Cleaning Solution Analysis

Analysis of contaminants left in cleaning (or final rinse) solutions may indicate that additional cleaning and rinsing are necessary [1], 

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Ozone can be analyzed by titrimetry, direct and colorimetric spectrometry, amperometry, oxidation—reduction potential (ORP), chemiluminescence, calorimetry, thermal conductivity, and isothermal pressure change on decomposition. The last three methods ate not frequently employed. Proper measurement of ozone in water requites an awareness of its reactivity, instabiUty, volatility, and the potential effect of interfering substances. To eliminate interferences, ozone sometimes is sparged out of solution by using an inert gas for analysis in the gas phase or on reabsorption in a clean solution. Historically, the most common analytical procedure has been the iodometric method in which gaseous ozone is absorbed by aqueous KI. 

Octachlorodibenzo- -dioxin. Pentachlorophenol was purified by sublimation and recrystallization to yield a product with the following composition trichlorophenol, 0.04% tetrachlorophenol, 0.07% and pentachlorophenol, 100.4 1%. Pentachlorophenol (300 grams, 1.13 mole) was dissolved in 900 ml of trichlorobenzene and chlorinated anhydrously for 18 hours at reflux. Ghlorine addition was stopped and the mixture was heated for 28 more hours at reflux. The crystalline product was washed with 2-liter portions of chloroform, IN NaOH, methanol, and water. Analysis by GLG suggested the presence of 5-15% heptachloro-dibenzo-p-dioxin. The mixture was carefully added to a cleaning solution of 200 ml water, 3.5 liters sulfuric acid, and 125 grams sodium dichromate. The mixture was heated at 150 °G for six hours. The product was recrystallized from hot o-dichlorobenzene and then from anisole. The purified product (160 grams, mp 329.8° 0.5°G) contained <0.1% heptachlorodibenzo-p-dioxin, determined by GLG. 

The EDX spectrum (Fig. 11.8) shows the main surface scale impurity peaks of silica, aluminium, sodium, chloride and iron. If this EDX is compared to that of a new, clean membrane surface (Fig. 11.9), the clean surface shows sulphur, carbon and oxygen, which is typical of a porous polysulphone support. It was concluded that the scale is amorphous, composed of aluminosilicate and silicate. These compounds are normally found in trace amounts in brine solutions. Analysis showed that the surface could be cleaned with hydrochloric acid and analysis of the dissolved scale was similar to the EDX spectrum analysis. Review of the plant operation determined that the precipitation was the result of high pH in combination with high silica concentrations in the brine. 

When using a pneumatic nebulizer, an unheated spray chamber, and a quadrupole mass spectrometer, ICP-MS detection limits are 1 part per trillion or less for 40 to 60 elements (Table 3.4) in clean solutions. Detection limits in the parts per quadrillion range can be obtained for many elements with higher-efficiency sample introduction systems and/or a magnetic sector mass spectrometer used in low-resolution mode. Blank levels, spectral overlaps, and control of sample contamination during preparation, storage, and analysis often prohibit attainment of the ultimate detection limits. 

Trap C consists of three gas-trapping bottles of equal volume joined in series, each capable of holding a maximum of about 4 ml of trapping solution. Prior to the analysis, all parts of the apparatus must be cleaned with cleaning solution. 

In general, the procedure as outlined works well and yields a clean solution for analysis. The normal precautions used with HF and HCIO4 must be followed. All fuming must, of course, be done in a hood, preferably one which has been constructed especially for HCIO4 work. 

With the ever-increasing need to improve quality and productivity in the analytical pharmaceutical laboratory, automation has become a key component. Automation for vibrational spectroscopy has been fairly limited. Although most software packages for vibrational spectrometers allow for the construction of macro routines for the grouping of repetitive software tasks, there is only a small number of automation routines in which sample introduction and subsequent spectral acquisition/data interpretation are available. For the routine analysis of alkali halide pellets, a number of commercially available sample wheels are used in which the wheel contains a selected number of pellets in specific locations. The wheel is then indexed to a sample disk, the IR spectrum obtained and archived, and then the wheel indexed to the next sample. This system requires that the pellets be manually pressed and placed into the wheel before automated spectral acquisition. A similar system is also available for automated liquid analysis in which samples in individual vials are pumped onto an ATR crystal and subsequently analyzed. Between samples, a cleaning solution is passed over the ATR crystal to reduce cross-contamination. Automated diffuse reflectance has also been introduced in which a tray of DR sample cups is indexed into the IR sample beam and subsequently scanned. In each of these cases, manual preparation of the sample is necessary (23). In the field of Raman spectroscopy, automation is being developed in conjunction with fiber-optic probes and accompanying... 

Analyses of extracts led to difficulties, mainly due to a lack of good long-term reproducibility for many laboratories. Capillary GC was found to offer good possibilities but its use was hampered by the absence of commercially available columns. Furthermore, sources of error were likely due to losses of MeHg. A Youden plot of raw and spiked extract demonstrated systematic errors (Figure 1) which was illustrated by the high CKs found between laboratories (Table 4.1 16.6 and 17.4% for raw and spiked raw extracts, respectively). Better results were obtained for the cleaned extract (12.5%) but the spread was still considered to be too high. However, a consequent improvement was obtained for the aqueous solution analysis (CF of 8.4%). 

A group of four people was used to complete 15 samples (which Included a blank sample, a sample spiked with ethylenethlourea, and a sample spiked with mancozeb) in one day. All glassware used was washed In a "Micro-Clean solution, rinsed with distilled water, and oven-dried Immediately prior to use. To minimize conversion of mancozeb to ETU during analysis samples were worked up continuously from 8 30 a.m. until 10 00 p.m. On most days conversions were less than 1% and even undetectable on some days. Unfortunately on two extresiely hot and humid days 3 and 5% conversions were experienced. 

An important distinction to be kept in mind is that between the instrumental detection limit (IDL) and the method detection limit (MDL) the IDL refers to an LOD determined using clean solutions of the analytical standard injected into the analytical instrument (e.g., LC-MS, GC-MS/MS) operated under stated conditions, while the MDL involves blank matrix samples spiked with known amounts of the calibration standard and taken through the entire extraction-cleanup-analysis procedure. This distinction is irrelevant to the question of how either of these LOD quantities is to be defined and measured (see below). 

Generally, cleaning solutions perform better when warm. Depending upon the particular solution, this temperature will be in the range of lOO F to 180°F (37.8°C to 82.2 C). The cleaning solution can be reused until it is too weak or too contaminated as determined by pH or concentration analysis. Experience will establish... 

Pelletier et al. [159] also measured additional spectra of other important solutions, (e.g., the SC-2 cleaning solution) used in semiconductor processes. These solutions appear to be less readily amenable to Raman analysis however, Pelletier et al. [159,160] noted that the analysis may be possible but further work was needed because some of the components could not be measured directly... 

A good method for studying passive film formation involves examining polarization curves. ° Theoretical anodic and cathodic polarization curves are shown in Figure 1. As the potential is shifted in the anodic (-I-) direction, the current (corrosion rate) increases. At a critical current density (/cnt), the current drops to a low value—indicating the onset of passivation. With the use of polarization curves, the solution conditions controlling passivation can be determined and described. Polarization curve analysis will be extensively used in the subsequent sections to describe passivation in chemical cleaning solutions. 

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