Tag Archives: Clean Rooms

Direct conductometric TOC analyzer alerts engineers to potentially damaging trihalomethane excursions in pharmaceutical water

By Terry Stange, PhD, and Matthew J. Smith, PhD, Hach Ultra Analytics

Total organic carbon (TOC) analyzers are becoming industry standard for monitoring purified water (PW) and water for injection (WFI) systems. Accuracy and stability are critical parameters for daily process monitoring of water distribution systems. Direct conductometric (DC) technology, self-calibrating conductivity circuits, and dynamic endpoint detection are being used in new-generation instruments to measure on-line TOC. Although the application of membrane conductivity (MC) for TOC measurement emerged in the mid-1980s, this technology was deterred from use in on-line PW and WFI applications due to the inherent instability of membrane-based TOC analyzers. MC-based analyzers suffer from continuous drift and instability owing to the constant change in CO2 transfer rates across the membrane in real-world, on-line applications. Variations in pH, temperature, membrane fouling, rouging, and dissolved gases (e.g., chlorine) all contribute to variations in CO2 transfer rates. These variations require frequent calibration of MC-based TOC analyzers compared to DC-based analyzers, which are also simpler to operate and maintain. DC TOC analyzers are based on the assumption that the only conductive species generated during UV oxidation is CO2–an assumption rarely violated in today’s advanced PW and WFI systems. When water conditions depart from normal ultra-pure water (UPW) levels, DC TOC analyzers can alert facilities engineers to subtle water chemistry changes that are otherwise ignored by MC-based TOC analyzers.

This article lays out the response of a TOC analyzer to hypothetical trihalomethane (THM) excursions in a UPW system. The sensitivity of DC analyzers to the halogen ions created during oxidation of THMs can alert UPW engineers to potential excursions that might harm the water system components or even violate the Environmental Protection Agency’s (EPA’s) requirements for total THMs in water used to manufacture pharmaceutical products. When incoming source water or UPW meets EPA requirements for THM levels, the TOC analyzers studied will never report a false positive TOC value. In the rare occurrence of THM excursions, the analyzer becomes more than just a TOC analyzer–it also becomes a THM event monitor.

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Virtual is for real


November 1, 2008

Many months ago, when we first started talking about the concept and prospect of hosting a “virtual” conference and exhibition, I have to admit I was a little skeptical about how realistic a possibility it actually was. I certainly don’t consider myself a novice to the power of the Internet (I still have my lifetime charter membership to AOL, after all), but I’m also pretty aware of the annoying shortcomings that can pop up and the potential pitfalls that remain, particularly with live events, virtual or not.

Now, however, I’m happy to tell you it’s the real deal. The totally virtual “CleanRooms Worldwide eVent” was–by every account I’ve heard so far, anyway–a great success. Held on October 21 from 8:00 a.m. to 6:00 p.m. Central time, the show brought together visitors from a host of industries and from countries all over the world. It would simply not be possible to accomplish this feat in any other way with a single-day, single-location, real-world event.

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Compiled by Carrie Meadows

Cleaning and disinfecting products are a vital part of ensuring that a clean environment is sterile and contaminant-free. But the type of clean space in question and the level of cleanliness that must be maintained will determine which products will accommodate your specific needs. This month’s spotlight offers a selection of cleaning and disinfecting technologies to keep your critical environment operating at peak cleanliness levels.

Cleaning and disinfection includes biodegradable option

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Connecticut Clean Room Corp. carries an assortment of cleaners and detergents ranging from general-purpose cleaning to the most critical environments. The company offers CR-2, a multi-purpose biodegradable cleaner, as well as a full line of cleaners and detergents for MicroNova such as Nova Clean, Mega Clean, and NovaHol. CCRC has added Accel TB ready-to-use disinfectant to its lineup of cleaning and disinfection solutions. CCRC can assist customers in selecting the right product for any critical environment. To receive a catalog or for information, call (860) 589-0049 and ask the Customer Care Team for more details.

Connecticut Clean Room Corporation
Bristol, CT
www.ctcleanroom.com

Advanced hydrogen peroxide-based disinfectant

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An EPA-registered intermediate-level disinfectant, Contec’s Accel TB is safe and fast acting with a broad-spectrum kill. It is based on accelerated hydrogen peroxide technology (AHP), a synergistic blend of commonly used, safe ingredients that, when combined with low levels of hydrogen peroxide, increase its germicidal potency and cleaning performance. The ready-to-use disinfectant is compatible with many common materials, including 316 and 304 stainless steel, natural and silicone rubber, and most plastics. Accel TB is suitable for use on environmental surfaces in pharmaceutical cleanrooms, compounding pharmacies, labs, and other GMP facilities where short contact time is beneficial. The solution is available in 32 oz. pour bottles, as well as 1- and 5-gal containers. Trigger sprayers are also available. To request a free trial or to learn more about this product, e-mail [email protected].

