Trace-Element Contamination--Findings of Study on the Cleaning of Sampler Caps, Nozzles, Bottles, and Bags for Trace-Element Work at the Part-Per-Billion Level In Reply Refer To: February 19, 1993 Mail Stop 412 OFFICE OF WATER QUALITY TECHNICAL MEMORANDUM 93.06 Subject: Trace-Element Contamination--Findings of Study on the Cleaning of Sampler Caps, Nozzles, Bottles, and Bags for Trace-Element Work at the Part-Per-Billion Level SYNOPSIS As part of the development of a new part-per-billion (ppb) protocol for collecting and processing samples for analysis of dissolved trace elements, the Office of Water Quality (OWQ) conducted a study on the effectiveness of cleaning plastic and Teflon 1/ D-77 sampler components (caps, nozzles, bottles, and bags) to reduce contamination. Procedures for both laboratory and field cleaning were tested. Nitric (HNO3) and hydrochloric (HCl) acids were compared for their effectiveness in cleaning, and tests were included to determine the amount of rinsing with deionized water (DIW) required to prevent carryover of nitrate, chloride, and methanol, or trace elements from methanol (a final methanol rinse is required on equipment when both trace elements and organics are collected). To determine the success of the cleaning procedures, test results were compared to values of one-half the target reporting level (RL) specified for each trace element for the ppb procedure. The major findings of the study were: 1. DIW blanks processed through equipment in an "initial condition" (before any cleaning) contained trace elements above one-half the target RL. 2. Dilute HNO3 and HCl solutions (approximately 5 percent by volume) were equally effective for cleaning both plastic and Teflon D-77 sampler caps, nozzles, bottles, and bags. 3. Carryover of chloride and nitrate from the use of HCl and HNO3, respectively, was not evident for either the laboratory or field cleaning procedure. 4. Both plastic and Teflon components are acceptable for trace- element sampling because the laboratory cleaning procedure reduced trace-element contamination well below the target RLs. 5. Both old and new plastic and Teflon components are acceptable because they were adequately cleaned by the laboratory procedure. ____________________ 1/ Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. 6. The field cleaning procedure was effective in reducing trace- element contamination for both plastic and Teflon sampler components to levels below one-half the target RLs for all constituents except beryllium (Be). Based on the test results, the OWQ has revised the field cleaning procedure. 7. Based on this study, in the D-77 bag sampler, Teflon bags are preferred and Reynolds Oven Bags are acceptable for use with the ppb protocol. 8. A laboratory cleaning procedure for plastic and Teflon bags was effective except for manganese (Mn) and zinc (Zn). Projects using bags should produce adequate equipment blanks to insure bag trace-element contamination is under control (less than one-half RLs). INTRODUCTION One of the key elements in developing a new ppb protocol for collecting and processing samples for dissolved trace elements is an adequate cleaning procedure. Cleaning procedures for both laboratory and field cleaning of sampler caps, nozzles, bottles, and bags were developed. In April 1992, the OWQ conducted a study on the effectiveness of newly developed laboratory and field procedures for cleaning plastic and Teflon sampler components used in D-77 samplers. This memo describes the major findings of the study. OBJECTIVES The objectives of the study were to: 1. Establish the efficacy of the proposed laboratory cleaning procedure (detergent scrubbing and soak, tap water rinse, dilute HCl soak, and copious DIW rinses) for precleaning those parts of surface-water samplers--for both plastic and Teflon components-- that come into direct contact with water-sediment samples. 2. Determine if the laboratory cleaning procedure is effective for both new and old sampler components. 3. Determine if HNO3 (a possible alternative cleaning agent) is better, equivalent, or worse than HCl (the cleaning agent selected for the procedure) for precleaning sampler components and bags. 4. Determine the amount of DIW rinsing required to prevent carryover of chloride, nitrate, and methanol or trace elements from methanol. 5. Establish the efficacy of the field cleaning procedure (dilute HCl rinses and copious DIW rinses) which is intended to be used between sampling sites to prevent trace-element carryover. STUDY COMPONENTS The study, designed by John Zogorski (OWQ), was conducted April 1-16, 1992, at the Central Region Branch of Regional Research facilities in Boulder, Colorado. Kathy Fitzgerald (OWQ), Bob Boulger (Colo.), and Dave Johncox (Colo.) conducted the study, which consisted of the following components: 1. Equipment blanks were collected from a series of plastic and Teflon bottles and bags (identified below) to assess their initial condition prior to cleaning. 