It''s a paradox. Most of the very technologies being used today to test water for contaminants actually return more pollution to the environment than the tested water itself. Nevertheless, as we all know, water testing is crucial to our health. Modern industry has unleashed tens of thousands of chemicals into the environment. Many of these chemicals are essential, but it''s the control of them that''s the issue. Without these chemicals we would not enjoy many products that we now take for granted, such as computers, smart phones, plastic baby bottles and disposable diapers. Just about every product the consumer can buy or touch depends on these chemicals and processes.
Bisphenol (BPA), for example, is used by manufacturers to make polycarbonate plastics used in items such as baby bottles and beverage containers. The problem is that over time BPA can leach from these containers, especially if they''ve been reused a lot. This and other widely used chemicals have been blamed for causing early puberty in girls, as young as seven or eight, and a host of other social and medical problems.
Pharmaceuticals are now a major problem around the world. Many common antidepressants are now found in lakes and oceans, not enough to affect big fish, but enough to affect smaller fish. They get there through human urine being flushed down into the sewer system and people wrongly disposing their pills in the toilet as well.
The biggest problem of all is PCBs, polychlorinated biphenyls. They once were used to manufacture electrical equipment such as capacitors. In fact, from 1947-1977 a capacitor plant on the Hudson River poured 1.3 million pounds of PCBs into the waterway. PCBs are long-lasting and persistent in the environment. They have been shown to cause changes in human DNA and are considered to be potent carcinogens.
The Environmental Protection Agency (EPA) reports strong indicators that PCBs cause cancer, and that they have also been associated with many other negative health effects, such as changes to the immune system, reproductive system, nervous system and endocrine system in humans.
Clearly water testing is critical, but how good is it if it returns more pollution to the environment?
The traditional methods of LLE and CLLE
Traditional methods used to test for contaminates in water were two processes called liquid-liquid extraction (LLE) and continuous liquid-liquid extraction (CLLE). LLE has been the standard for the last 30 years. In brief LLE testers, take two liters of a water sample, and then blend them with 60 milliliters of solvent. Shake well, (shaken not stirred). In the process, the added solvent attracts the contaminants. The mixture is then allowed to settle with the solvent and contaminants separating from the water and sinking to the bottom of a funnel where they are removed from the sample. This is repeated two more times, each time using 60 mls of new solvent. In the end, the solvent evaporates into the atmosphere, leaving the contaminants behind for further analytical measurement.
CLLE operates on a similar principle, but uses larger volumes of water and 500 ml of solvent, plus the mechanisms are more complex.
SPE process for testing contaminants
By contrast, a newer method called solid phase extraction (SPE) uses significantly lesser amounts of solvent (50-90 percent less) and incorporates a filtration process with absorbent disks. It''s a process that begins with placing these disks in the device, which then delivers the necessary solvents to condition each SPE disk. Next, the water to be tested is passed through these disks where contaminants are captured. The disks are then saturated with solvent, to elute out the analytes of interest.
This is a simplified version of the SPE processes that can be fully automated. It involves prepping and cleaning the system and extracting the contaminants from the water in a five step process using various solvents such as hexane, acetone and others. The solvents are then recovered in separate closed collection containers as well as the processed water sample.
The advantages of the automated SPE method include a much faster process time (set-up to extraction), taking about 26 minutes. And, it requires just one technician to process multiple samples simultaneously. Typical LLE takes several hours and multiple technicians, while CLLE uses one technician, more complex glassware and up to 24-48 hours to process a single water sample.
All three methods require solvent recovery technology, but the less solvent used for extraction lessens the amount that has to be recovered. As mentioned earlier LLE and CLLE methods use anywhere from 180-500 ml of solvent, while the SPE method uses a fraction of this amount. In addition, all waste solvent must be properly disposed of. Using a cost of $165 per drum and averaging two drums a month can add savings of $3,150 a year on disposal costs.
The automated SPE reduced-solvent method creates a safer working environment for analysts by reducing the chances of solvent exposure. Also the automated SPE technology is a closed system, which further enhances safety.
There are many other pluses: Cost, safety and simplicity are the main ones. Another safety example: LLE samples are placed in water baths on hot plates, and have to be watched closely as the solvent is boiled off. At the end of the process almost all of the 180 mls of solvent are released into the atmosphere. A technician has to be present to prevent samples from boiling dry. Contrast that with an automated SPE and concentration process featuring endpoint detection and shutoff, which automatically prevents the samples from accidentally boiling dry.
The automated SPE approach lets the analyst extract up to eight samples at a time while using much less solvent. This approach cuts the total cost of processing each sample, reduces the time required and minimizes human contact, while reducing greatly total solvent emissions to the environment.