Trace Element Analysis via ICP-OES using the Agilent 5800

1. Introduction
This standard operating procedure (SOP) describes a procedure for analysis of samples by inductively coupled plasma-optical emission spectrometry using the Agilent 5800.

Inductively coupled plasma optical emission spectroscopy (ICP-OES), sometimes also referred to as inductively coupled plasma atomic emission spectroscopy (ICP-AES), uses the energy from an inductively coupled plasma to promote an electron of atoms and ions within the sample to a higher energy level (= excitation). When the excited electron falls back to the ground state, light is emitted at specific wavelengths. These wavelengths are characteristic to the type of element and the light emission is proportional to the elemental concentration, allowing us to accurately measure concentrations of trace elements within a sample.

2. Scope
This procedure may be applied to any digested organic sample that is amenable to analysis by inductively coupled plasma-optical emission spectrometry. This includes several commodities like coffee, soy and cocoa beans.

3. Materials

Chemical/Solution Description Storage Location
Sample Digested organic sample of commodity that will be analyzed /
Water Millipore grade or equivalent Room 218b “Main lab”, A17
Diluted HNO3 solution (5%) Diluted Nitric Acid solution (5% or ±0.8 M) made from Nitric Acid Stock solution (65% or 10.3M), used for general cleaning, diluting and measurement blancs. Room 227 ‘’Stock room’’, D2
Element Stock (ES), ES Diluted 10x and ES Diluted 100x The Element Stock (ES) consists of a 1:1 mix of a Standard Multi-element Stock (33 elements) from Agilent and MilliQ water. This ES is also diluted 10x and 100x with a 5% HNO3 solution Room 227 ‘’Stock room’’, D2

4. Equipment

Equipment Description Storage Location
PPE Personal Protective Equipment, which includes safety glasses, a laboratory coat and nitrile gloves Room 218b ‘Main lab’’
ICP-OES Analyzer An Agilent 5800 ICP-OES analyzer by Agilent Technologies (Figure 1 left and top right) with semi-demountable torch (Figure 1 bottom right) Room 221 “FA Room’’, H8
Autosampler An Agilent SPS 4 Autosampler to facilitate sample introduction to the Agilent 5800 ICP-OES analyzer Room 221 “FA Room’’, H8

Figure 1: Functional components of the Agilent 5800 (left), input and output connections on the side of the ICP-OES instrument (top right) and semi-demountable torch with 1. Torch, 2. Top seal and 3. Torch body (bottom right)

5. Safety

5.1 H/P phrases for Ozone
Ozone can be generated by radiation from the light source lamps. Always ventilate the area surrounding the instrument such that the concentration of ozone does not exceed the maximum permissible level. All venting must be to outside air, never within the building.

5.2 Safety Summary: Ozone

5.3 H/P phrases for HNO3 (5%)

5.4 Safety Summary: HNO3 (5%)
Inhalation
- Corrosive to the respiratory tract
\=> Work in fume hood
Skin
- Causes severe skin burns
\=> Wear laboratory coat and safety gloves (nitrile)
Eyes
- Causes serious eye damage
\=> Wear safety glasses
Fire
- Oxidizer
\=> Keep away from heat sources
! Keep a neutralizing agent (Chemizorb or NaHCO3) nearby in case of accidental spills

5.5 Before starting analysis

5.5.1 Checklist

5.6 During analysis

5.6.1 General safety precautions

5.6.2 Indicator light

6. Analysis
If the semi-demountable torch has recently been cleaned and needs to be reinstalled, refer to Appendix I. If running an experiment for the first time or from shutdown, refer to Appendix II. To perform a dark current scan and wavelength calibration, refer to Appendix III.

6.1 Preparing the ICP-OES instrument
from standby1

1) Turn on the laboratory exhaust system (usually already turned on)
2) Check that the torch is clean and in good condition and installed with the torch handle fully closed
3) Check if the autosampler is connected to an Erlenmeyer with 5% HNO3 solution for washing. If the Erlenmeyer is empty, make new 5% solution according to Appendix IV
4) Check that all tubing on the spray chamber, nebulizer, peristaltic pump and autosampler is correctly connected (Figure 2)

Figure 2: Tubing of the Agilent 5800 with blue \= outlet and white \= inlet (left), tubing of the autosampler (right)

Tubes might slip loose if not attached correctly, causing major spills (Figure 3). If this issue persists, even after reattaching the tubes, you might consider wrapping a small piece of parafilm foil over the tubes so they don’t slip