2. Equipment was cleaned using the laboratory procedure, and equipment blanks were collected after various levels of DIW rinsing to determine: (a) if both new and old equipment could be adequately cleaned, (b) if plastic and Teflon equipment could be adequately cleaned, and (c) the amount of DIW rinsing needed. 3. Equipment was exposed to a solution containing a high trace- element concentration and was subsequently recleaned using the laboratory procedure; equipment blanks were collected after various levels of DIW rinsing to determine the efficacy of the laboratory cleaning procedure. 4. Equipment was exposed to a solution containing a high trace- element concentration and was subsequently cleaned using the field procedure; equipment blanks were collected after various levels of DIW rinsing to determine the efficacy of the field cleaning procedure. 5. Some of the equipment was cleaned with HCl and some with HNO3. SAMPLER COMPONENTS AND BAGS EVALUATED The following D-77 sampler components and bags were evaluated: Plastic (polypropylene) 1 new (OWQ) components 6 old (WA (2), CO, CA, KS (2)) Teflon components 1 new (KY) 5 old (NWQL 1/, CA, KY, MA, WA) Small plastic bags Glad brand 2 bags Reynolds Oven Bag 2 bags Large plastic bags Reynolds Oven Bag 2 bags (from Charlie Demas) Jensen Inert Tedlar 2 bags Small Teflon bags Corps of Engineers 2 bags (Vicksburg, MS) American Durafilm 2 bags Large Teflon bags American Durafilm 2 bags Jensen Inert 2 bags ______________________________________________________________ 1/NWQL = National Water Quality Laboratory. Three-liter sampler bottles were shipped to the Colorado District from the Districts listed in column 2 above. All bags, except for the oven bags from Charlie Demas, were purchased specifically for this study. The Glad and Reynolds bags were purchased at local grocery stores. CONSTITUENTS ANALYZED Most trace elements were analyzed with inductively coupled plasma mass spectrometry by the Methods Research and Development Program, NWQL, with a detection level of 0.2 ug/L. Constituents included aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), molybdenum (Mo), nickel (Ni), silver (Ag), thallium (Tl), thorium (Th), uranium (U), and zinc (Zn). Five other elements including iron (Fe), lithium (Li), selenium (Se), strontium (Sr), and vanadium (V) were analyzed by the Inorganic Program, NWQL. Selected equipment blanks were also analyzed for major elements and nutrients at the NWQL. DATA INTERPRETATION To determine the efficacy of the two cleaning procedures, equipment blank results were compared to the levels representing one-half the respective target reporting levels specified for the new trace-element protocol. These values were reported earlier in OWQ Technical Memorandum 92.12 and are given in table 1. Table 1.--Reporting limits of selected elements for NASQAN, 1991, and the new part-per-billion (ppb) protocol _________________________________________________________________ One-half target 1991 Target reporting NASQAN reporting limit limit for reporting limit 1/ for ppb protocol ppb protocol 2/ Element (ug/L) (ug/L) (ug/L) _________________________________________________________________ Al 10 10 5.0 Ba 2 2 1 Be 0.5 0.5 0.25 Cd 1 1 0.5 Co 3 1 0.5 Cr 1 1 0.5 Cu 1 1 0.5 Fe 3 3 1.5 Pb 1 1 0.5 Mn 1 1 0.5 Mo 10 1 0.5 Ni 1 1 0.5 Ag 1 0.2 0.1 Zn 3 3 1.5 _________________________________________________________________ 1/For samples in which specific conductance < 2,000 uS/cm. 2/Maximum limit set from all sources of contamination in the ppb protocol. The analytical data from this study are not presented in this memo, but are available for review. Contact the Chief, Office of Water Quality, for additional information. MAJOR FINDINGS 1. Many of the "initial condition" blanks (DIW blanks processed before any cleaning) contained trace-element concentrations in excess of one-half the target RL, especially Al, Cu, and Zn. This finding supports the need for a rigorous cleaning, beyond rinsing only with DIW. 2. Dilute HNO3 and HCl solutions (approximately 5 percent by volume) were equally effective for cleaning both plastic and Teflon D-77 sampler caps, nozzles, bottles, and bags. 3. Carryover of chloride and nitrate from the use of HCl and HNO3, respectively, was not evident for either the laboratory or field cleaning procedure. 