Polymer Comparisons for the Storage and Trace Metal Analysis of Ultrapure Water with the Agilent 7500cs ICP-MS Application

Size: px

Start display at page:

Download "Polymer Comparisons for the Storage and Trace Metal Analysis of Ultrapure Water with the Agilent 7500cs ICP-MS Application"

Chastity Collins
5 years ago
Views:

1 Polymer Comparisons for the Storage and Trace Metal Analysis of Ultrapure Water with the Agilent 7500cs ICP-MS Application Semiconductor Authors Brad McKelvey, Shelley McIvor, and Bill Wiltse Seastar Chemicals Inc McDonald Park Rd. PO Box 2219 Sidney, BC, Canada V8L 3S8 Abstract The aim of this study was to find a cost-effective means of storing ultrapure water (UPW). The target was to find a low cost material that was free from contaminating metals that might leach into the UPW during storage. Results for selected metals from the analysis of UPW stored over short and long periods are presented. Lowdensity polyethylene (LDPE) and high-density polyethylene (HDPE) were compared with Teflon perfluoroalkoxy polymer resin (PFA) and Teflon fluorinated ethylenepropylene (FEP). Introduction Cation contamination of samples or high-purity reagents from storage vessels is a critical consideration and a major challenge for analytical laboratories performing ultra trace metal analysis by inductively coupled plasma mass spectrometry (ICP-MS). Many times, poor instrument blanks and subsequently poor limit of detection (LOD) and background equivalent concentration (BEC) values can be traced to reagent/solution impurities. For almost 30 years, Seastar Chemicals Inc. (Canada), manufacturers of high-purity acids and ammonia for the laboratory market, has specialized in part-per-trillion (ppt) and sub-ppt multielement analytical determinations for the quality control of high-purity reagents. Ultrapure water (UPW) production and storage is a critical platform on which we build our reagent distillation, lab solutions/dilutions, and trace metal clean room work. Therefore, a major R&D focus at Seastar includes materials leaching and analysis for the improvement of product storage. Maintaining the trace metal quality of our products requires chemically inert engineered materials that are trace metal clean or leachable to an acceptable level. With the recent acquisition of our Agilent 7500cs, we are continuing to explore the lower limits of ICP-MS analytical capabilities to globally provide the highest purity acids available for trace metal analysis. Seastar s high-purity acid products are corrosive, therefore more expensive Teflon perfluoroalkoxy polymer resin (PFA) or Teflon fluorinated ethyenepropylene (FEP) are used for storage and shipping where polyethylene would be inappropriate. Because UPW is relatively inert, this study highlights short- and long-term storage results for select metals in UPW with less-expensive low-density polyethylene (LDPE) and high-density polyethylene (HDPE) compared with Teflon PFA and Teflon FEP. Instrumentation and Sample Preparation All samples were analyzed using the Agilent 7500cs ORS ICP-MS. The instrument is located in a class 1000 cleanroom with the autosampler located directly under ultra low penetrating air (ULPA) filtered air. All sample handling prior to analysis is done under class 100 or better conditions. All reagents used are Seastar Chemicals

