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Topic

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Introduction

2

Apparatus, Reagents, & Materials

3

Instrument Calibration/Verification

9

Sample Preparation

12

Sample Analysis

17

Quality Assurance/Quality Control

18

LIMS Integration

19

Health, Safety, & Environment

20

Maintenance & Troubleshooting

21

Software Guide

25


AnchorRTF320035003200380032003a00RTF320035003200380032003a00Introduction
Theory of Method
The Total Organic Carbon (TOC) instrument analyzes liquid samples by physically combusting the samples at 680°C for TOC or by chemically combusting the samples in 25% phosphoric acid for inorganic carbon (IC). The instrument measures the amount of carbon degraded to CO2 using nondispersive infrared gas analysis at 4.3 µm wavelength, calculated based on Lambert-Beer's law.
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Total Carbon (TC)
To analyze for Total Carbon (TC) a sample is delivered to the TC combustion tube filled with platinum catalyst and heated to 680°C. Carrier gas (purified air or oxygen) , along with the CO2 generated by combustion, flows through the reaction vessel to the dehumidifier and scrubber, where it is cooled, dried, and purified. It then it passes into the nondispersive infrared detector, which generates an analog signal that is digitized and processed by the TOC Control software. The peak area is proportional to the concentration of total carbon in the sample.
AnchorRTF4d0065006100730075007200
RTF4d0065006100730075007200 Inorganic Carbon (IC)
During inorganic carbon analysis the liquid sample is introduced into the reaction vessel, which is half filled with 25% phosphoric acid. The sample is purged with carrier gas (high purity air) through the acid solution. The phosphoric acid reacts only with inorganic carbon components (CO32- and HCO3), transforming them to CO2. The CO2 is carried fromthe IC vessel through the dehumidifier and scrubber to the NDIR detector.
Total Organic Carbon
TOC concentration can be obtained by subtracting the IC concentration from the TC concentration.
Note: Before operating the TOC system every operator must get either additional training from a senior technician or carefully study all three manufacturer TOC/ASI/Software manuals.
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RTF360032003300380036003a00 Apparatus, Reagents, & Materials
Laboratory Apparatus

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Instrument

Specification

Method

Combustion/nondispersive infrared gas analysis

Combustion temperature

680°C

Measurement range

4 ppb to 4000 ppm

Anaysis time

2–3 min each for TC and IC

Repeatability

<2000 ppm: 1% of full scale
2000–4000 ppm: 2% of full scale

Sample introduction

Automatic injector

Injection volume

50–2000 µL

Ambient temperature

5°–35°C

Dimensions

480 mm W x 520 mm D x 480 mm H

Weight

~46 kg



Figure 1-2. Schematic of TOC-5000A Interior (Front View).

Figure 1-3. Photograph of TOC-5000A Interior (Front View).

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Figure 1-4. Close-up Front View Flow Lines in Upper Right.


Autosampler
The autosampler allows automated carbon analysis in multiple samples.

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Figure 1-5. Autosampler Back View.

Figure 1-6. Autosampler Closeup.


Gas Generator
The Parker Balston (Whatman)78-40 TOC Gas Generator (Figure 1-7)converts compressed air into high purity carrier/combustion gas for the TOC analyzer with hydrocarbon levels < 0.1 ppm and CO2 level < 1 ppm.
The Gas Generator should be fed from the air compressor, not from an air tank, because of the high rate of air consumption. Incoming air should be relatively free of dust and water (typical air compressor produced air should meet these requirements).

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Figure 1-7. TOC Gas Generator. AnchorRTF350036003200300035003a00RTF350036003200300035003a00


Instrument Calibration/Verification

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Preparing Calibration Standards
Total Carbon
In a 100 mL volumetric flask, make up the following calibration levels to bracket general expected TC levels from the 100 ppm intermediate stock solution:


  • 100 ppb: 0.1 mL of 100 ppm + 99.9 mL zero water
  • 500 ppb: 0.5 mL of 100 ppm + 99.5 mL zero water
  • 1 ppm: 1.0 mL of 100 ppm + 99 mL zero water
  • 2 ppm: 2.0 mL of 100 ppm + 98 mL zero water
  • 5 ppm: 5.0 mL of 100 ppm + 95 mL zero water

...