Figure 3: Major spills of sample after incorrect attachment of tubing

5) Check that the torch compartment door is fully closed
6) Switch on the monitor and printer (if they are off)
7) Switch on the water chiller (if it is off)
8) If you have accessories fitted (like the autosampler), switch them on
9) Start the ICP Expert software. If the ICP Expert software needs to be reconnected to the ICP-OES, refer to Appendix V
10) To create a worksheet and develop a new method, refer to Appendix VI. To start from an existing worksheet, click on “New from” and select the existing worksheet you want to start from
11) Choose “Plasma on” from the arrow under the “Plasma” button
12) Ensure that the peristaltic pump is correctly set up. If you have not already done so, adjust the pressure bars on the peristaltic pump for even sample flow and drainage
13) Place the sample tubing from the peristaltic pump into the rinse solution (white) and the drain tubing (blue) into the drainage vessel
14) Click the “Pump” button in the ICP Expert software and choose “Normal” (15 rpm) from the arrow under the “Pump” button. The pump will be initialized and the solution will begin aspirating

6.2 Running the samples

1) Set up the autosampler with all solutions, if required
2) Click the “Analysis” tab
3) Ensure your samples are selected. This will be indicated by a check next to the “Rack:Tube” column. To select all solutions, select the checkbox next to the “Rack:Tube” title (Figure 4)

Figure 4: Selected samples in Rack:Tube column

4) Click the “Run” icon in the toolbar to begin the analysis, and follow the prompts
5) When the run is finished, remove the sample from the instrument room as soon as they are analyzed to prevent corrosion of instrument parts

6.3 Reporting results

1) To save the entire run, click ‘’File’’ > ’’Save as’’
2) To export results into a CSV file, click ‘’File’’ > ‘’LIMS’’ > ‘’Export’’

6.4 Turning off the instrument
Standby Mode with argon on2

1) The exhaust system MUST remain on if the gas supplies are on
2) Rinse the spray chamber by aspirating water for a few minutes
3) Extinguish the plasma by clicking the “Plasma Off” icon or choosing “Plasma Off” from the Analyze menu. The peristaltic pump stops automatically when the plasma is extinguished
4) Turn off the polychromator boost overnight, by deselecting Polychromator > Boost on the “Status” tab on “Instrument window”
5) To increase the pump tubing lifetime, loosen the peristaltic pump tubes by releasing the pressure bars and lift the tubes out of the grooves. Do this by pushing up the pressure bar screws (Figure 5). Allow the pressure bar to swing downwards and lift the tubing out of the grooves

Figure 5: Peristaltic pump with pressure bar screws pushed up and pressure bar freely down, allowing tubing to be loosened

6) Turn off the water chiller
7) Close the worksheet by clicking “Close” from the File menu but leave the ICP Expert software running. You may switch off the printer, monitor and any accessories if desired

Standby Mode with argon off3

1) Follow Steps a)-c) of the “Standby Mode with argon on’’ procedure
2) Turn off the argon gas supply
3) Follow Steps d)-f) of the “Standby Mode with argon on’’ procedure

Full shutdown4

1) Follow Steps a)-f) of the “Standby Mode” procedure
2) Switch off any accessories (where applicable), and then shut down the argon gas supply at the cylinder
3) Switch off the power at the front lower left of the instrument
4) Wait for the front power on/off switch green LED to stop blinking and then switch off the mains power switch on the left side of the instrument. This will turn off the complete instrument as well as the polychromator thermostatting system
5) Turn off the laboratory exhaust system
6) Exit the ICP Expert software, if it is no longer required, by choosing “Exit” from the File menu. Switch off the printer and monitor

7. Cleaning
Open the ‘Instrument’ Window and click on the ‘Maintenance’ Tab to follow the progress of maintenance and cleaning (Figure 6)

Figure 6: Window to follow progress on cleaning and maintenance tasks

Any spills in the sample compartment should be wiped up immediately. Clean the outside of the instrument with a soft, lint-free, cloth slightly dampened with pure water (do not use detergent or chemical solvents ) if contaminated. Clean the sample racks (autoclavable!) if contaminated Clean working area at the end of each day
Clean the torch 5 weekly or as soon as any discoloration appears on the outer tube of the torch. Do not use cleaning wire or abrasives like brushes or a scourer to clean the torch. Torch has to be dry before you use it again
Clean the nebulizer after every 1000 solutions measured Clean the spray chamber after every 2000 solutions measured
Remove and clean the water filter on the right side of the instrument annually (every 180 days)

