Manual Information

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This user guide is intended for use by scientists and technical staff who have laboratory experience with analytical instrumentation, preparing standards and samples, and data reduction; who have received an introduction and demonstration of the laboratory instrumentation aboard the JOIDES Resolution. Good laboratory practices and attention to laboratory safety are necessary while performing the procedures outlined in this user guide.

The user guide is to be used in conjunction with the Agilent 5100 and 5110 ICP-OES User’s Guide and the ICP Expert Help, both of which provide clear, detailed walkthroughs of instrument setup, operation, maintenance and troubleshooting procedures. Brief procedural videos are accessible through ICP Expert Help which demonstrate proper techniques when dealing with instrument components. The Agilent For Your Safety User’s Guide details additional safety information. Become acquainted with these resources before proceeding through this user guide.

Special Thanks

The JRSO wishes to thank Raymond M. Johnston and Jeff Ryan for their help and advice in fleshing out the solids methodology in this User Guide, as originally presented in the Exp. 366 IODP Proceedings Methods chapter. The JRSO also thanks Hans Brumsack for refining the interstitial water methodology as described on the Exp. 369 IODP Proceedings Methods chapter. The JRSO also thanks all of the many other geochemists who have provided help and advice over the many years of elemental analysis on the JOIDES Resolution.

Introduction and Theory of Operation

Inductively-coupled plasma optical emission spectrometry is a technique used to measure the elemental composition of a material by evaluating characteristic elemental spectra emitted during plasma heating. Dissolved sample flows through an introduction system in which the component molecules are desolvated, atomized and excited within an argon plasma. The transfer of energy from electronic and atomic collisions within the plasma excites elemental valence electrons across various atomic and ionic orbitals, which in turn release characteristic photons during electron de-excitation. Portions of these photons are directed through an optical chamber and ultimately fall upon a diffraction grating where they are reflected at angles determined by their wavelengths, separating them, like a prism, into discrete spectral orders. The photons impinge on an accurately aligned CCD or CMOS detector chip, and thus are mapped to a 2-D pixel array. A given element concentration is determined by locating its spectra within the array (i.e. on the chip), integrating the spectral intensity over a short time interval and comparing the results against a calibration curve of certified reference material.

The Agilent 5110 ICP-OES is used for routine shipboard measurement of interstitial water and hard rock matrices. The Waters method allows for simultaneous determination of major and minor dissolved elements. The Hard Rock method yields elements making up the major oxides, minor elements, and several trace metals that surpass the limits of detection. ICP-OES analytical results are heavily matrix dependent, thus the suite of elemental analytes may be altered on a per expedition basis depending upon the material collected.

Safety Considerations

Before conducting an analysis for the first time, consult the Agilent Technologies Agilent 5100 and 5110 ICP-OES User’s Guide and For Your Safety User’s Guide for a detailed review of safety issues. Listed below is a succinct overview of several important safety issues which are flagged, when appropriate, within the text:

• Ensure there is adequate storage space and ventilation for high-pressure argon gas bottles. Bottles must be secured to a rack, and the racks must be secured to the ship. The steel cap for each bottle must be in place whenever the bottles are not connected to the gas manifold. Use Swagelok Snoop Liquid Leak Detector to ensure proper seals at argon bottle and gas manifold connections.

• Samples and standards are made up in dilute solutions of concentrated nitric acid. Use proper PPE (nitrile gloves and eye protection) when handling acids. Always add acid to water. Be aware of the location of acid spill control and neutralization kits.

• Ensure the fume hood ventilation above the instrument is operational before igniting the plasma.

• The plasma torch is extremely hot during operation (6000 K). Do not handle the torch, RF coil, or other items within the torch compartment until ample time (>5 mins) has been given for the glassware to cool after operation. Wear heat resistant gloves if necessary.

The plasma emits ultraviolet and intense visible light. Ensure the torch compartment door is closed and sealed whenever igniting the plasma. Instrument safety interlocks will extinguish the plasma If the door is opened during operation, however, do not attempt to open the door while the plasma is active.