2 Baseline Quality. Many of our customers use our products in semiconductor applications; therefore, Seastar's quality control clean room handling and product certifications subscribe to SEMI guidelines for analysis and recoveries. The ICP-MS operating parameters are shown in Table 1. Table cs ORS ICP-MS Operating Parameters Parameters Cool Plasma Mode No Gas and Gas Mode RF Power (W) Sampling Depth (mm) Carrier Gas (L/min) Makeup Gas (L/min) Reaction Gas (ml/min) 0 0 (6 for H 2, 5.2 for He) Extract 1 (V) %120 6 Extract 2 (V) %6 %50 QP Bias (V) %5 %3 (%12 for H 2, %14 for He) Oct P Bias (V) %20 %6 (%17 for H 2, %16 for He) Nalge Nunc International (Rochester, NY) manufactured the bottles used in this study. The bottles are made from virgin resins with no pigments, additives, or stabilizers. The Teflon FEP and Teflon PFA bottles are manufactured using resins and conditions specific to Seastar Chemicals Inc. All bottles analyzed were 1 liter capacity for comparable surface area leaching. For this study, all bottles were washed with soap and water to remove manufacturing surface dust, then thoroughly rinsed with deionized water. Preleached bottles were filled with dilute high-purity acid and stored at 50 %C for two weeks, followed by thorough rinsing with deionized water. All sample preparation and data acquisition was performed in Class 100 or better clean room conditions. Six bottles of each polymer, three preleached and three nonleached, were filled with UPW and stored upright at room temperature for 21 days. Ten milliliter aliquots were decanted from each bottle, acidified with nitric acid to 2% (v/v) and analyzed by external calibration. Each bottle was then acidified with nitric acid to 2% (v/v), and allowed to leach for 24 hours at room temperature. Small aliquots were again analyzed by external calibration. Results and Discussion In preliminary investigations, unacidified UPW that was stored in both preleached and nonleached bottles had equivalent BECs to 2% v/v high-purity nitric acid. This suggests that no metals were being extracted from the polymer at the ph of ultrapure water (ph 5.2). To test the effect of ph, the same bottles were acidified with nitric acid to 2% (v/v) and stored again for 24 hours. The data in Table 2 summarizes the average result for each of the polymer types. The most common elements extracted were Ca, Fe, Mg, Al and Cu. All of the Teflon preleached bottles have no measurable extractables. Preleached LDPE had only four detectable elements that were all less than 10 ppt. Preleached HDPE had six detectable elements, which included 2

3 significant amounts of Ca and Al. For most applications, preleached LDPE containers are the best economical choice for UPW and dilute acid solutions. Table 2. Nonleached and Preleached Polymer Comparisons for Ultrapure Water Acidified to 2% (v/v) HNO 3 H 2 Mode Nonleached Preleached Nonleached Preleached Nonleached Preleached Nonleached Preleached Isotope avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt Ca < < <20 Cr 52 <3 <3 <3 <3 <3 <3 <3 <3 Fe < < <3 Se 78 <6 <6 <6 <6 <6 <6 <6 <6 Tl 205 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 Bi 209 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 He Mode Nonleached Preleached Nonleached Preleached Nonleached Preleached Nonleached Preleached Isotope avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt Ti 48 <0.8 < <0.8 <0.8 <0.8 V < <0.05 <0.05 <0.05 <0.05 Ni 58 <4 <4 <4 <4 7 9 <4 6 2 <4 Co < < <0.07 Zn <3 9 6 <3 <3 <3 <3 <3 Ga 71 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 <0.3 Ge 72 <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 <0.4 As 75 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 <0.8 Sr < < < <0.09 Zr 90 <0.2 <0.2 <0.2 < <0.2 <0.2 <0.2 Nb 93 <0.005 <0.005 <0.005 < < <0.005 Mo 98 <0.2 <0.2 <0.2 < < <0.2 Cd 114 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 Sn 120 <0.5 < <0.5 <0.5 <0.5 <0.5 <0.5 Sb 121 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Ba < < <0.1 W 182 <0.3 <0.3 <0.3 < < <0.3 3