Contec, Inc.
Spartanburg, SC
www.contecinc.com

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New Products


November 1, 2008

Compiled by Carrie Meadows

Leak-free PFA fittings

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Immediately available is a line of Pureloc® PFA fluoropolymer compression fittings in a dozen styles. Targeted for mating with fluoropolymer tubing, the fittings are used in clean applications such as semiconductor, food and beverage, pharmaceutical, chemical, medical and biomedical, laboratory, and chromatography. Made from virgin-grade, chemically inert PFA fluoropolymer, the fittings are suited for pure fluid applications where contamination-free systems are required. Purelocs consist of four precision-made parts (nut, gripper, ferrule, and body) that provide leak-proof connections. The fittings offer see-through construction to ensure proper fitting installation. The nut design has a ridged surface that is easy to grip and tighten. Purelocs may be disassembled and reused, saving purchase and inventory costs.

NewAge® Industries, Inc.
Southampton, PA
www.newageindustries.com/purelcmn.asp

Humidity and micro head sensors

New additions to the Cambridge AccuSense airflow analysis line, a humidity sensor (UHS1000) and micro head airflow and temperature sensor (UAS2000), provide more functionality for airflow and thermal analysis in the ATm2400/USB sensor line. The UAS2000 micro head airflow and temperature sensor uses patented pulse technology; smaller than 0.5 mm, it can record airflow and temperature inside the fins of a heatsink, between tightly spaced components, and in other small locations. The ATm2400 eliminates time-consuming and costly manual data recording and enables simultaneous measurement of air velocity, humidity, airflow, and surface temperatures at 36 locations. All of the data is recorded in real-time and can be analyzed and manipulated using Accutrac®, a Windows-based software package.

Degree Controls Inc.
Milford, NH
www.degreec.com

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By George Miller

Confronting the difficult head-on, Genzyme Corp. has achieved a high-level certification for energy and environmental design in its Framingham, MA R&D facility unveiled in late September.

The $125 million Science Center carries the gold certification from the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) green building rating system. Gold marks the second-highest level available in the system.

The certification encompasses design and construction criteria in site planning, material use, energy, indoor environmental quality, and water management.

The facility is one of only 10 labs to achieve this ratings level, according to company spokesperson Erin Emlock.

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By Hank Hogan

In October, Sematech (Austin, TX) hosted a symposium in Lake Tahoe, CA that could literally shine a new light on semiconductor cleanrooms. The subject of the meeting was the state of affairs in extreme ultraviolet (EUV) lithography, which gets its name from the use of a 13-nm wavelength source. In contrast, today’s lithography tools use a 193-nm source.

It’s a big change that brings a big payoff–and a few more challenges for cleanrooms and contamination control. The exact impact is unclear because the new sources will be deployed in the most advanced node. EUV lithography is expected to make its debut at the 22-nm half-pitch node, half the size of today’s state of the art. That feature size has its own implications.

“Everything in the industry is driven by the linewidth,” points out Jitze Stienstra, director of product marketing for semiconductor material-handling company Entegris (San Diego, CA office). He notes, though, that not all processes move at the same pace when it comes to contamination control needs. “Litho typically leads the pack in setting purity requirements.”

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By George Miller

As the wheels of Congress start grinding out legislation to protect federally funded biospecimen collections from inadvertent and malicious destruction, practitioners are of two minds about the government involvement.

The House Science and Technology Committee investigations and oversight subcommittee in September questioned officials of the Veterans Administration (VA) Pittsburgh Health Service on the destruction of a collection of Legionella bacteria. The destruction was ordered by Dr. Mona Melhem, associate chief of staff for clinical services in December 2006, just as arrangements were being made to transfer the collection to another facility.

In less than three hours, the 30-year collection was destroyed, according to testimony.