• Empty the waste container of acid residue after every batch analysis.

In This User Guide

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Apparatus, Reagents and Materials

Hardware

The complete Agilent 5110 ICP-OES system includes:

• Agilent 5110 Single View/Dual-View (SVDV) ICP-OES system equipped with the Automatic Valve Switching (AVS 6/7) option

• Agilent SPS4 4-rack autosampler

• Agilent G8481A Recirculating Chiller

• Mettler Toledo XS204 motion-compensated dual balance system

• Cahn Microbalance motion-compensated dual balance system

• Barnstead Reverse Osmosis Water Purification System

• Burrell Wrist-Action Shaker

• Thermolyne Muffle Furnace
  
  

Consumables

Reagents

• Reagent Water: 18 MΩ deionized water

• Sodium Chloride: Trace metal clean

• Nitric Acid (HNO₃): Trace metal grade, 70% concentrated. Warning: Always add acid to water.

• Element Stock Solutions: Certified 1000 ppm: Al, Ba, Ca, Co, Cr, Cu, Fe, Ge, K, Mg, Mn, Na, Nb, Ni, P, Sc, Si, Sr, Ti, V, Y, Zn, Zr

• Element Internal Standards: Certified 1000 ppm: Be, In, Sb, Sc, Y

• Argon Gas: Ultra high purity (UHP) grade

• IAPSO standard seawater is produced to have a specific conductivity, K₁₅, referenced to a known concentration of KCl at 15°C. It has been shown by Bacon et al. (2007) to be extremely consistent and stable over a reasonable period of time. It is assumed within this method that the concentration of the constituents in IAPSO standard seawater is, for all intents and purposes, the same as that of standard reference seawater. Using the numbers found in Millero (2008), substituting the averaged value for Gieskes (1991) and Summerhayes (1996) for lithium and alkalinity, the working concentrations are therefore:
  
  

1. The molarity values in this table except for Gieskes et al. (1991) were calculated from the g/kg values in the reference using the density of standard seawater at 15°C (1.025 kg/L) in order to match the standardized K₁₅ value for IAPSO seawater. 2. Gieskes et al. (1991) already given in terms of molarity. 3. Summerhayes et al. (1996); also quoted by the OSIL website as their reference for IAPSO constituents. 4. Pilson (1998). 5. Millero et al. (2008). N/A = not available from this author.

Methods for Preparation of Standards

Preparing Interstitial Water Standards

Preparing Reagents at the Start of Expedition

Prepare the following reagents at the beginning of an expedition and afterwards on an as-needed basis. For the relevant reagents listed below, the lithium carbonate (Li₂CO₃) is an optional addition.

• Internal Standards:

  • Interstitial Waters: 100 ppm Be, In, Sc, 200 ppm Sb: Add 10 mL of each Be, In, Sc and 20 mL Sb elemental reference standards (1000 ppm) to a 100 mL volumetric flask, make up with 2% trace metal clean nitric acid. 100 mL is enough for 1000 samples

  • Hardrock/Sediment: Same as the interstitial waters internal standard except no scandium (Sc) is added as it is present in rock/sediment matrices.

  • Acidified Synthetic Seawater: 35 g trace metal clean NaCl + 29 mL concentrated trace metal HNO₃ made up to 1 L with MQ water.

  • Nitric Acid Solutions: Add 14.3 mL of concentrated trace metal HNO₃ per 1 L of MQ water for each percentage point increase in concentration of acid solution (v/v), e.g. 1% HNO₃: 14.3 mL, 2%: 28.6 mL, 3%: 43 mL HNO₃. Warning: Always add acid to water.

    • Rinse Solutions: Make 5-10 L at a time.

