NFM 5.2.2.C (revised 6/1/2000)

 

Procedures for Processing Samples for Analysis of Dissolved Organic Carbon and Inorganic and Organic Particulate Carbon

 

EQUIPMENT

 

Dissolved Organic Carbon (DOC)

 

1.      0.45 um Gelman Supor capsule filter (QWSU Item No. Q398FLD)

2.      125 mL baked amber glass bottle (QWSU Item No. 28FLD) [Bottles for DOC samples have been baked at 4000C and meet a detection limit criterion for organic carbon of <0.1 mg/L detection limit for DOC.]

3.      Sulfuric Acid Preservative, 4.5N (QWSU Item No. Q438FLD)

4.      Organic-grade deionized water (DIW) [analysis of the water used must indicate less than 0.1 mg/L of organic carbon] or Pesticide- or VOC-free blank water (PBW or VBW) (NWQL Item Nos. N1590 and N1580)

5.      Aluminum foil

 

Total Particulate Carbon (TPC) and Particulate Inorganic Carbon (PIC)

[Particulate Organic Carbon (POC) is determined as TPC -PIC]

 

1.      Fluorocarbon polymer pressure-filtration assembly that holds a 25 mm filter (DOC-25)

4.      Ring stand and clamp to hold filtration unit

5.      0.2-um pore-size in-line filter (Acrodisc 50™) (QWSU Item No. Q69FLD)

6.      Peristaltic pump and C-Flex™ tubing

7.      25 mm, 0.7-um pore-size, pre-combusted glass fiber filters (NWQL Item No. Ni 620)

8.      2- Filter forceps, metal (QWSU Item No. Q347BACT)

9.      Glass cylinder, 100 mL

10.   6 in. x 6 in. aluminum foil squares (NWQL Item No. N1610)

11.   Whirl-Pak bags, 6 oz. And 18 oz. (QWSU Item Nos. Q22FLD and Q21FLD)

12.   Aluminum foil

13.   Cooler and Ice

14.   Replacement filter support screen, 25 mm, either stainless steel (Pall Gelman Laboratory Part number 79791) or polysulfone (Pall Gelman Laboratory Part number 87265) Pall Gelman Laboratory, 600 Wagner Road, Ann Arbor, MI, 48103-9019; phone (734)-665-0651 may be obtained if the one supplied with the DOC-25 is lost or damaged.

15.   Recommended --pressure gauge (glycerin filled, 0 to 30 psi; Cole Parmer cat. No. P-07370-70 or equivalent) inserted in to the side arm of a plastic TEE in-line between the peristaltic pump and the DOC-25.

 

OR

 

1.      Filtration flask, polypropylene

2.      Filter funnel, polysulfone, 25 mm with 2OO mL reservoir

3.      Peristaltic pump or hand pump and C-Flex™ tubing

4.      25 mm, 0.7-um pore-size, pre-combusted glass fiber filters (NWQL Item No. N1620)

5.      2- Filter forceps, metal (QWSU Item No. Q347BACT)

6.      Glass cylinder, 100 mL

7.      6 in. x 6 in. aluminum foil squares (NWQL Item No. N1610)

8.      Whirl-Pak bags, 6 oz. And 18 oz. (QWSU Item Nos. Q 22FLD and Q21FLD)

9.      Aluminum foil

10.   Cooler and Ice

 

 

EQUIPMENT CLEANING

 

Laboratory cleaning of the filtration equipment is described in section 3.3.4.C of the NFM.

 

DO NOT USE METHANOL OR ANY OTHER SOLVENT TO

CLEAN TPC, PIC, or DOC EQUIPMENT.

 

Field Cleaning

 

        Immediately after each use, rinse the filtration apparatus several times with organic-grade DIW.

§       While equipment is still wet, and before moving to the next site, disassemble and thoroughly rinse all parts with organic-grade DIW, PBW, or VBW

§       Reassemble fluorocarbon polymer pressure-filtration assembly and double-wrap all equipment in aluminum foil.

