Materials and cleaning procedures

Plastics have widely replaced metals and glassware in sampler construction, storage containers and sample processing, although most samplers still have external metal components (see Chapter 1). Materials that satisfy the high purity requirements for trace element studies are Teflon (PTFE), FEP, ETFE, polyethylenes, polypropylene, acrylic, quartz and Pyrex 

Plastic samplers are cleaned internally in a manner similar to that described for plastic bottles. Go-Flo samplers (Niskin type see Qiapter 1) are first thoroughly cleaned with a detergent, then rinsed with tap water and, after soaking in about 1 mol/L HQ (a.g.) for several days, flushed with a final rinse of purest distilled water. Afterwards, the samplers are wrapped in clean plastic bags for storage. 

Nuclepore filters are cleaned by soaking in cold 6 mol/L HQ (a.g.) for 3 days, rinsed with distilled water and soaked for emother 3 days at about 50 °C in 1 % ultrapure HQ. After a final rinse with purest water the filters are dried in open cleaned plastic petri dishes imder a clean bench over several days, and then stored in closed plastic dishes if the amoimt of particulate matter has to be determined by weighing. Otherwise, the empty filters are stored in containers under purest distilled water. Prior to use the filters (placed in the filter holder) are rinsed with about 250 mL of purest water. 

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All labware used for preparing and storing samples must be rigorously clean. The selection of materials and cleaning procedures for labware have been described, for instance, by Settle and Patterson (37) and Boutron (42). For the isotopic analysis of Greenland and Antarctic snow and ice sample preparation involves the evaporation of the sample in a preconditioned beaker, as reported by Chisholm et al. (29). The Pb contributions from extraneous sources can be reduced to -0.10 0.05 pg (30). 

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