A high‐performance, safer and semi‐automated approach for the δ¹⁸O analysis of diatom silica and new methods for removing exchangeable oxygen

<jats:title>Abstract</jats:title><jats:p>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<jats:sub>5</jats:sub> with a CO<jats:sub>2</jats:sub> 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°C and cooled down to 400°C in ∼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 (∼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‰ (1σ) and for biogenic silica <0.25‰ (1σ) for samples down to ∼0.3 mg. The semi‐automated fluorination line is the fastest method available at present and enables a throughput of 74 samples/week. Copyright © 2010 John Wiley & Sons, Ltd.</jats:p>