§       Place in sealable plastic bag.

 

 

Procedure for processing DOC samples using a 0.45-um pore size capsule filter:

 

DOC samples can be obtained from any of the following types of filters or filter media without statistically significant changes in DOC concentrations: 0.45-um pore size silver membrane filter, 0.7-um pore size, pre-combusted, glass-fiber filter, or the 0.45-um pore size Supor capsule filter manufactured by Gelman Corporation.

 

DO NOT FIELD RINSE DOC BOTTLE.

 

1.    Collect sample as described in NFM 4.

2.    Place a 125-mL baked glass bottle under the capsule filter.

3.    Fill bottle to shoulder, allowing room to add preservative.

4.    Cap and remove bottle from processing chamber and transfer it to preservation chamber

5.    Open DOC bottle in the preservation chamber along with other samples to be preserved with sulfuric acid; add contents of vial containing sulfuric acid to DOC bottle after preserving the nutrient sample (WCA or FCA) bottles.

6.    Cap the DOC bottle securely; shake bottle to mix sample and preservative.

7.    Remove DOC bottle from preservation chamber.

8.    Check that the bottle is labeled correctly and completely; place the bottle in a foam sleeve and then into an ice-filled shipping container.

9.    Maintain sample at or below 40C without freezing (NFM 5.5).

 

Order for filling filtered sample bottles from the capsule filter:

1. FA (trace elements)

2. FAM (mercury)

3. FCC or FCA (nutrients)

4. DOC (organic carbon)

5. FU (major ions)

6. FUR (radiochemicals)

7. Others

 

 

Procedure for processing DOC samples using the 47-mm, O.45-um pore size silver membrane filter and the 47mm stainless steel (unchanged from NFM 5.2.2.C) or fluorocarbon polymer pressure-filtration unit (DOC-25):

 

 These procedures are unchanged from those presented in the National Field Manual.

 

Procedure for processing DOC samples using the 0.7-um pore size, pre-combusted, glass-fiber filter and DOC-25 filtration apparatus OR vacuum filtration unit:

 

1.    Collect the sample for the DOC analysis as instructed in NFM 4.

2.    Cover the bench or table with a sheet of aluminum foil to make a clean work surface. Put on appropriate disposable, powderless gloves. Assemble necessary equipment on the clean work surface.

a.    If using the DOC-25 filtration apparatus, to remove airborne particulates, attach an in-line, 0.2-um pore-size filter (Acrodisc 50™) to the inlet side of a dry pump hose between the filter apparatus and the peristaltic pump.

b.    Change gloves.

c.    Remove the aluminum foil wrapping from equipment.

3.    Remove the bottom of the filtration apparatus OR lift the top part of the filter funnel.

4.    Using metal filter forceps, place a 25mm, 0.7-um pore size, pre-combusted glass-fiber filter on the base of the filtration apparatus, and screw the barrel onto the filter base OR replace the top part of the filter funnel and cover it with a small piece of aluminum foil. Make sure filter is not wrinkled or torn.

5.    Screw the top part of the filter apparatus onto the barrel and attach the tubing from the peristaltic pump to the top outlet OR attaché the hand pump to the filter flask.

6.    Filter the DOC sample:

a.    Open the top of the barrel of the filter apparatus OR uncover the top of the filter funnel and pour about 100 mL of whole water sample in. The whole water sample should be a sub-sample collected from the churn splitter or the cone splitter. For water with large concentrations of suspended materials, collect the sample first into a baked glass bottle, allow suspended materials to settle, and pour 100 mL of the clear supernatant into the filter barrel.

b.    Screw the top part of the filter apparatus onto the barrel OR recover the filter funnel with the aluminum foil.

7.    Apply pressure or suction to start the flow of sample water through the filtration apparatus. If using a pressure gage, the pressure must be regulated to less than 15 lb/in2.

 

 

DO NOT FIELD RINSE DOC BOTTLE.

