Signal-Smoothing and Mercury-Removing Device for Laser Ablation

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Article

A novel “wave” signal smoothing and mercury removing device for laser ablation quadrupole and multiple collector ICP-MS analysis: application to lead isotope analysis Zhaochu Hu, Wen Zhang, Yongsheng Liu, Shan Gao, Ming Li, Keqing Zong, Haihong Chen, and Shenghong Hu Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/ac503749k • Publication Date (Web): 16 Dec 2014 Downloaded from http://pubs.acs.org on December 21, 2014

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Analytical Chemistry

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A novel “wave” signal smoothing and mercury

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removing device for laser ablation quadrupole and

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multiple collector ICP-MS analysis: application to

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lead isotope analysis

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†,‡

Zhaochu Hu

†

†

†

†

State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, P.R. China

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‡

The Beijing SHRIMP Center, Institute of Geology Chinese Academy of Geological Sciences, Beijing 102206, P.R. China

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*Author to whom correspondence should be sent. E-mail:

[email protected]

Tel.: +86 27 61055600, Fax: +86 27 67885096

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†

Chen , and Shenghong Hu

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11

†

†

7

10

†

*, Wen Zhang , Yongsheng Liu , Shan Gao , Ming Li , Keqing Zong , Haihong

Submitted to Analytical Chemistry 1

ACS Paragon Plus Environment


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For TOC only

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ABSTRACT:

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A novel “wave” signal smoothing and mercury removing device has been developed

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for laser ablation quadrupole and multiple collector ICP-MS analysis. With the

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“wave” stabilizer that has been developed, the signal stability was improved by a

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factor of 6.6 to 10, and no oscillation of the signal intensity was observed at a

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repetition rate of 1 Hz. Another advantage of the “wave” stabilizer is that the signal

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decay time is similar to that without the signal smoothing device (increased by only 1

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to 2 s for a signal decay of approximately four orders of magnitude). Most of the

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normalized elemental signals (relative to without the stabilizer) lie within the range of

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0.95 to 1.0 with the “wave” stabilizer. Thus, the “wave” stabilizer device does not

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significantly affect the aerosol transport efficiency. These findings indicate that this

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device is well-suited for routine optimization of ICP-MS, as well as low repetition

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rate laser ablation analysis, which provides smaller elemental fractionation and better

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spatial resolution. With the “wave” signal smoothing and mercury removing device,

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the mercury gas background is reduced by one order of magnitude. More importantly,

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the

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is reduced from 256 mv to 0.7 mv by the use of the “wave” signal smoothing and

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mercury removing device. This result suggests that the mercury is almost completely

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removed from the sample aerosol particles produced by laser ablation with the

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operation of the “wave” mercury removing device. The “wave” mercury removing

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device that we have designed is very important for Pb isotope ratio and accessory

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mineral U-Pb dating analysis, where removal of the mercury from the background gas

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Hg signal intensity produced in the sulfide standard MASS-1 by laser ablation

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and sample aerosol particles is highly desired. The “wave” signal smoothing and

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mercury removing device was applied successfully to the determination of the

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206

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Keywords: signal smoothing device, mercury removing device, lead isotope, laser

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ablation, ICP-MS, MC-ICP-MS.

Pb/204Pb isotope ratio in samples with low Pb content and/or high Hg content.

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INTRODUCTION

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Laser ablation is becoming one of the most important technologies for direct solid

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sampling in analytical chemistry.1–4 In LA-ICP-MS analysis, it is well know that the

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sample position in the ablation cell influences signal stability significantly in one

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volume cell.5 In addition, laser ablation produced signals change quickly with time

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during single hole ablation at a high repetition rate, which makes it difficult to

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optimize the instrumental parameters for ICP-MS or MC-ICP-MS analysis.6 For

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dating 5 µm zircon metamorphic rims, a lower laser ablation repetition rate such as 1

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Hz is required6,7 Elemental fractionation is also significantly reduced at a lower laser

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ablation repetition rate, because it is strongly related to the depth-to-diameter ratio of

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the ablation crater.8 However, a lower repetition rate results in an unstable signal that

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deteriorates the analytical precision. Due to the sequential nature of some ICP-MS

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analysis (only one m/z value is detected at any one time), this may also lead to

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undesired spectral skew when certain dwell times are chosen during data acquisition.9

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Spectral skew is an error in relative signal levels for several m/z values across a

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transient signal that arises from the need to scan a spectrum while the input sample

