Rapid determination of soluble reactive silicate in seawater by flow injection analysis with spectrophotometric detection and its application

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1 Acta Scientiae Circumstantiae Vol 31 No 5 May J Huang Y M Yuan D X Peng Y Z et al 2011 Rapid determination of soluble reactive silicate in seawater by flow injection analysis with spectrophotometric detection and its application J Acta Scientiae Circumstantiae * μmol L ~ μmol L % ~ 109 3% min 11 7 μmol L - 1 RSD 1 6% n = X131 2 A Rapid determination of soluble reactive silicate in seawater by flow injection analysis with spectrophotometric detection and its application HUANG Yongming YUAN Dongxing * PENG Yuanzhen LIU Chengyu State Key Laboratory of Marine Environmental Science Environmental Science Research Center Xiamen University Xiamen Received 2 August 2010 received in revised form 13 September 2010 accepted 13 September 2010 Abstract A new flow injection analysis method for rapid determination of soluble reactive silicate in seawater is established based on the reaction of silicate with ammonium molybdate to form a yellow silicomolybdate complex and further reduction to silicomolybdenum blue by ascorbic acid Under the optimum conditions the detection limit was 0 5 μmol L - 1 the linear and recovery ranges for real seawater samples were 2 5 ~ μmol L - 1 and 103 6% ~ 109 3% respectively Only 4 5 min was needed to analyze one sample in triplicate The relative standard deviation RSD was 1 6% n = 12 for seawater samples obtained from the South China Sea with a silicate concentration of 11 7 mol L - 1 The proposed method is simple fast requires little sample and showed no interference from salinity > 14 The method was successfully applied to measure the soluble reactive silicate in seawater samples in Xiamen's Western Harbor Keywords flow injection analysis soluble reactive silicate silicomolybdenum blue seawater 1 Introduction ~ 0 5 μm No 2007AA Supported by the National High Technology Research and Development Program of China No 2007AA yongminghuang@ xmu edu cn * yuandx@ xmu edu cn Biography HUANG Yongming 1984 male yongminghuang@ xmu edu cn * Corresponding author yuandx@ xmu edu cn

2 Experimental FIA mm 723PC 2 cm U HH V /V 10 min 2005 Milli-Q Milli-Q Millipore 1L 100 mg SiO mol L Amornthammarong and Zhang 2009 ml 1 L 8 35 g NH 4 6 Mo 7 O 24 4H 2 O 1 L 0 2 mol L g L g L - 1 Amornthammarong and Zhang 2009 Chen et al Huang et al 2009 Ma et al 2009 FIA 812 nm FIA - 1 MC1 MC2 MC ml min mL min μL Fig 1 1 Flow injection analysis manifold for rapid determination of soluble reactive silicate in seawater

3 μm 7 0 g L g L μl MC1 ml min MC2 MC3 3a U 0 2 mol L Ma et al 2009 MAGIC 1 mol L - 1 NaOH h 3b 30 μmol L μmol L g L KK E N 125 m PVC 250 ml 3c 24 h 4 g L - 1 Fig 2 2 Sampling stations in Xiamen's Western Harbor 3 Result analysis g L ~ 700 μl 3d 600 μl 600 μl MC1 MC2 1 m MC3 2 5 m

4 ml min ml min - 1 Fig 3 3 Results of optimization experiments ~ 65 3e 3e 0 5 ~ 15 nmol L ~ 65 nmol L

5 5-939 μmol L μmol L μmol L μmol L ~ 200 μmol L g L g L E N E N % ~ 109 2% Table 1 1 n = 3 Determination of seawater sample and recovery tests n = 3 / / μmol L - 1 μmol L ± Fig ± % ± 0 5% Effect of oxalic acid concentration on eliminating the ± % ± 0 3% interference of phosphate ± ~ ± % ± 0 2% 20 μmol L Schlieren % 14 2 Table 2 Comparison of the proposed method with the standard siliconmolybdenum yellow method for determination of seawater ~ μmol L - 1 A = C Si C Si μmol L n = 7 R 2 = 11 7 μmol L - 1 RSD 1 6% n = SD ~ 98 2 μmol L samples C Si ± SD n = 3 / μmol L - 1 t P = 95% ± ± ± ± 0 4

6 Table 3 3 n = 3 Press 193 in Chinese Concentrations of soluble reactive silicate in surface seawater in Xiamen's Western Harbor n = 3 / μmol L - 1 S ± 0 1 S ± 0 2 S ± 0 3 S ± 0 1 S ± 0 2 S ± 0 2 S ± 0 2 S ± Conclusions 1 - Ma J Yuan D X Zhang M n = detection J min 3 h μmol L ~ μmol L - 1 seawater silicate J 11 7 μmol L in Chinese RSD 1 6% J 3 analysis J in Chinese yuandx@ xmu edu cn References Amornthammarong N Zhang J Z 2009 Liquid-waveguide spectrophotometric measurement of low silicate in natural waters J Talanta Chen G H Yuan D X Huang Y M et al 2008 In-field determination of nanomolar nitrite in seawater using a sequential injection technique combined with solid phase enrichment and colorimetric detection J Analytica Chimica Acta M 193 Chen G Z 1965 Seawater Analytical Chemistry M Beijing Science 1999 M 3-15 Fang Z L 1999 Flow Injection Analysis M Beijing Science Press 3-15 in Chinese 2008 GB S National Marine Environmental Monitoring Center 2008 GB The specification for marine monitoring Part 4 Seawater analysis S Beijing Standards Press of China in Chinese 1997 M Guo J B 1997 Chemical Oceanography M Xiamen Xiamen University Press in Chinese Huang Y M Yuan D X Ma J et al 2009 Rapid speciation of trace iron in rainwater by reverse flow injection analysis coupled to a long path length liquid waveguide capillary cell and spectrophotometric detection J Microchimica Acta et al 2009 Reverse flow injection analysis of nanomolar soluble reactive phosphorus in seawater with a long path length liquid waveguide capillary cell and spectrophotometric Talanta J Pan W J Shao M H Xu Z Z et al 2006 Study on fast monitoring of Journal of Dalian Maritime University Peng Y Z Zhang M Ma J et al 2009 Determination of trace silicate in water for semiconductor industry by flow injection automatic Chinese Journal of Analytical Chemistry J Wang N Yuan Z C Li Z F et al 2005 Chemical technique optimization for determination of seawater silicate with ascorbic acid as the reducing agent J Ocean Technology in Chinese 2008 J Yang D F Yu Z J Zhang K et al 2008 The limitation of nutrient silicon for phytoplankton growth in the global marine areas J Marine Environmental Science in Chinese 2003 J Yuan Z C Du J L Zou C S et al 2003 Chemical technique optimization of seawater silicate in-situ autonomous monitoring technology J Ocean Technology in Chinese