  • 100 ppb: 0.1 mL of 100 ppm + 99.9 mL zero water
  • 500 ppb: 0.5 mL of 100 ppm + 99.5 mL zero water
  • 1 ppm: 1.0 mL of 100 ppm + 99 mL zero water
  • 2 ppm: 2.0 mL of 100 ppm + 98 mL zero water
  • 5 ppm: 5.0 mL of 100 ppm + 95 mL zero water

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RTF310030003100310030003a00Setting up the Sample Table for Calibration Curve


Step

Action

    1

From the TOC Control screen select File > Open Sample Table and open a new or previously saved calibration Sample Table (Fig 8).

    1

Click in the first line of the Sample Table and select Edit > Insert Standard.

    2

On the TOC Control screen toolbar, select View > Calibration Curve List.

    3

On the Calibration Curve List dialog box, select New (Fig 9).

    4

On the Conditions tab (Fig 10), enter the following:

  • Title and File Name for the calibration
  • Analysis Type (TC or IC)
  • Change Calculation Method to Lin. Regression without Zero Shift (FIG).
  • The Range and Injection Volume fields will be autofilled after completing information in the Data tab.
    5

Select the Data tab and enter information requested into the data table.

    6

Click OK and save the calibration information and Yes to use as method default parameters.

    7

Save the Sample Table.


Figure 1-8. Calibration Sample Table.




Figure 1-9. Calibration Curve List Dialog Box.




Figure 1-10. Calibration Curve Conditions Tab.


Running a Calibration Curve


Step

Action

    1

Place calibration curve standards in autosampler spaces S1–S8.

    2

Verify status of instrument and baseline: View > Background Monitor then close Background Monitor screen.

    3

Select Measure > Start or click Start on the instrument control bar. When the Standby screen opens, select Keep Running and click OK.

    4

To monitor the status of the measurements, select View > Realtime Window or select Realtime Window on the toolbar.

    5

When the calibration runs are complete the instrument status bar will indicate Ready.

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Evaluating the Calibration Curve


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Step

Action

    1

Select View > Calibration Curve or click the Calibration Curve button on the toolbar.

    2

Select the Curve tab to see the curve data in graphical format.

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    3

Check the correlation coefficient (R2), which was calculated using the linear relationship of the concentration vs. area. R2 > 0.995 indicates an acceptable calibration.

    4

Select the Data tab to view standard deviation and coefficient of variation statistics.

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    5

Individual peaks or injections can be viewed using View > Peak Profile > Display.

    6

If the calibration is acceptable, specify the calibration file (CAL) name in the method and close the Calibration window.

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Running a Calibration Verification


Step

Action

    1

Run a midpoint curve standard as an "unknown" sample in the Sample Table.

    2

Apply the calibration curve to calculate the sample results.

    3

Open View > Injection Table or click the Injections button on the toolbar to examine the sample results in the Concentration column and the result of the Outlier Test. For acceptable calibration verification, CV should be >0.90.

    4

Close the Injection Table screen.


Sample Preparation


Overview
Samples are prepared by squeezing interstitial waters from sediment cores. Total organic carbon is run on unfiltered interstitial water samples; dissolved organic carbon (DOC) is run on interstitial water samples filtered through a 0.45 µm membrane.
Interstitial waters are diluted ~1:5 before running on the TOC analyzer and the analyzer is calibrated for quantitation of sample results. Running samples involves the following steps:


Step

Action

    5

Set up hardware (see Setting up the Sample Table for Calibration Curve)

    6

Set up software (see Preparing TOC Software )

    7

Set up autosampler (see Preparing the Autosampler)

    8

Set up sample table (see Setting up a Sample Table and Selecting a Calibration Curve)

    9

Run samples (see Running Samples)

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Preparing TOC Analyzer Hardware


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Step

Action

    1

Make sure tubing and cables are connected properly to the instrument.