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concentration is changing.9 This is especially true for the recently designed VOLM

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chamber10, Laurin two-volume ablation cell11, MMG sample cell12, and laminar flow

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ablation cell13 whose cell-related memory effects are significantly reduced. To

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overcome these problems, Tunheng and Hirata14 developed novel baffled-type and

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cyclone-type signal smoothing devices. These stabilizers can provide a smoother

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signal at a repetition rate of 2 Hz, but the wash out time can become significantly 5



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longer (approximately 20–40 s), and the resulting signal intensity is 15-20% lower. A

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“squid” signal smoothing device (Laurin Technic, Australia) has been designed to

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produce smooth signals even at very low laser repetition rates down to 1 Hz.11 This

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“squid” signal smoothing device splits the carrier gas (He + Ar) and sample aerosol

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line into ten tubes with optimally differing lengths. After recombination into one gas

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line, a smoothed signal is produced. However, the washout time is improved by a

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factor of 2.2 (from 4 s to 9 s for a signal decay of 5 orders of magnitude). Hu et al.6

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have developed a simple “wire” signal smoothing device for LA-ICP-MS analysis.

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With this “wire” signal smoothing device, no oscillation of the signal intensity was

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observed, even at a repetition rate of 1 Hz. This “wire” signal smoothing device has

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been used successfully for high spatial resolution U-Pb dating in zircon at low

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repetition rates of 1 to 2 Hz. Compared to other signal smoothing devices, the

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significant advantage of the “wire” smoothing device is that the signal washout time

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is similar to that without the signal smoothing device. However, the “wire” stabilizer

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device acts as a “particle filter” to a certain extent because the resulting signal

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intensity achieved with the stabilizer is lower than that without the stabilizer (10-30%).

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From the above observation, the trade-off between signal intensity and wash out time

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is clearly a matter of compromise, which should be carefully considered during the

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design of the signal smoothing device.

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Lead isotope analysis in glass, sulfide minerals and feldspar and U-Pb dating of

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accessory minerals (e.g., zircon) are very popular applications of LA-MC-ICP-MS /

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LA-ICP-MS in the earth sciences.15–20 For correction of common-Pb using the 6


204

Pb

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intensity in accessory minerals U-Pb dating, a small variation in the

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can produce a large uncertainty in signal intensities for radiogenic

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components.21 Precise determination of the signal intensity of

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important. However,

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interference with 204Hg. Reduction of the mercury background in the ICP-MS is thus

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highly desirable. Mercury may be present in the Ar and He gases. Reduction of the

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Hg signal can be achieved by filtering the Ar and He gas using activated charcoal19,

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gold-coated sand20 or gold-coated glass wool22. A reduction of approximately 50% in

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Hg signal is achieved by using these devices. Hirata et al.21 have developed a novel

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Hg-trapping device using an activated charcoal. Higher reduction efficiency of Hg

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signals was obtained with a larger volume of activated charcoal. For example, the Hg

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signals were reduced by a factor of 3 with a volume of charcoal filter of 200 ml.

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However, too high a volume of charcoal filter (e.g., 400 ml) resulted in lowering the

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signal intensity of Pb and U (approximately 40%). Aside from Ar and He gases, Hg

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also may be present in many mineral samples such as sulfides. Thus, removing Hg

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from laser ablation produced sample aerosol particles during lead isotope and U-Pb

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dating analysis is also highly desirable.

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Pb intensity

Pb and

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Pb

Pb is thus highly

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Pb has the lowest isotopic abundance and share an isobaric

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In this study, we have designed a novel “wave” signal smoothing and mercury

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removing device for laser ablation ICP-MS analysis. The performance of the “wave”

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signal smoothing and mercury removing device was evaluated based on signal

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stabilities, signal intensities, washout time and the reduction efficiency of Hg. In the

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end, we applied this device to lead isotope analysis in sulfides and glasses by using 7



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laser ablation MC-ICP-MS.

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EXPERIMENTS

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Instrumentation.