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Since September, the U.S. Food and Drug Administration (FDA) has been investigating possible contaminated milk-based products coming out of China. The FDA is advising consumers not to consume the following products because of possible melamine contamination:

  • YILI Brand Sour Milk Drink
  • YILI Brand Pure Milk Drink
  • Blue Cat Flavored Drinks
  • White Rabbit Candies
  • Mr. Brown Mandehling Blend Instant Coffee (3-in-1)
  • Mr. Brown Arabica Instant Coffee (3-in-1)
  • Mr. Brown Blue Mountain Blend Instant Coffee (3-in-1)
  • Mr. Brown Caramel Macchiato Instant Coffee (3-in-1)
  • Mr. Brown French Vanilla Instant Coffee (3-in-1)
  • Mr. Brown Mandheling Blend instant Coffee (2-in-1)
  • Mr. Brown Milk Tea (3-in-1)
  • Infant formula manufactured in China

FDA is pursuing an investigation into milk and milk-based products from China, such as this TriStar Food Blue Cat flavored drink, due to possible melamine contamination. Photo courtesy of FDA/ TriStar Food Wholesale Co.
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It has been reported that a number of infants in China who have consumed Chinese manufactured infant formula are suffering from kidney stones, a condition the agency says is rare in infants. The Chinese manufactured infant formula may be contaminated with melamine. Melamine artificially increases the protein profile of milk and can cause kidney diseases such as those seen in the Chinese infants.

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Buying swabs in bulk at the lowest price may seem like a cost-effective choice, but those little penny-per-use disposable devices can track contamination into a cleanroom, cloud test results, and cause ESD events if they aren’t chosen with care.

By Sarah Fister Gale

Every year, cleanroom operators invest millions of dollars outfitting their facilities with the latest equipment, technology, monitoring devices, and air handling systems. These big picture items get intense scrutiny in the planning phase of new and upgraded facilities because they cost a fortune and are at the core of maintaining a clean and smooth-running manufacturing environment that will achieve optimal yields.

But, as so many cleanroom operators have learned over the years, cleanliness is in the details. A $4 million lithography tool can be taken down by a seemingly inconsequential material, such as a ten cent swab that sheds fibers as it cleans surfaces in the cleanroom. The wrong swab can also contain microscopic contaminants that cloud environmental test results, leave adhesive residues on equipment surfaces when the swab head reacts with harsh chemicals, create electrostatic discharge (ESD), or leave behind materials that can raise alarms in operations that require strict levels of particulate control.

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Ultra-trace bulk analysis of polysilicon helps meet production demands for high-purity silicon in solar-cell market

By J.D. Robertson, M.D. Glascock, and H. Newcomb, University of Missouri Research Reactor Center

The rapid growth in solar cell production has fueled demand for high-purity silicon. About 90 percent of the current solar cell market is based on solar cells using silicon, and the majority of the raw material for the process is derived from polycrystalline silicon. The demand for polysilicon from the solar industry is growing at up to 40 percent annually and it is anticipated that the use of polysilicon for solar cells will be three to four times that of the semiconductor industry in about 10 years.1 The projected global demands for polysilicon are such that the two largest polysilicon producers have announced plans to increase their production capacities to more than 58,000 metric tons in the next three years, and several other companies, with no prior polysilicon experience, are constructing facilities to enter the market.1

Although the purity requirements of silicon for solar cells (five to seven 9s) are lower than those for semiconductors (nine 9s), the power conversion efficiency of solar cells is largely dependent on impurity levels in the silicon raw materials. Measurement of element concentrations in the polysilicon raw material and the process wafers is therefore essential as new polysilicon production technologies are developed to lower solar-cell production costs and for the maintenance of quality control during the manufacturing of solar cells. The quality control of the polysilicon is especially important as new producers of this high-purity material enter the market. Since it was first applied in 1960 for the analysis of tantalum,2 instrumental neutron activation analysis (INAA) continues to be one of the most sensitive and accurate techniques for meeting industries’ needs for the trace element analysis of high-purity silicon. In keeping with the industry expansion, the demand for INAA of high-purity silicon at the University of Missouri Research Reactor Center (MURR) has more than doubled over the last three years. This article presents a brief overview of INAA of high-purity silicon.

INAA technique

The idea of using neutrons as an analytical probe for elemental analysis was first proposed and demonstrated by Von Hevesy and Levi for the analysis of trace quantities of rare earths in geological materials in 1936. Since then, the sensitivity, selectivity, and precision of INAA have made it a versatile and widely employed elemental analysis techniques. Because most materials are “transparent” to both the probe (neutrons) and the signal (gamma rays), there are few matrix effects associated with the analysis, and standardization of the measurement is simple and straightforward. Moreover, because little, if any, sample manipulation is required, INAA is a highly sensitive technique that can be applied to bulk samples and is relatively free of reagent and laboratory contamination.

