development of a fully automated open-column …...-icp-ms. yang et al. (2010b) and li et al. (2011)...

74 T. Miyazaki, B.S. Vaglarov, M. Takei, M. Suzuki, H. Suzuki, K. Ohsawa, Q. Chang, T. Takahashi, Y. Hirahara, T. Hanyu, J. Kimura and Y. TatsumiJournal of Mineralogical and Petrological Sciences, Volume 107, page 74─86, 2012

doi:10.2465/jmps.110520T. Miyazaki, [email protected] Corresponding author

Development of a fully automated open-column chemical- separation system—COLUMNSPIDER—and

its application to Sr-Nd-Pb isotope analyses of igneous rock samples

Takashi Miyazaki*, Bogdan Stefanov Vaglarov*, Masakazu Takei**, Masahiro Suzuki**, Hiroaki Suzuki**, Kouzou Ohsawa**, Qing Chang*, Toshiro Takahashi*, Yuka Hirahara*,

Takeshi Hanyu*, Jun-Ichi Kimura* and Yoshiyuki Tatsumi*

*Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan

**HOYUTEC Co. Ltd., 2-8-111 Yoshinodai, Kawagoe 350-0833, Japan

A fully automated open-column resin-bed chemical-separation system, named COLUMNSPIDER, has been developed. The system consists of a programmable micropipetting robot that dispenses chemical reagents and sample solutions into an open-column resin bed for elemental separation. After the initial set up of resin col-umns, chemical reagents, and beakers for the separated chemical components, all separation procedures are au-tomated. As many as ten samples can be eluted in parallel in a single automated run. Many separation proce-dures, such as radiogenic isotope ratio analyses for Sr and Nd, involve the use of multiple column separations with different resin columns, chemical reagents, and beakers of various volumes. COLUMNSPIDER completes these separations using multiple runs. Programmable functions, including the positioning of the micropipetter, reagent volume, and elution time, enable flexible operation. Optimized movements for solution take-up and high-efficiency column flushing allow the system to perform as precisely as when carried out manually by a skilled operator. Procedural blanks, examined for COLUMNSPIDER separations of Sr, Nd, and Pb, are low and negligible. The measured Sr, Nd, and Pb isotope ratios for JB-2 and Nd isotope ratios for JB-3 and BCR-2 rock standards all fall within the ranges reported previously in high-accuracy analyses. COLUMNSPIDER is a ver-satile tool for the efficient elemental separation of igneous rock samples, a process that is both labor intensive and time consuming.

Keywords: Fully automated, Open column, Chemical separation, Sr-Nd-Pb isotope, Pipetting robot

INTRODUCTION

Radiogenic isotope ratios of Sr, Nd, and Pb are funda-mentally important geochemical data used in research into the evolution of the Earth (e.g., Dickin, 1995). Separation of these elements from the rock sample matrix is a prereq-uisite for any isotope ratio determination, either by ther-mal ionization mass spectrometry (TIMS), or by multiple-collector inductively-coupled-plasma mass spectrometry (MC-ICP-MS). To facilitate these isotope studies, various separation methods using open-column chemistry have been developed (see the review in the next section).

With the increasing demand for the analysis of large numbers of samples, it has become crucial to improve an-alytical throughput. Modern TIMS and MC-ICP-MS in-struments feature automation functions including sample exchange, conditioning, tuning, and measurement. In con-trast, sample preparation processes, such as cleaning, crushing, acid digestion, and chemical separation, are time consuming and labor intensive, as compared to the final measurement stage. The chemical treatment of solid Earth rock samples for isotope analysis comprises three processes: (1) acid decomposition of the sample, (2) ele-mental separation, and (3) sample dilution (MC-ICP-MS) or sample loading onto filaments (TIMS). The most time-consuming of these processes is elemental separation us-

75Fully automated open-column separation system COLUMNSPIDER

ing open-column resin-bed chromatography. In order to improve sample throughput, the follow-

ing chemical procedures have been developed. Sequential separation of multiple-element components from a single sample aliquot allowed a shortening of the digestion step (Pin et al., 1994; Le Fèvre and Pin, 2005; Pin and Zaldue-gui, 1997; Míková and Denková, 2007; Makishima et al., 2008; Yang et al., 2010a). Makishima et al. (2008) de-creased the number of evaporation steps involved in the sequential separation of Sr, Nd, and Pb in order to opti-mize the analysis using MC-ICP-MS. Yang et al. (2010b) and Li et al. (2011) developed a direct measuring method for 143Nd/144Nd isotope ratios from rare earth element (REE) components using MC-ICP-MS and TIMS with-out Nd separation; however, the analytical accuracy is limited owing to isobaric overlap with Sm.