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Experiments were conducted using an Agilent 7500a ICP-MS (Agilent Technology,

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Tokyo, Japan) and a NEPTUNE Plus MC-ICP-MS (Thermo Fisher Scientific,

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Germany), which are connected to a Geolas 2005 excimer ArF laser ablation system

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(Lambda Physik, Göttingen, Germany) at the State Key Laboratory of Geological

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Processes and Mineral Resources, China University of Geosciences in Wuhan. The

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standard ablation cell in the GeoLas 2005 system is a closed design cell and consists

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basically of a cylinder with a volume of approx. 51 cm3 with an inlet nozzle (i.d. < 0.5

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mm) and a gas outlet (i.d. 1.8 mm). The energy density of the laser ablation that was

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used in this study was 5.0 J cm-2. Helium was used as the carrier gas within the

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ablation cell and was merged with argon (makeup gas) after the ablation cell. Details

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of the instrumental operating conditions and measurement parameters are summarized

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in Table 1.

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“Wave” signal smoothing and mercury removing device.

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Figure 1 illustrates the schematic diagram of the “wave” signal smoothing and

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mercury removing device (a) and the connection position of the smoother in the

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LA-ICP-MS system (b). The “wave” device essentially consists of a stainless steel

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cylinder filled with nine smoothing elements, with a volume of approximately 94 cm3. 8


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Each smoothing element consists of seven intersecting corrugated plates (thickness:

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0.15 mm; corrugation angle: 45°; wave height: 4 mm; pitch of waves: 7 mm) (Figure

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1a). The length of seven corrugated plates is fixed at 30 mm. The widths of the seven

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corrugated plates are 9 mm, 14 mm, 18 mm, 20 mm, 18 mm, 14 mm and 9 mm,

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respectively. In position A, only the He carrier gas flows through the stabilizer,

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whereas in position B, both the He carrier gas and the Ar makeup gas flow through

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the stabilizer.

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The surface of all the corrugated plates and the inner surface of the stainless steel

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cylinder were coated with ultrapure gold. The thickness of the gold coating is

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approximately 10 µm. The mercury in the carrier gas is expected to be trapped by the

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gold during transport through the “wave” stabilizer, in which the mercury frequently

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collides with the gold surface of the corrugated plates and the stainless steel cylinder.

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RESULTS AND DISCUSSION

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Effect on signal stability.

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Figure 2 shows the U signal profile produced by continuous ablation of the NIST

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SRM 610 glass at a repetition rate of 1 Hz and a spot size of 60 µm with and without

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the “wave” device at position A and B. It can be seen that a smooth signal is obtained

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even at a repetition rate of 1 Hz by using the “wave” device. The stability of the U

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signal is improved from 18.6% to 2.81% and 1.85% for the “wave” device at

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positions A and B, respectively. The magnitude of the variability was calculated by

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subtracting the mean intensity estimated by the exponential decay pattern.14 When the 9



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laser ablation produced aerosol particles are transported into the “wave” device, the

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aerosol stream is divided into many parts and deflected in different directions by the

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first smoothing elements, and these different aerosol parts continue to recombine and

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re-separate while passing through another eight smoothing elements. The different

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traveling pathways of the laser ablation produced sample aerosol particles in the

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“wave” device which lead to different exit times, defined as the time needed for the

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aerosol particles to travel through the stabilizer, that ultimately contribute to the

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stabilization. As shown in Figure 2, the stability of the U signal intensity in position A

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(1.85%) is better than that in position B (2.81%). This should be attributed to the

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reduced residence time of the sample aerosol particles in “wave” stabilizer in position

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B than that in position A due to the increased carrier gas flow rate in position B (He +

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Ar), which subsequently reduces the difference in exit time for the different parts of

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the sample aerosol in the stabilizer. This result also suggests that the expected

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improvement of signal smoothing by the mixing of He and Ar in the “wave” stabilizer

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is limited, which cannot compensate for the reduced smoothing effect due to the

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reduced exit time difference among the different aerosol particles in position B (He +

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Ar).

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Effect on washout time.

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The washout time refers to the time required for the signal to drop back to background

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levels after cessation of ablation. For high spatial resolution and high sample

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throughput analysis, the washout time should be as short as possible for the designed 10


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signal smoothing device. Compare to that without “wave” stabilizer, the washout time

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is increased by 1 s and 2 s for signal decay of approximately 4 orders of magnitude

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with the “wave” stabilizer at position B and position A, respectively (Figure 3). This

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result indicates that the “wave” signal stabilizer has a limited effect on washout time.

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In comparison with previously developed signal stabilizers such as the baffled-type

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stabilizer14, the cyclone-type stabilizer14 and the “squid” signal stabilizer11, this is an

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important advantage for our designed “wave” signal stabilizer.

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Effect on signal intensity.

