solution (Table I), based on a formulation developed by Carmen and Kahn (20), containing biologically important low molecular weight molecules in blood. The elastomer test samples were exposed to the synthetic plasma for periods extending from 20 weeks to one year. Gravimetric analysis was performed biweekly for 20 weeks and again at 52 weeks. 

Electrode response is affected by ionic strength variations because of the associated effect on activity coefficients [9]. This makes an assessment of ionic strength on the test solution desirable. However, because of the powered term in /x = SC, conductance monitoring may not always be satisfactory, unless, of course, the individual ionic contributions (concentrations, C, and valence, z) are known from previous analyses. Such information is useful for preparing calibration standards of the same ionic strength range as the sample under examination and is the basis of synthetic sea water samples as calibrants. Calcium chloride standards in 0.150 mol dm sodium chloride is a similar ploy used in calibrating... 

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