Despite the efforts to develop chemical procedures, a considerable number of chemical steps are still involved in the separation processes. The processes include repeti-tive human manipulations with long waiting times, such as for pipetting, and therefore, should be automated where possible. To automate the processes, several approaches have been applied. One approach is to use high-perfor-mance liquid chromatography (HPLC) instead of open-

column resin-bed chromatography (Stray, 1992; Na et al., 1995; Griselin et al., 2001; Meynadier et al., 2006). How-ever, the HPLC technique is not applicable to high matrix samples, and large amounts of organic materials left in the final fraction prevent ionization during TIMS. Shibata et al. (2007) developed a semiautomated open-column resin separation system in which a multiple-channel peristaltic pump was used to transfer sample solutions and chemical reagents to the columns. The volume of transferred solu-tions and loading times were programmed so that the op-erators were spared these lengthy loading procedures. Their system, however, required manual operations to change sample/reagent solutions and eluent/element frac-tion collection beakers. Manual washing of the transfer tubing was also necessary if one intended to use the same tubing throughout the procedure.

To realize a more hands-free automated separation system, we introduced a micropipetting robotic dispens-ing system to replace the peristaltic pump used by Shibata et al. (2007). The advantages of this system are as fol-lows: (1) flexible and precise positioning of the pipetter head, (2) flexible and precise control of liquid volumes for delivery, and (3) disposable pipetter tips that prevent crosscontamination between samples and reagents. How-ever, there was no commercially available pipetting robot capable of tolerating the vapors from corrosive acids, such as HF, HCl, HNO3, and HBr.

Japan Agency for Marine-Earth Science and Tech-

nology (JAMSTEC) and HOYUTEC Co. Ltd. have co-

developed a fully automated open-column chemical-sep-aration micropipetting robot named COLUMNSPIDER, which can simultaneously deal with 10 samples in an ele-mental separation. By using COLUMNSPIDER, we have dramatically reduced the human work involved in sample preparation. In this paper, we describe the details of COL-UMNSPIDER. Results from its application to Sr-Nd-Pb isotope analyses of the geostandard JB-2, JB-3, and BCR-2 rock samples are also reported.

CHEMICAL SEPARATIONS FOR Sr, Nd, AND Pb

Since the early pioneering work of Aldrich et al. (1953), H+-form cation-exchange chromatography has been widely used as the conventional method for the separation of Sr from silicate rock samples, as seen in previous studies (e.g., Kagami et al, 1987). Yoshikawa and Nakamura (1993) developed a method to separate trace amounts of Sr from samples with high Mg and Ca concentrations by combining H+-form cation-exchange chromatography with pyridinium-form ion-exchange chromatography us-ing 1, 2-diaminocyclohexane tetraacetic acid (DCTA) (Birck, 1986). Recently, crown-ether-based resins specifi-cally designed for Sr separation (Sr-spec. resin) (Horwitz et al., 1992) have been used widely (Pin and Bassin, 1992; Misawa et al., 2000; Ishizuka et al., 2003; Balcaen et al., 2005; Ohno and Hirata, 2007; Míková and Den-ková, 2007; Shibata et al. 2007; Makishima et al., 2008; Takahashi et al., 2009). In the case of Nd separation, NH4

+-form cation exchange with 2-hydroxyisobutyric acid (HIBA) (Kagami et al., 1987; Walker et al., 1989; Makishima and Nakamura 1991; Shibata and Yoshikawa, 2004; Shibata et al., 2007; Hirahara et al., 2009) or extrac-tion resin with bis-(2-ethylhexyl) hydrogen phosphate (HDEHP) (Richard et al., 1976) are used after removing major elements by H+-form cation-exchange chromatog-raphy. An extraction resin with an HDEHP coating has become commercially available (Ln-spec. resin) and is now widely used for Nd separation (Pin and Zalduegui, 1997; Ishizuka et al., 2003; Le Fèvre and Pin, 2005; Li et al., 2007; Míková and Denková, 2007; Makishima et al., 2008; Yang et al., 2010a). In the case of Pb, anion ex-change with a HBr medium (Manhes et al., 1978; Koide and Nakamura, 1990; Woodhead and Hergt, 2000; Kuri-tani and Nakamura, 2002; Blichert-Toft et al., 2003; Kimura and Nakano, 2004; Miyazaki et al., 2009) or ex-traction resins, such as Sr- and Pb-specific resins (Hor-witz et al., 1994; Gale, 1996; Weiss et al., 2004; Makishi-ma et al., 2007, 2008), are used for the separation.