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Figure 4 shows the normalized signal intensities of 63 elements (relative to without

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the stabilizer) at different test times. These signals were produced using a laser

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ablation repetition rate of 6 Hz lasting 50 s at a spot size of 44 µm on the glass

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standard NIST SRM 610. It would be better if the designed “wave” stabilizer device

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did not affect the signal intensity or remove aerosols in an elementally selective way.

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It can be seen that most of the normalized elemental signals lie within the range of

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0.95 to 1.0. Compared with previously developed signal stabilizers, such as the

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baffled-type stabilizer14, the cyclone-type stabilizer14 and the “wire” signal stabilizer6,

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this is an important advantage for the designed “wave” signal stabilizer.

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111

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when measured at different times. The reason for this is unclear. Further work on the

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Zn, Cd, Sb and Te deposition is needed to identify the specific mechanisms. The large

Cd,

Zn,

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111

Sb and 126Te and

Cd,

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195

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Zn,

103

Rh,

Pt are significant exceptions. The normalized signals of

Sb and 126Te are consistently lower (lie within the range of 0.90-0.95)

11



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variation ranges for 103Rh and 195Pt (0.93–1.16) may be related to their heterogeneous

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distribution in NIST 610 glass.23,24 These results suggest that the “wave” stabilizer

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does not significantly affect the aerosol transport efficiency and remove aerosols in an

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elementally selective way for the operating conditions used in this study.

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Removing Hg from the carrier gas and the sample aerosol. Figure 5 shows the

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Hg, 204Pb and 208Pb signal profile produced by laser ablation

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of the MASS-1 sulfide standard at a repetition rate of 8 Hz with and without the

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“wave” device at position A using MC-ICP-MS. It can be seen that the gas

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background of mercury in LA-MC-ICP-MS is reduced from 6 mv to 0.5 mv by using

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the “wave” device. This reduction is important for Pb isotope and U-Pb dating

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analysis in samples with a low Pb content using LA-MC-ICP-MS. The mercury

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content is 57 µg g-1 in MASS-1. The laser ablation produced 202Hg signal intensity in

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MASS-1 is 256 mv and 0.7 mv for without and with the “wave” device, respectively.

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A reduction factor of 366 for the

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the Hg is also almost completely removed from the laser ablation produced sample

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aerosol particles. In contrast, the signal intensity of

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without the “wave” device. We propose that Hg is enriched and transported primarily

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in the small particulate form due to its volatility and hence can interact well with the

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gold coating on the surfaces of the different corrugated plates in the smoothing

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elements and the inner surface of the stainless steel cylinder compared to other more

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refractory elements such as Pb, which are transported predominantly as normal solid

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Hg signal was obtained. This result suggests that

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Pb is similar for both with and

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aerosol particles. However, the mechanisms that cause this effect need further

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investigation.

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Application to lead isotope analysis.

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Lead isotopes have been widely applied for the fingerprinting and identification of

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geological processes.17,18 LA-MC-ICP-MS is one of the most powerful tools for lead

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isotopic analysis.15–18 The low abundance of 204Pb (~1.4% of all common Pb) and the

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isobaric interference of

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the main problems in obtaining the high precision measurements of the

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206/207/208

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the determined

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NIST SRM 614, AHTO-G, StHs6/80, T1-G ), sulfide standard MASS-1, and natural

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sphalerite ZnS-1 from reference values both with and without the “wave” device. It

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can be seen from Figure 6 that the agreement between our data obtained with the

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“wave” device was much better than the data obtained without the mercury removing

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device. This is particularly true for low Pb content samples ML3B-G (Pb = 1.38 µg

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g-1), BHVO-2G (Pb = 1.70 µg g-1), NIST SRM 614 (Pb = 2.32 µg g-1) and AHTO-G

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(Pb = 5.67 µg g-1). For high Hg content sample MASS-1 (Hg = 57 µg g-1), the

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determined

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value by 1% without use of the “wave” signal smoothing and mercury removing

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device. Excellent agreement between the determined values and the reference value in

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MASS-1 is obtained by using our developed mercury removing device. The

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Hg from the carrier gas and samples are considered to be

Pb/204Pb by using LA-MC-ICP-MS. Figure 6 shows the relative deviation of

206

206

Pb/204Pb isotope ratios in glass standards (ML3B-G, BHVO-2G,

Pb/204Pb values in MASS-1 are consistently higher than the reference

13



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Pb/204Pb isotope ratios determined in natural sphalerite ZnS-1 are scattered for

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different laser ablation spot analyses without the “wave” device because the Hg and

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Pb contents are highly varied for different laser ablation sampling locations in natural

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sphalerite sample ZnS-1 (204Hg/204Pb = 0.186-6.419). By using our mercury removing

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device, the

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locations in natural sphalerite sample ZnS-1 are very consistent. These results

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demonstrate that the “wave” device that we have developed is well suited for lead

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isotope analysis in low Pb content samples and/or high Hg content samples.