    2

Check compressed air feed line (65–80 psi) for the Gas Generator (if using an ultra-high purity air tank the delivery pressure be set to 80 psi (not to exceed 100 psi).

    3

Check that the Gas Generator is in ready condition. THC light green and no CHECK SYSTEM/ OVERFLOW lights on.

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    4

Fill the humidifier with distilled water until the water level is between the white lines. Make sure the rubber stopper is fully plugged in.

    5

Fill IC vessel with 75–100 mL of 25% phosphoric acid solution.

    6

Make sure all drain lines have a negative slope alignment. Empty the drain container, if required.

    7

Check position of three-way cock arm. The cock arm should be in the left position (Fig 4).

    8

Ensure TOC main power switch is turned on and black switch on front top right side (behind instrument door) is in PC CONTROL position.

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Figure 1-11. Software TOC Control Screen with Blank Sample Table. AnchorRTF360033003000380035003a00RTF360033003000380035003a00



Preparing TOC Software


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Flow should be 150 mL/min, and pressure should be ~450 kPa. Adjust flow or pressure to target values using the Carrier gas pressure controller and Carrier gas flow controller next to the flow meter (see Fig 4).


Step

Action

    1

Click on the TOC Control icon on the computer desktop (see #1 on Fig 11). Type DAQ for username and password to open the TOC Control screen.

    2

From the Toolbar on the TOC Control screen, select Measure > Connect (#3 on Fig 11), and at the bottom of the Control screen click the TOC button (#4 on Fig 11).
The message bar (#5 on Fig 11) should say Connected.

    3

Check the carrier gas flow meter and pressure gage on the front panel of the TOC analyzer.

Wiki Markup
4

On the TOC Control screen, select View > Background Monitor (#6 on Fig 11) to open a background window. .

5

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Close the Background window.


6

On the TOC Control screen select Options > Instrument Conditions (#7 on Fig 1) to set up and/or verify TOC, ASI, and RS232 settings as follows:

TOC

  • Furnace = on
  • Auto ranging = on
  • Inj volume = on
  • Auto regenerating = on
  • Syringe size = 250 µm

ASI

  • ASI used = on
  • High sensitivity vials = on
  • Rinse = on
  • No. of washes = 4

RS232

  • RS232 = COM1
  • Baud rate = 2400
  • Parity = none
  • Stop bits = 1

...


Preparing the Autosampler


Step

Action

    1

Fill autosampler rinse bottle (Fig 5) with fresh zero water.

2

Fill high-sensitivity 50 mL autosampler glass vial with zero water and place it to S1 tray position. Remove tray cover or make sure it's in the correct position.

  • Each vial in the autosampler tray must be filled to the top and covered immediately with wax paper or sealed with special caps to prevent CO2 penetration. After the sealed surface is pierced by the autosampler needle, the vials will remain usable for only a limited time (usually a few hours).
    3

Remove bubbles from the syringe (Detect Zero point): on the TOC Control screen select Options > Maintenance > Zero point detection.
The ASI arm and tray will start moving and the syringe/4-port valve will perform the bubble removing procedure.

...

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Setting up a Sample Table and Selecting a Calibration Curve


Step

Action

    1

From the TOC Control screen select File > Open Sample Table to create a new Sample Table (#8 in Fig 11) or open an old Sample Table (#9 in Fig 8).

    2

Fill in the Sample Table with sample type, name, ID, and analysis.

    3

To specify a method on the Sample Table, select View > Methods on the TOC Control screen to open a saved method or create a new method.

    4

Fill in information on the General and Method tabs of the Method screen (Fig 12).

    5

To specify a calibration curve to apply to the samples, select View > Calibration on the TOC Control screen to open a dialog box showing a list of calibration curves saved in the CALIBR folder (Fig 9).

    6

On the Calibration Curve List dialog box, click Open to select a saved calibration curve.

    7

Save the Sample Table.

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Figure 1-12. IC Method Tabs.