76 T. Miyazaki, B.S. Vaglarov, M. Takei, M. Suzuki, H. Suzuki, K. Ohsawa, Q. Chang, T. Takahashi, Y. Hirahara, T. Hanyu, J. Kimura and Y. Tatsumi

COLUMNSPIDER: FULLY AUTOMATED COLUMN SEPARATION SYSTEM

COLUMNSPIDER was installed in a class 100 clean room at Institute for Research on Earth Evolution (IF-REE), JAMSTEC. System overview photographs and those of its constituent units are shown in Figure 1. The system comprises a pipetting robot unit and a control unit with a programming input/output (I/O) terminal (Fig. 1a).

Pipetting robot unit

The pipetting robot unit consists of a pipetter head, col-umn and sample beaker racks, a tip rack, a reagent bottle

stand, and a collection stage (Fig. 1b). The pipetting robot unit was installed in a class 10 clean ventilator. To protect against corrosive vapors from various acids, the cabinet of the pipetting robot unit was constructed using polyvi-nyl chloride panels with plastic screws. Metal and elec-tronic parts used for the pipetter head were coated or sealed with a fluorocarbon polymer.Pipetter head. The pipetter head moves along the perpen-dicular X- and Y-axes and has a nozzle connected to a motor-driven syringe with a 300 µL inner volume (Fig. 1c). The nozzle also moves along the Z-axis of the pipet-ter head and can fit and release a micropipetter tip (200 µL, long filter tip, WATSON Co. Ltd., JAPAN). There is a pressure sensor between the nozzle and the syringe to de-

Figure 1. Photographs of the fully automated open-column chemical-separation system, COLUMNSPIDER. (a) An overview of the system, (b) pipetting robot unit, (c) pipetter head, and (d) inside the collection stage (vacuum chamber not visible) and sample and column racks.


tect reagent and sample-solution surface levels to prevent overinsertion of the pipetter tip into the solutions (Fig. 1c).Column and sample beaker racks. Up to 10 columns and 10 sample beakers can be set in the column and sam-ple beaker racks (Fig. 1d). By using appropriate adapters, the column rack can be made to accommodate different column sizes. The current model uses column adapters of four different sizes for four different miniature columns, with 1 mL, 0.3 mL, 0.1 mL, and 0.05 mL resin volumes.

Beakers containing decomposed sample solutions are set on the sample-beaker rack behind the column rack. The beaker rack has special beaker holders using which beakers of different sizes can be stored. The current model uses three different Teflon beakers with capacities of 5 mL, 7 mL, and 15 mL (Savillex ©, Minneapolis, USA).Tip rack. Two pipette-tip boxes, each containing 96 tips (total 192 tips), can be loaded in the tip rack.Reagent bottle stand. A maximum number of eight 100 mL chemical reagent bottles can be set on the reagent bottle stand. Two bottle stands are equipped with heaters and can warm up, and keep the bottles at a constant tem-perature between the ambient temperature and 70 °C.Collection stage. Two rows of 10 collection beakers and a common waste trough are provided. Up to two collec-tion beakers can be used for each open resin column so that fractions may be separately collected from the same column, if required. The collection beakers and the waste trough are set on a collection stage, and this stage moves along the system’s Y-axis to place the collection beakers or waste trough, as appropriate, below the columns. In or-der to prevent splashes by droplets falling from the resin columns, the collection stage moves vertically to position the columns’ bottom aperture below the upper surface level of the collection beakers and waste trough. Addi-tional vacuum chambers, two for the two collection-bea-ker rows and one for the waste trough, are available as an option to facilitate column elution and prevent stacking of the solutions in the columns.

Control unit and other devices

A programmable logic controller (PLC) provides overall control of the actuator units (Fig. 1a). The COLUMNS-PIDER control software interface is stored in one of the PLC’s memory chips. An I/O terminal with a touch panel display provides a programming interface. Separation procedure sequences and control parameters are set at the I/O terminal.

