title: A high-performance, safer and semi-automated approach for the delta18O analysis of diatom silica and new methods for removing exchangeable oxygen.
abstract: The determination of the oxygen isotope composition of diatom silica in sediment cores is important for paleoclimate reconstruction, especially in non-carbonate sediments, where no other bioindicators such as ostracods and foraminifera are available. Since most currently available analytical techniques are time-consuming and labour-intensive, we have developed a new, safer, faster and semi-automated online approach for measuring oxygen isotopes in biogenic silica. Improvements include software that controls the measurement procedures and a video camera that remotely records the reaction of the samples under BrF(5) with a CO(2) laser. Maximum safety is guaranteed as the laser-fluorination unit is arranged under a fume hood in a separate room from the operator. A new routine has been developed for removing the exchangeable hydrous components within biogenic silica using ramp degassing. The sample plate is heated up to 1100 degrees C and cooled down to 400 degrees C in approximately 7 h under a flow of He gas (the inert Gas Flow Dehydration method--iGFD) before isotope analysis. Two quartz and two biogenic silica samples (approximately 1.5 mg) of known isotope composition were tested. The isotopic compositions were reproducible within an acceptable error; quartz samples gave a mean standard deviation of <0.15 per thousand (1sigma) and for biogenic silica <0.25 per thousand (1sigma) for samples down to approximately 0.3 mg. The semi-automated fluorination line is the fastest method available at present and enables a throughput of 74 samples/week.
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, D-14473 Potsdam, Germany. bernhard.chapligin@awi.de
authors.forename: B
authors.initials: B
authors.lastname: Chapligin
authors.forename: H
authors.initials: H
authors.lastname: Meyer
authors.forename: H
authors.initials: H
authors.lastname: Friedrichsen
authors.forename: A
authors.initials: A
authors.lastname: Marent
authors.forename: E
authors.initials: E
authors.lastname: Sohns
authors.forename: H-W
authors.initials: HW
authors.lastname: Hubberten
mesh_terms: D057205:Automation, Laboratory / Q000295:instrumentation / Q000379:methods; D003890:Desiccation; D017377:Diatoms / Q000737:chemistry*; D006371:Helium; D007474:Ion Exchange; D010103:Oxygen Isotopes / Q000737:chemistry* / Q000302:isolation & purification; D010163:Paleontology; D011791:Quartz / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D010103:Oxygen Isotopes; D011791:Quartz; D006371:Helium; D012822:Silicon Dioxide