 

 

8.    Place a 125-mL baked glass bottle under the discharge tube of the filter apparatus and fill to the shoulder with sample filtrate, allowing room to add a vial of sulfuric acid preservative. If the filter clogs before 100 mL for the DOC analysis can be filtered, depressurize the filtration unit, empty the remaining volume of unfiltered sample water in the filter unit, remove the clogged filter media and replace with a new glass-fiber filter. Start at Step 4 above.

9.    After the DOC sample bottle has been filled, cap the bottle and transfer it to the preservation chamber.

10. Depressurize the filter apparatus.

11. Open DOC bottle in the preservation chamber along with other samples to be preserved with sulfuric acid, add contents of vial containing 4.5N sulfuric acid preservative to DOC bottle after preserving the nutrient sample (WCA or FCA) bottles. Cap the DOC bottle securely and shake to mix sample and preservative; remove the bottle from the preservation chamber.

12. Check that the bottle is labeled correctly and completely. Place the bottle in a foam sleeve before placing in an ice-filled shipping container.

13. Chill the DOC sample and maintain at or below 40C without freezing (section 5.5).

 

 

Procedure for processing TPC and PIC samples:

 

Analysis of the suspended material retained on the 0.7-um pore size, pre-combusted, glass fiber filter for TPC and PIC requires that the volume of sample passed through each filter be measured and recorded on the field sheet and the Analytical Services Request Form (ASR). The amount of water that needs to be filtered in order to obtain a sufficient quantity of material for the analysis depends on the suspended-sediment concentration and/or the concentration of humic and other substances that cause colored water, such as organic and inorganic colloids. A graph of the historical stream stage versus suspended-materials concentration will aid in estimating suspended-material concentrations at a given site. Guidelines for selecting the volume of sample to be filtered for POC analysis, based on suspended-material concentrations, are shown in table 1.

 

Table 1. Guidelines for selecting the volume needed for filtration of samples for analysis of particulate carbon.

[Guidelines are based on sand-sized materials; other physical property factors and chemical composition were not taken into account. mg/L, milligrams per liter; mL, milliliters; >, greater than]

 

Approximate suspended-materials concentration (mg/L)

Volume of sample to be filtered (mL)

1-30

250

>30-300

100

>300-1,000

30

>    1,000

10

 

 

1.     Data-quality requirements of the study and site characteristics determine where the sample will be taken. If collecting sample at the centroid of flow with a weighted-bottle sampler collect the TPC/PIC sample(s) in 125-mL baked glass bottles.  Subsamples from a cone splitter may be collected in a pesticide bottle from which smaller aliquots for filtering may be taken. Subsamples from a churn splitter can be withdrawn directly into a pesticide bottle or a clean graduated cylinder.  (NOTE: An experiment is now being planned to test the possibility of particles of the sediment churn breaking off and being captured on the filter.  Results of this experiment and final recommendations on taking TPC/PIC samples from the churn will be released as soon as possible.)  Cap all bottles securely.

2.    Cover the bench or table with a sheet of aluminum foil to make a clean work surface. Put on disposable, powderless gloves. Assemble necessary equipment on the clean work surface.

a.  To remove airborne particulates, attach an in-line, 0.2-um pore-size filter (Acrodisc 50™) to the inlet side of a dry pump hose between the filtration apparatus and the peristaltic pump.

b. Attach pump tubing to pump.

c. Remove the aluminum foil wrapping from equipment.

d. Change gloves.

3.    Open the bottom of the DOC-25 filtration unit OR open the filter funnel.

4.    Using metal filter forceps, place a 25-mm, 0.7-um pore size, pre-combusted, glass fiber filter on the support screen in the base of the DOC-25 apparatus, and screw the filter base onto the barrel (there is no gasket in the DOC-25 apparatus) OR place the filter on the base of the filter funnel. Make sure filter is not wrinkled or torn. Place the DOC-25 apparatus in the ring stand clamp.