The vacuum pump, for the vacuum chambers used in the collection stage, is positioned behind the control unit (not shown in Fig. 1a).

CONTROL SOFTWARE FOR COLUMNSPIDER

COLUMNSPIDER has several actuators. The pipetter head has four stepping motors for the horizontal X- and Y-axis movement of the pipetter head, for the vertical Z-

axis motion of the nozzle, and for the movement of the sample-uptake-release syringe. The collection stage has two stepping motors for Y- and Z-axis movement. The bottle heater, vacuum pump, and air valves for vacuum chambers also have actuators to be controlled. Using a combination of these actuators and devices, open-column separation movement has to be made possible for (1) sample and reagent injections, (2) beaker and pipette-tip changes, and (3) heating of reagents and vacuuming of the elution chambers.

The PLC unit controls all parameters and move-ments for COLUMNSPIDER. The PLC command struc-ture identifies one separation protocol as a protocol. A protocol consists of (1) basic control unit (BCU) files for controlling the pipetter head and collection-stage actions and (2) initial setup (IS) files for control of the heater tem-perature and column/beaker assignments (Fig. 2).

Basic control unit

For manual operation, the procedure for each separation method is divided into several processes. For example, the separation method of the Rb+Sr-REE column consists of 10 consecutive processes (Table 1) (Takahashi et al., 2009). The COLUMNSPIDER control software treats each process as a basic control unit (BCU). The BCU controls the pipetting robot to execute all actions needed for each process. By connecting multiple BCUs, an opera-tion protocol can be programmed for individual column separation methods. The operation protocol for the Rb+Sr-REE column separation is programmable using 10 separate BCU processes (Table 1). Following the same method, the operating protocol for Pb column separation is programmed using 7 separate BCU processes (Table 1) (Miyazaki et al., 2009). An individual IS file is combined with each set of BCUs for additional control-parameter setup options (initial set up (IS) boxes in Fig. 2)

One BCU, for example, consists of 11 separate actu-ator actions, as described in Figure 3. In Step 1, the bottle temperature is checked. If the bottle temperature is below the temperature defined in the IS file, the BCU waits for the bottle temperature to reach the target temperature. In Step 2, the position of the collection beaker or waste trough is adjusted by movement of the collection stage (values are defined in the IS file). In Step 3, when no pi-pette tip is in the nozzle, the pipetter head moves to fit a new pipette tip. In Step 4, the pipetter head moves to the


take-up position. When programmed, the mixing of a sample solution or reagent by drawing up and releasing the solution is performed in Step 5. In Steps 6 to 8, the solution is taken up into the pipetter tip, the pipetter head moves to the release position, and the pipetter head re-leases the solution into a column or sample beaker. In Step 9, the pipetter head moves into position for the pi-pette tip to be removed. If the same pipette tip is used in the following step, then Step 9 is omitted. Alternatively, any residue present in the pipette tip may be removed in this step. The vacuum pump runs in Step 10 to reduce pressure inside the vacuum chamber, thereby aiding elu-tion in the open column. Steps 3 to 10 are repeated ac-cording to either the number of resin columns or the num-ber of repeated solution injections (in the case of injection volumes greater than 200 µL), or both. Before proceeding to the next process, a pause time can be set for the final step, to ensure complete elution through the resin.

The BCU control parameters that refer to the take-up, mixing and release actions of a solution, and other ac-

tions are listed in Table 2. The number of injections is cal-culated automatically from the result obtained by dividing the [Volume of total liquid poured into each column or sample beaker] value by the [Liquid volume of injection] value. The time interval for each injection is determined automatically from the calculated number of injections and the value of the [Average flow rate in resin column] parameter.

Each BCU has optional flags for [immediate execu-tion], [non-execution (= skip)] or [pause after execution]. It is possible to avoid needless BCUs by using the option-al [skip] flag. Pausing and restarting (or starting) partway through a protocol is also possible using the [pause] flag for manual intervention, if necessary.

Operational protocol

The operation menu in the I/O unit contains protocols corresponding to separation methods (e.g., Rb+Sr-REE separation, Pb separation) (Fig. 2). Each protocol is a

Miyazaki et al.

Fig. 2

Figure 2. Block diagram of the operation software. Separation protocols are programmed with basic parameters through the operation menu.


combination of IS and BCU files. Up to 10 different pro-tocols can be stored for each element separation method. In total, 50 protocols can be stored in the PLC memory, and the protocols are not limited to the isotope analyses shown in Figure 2. During routine operation, the number of samples and protocol ID numbers are the only input commands displayed in the start menu.