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anchorRTF320032003000360032003a00RTF320032003000360032003a00


Sample Analysis

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Running Samples


Step

ActionAction

    1

Load the sample vials into the autosampler in positions that correspond to the Sample Table.

    2

Verify status of instrument and baseline: View > Background Monitor, then close Background Monitor screen.

    3

Select Measure > Start or click Start on the instrument control bar. When the Standby screen opens, select Keep Running and click OK.

    4

To monitor the status of the measurements, select View > Realtime Window or select Realtime Window on the toolbar.

    5

When the sample runs are complete the instrument status bar will indicate Ready.

    6

Sample results calculated from the loaded calibration file will display in the Sample Table Mean Area and Result columns.

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Quality Assurance/Quality Control


Analytical Batch


Blanks
The TOC analyzer has an automated TC Blank Check Program that runs zero water blanks from 4 different vials a total of 10 times.


Step

Action

    1

Place vials filled with zero water in autosampler positions S1–S4.

    2

On the autosampler control panel, open the Maintenance screen and select TC Blank Check.

    3

The autosampler injects S1 twice, S2 three times, S3 three times, and S4 twice and then returns to Home.



Calibration
Calibration Verification
Precision
Accuracy

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LIMS Integration


Overview
TC/IC/TOC analysis results are manually entered into the LabWare LIMS client by the technical staff once the scientist(s) is (are) finished reducing the data.
LIMS Components
Results are stored in the LIMS database associated with an analysis code and an analysis component. Analysis codes and their components, definitions, and units are listed below.

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Analysis

Component

Definition

Unit

TOC

carbon_total

Concentration

ppm

 

inorganic_carbon_total

Concentration

ppm

 

organic_carbon_total

Concentration

ppm

 

run_test

link to calibration test

 

TOC_QAQC

carbon_total

Concentration

ppm

 

inorganic_carbon_total

Concentration

ppm

 

organic_carbon_total

Concentration

ppm

 

run_test

link to calibration test

 

 

cal_filename

calibration file

 

 

method_filename

 

 

 

run_filename

 

 

...



Health, Safety, & Environment


Safety


The list of TOC operation safety rules, issued by general chemistry laboratory safety, oven safety, handling of concentrated H3PO4 and automatic machine operation safeties as well, should be as following:

...

  • The contents of the waste bottle (when it's full) need to be checked for neutral pH, corrected if necessary to neutral point with sodium carbonate, and disposed to the sink.

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Maintenance & Troubleshooting


Scheduled Maintenance


Daily


  • Check water level in humidifier and dehumidifier pot
  • Check acid level in IC reaction vessel
  • Inspect drain line positions and empty drain jar, if necessary
  • Refill autosampler rinse bottle with distilled water
  • Keep a lint-free environment when cleaning; even small sized particles can clog the sample needle, tubing, or 4-port valve!
  • Use only distilled water for cleaning procedures--no other solvents. Wipe surfaces with a water-dampened cloth.
  • Always make sure the oven has cooled down (~30 min) before the TOC ventilators go off.
  • Proper care must be taken at all times when the TOC is switched off. Usually the TOC combustion oven is working when instrument power with ventilator is going down.
  • In case of an emergency power black out, remove the TOC cover panels to let heat escape from the oven without significant warming-up of electronic and plastic TOC parts.

...

  • Replace halogen scrubber (PN 630-00992) when it turns blue, green, or black. After replacement, wait about an hour for baseline to stabilize.
  • Replace or regenerate high-sensitivity TC catalyst when sensitivity and repeatablility become unacceptable.
  • Wash TC combustion tube interior with 1+2 HCl solution, rinse in water, and dry when washing or replacing catalyst.
  • Replace TC combustion tube when it becomes broken or cracked or leaks gas. Regardless of the color or transparency of the glass tube, it can be used until it begins to leak.