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Pb/204Pb isotope ratios determined in different laser ablation sampling

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CONCLUSIONS

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The “wave” signal smoothing and mercury removing device that we developed is

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able to provide smooth signals even at a low laser repetition rate of 1 Hz, which

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makes it well suited for routine optimization of LA-ICP-MS and LA-MC-ICP-MS as

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well as low repetition rate laser ablation analysis. Not only the mercury in the carrier

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gas was effectively removed, but also the mercury in the laser ablation produced

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sample aerosols was significantly removed. This reduction of the mercury signal is

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important for lead isotopes and for U-Pb dating analysis by LA-MC-ICP-MS where

272

low

273

“wave” signal smoothing and mercury removing device has been used successfully

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for lead isotope analysis in low Pb content samples, as well as in high Hg content

275

samples.

204

Hg signals are necessary for precise and accurate analyses. The developed

276 14


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AUTHOR INFORMATION

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*Corresponding Author

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E-mail: [email protected]. Tel.: +86 27 61055600, Fax: +86 27 67885096

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Author Contributions

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The manuscript was written through the contributions of all of the authors. All the

282

authors have given approval to the final version of the manuscript.

283

Notes

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The authors declare no competing financial interest.

285 286

ACKNOWLEDGMENTS

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We thank Klaus Peter Jochum for providing MPI-DING reference glasses.

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Thoughtful comments by Reinhard Niessner and two anonymous referees have

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significantly improved the manuscript. This research is supported by the National

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Nature Science Foundation of China (Grants 41273030, 41322023, and 41373026),

291

the Fundamental Research Funds for National Universities, the CERS-China

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Equipment and Education Resources System (CERS-1-81), the State Administration

293

of the Foreign Experts Affairs of China (B07039), the Opening Foundation of the

294

Beijing SHRIMP Center (National Science and Technology Infrastructure), and the

295

MOST Special Fund from the State Key Laboratory of Geological Processes and

296

Mineral Resources.

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(12) Fricker, M. B.; Kutscher, D.; Aeschlimann, B.; Frommer, J.; Dietiker, R.; Bettmer, J.;

315

Günther, D. Int. J. Mass Spectrom., 2011, 307, 39–45.

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(13) Gurevich, E. L.; Hergenröder, R. J. Anal. At. Spectrom., 2007, 22, 1043–1050.

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(14) Tunheng, A.; Hirata, T. J. Anal. At. Spectrom., 2004, 19, 932–934.

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319

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2012, 99, 1–17. (18) Standish, C.; Dhuime, B.; Chapman, R.; Coath, C.; Hawkesworth, C.; Pike, A. J. Anal. At. Spectrom., 2013, 28(2), 217–225.

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17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

338 339 340

Table 1 Summary of the operating conditions used for LA-ICP-MS measurements. GeoLas Laser ablation system Wavelength

193 nm, Excimer laser

Repetition rate

1, 6, 8 Hz

Pulse length

15 ns

Energy density

5 J cm-2

Spot sizes

44, 60, 90 µm

Ablation cell gas

Helium

Makeup gas

Argon

Agilent 7500a ICP-MS RF power

1350 W

Plasma gas flow rate

14.0 l min-1

Auxiliary gas flow rate

1.0 l min-1

Sampling depth

5.0 mm

Ion optic settings

Typical

Dwell time per isotope

10 ms

Detector mode

Dual

Neptune Plus RF Power

1250 W

Plasma gas flow rate

16.0 l min-1

Auxiliary gas flow rate

0.9 l min-1

Instrument resolution

400 (low)

Block number

1

cycles of each block

200

Integration Time (s)

0.524 s

341 342 343

18


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344

Figure captions

345

Figure 1. Schematic diagram of (a) the “wave” signal smoothing and mercury

346

removing device and (b) the connection position of the smoother (position A or

347

position B) in the LA-ICP-MS system. In position A, only the helium carrier gas

348

flows through the stabilizer. In position B, both the helium carrier gas and the argon

349

makeup gas flow through the stabilizer.