Sr and Nd separations can be accomplished by con-secutive runs of the Sr or Sm-Nd protocols following the Rb+Sr-REE protocol because the chemical separation of Sr and Nd consist of two rounds of chemical separation (i.e., Rb+Sr-REE collection for the first round and Sr pu-rification from the Rb+Sr collection and Nd purification from the REE collection for the second round).

The time required for a single run depends on the settings in the protocol, the number of samples (<10), pi-petter parameters (number of mixing step, etc.), and paus-es between BCU processes. For example, the time re-quired to process 10 samples using Rb+Sr-REE separation is 20 h and 40 min (Table 1), while Pb separa-tion for 10 samples takes 9 h 40 min (Table 1).

SPECIAL FUNCTIONS OF COLUMNSPIDER

COLUMNSPIDER has several special functions that per-form precise column separations. These functions gener-ally follow manual separation procedures.

Complete sample transfer from sample beaker to separation column

After sample-solution transfer into the open resin column, a small amount of the sample solution may remain at the bottom of the sample beaker. In order to maximize ele-ment recovery, it is desirable to transfer all of the sample solution to the column. In the case of manual operation, a reagent may be added to the sample beaker to dissolve the remaining solution, and the resulting solution is then transferred to the column, thus transferring almost the en-tire sample solution. COLUMNSPIDER can mix a sol-vent with any sample solution remaining in the sample beaker by repeated pipette suction and discharge actions. Thus, it is possible to dissolve the remaining sample solu-tion and transfer it to the column in a similar manner to

Table 1. Analytical flow of the Rb+Sr-REE and Pb column sepa-ration procedures

Table 2. Setting parameters of a basic control unit


the manual procedure. All parameters related to this func-tion can be set in a BCU (see mixing action in Table 2).

Column washing

The sample solution or the reagents are injected into the open resin column according to the previously defined elution profile. Accurate changeover from the sample so-lution to the eluent solutions, and between different elu-ents, is essential. Small drops of the sample solution may remain on the walls of the open resin column and reser-voir. Such residues may adversely affect the elution curve by contaminating the eluent solution added in subsequent steps.

During manual operation, column/reservoir washing is performed by gradually pouring the reagent around the circumference of the inner walls of the column reservoir (Fig. 4a). Motion of the COLUMNSPIDER pipetter unit is limited to the X, Y, and Z axes. It is not possible to tilt the pipetter tip; instead, COLUMNSPIDER uses a custom column-washing procedure.

By precisely controlling the loading position, COL-UMNSPIDER loads the sample solution exactly at the

center of the column top face, close to the resin bed, so that the column reservoir is wetted only in the lower fun-nel region (Fig. 4b). Eluent loading is carried out from a greater height, and the pipetter tip is moved along the cir-cumference of the column’s inner walls (Fig. 4b). Any re-maining sample solution in the funnel region is dissolved

Miyazaki et al.

Fig. 3

Figure 3. Flow chart of the actions executed by one BCU in a single separation process.Miyazaki et al.

Fig. 4

Figure 4. (a) Manual sample washing procedure. (b) Injection of the sample solution and COLUMNSPIDER washing procedure.


by the eluent and transferred onto the resin bed. The rota-tion velocity of the pipetter tip and the discharge rate are synchronized to ensure efficient washing. The same meth-od is applied to the eluent when the eluent is changed. These settings are available through BCU programming (see Release action in Table 2).