8 Maintenance

Check and, if necessary, empty the drain vessel every hour
Inspect the condition and cleanliness of the torch daily Check exhaust system daily Inspect the torch daily for injector blockage or other damage Check the nebulizer daily for blockage or pulsation during operation Inspect the pump tubing daily and replace if it is flat or has lost its elasticity Complete a visual check of the spray chamber daily to confirm that all connections are not leaking and secure, and that the waste is draining correctly Check argon gas pressure daily
Replace peristaltic pump tubing weekly (=every 40 hours that the plasma is ignited) Inspect cone (axial) or snout (radial) weekly. Clean if required. Check the other sample introduction tubing and O-rings weekly
Check the condition of the filter in the air inlet on top of your instrument monthly. Remove the air inlet filter assembly and replace the filter element if there is a build-up of dust and dirt. Check the water level in the water chiller monthly Check/clean the heat exchanger (radiator) on the chiller monthly to remove any buildup of dust and dirt. Inspect the external gas supply system monthly for leaks including the tubing connected to the instrument, and stress cracks. Replace any damaged, leaking or worn components. Check the other sample introduction and transfer tubing and O-rings monthly. Look for excessive wear, poor sealing or kinks and replace as necessary. Inspect the removable axial and radial pre-optics windows for cleanliness monthly. Clean or replace as necessary. Perform a wavelength calibration monthly.
Drain and replace chiller coolant annually Drain the coolant from the cooling system annually and refill/ treat with an appropriate algaecide. Replace the argon purge gas filter annually

9. Waste disposal

10. Appendices

I. (Re-)assembly of the semi-demountable torch

1) Place the top seal back on the quartz tube-set, slide the clean seal back onto the tube-set from the bottom end, making sure the top flat face of the seal is positioned facing the top of the tube-set (Figure 7)

Figure 7: The top seal being refitted to the quartz outer tube-set

2) Slide the top seal approximately 1/3 the way up the quartz tube-set and position it so the top face of the seal is aligned with the bottom of the “T” alignment mark as shown in Figure 8

Figure 8: The top seal aligned with the alignment mark on the quartz outer tube

3) Gently slide the quartz tube-set into the torch body, avoiding contact with the injector as shown in Figure 9

Figure 9: Torch inserted into torch body

4) Position the quartz tube-set so that the groove on the torch body aligns with the “T” alignment mark on the quartz tube-set as shown in Figure 10

Figure 10: The alignment mark on the quartz outer tube-set should be aligned with the groove on the torch body

5) Press the quartz outer tube-set fully into the torch body and then press down on the top seal to secure the tube-set in place. See Figure 11

Figure 11: Ensure the seal is properly seated by pressing firmly on the top edges

II. Preparing the instrument for the first time or from shutdown6

1) Check that the exhaust and External Inlet Duct Adapter (if used) lines are secured to the ICP-OES instrument, and that the air filter is not blocked
2) Turn on the laboratory exhaust system
3) Ensure the gas and water lines are connected to the ICP-OES instrument
4) Turn on the gas supply
5) Switch on the water chiller
6) Ensure that the gas and water supplies are turned on and set to the correct pressures, and that the water chiller is set to the correct temperature
7) Check that the torch is clean and in good condition and installed with the torch handle fully closed
8) Check that all tubing on the spray chamber, nebulizer and peristaltic pump is installed and correctly connected
9) Check that the plasma compartment door is fully closed
10) Check that the Ethernet LAN cable is connected to the computer or Local Area Network
11) Switch on the computer, monitor and printer
12) Plug the ICP-OES cable into the wall socket and set the mains power switch on the left side of the instrument to ‘On’
13) Press the Power on/off button on the front of the instrument. The power on/off LED will display green when it is on. The ICP-OES is now in standby state, which continually purges and thermostatically controls the polychromator
14) Double-click the ICP Expert desktop icon to start the ICP Expert software. The Start page will appear

III. Performing a dark current scan and wavelength calibration

1) Turn on the external exhaust
2) Open the Instrument Window in the ICP Expert software
3) Connect the software to the instrument, if needed ( see 7.3.?)
4) Click “Calibrate” in the ‘Detector’ section. Once the detector calibration is completed, the date and time of the last successful calibration will be displayed, confirming the detector measurement has been completed.
5) Ensure a standard glass concentric nebulizer, a double pass spray chamber and the appropriate plasma torch (for radial or dual view) are installed. Use manual sampling. The recommended peristaltic pump tubing is White/White for the pump and Blue/Blue for the drain
6) Ignite the plasma
7) Check that the Polychromator Boost purge is on:

On the ‘Instrument’ window of the ICP Expert software, click the “Status” tab and check that under the Polychromator section “Boost” is selected

If the instrument was turned on from an idle state, the wavelength calibration in Steps 8-9 can be performed immediately. If the instrument was turned on after more than a few hours of being unpowered, the polychromator can take several hours to stabilize the temperature and to purge

