Instructions for DOC/TOC sampling:

by:  Edward T. Peltzer, WHOI.
rev:  22 October 1996.


First and foremost, avoid sample contamination at all steps.  DOC is the
easiest of all analyses to contaminate so it requires the utmost in care to
avoid contamination.  Anything organic can and probably has contaminated DOC
samples in the past.  Above all else, keep your fingers out of the sample.
To be safe, don't even think about contamination while sampling!  ;-)


1.  Sampling devices (Niskin bottles) must be well flushed with seawater
prior to use.  Do not clean the bottles with organic solvents or detergents
as these can invade tiny cracks and leach forever into the samples.

2.  Absolutely no tygon tubing should ever come into contact with the sample
or sampler.  If tygon tubing must be used by others to draw samples then DOC
sampling should precede the drawing of these other samples.  [The experiment
has been done many times, so don't even try to get away with it.  I won't
even bother analyzing samples where tygon tubing has been used to draw other
samples before the DOC samples.  It will just be a waste of my time and
resources, so don't waste your time or resources trying.]  If drawing tubes
must be used, then use clean and new silicone or teflon (TFE, PTFE) tubing.

3.  Niskin bottles should have red-silicone O-rings (not black Buna-N or
viton) and heavy-wall silicone tubing "springs".  Nylon, teflon or poly-
propylene coated steel springs are also acceptable but make sure these are of
high quality and free of nicks, etc.  Teflon or polypropylene stopcocks and
nipples are acceptable.  Be sure to check that the O-rings on the stopcocks
are red-silicone as well.

4.  When collecting samples with Niskin bottles on a wire, lower bottles
several hundred meters to rinse first, then raise to depth if collecting
shallower than 400m.

5.  When collecting surface samples, again, lower to several hundred meters
first, then raise to the appropriate depth.  DO NOT ALLOW THE BOTTLE TO
BREACH THE SURFACE PRIOR TO CLOSING.  If the surface bottle breaches, even if
just exposed for an instant, the sea-surface micro-layer will coat the inside
of the bottle and contaminate the sample.

6.  When drawing samples from an underway system be sure that:

	- continuous flow is maintained through the system.
	- flush drawing line 5 mins before collecting sample.
	- use only silicone or teflon tubing to draw sample.

7.  Rinse the sample bottle (but not the cap) prior to filling:  fill the
bottle to ~2/3rds to 3/4ths full with sample, invert, and drain.  Shake the
last remaining drops from the bottle.  Do not allow the bottle to touch the
drawing tube or stopcock nipple at any time.

8.  Fill the sample vial ~3/4 full:  30 mL in a 40 mL vial;
                                     80 mL in a 100 mL bottle.

9.  If samples are to be filtered:

	- use only pre-fired (overnight at 500 deg C) glass-fiber filters.
	- use only in-line filtration systems.
	- rinse the filter and holder thoroughly before collecting the
          samples.  A minimum rinse volume of 50 mL is recommended.

10.  Add 5 uL 50% H3PO4 (w/w) per mL of sample to each vial/bottle:

		150 ul H3PO4 to a 30 mL sample,
                400 ul H3PO4 to a 80 mL sample.

11.  Cap securely, seal with teflon tape, NUMBER and RECORD each sample.
Samples can be numbered on the top (green cap) with a permanent black
marker.  The vials can be numbered SEQUENTIALLY or by Station, Cast and
Niskin number.  When freezing samples, do not use stick on labels on the
vials; they will not fit in the freezing block if you do.  Record each sample
or cast immediately after collection.  When collecting underway samples,
please remember to record temperature and salinity as well.

12.  Store the 80 mL samples at 4 deg C in a refrigerator free of plankton
tows, fish or organic solvents prior to shipboard analysis.

13.  Store the 30 mL samples frozen for shipment to the lab.  Observe the
same precautions regarding simultaneous storage with biological specimens or
solvents as in step #12.  Prior to freezing, make sure that the outside of
the vials are clean and dry.  Place the samples in an aluminum block kept at
-20degC for quick freezing.  The holes in the aluminum block should be 1 mm
in diameter larger than the vial diameter.

14.  If samples are to be returned to WHOI for analysis, ship samples packed
in blue-ice to keep cool.  Frozen samples stay cold longer than refrigerated
ones.  Freeze the blue-ice at -20 deg C overnight first.  Freezing the empty
cooler at -20 deg C overnight prior to shipping works best.  Make sure that
the samples are well padded (bubble-wrap) and tight so that no shifting can
occur during transport.

15.  Hand carrying the samples as excess baggage works best.



PLEASE NOTE:

50% H3PO4 (w/w) is prepared by adding 76.47 gms of 85.0% H3PO4 to a bottle,
then diluting with 53.53 gms of carbon free distilled water.  Adjust these
proportions according to the assay on your bottle.



ORDERING INFORMATION:

Sample vials						Cat. No.

	Fisher Scientific	40 mL pyrex vials	03-339-5C
				caps green 24-400	02-883-3F

	National Scientific	teflon cap liners	B7817-24