      • Interstitial waters: 3% nitric (Use trace metal nitric acid)

      • Hardrock/sediment: 10% nitric (Use trace metal nitric acid)

• Matrix:

  • Interstitial waters: 2% trace metal nitric

  • Hardrock/sediment: 10% trace metal nitric, Optional: 53.25 g of ultrapure Li₂CO₃ may be added as an ionization buffer. Ensure the Li₂CO₃ is fully dissolved

Preparing the Calibration Standards

The calibration standards follow a matrix-matched internal standard approach that spans the range of expected concentrations of the pore water analytes. The recipe may need to be adjusted on a case-by-case basis. For the Interstitial Waters Method, two batches of standards must be prepared—a serial dilution of an in-house elemental cocktail and a serial dilution of IAPSO Seawater.

Preparing and Measuring Major Cation Salt Solutions:

Frequently, dissolved major cations increasing downhole surpass the upper bound of IAPSO concentrations and the certified 1000 ppm standards at working dilutions. These elements may be constrained within calibration curves by increasing the dynamic range of the calibration solutions with major cation salt doping. Primary salt solutions are prepared and concentrations are determined by ICP once at the beginning of an expedition and carried through further standard cocktails. There is no need to heat salts in the oven to desiccate. Note: magnesium chloride hexahydrate decomposes to magnesium tetrahydrate at 116.6°C:

• 1% Potassium: Make up 1.94 g of potassium chloride (KCl, 74.5513 g/mol) in 100 mL MQ water

• 1% Magnesium: Make up 9.13 g of magnesium chloride hexahydrate (MgCl₂H₁₂O₆, 203.31 g/mol) in 100 mL MQ water

• 1% Calcium: Make up 3.8 g of calcium chloride dihydrate ( CaCl₂H₄O₂, 147.008 g/mol) in 100 mL MQ water

• 3.5% NaCl: Acidified Synthetic Seawater reagent

Measure each solution against certified reference standards to acquire accurate concentrations for further standard dilutions.

• Working salt solutions: Pipette 1 mL of each 1% K, Mg, and Ca salt solution, and 286 µL of 3.5% NaCL into a single 100 mL volumetric flask and make up with 2% trace metal HNO₃. With this solution, prepare 5-7 replicates of a 1:10 dilution (1 mL solution + 9 mL 2% HNO₃) to be run by ICP. Vortex mix the aliquots. Each yields roughly a 10 ppm solution containing each major cation.

• Primary Certified Standard: Pipette 5 mL of each the 1000 ppm Ca, K, Mg, and Na standards into a 50 mL volumetric flask and make up with 2% trace metal HNO₃.

Make up 6 calibration standards according to the following scheme:

Use the template IODP_STANDARD_SALTSOLUTIONS_TEMPLATE to evaluate the 5-7 replicates against the above calibration standards. For each wavelength used, average the concentrations for the 5-7 replicates. Multiply the Ca, K, and Mg concentrations by a factor of 1000, and Na by a factor of 3500 to give the original 1% salt concentrations in ppm. In judging each element’s concentration, average all samples across all wavelengths after removing any erroneous/problematic lines. To start this analysis follow the steps given in Performing an ICP-OES Analysis. Adjust and update the concentrations of Na, Mg, Ca, and K listed in Table 1 to reflect the values measured in the 1% salt solutions.

Preparing Interstitial Water Working Standards:

Prepare a primary cocktail standard according to the recipe shown in columns 2 and 3 of Table 1. Pipette all individual standards into a single 100 mL volumetric flask and bring to volume with 2% trace metal HNO₃. Na, Mg, Ca, and K values are from the major salt solutions which are determined in the preceding step, the remaining standards are 1000 ppm SPEX CertiPrep reference standards.

Table 1: Recipes of the primary cocktail and IAPSO (highlighted in blue) used to create working standards, and final concentrations of the working standards. Serially dilute the in-house cocktail and IAPSO according to the scheme given in Table 2. Na, Mg, Ca, and K are from the major salt solutions. Adjust concentrations accordingly. Iron and manganese values were excluded from IAPSO due to their low concentrations, and barium due to its precipitation with sulfate. Be wary of silicon concentrations in IAPSO due to its storage in glass containers.