Signal-Smoothing and Mercury-Removing Device for Laser Ablation

Dec 16, 2014 - The Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 102206, People's Republic of. China...
0 downloads 0 Views 613KB Size
Subscriber access provided by UZH Hauptbibliothek / Zentralbibliothek Zuerich

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

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 26

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

Analytical Chemistry

1

A novel “wave” signal smoothing and mercury

2

removing device for laser ablation quadrupole and

3

multiple collector ICP-MS analysis: application to

4

lead isotope analysis

5 6

†,‡

Zhaochu Hu









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

9



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

12 13 14 15 16 17

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

zchu@vip.sina.com

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

18 19 20 21



Chen , and Shenghong Hu

8

11





7

10



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

Submitted to Analytical Chemistry 1

ACS Paragon Plus Environment

Analytical Chemistry

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

22

For TOC only

23

24 25 26 27

2

ACS Paragon Plus Environment

Page 2 of 26

Page 3 of 26

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

Analytical Chemistry

28

ABSTRACT:

29

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

30

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

31

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

32

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

33

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

34

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

35

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

36

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

37

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

38

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

39

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

40

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

41

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

42

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

43

the

44

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

45

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

46

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

47

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

48

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

49

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

202

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

3

ACS Paragon Plus Environment

Analytical Chemistry

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

50

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

51

mercury removing device was applied successfully to the determination of the

52

206

53

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

54

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

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

55 56

4

ACS Paragon Plus Environment

Page 4 of 26

Page 5 of 26

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

Analytical Chemistry

57

INTRODUCTION

58

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

59

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

60

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

61

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

62

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

63

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

64

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

65

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

66

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

67

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

68

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

69

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

70

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

71

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

72

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

73

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

74

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

75

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

76

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

77

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

78

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

ACS Paragon Plus Environment

Analytical Chemistry

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 6 of 26

79

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

80

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

81

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

82

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

83

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

84

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

85

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

86

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

87

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

88

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

89

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

90

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

91

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

92

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

93

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

94

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

95

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

96

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

97

design of the signal smoothing device.

98

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

99

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

100

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

ACS Paragon Plus Environment

204

Pb

Page 7 of 26

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

Analytical Chemistry

204

101

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

102

can produce a large uncertainty in signal intensities for radiogenic

103

components.21 Precise determination of the signal intensity of

104

important. However,

105

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

106

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

107

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

108

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

109

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

110

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

111

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

112

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

113

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

114

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

115

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

116

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

117

dating analysis is also highly desirable.

204

207

Pb intensity

Pb and

206

Pb

Pb is thus highly

204

Pb has the lowest isotopic abundance and share an isobaric

118

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

119

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

120

signal smoothing and mercury removing device was evaluated based on signal

121

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

122

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

ACS Paragon Plus Environment

Analytical Chemistry

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

123

laser ablation MC-ICP-MS.

124 125

EXPERIMENTS

126

Instrumentation.

127

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

128

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

129

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

130

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

131

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

132

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

133

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

134

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

135

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

136

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

137

of the instrumental operating conditions and measurement parameters are summarized

138

in Table 1.

139 140

“Wave” signal smoothing and mercury removing device.

141

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

142

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

143

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

144

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

ACS Paragon Plus Environment

Page 8 of 26

Page 9 of 26

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

Analytical Chemistry

145

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

146

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

147

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

148

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

149

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

150

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

151

the stabilizer.

152

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

153

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

154

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

155

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

156

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

157 158

RESULTS AND DISCUSSION

159

Effect on signal stability.

160

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

161

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

162

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

163

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

164

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

165

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

166

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

ACS Paragon Plus Environment

Analytical Chemistry

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

167

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

168

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

169

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

170

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

171

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

172

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

173

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

174

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

175

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

176

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

177

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

178

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

179

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

180

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

181

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

182

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

183

Ar).

184 185

Effect on washout time.

186

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

187

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

188

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

ACS Paragon Plus Environment

Page 10 of 26

Page 11 of 26

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

Analytical Chemistry

189

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

190

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

191

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

192

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

193

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

194

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

195

important advantage for our designed “wave” signal stabilizer.

196 197

Effect on signal intensity.

198

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

199

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

200

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

201

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

202

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

203

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

204

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

205

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

206

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

207

111

208

66

209

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

210

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

Cd,

Zn,

121

111

Sb and 126Te and

Cd,

121

195

66

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

ACS Paragon Plus Environment

Analytical Chemistry

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 12 of 26

211

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

212

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

213

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

214

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

215 216 217

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

202

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

218

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

219

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

220

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

221

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

222

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

223

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

224

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

225

A reduction factor of 366 for the

226

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

227

aerosol particles. In contrast, the signal intensity of

228

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

229

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

230

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

231

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

232

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

202

Hg signal was obtained. This result suggests that

208

Pb is similar for both with and

12

ACS Paragon Plus Environment

Page 13 of 26

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

Analytical Chemistry

233

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

234

investigation.

235 236

Application to lead isotope analysis.