4. The laboratory cleaning procedure (detergent scrubbing and soak, tap water rinse, dilute HCl soak, and copious DIW rinses) was effective in reducing trace-element contamination to levels well below one-half the target RLs for both plastic and Teflon sampler components. Therefore, either plastic or Teflon components can be used with the D-77 sampler for trace-element sampling at the ppb level. 5. Both new and old plastic and Teflon D-77 components were adequately cleaned by the laboratory cleaning procedure. Therefore, both new and old components may be used with the new ppb protocol. 6. The field cleaning procedure (dilute HCl rinses and copious DIW rinses) was effective in reducing trace-element contamination for both plastic and Teflon sampler components to levels below one- half the target RLs for all constituents except Be. Blanks from both the plastic and Teflon components were found to contain Be at levels slightly above one-half the target RL (0.25 ug/L). Low- level hits of Cu were also consistently found for both plastic and Teflon components; however, detected levels were consistently below one-half of the target RL (0.5 ug/L). Based on the test results, the OWQ has revised the field cleaning procedure. 7. The following types of bags were evaluated: Teflon (Jensen Inert and American Durafilm), and plastic (Glad and Reynolds Oven brands). After a futile attempt to detergent wash Glad plastic bags and Reynolds oven bags, the study team decided that this step should be eliminated from the laboratory cleaning procedure (it is possible to wash the thicker Teflon bags). Laboratory cleaning of plastic and Teflon bags thus consisted of an acid (HCl) soak and copious DIW rinses. Because plastic and oven bags are inexpensive, they can be disposed of after use, which eliminates the need for field cleaning. The field cleaning procedure was effectively used on the Teflon bags. One of the plastic Glad bags developed holes during the laboratory cleaning and rinsing process; because oven bags are sturdier, they are the preferred choice for non-Teflon bags. Based on this study, for use in D-77 bag samplers, Teflon bags are preferred, Reynolds Oven Bags are acceptable, and the other tested bags are unacceptable for use with the ppb protocol. 8. The laboratory cleaning procedure for plastic and Teflon bags was effective in consistently reducing trace-element contamination to levels below one-half of the target RLs for all constituents except manganese (Mn) and zinc (Zn). Two of the 10 equipment blanks for plastic bags contained Mn above one-half the target RL (0.50 ug/L) (small plastic bag = 0.61 ug/L; large plastic bag = 0.50 ug/L). One of the 21 equipment blanks for plastic and Teflon bags contained Zn above one-half the target RL (1.50 ug/L) (small Teflon bag = 1.50 ug/L), although approximately 50 percent of all blanks contained detectable levels of Zn. Based on these results, acid soaking with copious DIW rinses is effective for cleaning plastic and Teflon bags for all constituents except possibly Mn and Zn. Projects that choose to use plastic and Teflon bags should incorporate more than the normal percentage of equipment blanks into their quality control plan to determine if contamination from the sampler bag actually occurs. SUMMARY Previous studies have shown that the D-77 and DH-81 samplers are the least contaminating samplers for dissolved trace-element sample collection. This study was conducted to test the effectiveness of procedures for cleaning the plastic and Teflon components of these samplers. Only 3-liter D-77 bottles were tested, but the results should apply to any size bottle made of the same materials. The study showed that (a) cleaning beyond DIW rinsing is necessary, (b) the laboratory cleaning procedure is effective for ppb-level work for both plastic and Teflon, and for both new and old equipment, (c) the field cleaning procedure is not completely effective and needed to be modified, (d) plastic bags can be cleaned with acid (HCl) soaks and DIW rinsing prior to use, but should be disposed of after use, and (e) Teflon bags can be cleaned and reused. Art Horowitz will be conducting training sessions in each of the Regions on the new cleaning procedures beginning in April 1993. Following training, side-by-side comparisons of the new and old procedures will be done in at least one District in each Region. The results will be evaluated, modifications will be made if necessary, and additional training will then be completed. Full implementation of the ppb sampling procedure is scheduled for October 1993. David A. Rickert Chief, Office of Water Quality This memorandum refers to Office of Water Quality Technical Memorandum 92.12. Key Words: Contamination, samplers, trace element Distribution: A, B, S, FO, PO