In INAA, stable nuclei in the sample undergo neutron-induced nuclear reactions when the sample is exposed to a flux of neutrons. The most common neutron reaction is neutron capture by a stable nucleus (AZ) that produces a radioactive nucleus (A+1Z). The “neutron-rich” radioactive nucleus then decays, with a unique half-life, by the emission of a beta particle. In the vast majority of cases, gamma rays are also emitted in the beta decay process and a high-resolution gamma-ray spectrometer is used to detect these “delayed” gamma rays from the artificially induced radioactivity in the sample for both qualitative and quantitative analysis. A schematic illustration of the neutron capture INAA process is given in Fig. 1.

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The energies of the delayed gamma rays are used to determine which elements are present in the sample, and the number of gamma rays of a specific energy is used to determine the amount of an element in the sample. For example, when a sample that contains iron is irradiated, a fraction of the 58Fe atoms in the sample will capture a thermal (or low energy) neutron and become 59Fe. The 59Fe atoms are radioactive and have a half-life of 44.5 days. When the 59Fe atoms beta decay to 59Co, a 1,099-keV gamma ray is emitted 56 percent of the time. The amount of iron in the original sample can be determined by measuring the number of 1,099-keV gamma rays emitted from the sample in a given time interval after the sample has been exposed to a flux of neutrons. A description of the procedures used to quantify an analyte in INAA is beyond the scope of this article. The physical principles of the analysis are so well understood that neutron activation analysis is one of the primary techniques used by the National Institute of Standards and Technology (NIST) to certify the concentration of elements in standard reference materials.

Although there are few matrix effects in INAA, direct and indirect interferences are possible. A direct interference occurs when the radioactive species or gamma ray of interest is produced by multiple nuclear reactions. For example, measurement of 28Al that is produced by thermal neutron capture on 27Al is frequently used to quantify trace amounts of aluminum in a sample. However, in polysilicon, 28Al is also produced in significant quantities through a high-energy neutron absorption reaction followed by proton emission on 28Si. To quantify aluminum in a high silicon matrix, one must account for the alternate production of 28Al by this reaction. A direct interference can also occur when the same energy gamma ray is emitted by two different isotopes. This spectral interference can be easily accounted for by the difference in half lives between the two isotopes and/or by monitoring multiple gamma rays from each isotope. An indirect interference occurs when the activity generated by a dominant species in the sample impacts the signal-to-noise ratio of the analyte of interest by changing the background in the gamma ray spectrum. A detailed description of how direct and indirect interferences are resolved in the application of INAA to solar-grade silicon can be found in an article by Revel et al.3


Figure 2. Silicon samples for irradiation. Photo courtesy of University of Missouri Research Reactor Center.
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Scientists at MURR have been performing trace element INAA of silicon samples for more than 30 years. A complete description of our analytical protocol can be found in an article by Herrera et al.4 The most common samples are semiconductor silicon, polished wafers, ingot chunks, polysilicon blocks, and polysilicon beads. Samples with masses typically ranging from 10 to 80 g are loaded into individual graphite containers (Fig. 2). These containers are then bundled and placed in a reactor irradiation position where the samples are exposed to a neutron flux for 54 hours. After a decay period of 48 hours, the samples are either cleaned with deionized water in an ultrasonic bath or subjected to a mild or harsh etching procedure. The mild etch is used when a light surface cleaning of the sample is required by the client, and the harsh etch procedure is employed when the client requests that the entire sample surface be removed. After the cleaning/etching procedure, the samples are dried, weighed, placed in plastic containers, and counted on low-background, high-resolution gamma-ray spectrometers. Two counts are performed on each sample. The first 30-minute count is performed immediately after the cleaning/etching and is used to measure radionuclides having half-lives in the range of 12 to 48 hours. The second six-hour count is performed after a minimum decay of 14 days and is used to measure the longer-lived radionuclides. The sensitivities able to be obtained for 40 elements in high-purity silicon using INAA at MURR are given in the table.


Table 1: INAA limits of detection for high-purity silicon
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Advantages and disadvantages of INAA

The major advantage of INAA is that it provides accurate results for large, bulk samples (tens of grams) without having to dissolve or digest the sample. Moreover, by employing an appropriate surface etch procedure, it is possible to ensure that the trace elements observed in the INAA measurement are coming from the bulk material and are not a result of surface contamination at the production facility or in the analytical lab