237

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

238

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

239

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

240

isobaric interference of

241

the main problems in obtaining the high precision measurements of the

242

206/207/208

243

the determined

244

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

245

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

246

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

247

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

248

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

249

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

250

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

251

determined

252

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

253

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

254

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

204

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

ACS Paragon Plus Environment

Analytical Chemistry

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

255

206

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

256

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

257

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

258

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

259

device, the

260

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

261

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

262

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

206

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

263 264

CONCLUSIONS

265

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

266

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

267

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

268

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

269

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

270

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

271

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

274

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

ACS Paragon Plus Environment

Page 14 of 26

Page 15 of 26

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

Analytical Chemistry

277

AUTHOR INFORMATION

278

*Corresponding Author

279

E-mail: zchu@vip.sina.com. Tel.: +86 27 61055600, Fax: +86 27 67885096

280

Author Contributions

281

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

284

The authors declare no competing financial interest.

285 286

ACKNOWLEDGMENTS

287

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

288

Thoughtful comments by Reinhard Niessner and two anonymous referees have

289

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

290

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

291

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

292

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.

297

15

ACS Paragon Plus Environment

Analytical Chemistry

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

298

REFERENCES

299

(1) Russo, R. E.; Mao, X. L.; Liu, H. C.; Gonzalez J.; Mao, S. S. Talanta, 2002, 57, 425–451.

300

(2) Günther D.; Hattendorf, B. TrAC, Trends Anal. Chem., 2005, 24, 255–265.

301

(3) Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J. Chem. Geol., 2012, 330–331, 260–273.

302

(4) Orellana, F. A.; Gálvez, C. G.; Orellana, F. A.; Gálvez, C. G.; Roldán, M. T.; García-Ruiz, C.;

303

Roldán, M. T.; García-Ruiz, C. TrAC, Trends Anal. Chem., 2013, 42, 1–34.

304

(5) Bleiner, D.; Günther, D. J. Anal. At. Spectrom., 2001, 16, 449–456.

305

(6) Hu, Z. C.; Liu, Y. S.; Gao, S.; Xiao, S. Q.; Zhao, L. S., Günther, D.; Li, M.; Zhang, W.; Zong,

306

K. Q. Spectrochimica Acta Part B, 2012, 78, 50–57.

307

(7) Cottle, J. M.; Horstwood, M. S. A.; Parrish, R. R. J. Anal. At. Spectrom., 2009, 24, 1355–1363.

308

(8) Mank, A. J. G.; Mason, P. R. D.; J. Anal. At. Spectrom., 1999, 14, 1143–1153.

309

(9) Schilling, G. D.; Andrade, F. J.; Barnes, J. H.; Sperline, R. P.; Denton, M. B.; Barinaga, C.J.;

310 311 312

Koppenaal, D. W.; Hieftje, G. M. Anal. Chem., 2007, 79, 7662–7668. (10) Liu, Y. S.; Hu, Z. C.; Yuan, H. L.; Hu, S. H.; Chen, H. H. J. Anal. At. Spectrom., 2007, 22, 582–585.

313

(11) Müller, W.; Shelley, M.; Miller, P.; Broude, S. J. Anal. At. Spectrom., 2009, 24, 209–214.

314

(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.

316

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

317

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

318

(15) Woodhead, J.; Hergt, J.; Meffre, S.; Large, R. R.; Danyushevsky, L.; Gilbert, S. Chem. Geol.,

319

2009, 262(3–4), 344–354. 16

ACS Paragon Plus Environment

Page 16 of 26

Page 17 of 26

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

Analytical Chemistry

320

(16) Souders, A. K.; Sylvester, P. J. J. Anal. At. Spectrom., 2010, 25(7), 975–988.

321

(17) Darling, J. R.; Storey, C. D.; Hawkesworth, C. J.; Lightfoot, P. C. Geochim. Cosmochim. Acta,

322 323 324

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.

325

(19) Hirata, T.; Nesbitt, R. W. Geochim. Cosmochim. Acta, 1995, 59, 2491–2500.

326

(20) Jackson, S. E.; Pearson, N. J.; Griffin, W. L.; Belousova, E. A. Chem. Geol., 2004, 211,

327

47–69.

328

(21) Hirata, T.; Iizuka, T.; Orihashi, Y. J. Anal. At. Spectrom., 2005, 20, 696–701.

329

(22) Zhang, L.; Ren, Z. Y.; Nichols, A. R. L.; Zhang, Y. H.; Zhang, Y.; Qian, S. P.; Liu, J. Q. J.

330

Anal. At. Spectrom., 2014, 29, 1393–1405.

331

(23) Eggins, S.M.; Shelley, J.M.G.; Geostand. Newslett., 2002, 26, 269–286.

332

(24) Hu, Z. C., Liu,Y. S., Li, M., Gao, S.; Zhao, L.S.; Geostand. Geoanal. Res., 2009, 33,

333

319–335.

334 335 336 337

17

ACS Paragon Plus Environment

Analytical Chemistry

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

ACS Paragon Plus Environment

Page 18 of 26

Page 19 of 26

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

Analytical Chemistry

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

ACS Paragon Plus Environment

Analytical Chemistry

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 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

ACS Paragon Plus Environment

Page 21 of 26

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

Analytical Chemistry

380

381 382 383

Figure 1

384

21

ACS Paragon Plus Environment

Analytical Chemistry

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

ACS Paragon Plus Environment

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

Analytical Chemistry

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

ACS Paragon Plus Environment

95

Analytical Chemistry

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

ACS Paragon Plus Environment

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

Analytical Chemistry

0.1 0.01 0.001 0.0001 0

410 411 412 413 414 415

Figure 5

25

ACS Paragon Plus Environment

Analytical Chemistry

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

ACS Paragon Plus Environment