4 Table 2. Nonleached and Preleached Polymer Comparisons for Ultrapure Water Acidified to 2% (v/v) HNO 3 (continued) Normal Mode Nonleached Preleached Nonleached Preleached Nonleached Preleached Nonleached Preleached Isotope avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/s/ppt avg/sd/ppt avg/sd/ppt Be <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 B 11 <30 <30 <30 <30 <30 <30 <30 <30 Au 197 <5 <5 <5 <5 <5 <5 <5 <5 Pb < < < <0.2 Th 232 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 <0.09 U 238 <0.08 <0.08 <0.08 <0.08 <0.08 <0.08 <0.08 <0.08 Cool Mode Nonleached Preleached Nonleached Preleached Nonleached Preleached Nonleached Preleached Isotope avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt avg/sd/ppt Li 7 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Na 23 <5 < <5 8 6 <5 <5 <5 Mg < <1 Al <3 5 2 <3 K 39 <7 < <7 <7 <7 <7 <7 Mn < < < <0.2 Cu < < <0.9 Ag 107 <1 <1 <1 <1 <1 <1 <1 <1 To quantify the capability of preleached LDPE to maintain trace metal quality UPW over time, three separate bottles were analyzed after one year, two years, and three years. The data is summarized in Table 3. All elements were undetectable. Table 3. Individual ultrapure water samples stored in preleached low-density polyethylene for one, two, and three years. H 2 Mode Preleached LDPE Ca 40 <20 <20 <20 Cr 52 <3 <3 <3 Fe 56 <3 <3 <3 Se 78 <6 <6 <6 Tl 205 <0.3 <0.3 <0.3 Bi 209 <0.1 <0.1 <0.1 He Mode Preleached LDPE Ti 48 <0.8 <0.8 <0.8 V 51 <0.05 <0.05 <0.05 Ni 58 <4 <4 <4 Co 59 <0.07 <0.07 <0.07 Zn 64 <3 <3 <3 Ga 71 <0.3 <0.3 <0.3 Ge 72 <0.4 <0.4 <0.4 As 75 <0.8 <0.8 <0.8 Sr 88 <0.09 <0.09 <0.09 Zr 90 <0.2 <0.2 <0.2 Nb 93 <0.005 <0.005 <0.005 Mo 98 <0.2 <0.2 <0.2 Cd 114 <0.09 <0.09 <0.09 Sn 120 <0.5 <0.5 <0.5 Sb 121 <0.1 <0.1 <0.1 Ba 138 <0.1 <0.1 <0.1 W 182 <0.3 <0.3 <0.3 4

5 Table 3. Individual ultrapure water samples stored in preleached low-density polyethylene for one, two, and three years. (continued) Normal Mode Preleached LDPE Be 9 <0.1 <0.1 <0.1 B 11 <30 <30 <30 Au 197 <5 <5 <5 Pb 208 <0.2 <0.2 <0.2 Th 232 <0.09 <0.09 <0.09 U 238 <0.08 <0.08 <0.08 Cool Mode Preleached LDPE Li 7 <0.01 <0.01 <0.01 Na 23 <5 <5 <5 Mg 24 <1 <1 <1 Al 27 <3 <3 <3 K 39 <7 <7 <7 Mn 55 <0.2 <0.2 <0.2 Cu 63 <0.9 <0.9 <0.9 Ag 107 <1 <1 <1 bottles and labware exhibits unique elemental signatures and the value of extractables may differ from those reported in this study. The preleached LDPE bottles maintained elemental concentrations under 10 ppt for dilute nitric acid solutions and UPW with long-term storage. From a trace metal perspective, preleached LDPE is an excellent, cost-effective alternative to Teflon PFA and FEP for UPW and dilute acid solutions. For More Information For more information on our products and services, visit our Web site at Conclusions All labware for ultra trace metal analysis must be preleached prior to use with acidic solutions. The high standard deviations for elements detected in the nonleached bottles indicate significant bottleto-bottle variability. If possible, all bottles and labware should be uniquely identified and blank tested. The elemental signature of the extractables can later be used to determine the source of contamination problems. It is the experience of this laboratory that each manufacturer of polymeric 5

6 Agilent shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material. Information, descriptions, and specifications in this publication are subject to change without notice. Agilent Technologies, Inc Printed in the USA November 2, EN

Certificate of Analysis First issued: July 2000 Version: December 2007 MA-2c

Certificate of Analysis First issued: July 2000 Version: December 2007 MA-2c Gold Ore Table l - Certified value for gold and provisional value for silver Element Ag (µg/g) Au (µg/g) Mean 0.51 3.02 Within-laboratory