5.    Place a 100-mL graduated cylinder or other container under the DOC-25 filtration unit.

6.    Shake the sample vigorously to suspend all particulate matter.

 

7.    Pour an aliquot of the sample immediately into the barrel of the DOC-25 apparatus OR into the filter funnel, keeping particulates suspended in the sample bottle

8.    Screw the top part of the DOC-25 apparatus onto the barrel and attach the peristaltic pump tubing OR attach the pump tubing from the peristaltic pump or hand pump to the vacuum flask.

9.    Apply pressure or suction to start the flow of sample water through the filtration apparatus. If you are using a peristaltic pump to pressurize the DOC-25 installation of  a pressure gage in the line is recommended.  During pumping, a drop in pressure will signal when the last of the sample water has passed through the filter.

10. After an aliquot of sample has been filtered or filtrate is being collected at less than one drop per minute:

a.    Depressurize the DOC-25 apparatus.

b.    Remove the top of the DOC-25 apparatus or look into the top of the filter funnel.

c.    Check to see if there is water on the filter and if it is covered with particulates.

d.    If the filter is dry but not covered with particulates, add another aliquot of sample by repeating steps 6-9.

e.    After the filter is dry and covered with particulates, continue to step 11.

 

TECHNICAL NOTES:

It is important that all the water in the barrel be passed through the 0.7-um pore size, pre-combusted, glass-fiber filter leaving the filter "dry". To accomplish this, it might be necessary to filter the sample as small aliquots, repeating steps 6-10 until the filter is loaded to capacity.  Shake the sample to re-suspend particulates before pouring each aliquot into the barrel. It is recommended (but not required) that the sides of the barrel of the filter apparatus be rinsed to remove particles remaining on the barrel with PBW or VBW or organic-grade DIW before removing the filter from the filter holder.  Installing a pressure gage in the line when using the peristaltic pump to apply pressure will help determine when filtration in complete.  A drop in pressure will occur when all of the sample water has passed through the filter.

 

 

11. When the filtration is complete, depressurize the filter apparatus, pointing the DOC-25 apparatus away from your body, face, and other people.

12. Measure the total amount of filtrate in the graduated cylinder and record the volume on the field sheet and the ASR.

13. Discard filtrate in the graduated cylinder-Do not send to laboratory for analysis.

14. Change gloves.

15. Remove the bottom of the DOC-25 apparatus carefully OR lift the top of the filter funnel.

a.    Fold a 6 in. x 6 in. aluminum foil square in thirds; open it back up; place it on the work surface.

b. Using two metal forceps, remove the filter from the filter holder.

c. Place the filter on the aluminum foil square and fold it in half with suspended material on the inside, taking care not to lose any suspended material.

d.   Place the fold of the filter into the fold of the aluminum foil square and press the aluminum foil down on top of the filter to hold the folded filter in place.

16. Repeat steps 3-15 two more times until a total of 3 filters (2 for TPC and 1 for PIC) have been processed.

a. If the same volume of sample water was filtered through all 3 filters, they may all be placed in one aluminum-foil envelope. If different volumes have been filtered, three separate properly labeled aluminum foil envelopes are required.

17. Close the other flap of the aluminum foil; turn the ends up to make an envelope; label the aluminum foil envelope(s) with site identification, date and time, total filtered volume of sample, and laboratory sample designation code.

18. Place labeled aluminum foil envelope(s) into small Whirl-Pak bag(s) and seal the bag(s).

19. Place the Whirl-Pak bag(s) inside a large Whirl Pak bag and seal the large bag.

20. Place the bag in an ice-filled cooler and maintain the samples at or below 40C during storage and shipment to the laboratory.

 

 

Procedure for combined TPC/PIC/DOC sample processing:

 

Instead of using the capsule filter for the DOC filtration, samples for TPC and PIC and DOC analyses can be processed in combination using the equipment listed for the TPC/PIC processing. 

 

.