350

Figure 2. Uranium signal profile produced by continuous laser ablation without and

351

with “wave” device in position A (a) and position B (b). Signals were acquired using

352

a repetition rate of 1 Hz and a spot size of 60 µm in NIST 610.

353

Figure 3. Comparison of the aerosol washout time after 50 s of laser ablation without

354

and with the “wave” signal smoothing device at position A (a) and position B (b).

355

Figure 4. Signal intensities of 63 elements obtained with the “wave” signal stabilizer

356

normalized to conditions without the “wave” signal stabilizer by using a laser ablation

357

repetition rate of 6 Hz lasting 50 s with a spot size of 44 µm in NIST SRM 610.

358

Different symbol colors mean different test times.

359

Figure 5. Signal profiles of

360

laser ablation without (a) and with (b) the “wave” signal smoothing device. Signals

361

were acquired using a repetition rate of 6 Hz and a spot size of 44 µm in sulfide

362

standard MASS-1.

363

Figure 6. The relative deviation of the determined

364

standards, sulfide standard MASS-1 and natural sphalerite ZnS-1 from reference

365

values both with and without the “wave” signal smoothing and mercury removing

202

Hg,

204

Hg+204Pb and

206

208

Pb produced by continuous

Pb/204Pb isotope ratios in glass

19



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Page 20 of 26

366

device. Each data point represents one single spot analysis with a spot size of 90 µm.

367

Error bars represent the within-run precision (2σ) for single spot analysis. For glass

368

standards analysis, the

369

counters. For the sulfide standard MASS-1 and natural sphalerite ZnS-1,

370

204

371

from the GeoReM database (http://georem.mpch-mainz.gwdg.de/).

202

Hg and

204

Hg +

204

Pb signals are detected by using ion 202

Hg and

Hg+204Pb were measured using Faraday cups. The reference values used are taken

372 373 374 375 376 377 378 379

20


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380

381 382 383

Figure 1

384

21



400000

without stabilizer

Signal intensity / CPS

(a)

with "wave" stabilizer

300000

200000

100000 Position A 0 0

20

385 386

40 60 Time / s

400000

80

100

without stabilizer

(b) Signal intensity / CPS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 26

with "wave" stabilizer

300000

200000

100000 Position B 0 0

387 388 389 390

20

40 60 Time / s

80

Figure 2

391 392 393 394 395 396 397

22


100

Page 23 of 26

1000000

(a) Signal intensity / CPS

100000

without stabiliz er with "wave" stabilizer

10000 1000 100 10 65

70

75

398

80 Time / s

85

90

95

1000000

(b) 100000 Signal intensity / CPS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


without stabiliz er with "wave" stabilizer

10000 1000 100 10 65

399 400 401 402

70

75

80 Time / s

85

90

Figure 3

23


95


403 1.20 1.10 Normalized signal

1.00 0.90 0.80 0.70 Li Be B Na Mg Al Si P K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Rb Sr Y Zr Nb Mo Rh Ag Cd In Sn Sb Te Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Pt Au Pb Tl Pb Bi Th U

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

404 405

Figure 4

406 407

24


Page 24 of 26

Page 25 of 26

408 10

(a)

Signal intensity / V

1 0.1 0.01

202Hg 204Pb 208Pb

0.001 0.0001 0

20

40 60 Time /s

80

100

20

40 60 Time /s

80

100

409 10

(b)

1 Signal intensity / V

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.1 0.01 0.001 0.0001 0

410 411 412 413 414 415

Figure 5

25



416 4 3

Accuracy (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 26

2 1 0 -1 -2 -3 -4

417 418 419

w i th “wave” signal smoothing and mercury removing device w i thout “wave” signal smoothing and mercury removing device

206Pb/ 204Pb

M L 3 BB- G

B H V OO- 2G

( 1 . 38 ppm) ( 1 . 70 ppm)

N IS T61 4

A H T OO-G

( 2 . 32 ppm) ( 5 . 67 ppm)

S t Hs6/80

T 1-G

M A S SS- 1

Z n S -1

( 1 0 .3 ppm)

( 1 1 .6 ppm)

( 6 7 ppm)

( 8 8 - 410 ppm)

Figure 6

26


Signal-Smoothing and Mercury-Removing Device for Laser Ablation

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