Hardware Troubleshooting


Unstable Baseline


  • Leak in carrier gas
  • TC catalyst needs to be replaced
  • Dehumidifier not operating correctly
  • Environmental: vitration, ambient temperature, power supply
  • NDIR defective

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Bubbles in Sample/Syringe Tubing
Bubbles in the sample tubing affect the accuracy of an analysis. If bubbles are noted in the sample tubing, they need to be removed before beginning an analysis.


Step

Action

    1

Select Options > Maintenance > Mechanical Check > TOC.

    2

Move the syringe plunger up and down using the plunger height control on the left while changing the position of the 4-port valve to Sample, TC port, or IC port.

    3

When the sample goes to the TC/IC waste line, do not bring the syringe plunger all the way up.

...

  • If the needle is bent, unscrew it and remove it from the autosampler arm. Usually the needle can be straightened. If not, then replace the needle. When replacing the needle in the autosampler arm, ensure the needle height and alignment above the rinse/sample vials are positioned correctly before tightening down the arm.
  • If the 4-port valve is stuck, take it apart and check for breakage or particle contamination, as those can cause rotation failure.


Autosampler Troubleshooting


Regenerating TC Catalyst


Step

Action

    1

Place a vial containing 2 mM HCl in position S1.

    2

Open the autosampler Maintenance screen and select Regeneration of TC Catalyst.

    3

The sampling needle moves to the S1 vial then to the rinse water receptacle and rinses the injection needle 3 times.

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Replacing Rinse Water Pump Head


Step

Action

    1

After ~300 hr running time, replace the pump head assembly (PN 042-00405-11).

    2

Take off the small cover attached to the side of the autosampler.

    3

Pull out the pump head (white plastic) from the pump body (black plastic) by picking the claws of both sides with fingers.

    4

Replace the pump head by disconnecting the elastic tubes from the Teflon tubes and connecting new ones.

    5

Remount the pump head and cover.

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Removing the Syringe


Step

Action

    1

Unscrew the plastic plunger holder on the bottom of the syringe (may use pliers).

    2

Unscrew the syringe body from the 4-port valve stand.

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  • 1-800-477-1227, ext 1442
  • Leonardo Ponds

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Software Troubleshooting


Toolbar options don't respond properly

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  • Normally the Gas Generator should be connected to the TOC through blue plastic tubing. In this case, the outlet flow rate of the Gas Generator is controlled by the TOC flow controller (150 mL/min). If the Gas Generator outlet flow line is disconnected and open to the atmosphere, the flow rate will vary, depending on the inlet pressure. When outlet flow is higher than 1250 mL/min, the Gas Generator front panel overflow indication light will turn yellow. In this situation, the technician should correct the flow rate, because overflow conditions will cause the Gas Generator catalyst module to cool and will not produce appropriate quality air.
  • The outlet flow reading may drop below 150 mL/min or have no flow at all. This will significantly affect the TOC flow rate. The most common reason for such a malfunction is the final filter or other filters are clogged. Replace the filters to fix this problem.
  • If the CHECK SYSTEM light located on the bottom of the front panel starts flashing, and especially when it turns to a permanent yellow light, the catalyst unit needs to be exchanged for a new one. Normally happens once every 2–3 yr of constant Gas Generator use.
  • Every 4–5 min a pneumatic switch triggers audibly between the dryer and co-remover towers on the back of the Gas Generator. If the interval time between switches is ~10 min, there may be problems with the Gas Generator.

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Software Guide


TOC-Control Screen Toolbar Functions

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Message

Procedure

Sparging

ASI sparging on

Washing

Rinsing sample syringe

Sampling

Aspirating sample into syringe

Injecting

Injecting sample into furnace or reaction vessel

Measuring

Integrating peak profile data

Draining

Draining the sample

Waiting: Interval setting

Waiting for interval setting

Waiting: Ready status

Waiting: ready status is NG (no good)

Waiting: POC

Waiting for POC bubbler

Waiting: ESU

Waiting for ESU

Waiting: Other

Waiting for other

ASI moving

ASI moving

IC regenerating

Automatic regeneration of IC fluid

Bubbling

Bubbling (POC bubbler)


Instrument Status Bar


Instrument Control Bar Buttons

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