APPLICATION OF COLUMNSPIDER TO THE ELEMENTAL SEPARATION OF

GEOLOGICAL SAMPLES

We tested COLUMNSPIDER elemental separation by an-alyzing blanks and determining the Sr-Nd-Pb isotope ra-tios of rock standards provided by the Geological Survey of Japan and the United States Geological Survey. The chemical procedures used for this test followed those ad-opted by Kimura and Nakano (2004), Takahashi et al. (2009), Hirahara et al. (2009) and Miyazaki et al. (2009). Sr and Nd isotope ratios were measured using TIMS (Tri-ton; Thermo-Finnigan) equipped with nine Faraday cups and using a static multicollection mode. Isotopic fraction-ation in the Sr and Nd isotope ratios was corrected to 86Sr/88Sr = 0.1194 and 146Nd/144Nd = 0.7219. The mean 87Sr/86Sr value in the NIST 987 standard was 0.710248 ± 0.000026 (2 standard deviation (2sd), n = 51) and the mean 143Nd/144Nd value in the JNdi-1 standard was 0.512096 ±0.000009 (2sd, n = 33). Pb isotope ratios were determined by MC-ICP-MS (Neptune; Thermo Fischer Scientific). The mass fractionation factors of Pb were cor-rected using Tl as an external standard. Additional mass-dependent interelement fractionations were also corrected (Kimura and Nakano, 2004). The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios from repeated measurements of NIST 981 were 16.9315 ± 0.0017, 15.4850 ± 0.0019, and 36.6786 ± 0.0065 (2sd, n = 87), respectively. Pb isotope data are presented after recalibration using the NIST 981 values of 206Pb/204Pb = 16.9416, 207Pb/204Pb = 15.5000, and 208Pb/204Pb = 36.7262, as reported by Baker et al. (2004).

Table 3 shows the procedural Sr, Nd, and Pb blanks and the Sr, Nd, and Pb isotope ratios for the rock stan-dards, along with previously reported isotope ratios. The procedural Sr blanks for the Rb+Sr-REE and Sr protocols (Fig. 2) were 10.5 pg and 8.3 pg, respectively. The blank levels used by the Rb+Sr-REE and Sr protocols are com-parable to those of a manual Sr separation using only a Sr column (Sr; 11 ± 3 pg), as reported by Takahashi et al. (2009). The Nd procedural blank for the Rb+Sr-REE pro-tocol was <2 pg. This blank level is lower than the Rb+Sr-REE column blank (Nd; 2.84 pg) reported by Hi-rahara et al. (2009). The Sr and Nd blank levels deter-mined in this study were far less than 1% of a typical sample size (>100 ng) and also much smaller than those

in other laboratories (Hamamoto et al., 2000; Sr ≤0.91 ng and Nd ≤0.39 ng). The total procedural blank for Pb was <34 pg, comparable to that reported by Kuritani and Na-kamura (2002) (Pb = 31 pg). The blank level for Pb was negligible in our routine analysis, but a blank correction may be necessary for samples with Pb content less than 6 ng.

87Sr/86Sr values for JB-2, separated using the Rb+Sr-REE COLUMNSPIDER protocol with a manual Sr sepa-ration and also using the combination of the Rb+Sr-REE and Sr protocols, were 0.703663 ± 0.000020 (2sd, n = 7) and 0.703666 ± 0.000007 [2 standard error of mean (2se)], respectively. Our results are within the range of previously reported values, 0.703640 − 0.703699, after normalization using NIST 987 (87Sr/86Sr = 0.710248).

143Nd/144Nd values for JB-2, separated using the Rb+Sr-REE protocol with manual Sm-Nd separation and also using the combination of the Rb+Sr-REE and Sm-

Nd protocols, were 0.513091 ± 0.000007 (2sd, n = 7) and 0.513089 ± 0.000009 (2se), respectively. Two sets of 143Nd/144Nd analyses for JB-3 and BCR-2, separated us-ing the combination of the Rb+Sr-REE and Sm-Nd pro-tocols, yielded the values 0.513043 ± 0.000009 (2se) and 0.513052 ± 0.000009 (2se) for JB-3, and 0.512602 ± 0.000008 (2se) and 0.512624 ± 0.000011 (2se) for BCR-

2. We used the JNdi-1 Nd isotope standard solution for checking the reproducibility of the TIMS results. It is not possible to normalize the previously reported Nd isotope values without the associated JNdi-1 values for these samples. As many of the previous Nd isotope analyses were associated with La Jolla or Ames Nd-reference stan-dard analyses, we applied the factor 1.000503 (Tanaka et al., 2000) to calculate the JNdi-1 value from the La Jolla value and 0.999965 (Li et al., 2007) to calculate the JNdi-1 value from the Ames Nd-reference solution used by Yang et al. (2010a). After normalization, the ranges of the previously reported values for JB-2, JB-3, and BCR-2 become 0.513029-0.513095, 0.513020-0.513073 and 0.512596-0.512633, respectively. Our present results are well within these ranges.