8) Aspirate the wavelength calibration solution (from Agilent) and then select the “Calibration” tab
9) Click “Calibrate” in the ‘Instrument’ section to perform a wavelength calibration
10) A pass or fail mark will appear indicating whether the instrument calibration is complete
11) To save and view the calibration data, refer to the User’s Guide

VI. Creating a 5% HNO3 solution
To create a 5% HNO3 solution from a 65% HNO3 stock solution, we use the following general dilution equation:

c1V1=c2V2

where

Let’s say we want to make 500 mL of a 5% HNO3 solution. That means we must find out how much volume of our stock solution (65%) we must dilute with water. Reworking the equation gives the following:

c1V1=c2V2

V1=c2V2c1

V1=5% . 500 mL 65%=38,46 mL

We must thus dilute ± 38,5 mL of HNO3 (65%) up to 500 mL with MilliQ water. In practice, we first add a considerable amount of MilliQ water to a 500 mL Erlenmeyer flask and THEN add the 38,5 mL HNO3 (always add water before acid to prevent reactive splashing). Finally, we work up with MilliQ water to 500 mL.

V. Connecting ICP Expert software to the ICP-OES

1) Start the ICP Expert software by double-clicking on the desktop icon
2) Click “Instrument”
3) Click “Connect”
4) Enter the IP address of the instrument or select an existing instrument
5) Click “Connect”
6) Click “Close”

VI. Creating a new worksheet and developing a new method
Creating a new worksheet

1) Click “New Quantitative” or “IntelliQuant Screening” from the “Start” page or the File menu.

Opening an existing worksheet

1) Click “Open” from the Start page or from the File menu. A list of recently used files will be displayed

Creating a new worksheet from a template

1) Click “New From” on the Start page or “New From Template” from the File menu

Develop a method

1) Select the features and accessories on the “Configuration” page to be used during analysis. (Some features are only available in ICP Expert Pro software)
2) On the “Elements” page, select the element(s) from the “Element” drop-down box or type the element name or symbol. Click “Add Analyte” to add the primary wavelength for the selected element OR add the wavelength you wish to use from the list of available wavelengths displayed.7 The element will appear in the table
3) Check that there are no known interferents or other analytical lines close to the selected analytical line. Their relative intensity will govern how close the lines can be to each other. For example, if your matrix contains an element that is not of analytical interest, but is a potential interferent and has a line close to one of your analytical lines, the concentration of that element in your matrix will determine whether you need to choose another analytical line
4) Make any required adjustments to each element including selecting a different wavelength, entering additional information into the “Label” column, and selecting the type (choose from analyte, internal standard or interferent)
5) Click “Conditions” to modify both common settings for the run and settings for each element. Up to eight different measurement conditions can be used
6) Click “QC” to enter the method detection limits, select the QC tests to be used and which error actions should be performed if an error occurs.
7) Click “IEC” to enter the concentration of the elements in your analyte and interferent standards
8) Click “Standards” to enter the concentration of the elements in your standards and select whether to use other options such as “Standard Additions” or “MultiCal”. In addition, also select whether to use the blank in calibrations and whether to enable reslope
9) Click “Sequence” to specify the number of samples, insert QC tests, select the solution type, edit the sample labels and end of run actions.
10) Click “FACT” to manually create FACT models or to set the method up to automatically create them during analysis
11) If you are using an autosampler, click the “Autosampler” tab to select the racks and probe depth (if needed). Depending on the autosampler selected, options may vary

  1. Instrument is ready for analysis within 20 minutes after lighting the plasma. If using wavelengths below 189 nm: purging the polychromator can take up to several hours. ↩

  2. Can be operational again in \<20 minutes from plasma ignition ↩

  3. For overnight, weekend, and long-term shutdown. Can be operational again in 30 minutes from plasma ignition ↩

  4. Restarting the instrument to be ready for analysis again will take several hours due to the gas purge and polychromator thermal stabilization time ↩

  5. The torch and torch compartment may become extremely hot during instrument operation and remain hot for some time after the plasma has been switched off. Allow the plasma compartment to cool for at least five minutes before accessing the plasma compartment. Allow the torch to cool for two minutes before touching the outer tube or attempting to dismantle the torch or wear heat-resistant gloves. ↩

  6. The polychromator thermal stabilization can take up to several hours from long term shutdown. ↩

  7. It is recommended to add multiple wavelengths for each element. Similar results for each wavelength indicate there are no interferences present. If there are different results, check IntelliQuant for the right wavelength to report. ↩

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