1.      Follow steps 1-20 for the TPC/PIC processing, EXCEPT.

2.      Place a 125-mL baked glass bottle under the discharge tube of the filtration apparatus and fill the bottle to the shoulder with the sample filtrate for the DOC analysis, allowing room for the addition of the sulfuric acid preservative.

a.     If the filter clogs before the entire volume of sample in the filtration apparatus can be filtered, start the process over and filter a smaller volume of water. If the filter continues to clog, this combined TPC/PIC/DOC method cannot be used. Start over and filter TPC/PIC and DOC samples separately.

b.     If the volume needed for the TPC/PIC analyses is insufficient for a DOC analysis (less than 100-mL), two or more filtrations through separate filters can be combined into one DOC bottle. (Two filters are required for the TPC analysis and one filter for the PIC analysis; record the total volume of sample that passed through each of the retained filters).

c.     If the volume needed for TPC/PIC analyses is greater than the 100-mL of sample to be used for DOC analysis, remove DOC bottle after filling of filtrate to shoulder of bottle and then continue filtering until the entire volume needed for the TPC/PIC analyses have been filtered. Record total volume filtered on the field sheet and ASR and discard extra filtrate.

3.      After the DOC sample bottle has been filled, cap the bottle and transfer it to the preservation chamber.

4.      Depressurize the filter apparatus, pointing the DOC-25 apparatus away from your body, face, and other people then disconnect the hose from the filter apparatus cylinder and remove the top.

5.      Using no more than a total of 10 mL of organic-grade DIW, PBW, or VBW:

a.      Rinse the residual suspended material from the bottle that was used to measure the sample volume and pour into the filter barrel.

b.      Rinse any residual suspended matter from the sides of the filter barrel.

6.      Replace the top of the filter apparatus, attach the pressure hose, and pressurize, passing the rinse water through the filter. Discard rinse water to waste.

7.      After completing the rinse:

a.     Depressurize the filtration apparatus.

b.     Fold a 6 in. x 6 in. aluminum foil square in thirds; open it back up; place it on the work surface.

c.     Disassemble the bottom of the filtration assembly and, using two metal forceps, remove the filter from the filter holder.

d.     Place the filter on the aluminum foil square and fold it in half with suspended material on the inside, taking care not to lose any suspended material.

e.   Place the fold of the filter into the fold of the aluminum foil square and press the aluminum foil down on top of the filter to hold the folded filter in place.

8.      Repeat steps 4-16 two more times until a total of 3 filters (2 for TPC and 1 for PIC) have been processed.

a.    If the same volume of sample water was filtered through all 3 filters, they may all be placed in one aluminum-foil envelope. If different volumes have been filtered, three separate properly labeled aluminum foil envelopes are required.

9.      Close the other flap of the aluminum foil; turn the ends up to make an envelope; label the aluminum foil envelope(s) with site identification, date and time, total filtered volume of sample, and laboratory sample designation code.

10.   Place labeled aluminum foil envelopes into small Whirl-Pak bags and seal the bags.

11.   Place the small Whirl Pak bag(s) inside a large Whirl-Pak bag and seal the large bag.

12.   Place the bag in an ice-filled cooler and maintain the samples at or below 40C during storage and shipment to the laboratory.

13.   For TPC and PIC samples submitted to NWQL, record the volumes of sample filtered for each of the filters on the comment line of the ASR form.

14.   Open DOC bottle in the preservation chamber along with other samples to be preserved with sulfuric acid; add the contents of a vial containing 4.5N sulfuric acid preservative to the DOC bottle after preserving the nutrient sample (WCA or FCA) bottles. Cap the bottle securely and shake to mix sample and preservative; remove bottle from preservation chamber.

15.   Check that the bottle is labeled correctly and completely and place the bottle in a foam sleeve before placing in an ice-filled shipping container. Chill the DOC sample and maintain at or below 40C without freezing (NFM section 5.5)

 

FOR TPC AND PIC ANALYSES, RECORD TOTAL VOLUME OF WATER SAMPLE THAT PASSED THROUGH EACH OF THE O.7-um PORE SIZE, PRE-COMBUSTED, GLASS-FIBER FILTER.