206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values for JB-2 separated using the Pb protocol were 18.3445 ± 21, 15.5645 ± 12, and 38.2852 ± 41 (2sd, n = 22), respective-ly. These values are within the previously reported ranges for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values, i.e., 18.3364-18.3447, 15.5617-15.5650, and 38.2722-

38.2865, respectively, after recalibration using the NIST 981 values of 206Pb/204Pb = 16.9416, 207Pb/204Pb = 15.5000, and 208Pb/204Pb = 36.7262, as reported by Baker et al. (2004).

82 T. Miyazaki, B.S. Vaglarov, M. Takei, M. Suzuki, H. Suzuki, K. Ohsawa, Q. Chang, T. Takahashi, Y. Hirahara, T. Hanyu, J. Kimura and Y. TatsumiTa

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COMPARISON WITH OTHER METHODS

The main advantage of COLUMNSPIDER is that this system can faithfully reproduce the low-blank separation methods developed for manual pipetting. The procedural blanks for Sr, Nd, and Pb during chemical separation by COLUMNSPIDER are comparable or lower than those of manual pipetting, as shown in the previous section. We could not determine the Nd blank for Sm-Nd column chromatography. However, we can estimate it from the blank levels of Nd for the Rb+Sr-REE column chroma-tography, for which additional contamination by COL-UMNSPIDER is negligible.

Data on the blank levels from the semiautomated separation carried out by Shibata et al. (2007) has not been reported, and hence, these blank levels are not avail-able for comparison. The Sr and Nd blanks from HPLC methods are higher than those of COLUMNSPIDER. Ac-cording to Stray (1992) and Meynadier et al. (2006), Sr blanks in their HPLC systems were 50 pg and 55-180 pg, respectively, in contrast to 19 pg blank (Rb+Sr-REE pro-tocol + Sr protocol) in our study. Griselin et al. (2001) re-ported the Nd blank in their HPLC system to be 10-15 pg, which is higher than our estimated value of <3 pg (Rb+Sr-REE protocol + Sm-Nd protocol) (Blank of Sm-

Nd protocol (<3 pg) is estimated from the value of manual Sm-Nd column chromatography performed in our labora-tory (Hirahara et al., 2009)).

The required operation time for elemental separation using COLUMNSPIDER is almost equal to that for man-ual pipetting. According to Shibata et al. (2007), the time required by their semiautomated system for elemental separation is identical to that for manual pipetting. COL-UMNSPIDER, however, can provide shorter times be-cause there is no need for manual intervention (e.g., changes of reagent bottles etc.) over the entire sequence of the elemental separation.

HPLC systems can drastically shorten the time re-quired for element separation. For example, it takes 20 min after sample injection to the end of Sr-fraction col-lection. An additional time of 50 min is required for cleaning the HPLC (Meynadier et al., 2006). A major dis-advantage is that the HPLC system can treat only one sample per separation run. Separation of 10 samples takes about 12 h in their system. Pretreatment for the removal of a high sample matrix are sometimes needed for HPLC, which prevents the automation of the complete HPLC separation process. Na et al. (1995) and Griselin et al. (2001) used an HPLC system only for Nd separation from REE fraction. REE separation from a dissolved rock solu-tion was carried out by open-column chromatography. In contrast to this, COLUMNSPIDER is flexible and appli-

cable to almost all open-column chemical-separation pro-cedures, as described in the above sections.

CONCLUSION

We have developed a new fully automated open-column resin-bed chemical-separation system, COLUMNS-PIDER, to reduce the elemental separation workload in Sr, Nd, and Pb isotope analyses. The total procedural blanks and isotopic compositions of the JB-2, JB-3, and BCR-2 rock samples were comparable to those obtained by careful manual operation by skilled operators. Analyti-cal results for the standard rocks agreed very well with previously reported results. These results indicate that COLUMNSPIDER is a versatile tool for isotope ratio analysis of small volume samples in the field of solid Earth science. COLUMNSPIDER’s flexible customiza-tion makes possible a wide range of potential applica-tions. COLUMNSPIDER, as well as any future develop-ments, is available from HOYUTEC Co., Ltd.

ACKNOWLEDGEMENT

We would like to thank an anonymous reviewer for the constructive comments; we are also grateful to T. Kuritani and the associate editor, T. Hirajima for their insightful and constructive comments.

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Manuscript received May 20, 2011Manuscript accepted December 21, 2011Published online April 7, 2012Manuscript handled by Takao Hirajima

development of a fully automated open-column …...-icp-ms. yang et al. (2010b) and li et al. (2011)...

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