Testing cleaning solutions

This left something else as the possible cause of the variability. When we considered the nature of the test, which was sensitive to parts per million of organic materials, we realized that one possibility was contamination of the glassware by the soap used to clean it. We next cleaned all glassware with chromic acid cleaning solution, and reran the tests, with the result as shown in Table 9-5. 

Substrate Characterization. Test coupons and panels of 7075-T6 aluminum, an alloy used extensively for aircraft structures, were degreased In a commercial alkaline cleaning solution and rinsed In distilled, deionized water. The samples were then subjected to either a standard Forest Products Laboratories (FPL) treatment ( 0 or to a sulfuric acid anodization (SAA) process (10% H2SO4, v/v 15V 20 min), two methods used for surface preparation of aircraft structural components. The metal surfaces were examined by scanning transmission electron microscopy (STEM) In the SEM mode and by X-ray photoelectron spectroscopy (XPS). 

Fig. 5.12 (a) Medieval coins from the Preuschdorf s hoard, as found (left) and after cteaning with chemicats (right)-, (b) Cross section of a test sample (80% Ag/20% Cu) showing the influence of 48 h of immersion in a cleaning solution ( silver dip ) on the surface composition (after [278])... 

An alternative to determining the quantity of residue left in the equipment is to monitor the effluent of cleaning solution for the presence of residue. If it can be shown that the residue is readily soluble in the cleaning solution and the test method is sufficiently sensitive, the acceptance criteria for cleanliness might involve washing until the residue drops below the quantifiable limit of the test method or reaches an acceptably low steady state in the effluent. 

Take a glass rod, and test each solution for its pH. Carefully dip one end of the glass rod into a solution and touch a piece of pH paper. Between each test, be sure to clean and dry the glass rod. Record the pH by comparing the color of the paper with the chart on the dispenser. 

Magnesium Oxide and Water. Bum a piece of magnesium ribbon held in pincers so that the ash falls into a clean dish. Stir half of the ash into a small beaker full of water and test the solution with litmus. Wet the other half of the ash with a single drop of water and place the moistened mass on one side of a strip of red litmus paper. Look on the other side of the paper and note that in a little while the center of the wet spot turns blue. 

Repeat step 4 with the K2SO4 and with each of the remaining solutions in the well strip. For each solution that you test, record the color of each flame and the wavelength observed with the spectroscope. After the solutions are tested, clean the wire thoroughly, rinse the well strip with distilled water, and collect the rinse water in the waste beaker. 

Test a drop of the NaCl solution in the flame, and then view it through the spectroscope. (Do not use the cobalt glass.) Record your observations. Clean the wire, and rinse the well strip with distilled water. Pour the rinse water into the waste beaker. Place a few crystals of NaCl in a clean well, dip the wire in the crystals, and do the flame test once more. Record the color of the flame test. Clean the wire, and rinse the well strip with distilled water. Pour the rinse water into the waste beaker. 

If not done carefully, ion suppression can severely distort the determination of assay recovery. For example, if the recovery of a liquid—liquid extraction is to be evaluated, the comparison of analyte peak response from a spiked, extracted matrix sample to the analyte peak response from a clean solution is not appropriate. The compound in clean solution will ionize much more readily than the compound in extracted matrix, so that when the ratio of response extracted to response nonextracted is calculated, an erroneously low estimate of recovery will result. If this type of recovery estimate is to be conducted, it is much better to extract an aliquot of blank matrix and spike the analyte into this residue for use as the recovery standard. In this way, the ionization environment of the recovery test sample and standard are approximately equal and a meaningful estimate of recovery can be made. 

Static soaking tests can also be done which eliminate the contribution of the mechanical action of the abrader test. The surface has a volume of the cleaning solution trapped within a ring (like a rubber washer), and covered to stop evaporation. After a set time the cleaning solution is poured off, the surface rinsed, and the area evaluated (either by eye or by reflectometer) to determine degree of stain removal. This can also be used as a test for damage to the surface by the cleaner if done on an unsoiled surface. 

Wipe cleaners can be tested in one of two ways either just the cleaning solution can be tested (using the methods outlined above for spray or dilutable cleaners) or the final wipe itself with cleaning solution on the nonwoven substrate can be tested. The testing of the wipe for cleaning performance would have to be, because of the form, abrader testing. In this case, however, there would be no question of how to apply the cleaner, or how much, if wet wipes are used. 

As part of the validation of the cleaning method, the cleaned surface is sampled for the presence of residues. Sampling should be made by an appropriate method, selected on the basis of factors such as equipment and solubility of residues. For example, representative swabbing of surfaces is often used, especially in areas that are hard to clean or where the residue is relatively insoluble. Analysis of rinse solutions for residues has also been shown to be of value where the residue is soluble or difficult to access for direct swabbing. Both methods are useful when there is a direct measurement of the residual substance. However, it is unacceptable to test rinse solutions (such as purified water) for conformance to the purity specifications for those solutions instead of testing directly for the presence of possible residues. 

Electrochemical Remediation Heavy metals and other contaminants can be removed from the soil and groundwater with the help of electrokinetic phenomena (electroosmosis, electrophoresis, electrolysis). In electrochemical remediation processes, a continuous electrical field is generated with electrodes that are inserted into the contaminated soil (Shapiro etal. 1989 Ottosen etal. 1995 Hansen etal. 1997). Laboratory and pilot tests have been conducted, for example, with acetic acid as cleaning solution (Renaud 1990). With elec-... 

Contaminants may be of three general types particulates, highly polar (ionic) residues, and nonpolar (grease-Uke) residues. In many production environments, all three types are present and several solvents and cleaning processes may be required to remove them. Both the choice of solvent or cleaning solution and the cleaning process are critical, and several theoretical principles may be followed in their selection. Ultimately, cleaning is more an art than a science, and the procedure chosen should be experimentally verified in each case. Qualitative and quantitative tests can be performed to determine the efficiency of a selected solvent and process. 

High levels of chloroform—a. listed hazardous waste under RCRA— were observed in EDS cleaning solutions from the RMA tests (Appendix C, Table C-1). The source appears to be the particulartypeof lubricant/sealant used to seal joints. The chloroform is therefore not a necessary constituent of the waste stream and could be eliminated by using a different formulation of sealant/lubricant. 

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