Professor Labuza comments that picric acid should not be flushed downs sinks
in laboratories, though he makes no suggestions as how small amounts of
picric acid should be disposed of. While no one can disagree that hazardous
materials in principle should not be disposed of carelessly I think we need
to consider quantities and risks here. According to chemical safety sheets
picric acid is not acutely toxic by ingestion, though it can cause
irritation or allergic reactions on contact with the skin. Workers in
chemical laboratories are aware of hazards - much more so than when I
started my career as a chemist - and labelling of reagents carries
information on hazards so anyone handling picric acid should be aware of the
hazards of handling the chemical and take appropriate precautions. It is
common practice, if not compulsory, to wear safety goggles in laboratories,
and disposable gloves to use when handling chemical are usually available.
The main hazard of picric acid is that of explosion. (The explosion that
devastated Halifax, Nova Scotia, was caused by a cargo vessel carrying
picric acid catching fire after a collision). It explodes on heating to
300ºC or by any means that causes this temperature to be reached in the dry
material, for example friction, sparks, percussion. Keeping the picric acid
wet guards against this hazard. The are risks associated with disposing of
chemicals into drains including build up of explosive vapours in the case of
volatile solvents, toxicity to persons exposed to the effluents, toxicity to
living things, especially aquatic animals, exposed to the effluent. Picric
acid is not volatile and judging from information in chemical data sheets it
is of low toxicity to fish, and there does not seem to be any information on
effects of human contact toxicity of low concentrations of picric acid. I
imagine the amount of waste picric acid to be disposed of following the
making of the stock solution for TMA determination might be in the order of
a gram or so; excess crystals can be scraped back into the original bottle,
and what is left is a small residue of crystals adhering to the filter paper
and what is absorbed in the filter paper. I consider it is safe to wash the
filter paper well in the sink and flush the waste away.
I found on the Internet the Safety Data Sheet for picric acid issued by the
Division of Occupational Health and Safety, National Institutes of Health.
With regard to disposal it advises:
"1. Chemical inactivation: No validated method reported.
2. Decontamination: Turn off equipment that could be affected by picric acid
or the materials used for cleanup. Do not sweep or brush large spills of
solid picric acid except under the supervision of an explosives expert. If
there is any uncertainty regarding the procedures to be followed for
decontamination, call the NIH Fire Department (dial 911) for assistance. For
small amounts of spilled picric acid solutions use absorbent paper to mop
up. Wipe off surfaces with hot water, then wash with copious quantities of
water. Glassware should be rinsed (in a hood) with hot water, followed by
soap and water. Animal cages should be washed with water.
3. Disposal: Large quantities of picric acid should be disposed of only by
explosives experts. No waste streams containing picric acid shall be
disposed of in sinks or general refuse. Surplus picric acid or chemical
waste streams contaminated with picric acid shall be handled as hazardous
chemical waste and disposed of in accordance with the NIH chemical waste
disposal system. Nonchemical waste (e.g., animal carcasses and bedding)
containing picric acid shall be handled and packaged for incineration in
accordance with the NIH medical-pathological waste disposal system.
Potentially infectious waste (e.g., tissue cultures) containing picric acid
shall be packaged for incineration, as above. Burnable waste (e.g.,
absorbent bench top liners) minimally contaminated with picric acid shall be
handled as potentially infectious waste and packaged for incineration, as
above. Absorbent materials (e.g., associated with spill cleanup) grossly
contaminated shall be handled in accordance with the chemical waste disposal
system. Radioactive waste containing picric acid shall be handled in
accordance with the NIH radioactive waste disposal system."
Section 2 suggests that washings and rinsings that could contain picric acid
would go to the laboratory drain. Section 3 refers to large quantities and
waste streams, hardly the situation pertaining to disposal of the residues
after making up the stock picric acid
Shuming raised a very pertinent point in the determination of TMA by the
picrate method, and one that is not dealt with in the published descriptions
of the procedures. There is quite a large literature on TMA in fish and most
papers cite the original Dyer (1945) paper or an appropriate edition of the
AOAC Official Methods. Some, as well as citing a reference, also summarise
the procedure in the paper. I not aware of any of the many papers describing
procedures for the picrate method referring to the point Shuming raised.
Dyer in his original paper just refers to dissolving 2g of picric acid in
toluene. Dyer's procedure is a modification of the method described by
Richter (1938) who just refers to "... 2% picric acid in chloroform ...".
Formal detailed descriptions of the procedure have appeared in the Journal
of the Association of Official Analytical Chemists and in one of them
(Boland & Paige, 1971) appears the direction:
"(c) Picric acid solns.-(1) Stock soln. - Dissolve 2 g dry picric acid
(Caution; See 46.029) in 100 ml H2O - free toluene., (2) Working soln.- Dil.
1 ml stock soln to 1 00 ml with H2O - free toluene."
Note the requirement for "dry picric acid". I don't think this would get
past laboratory safety officers nowadays. Unfortunately I do not know what
section 46.029 says. The picrate method has appeared in the AOAC Official
Methods of Analysis for many years. I do not access to the current or
previous editions to check on any changes in the procedure, but I have a
copy of the procedure, Official Method 971.14, from the 1995 edition. The
appropriate section states:
"Picric acid solutions - (1) Dissolve 2g of picric acid (Caution: See
Appendix B, safety notes on picric acid) in 100ml H2O-free toluene ."
Again I do not have a copy of the Appendix B referred to here, but perhaps a
reader could summarise what it advises. What strikes me about the AOAC
publications and the Official methods is that the papers in the former would
have been refereed and the procedures in the Official Methods would have
been considered by committees of experts, yet no one seems to have
considered including advice on making up the stock solution from wet picric
acid. It has been left to individual laboratories to devise their own
procedures. I suspect that the concentration of picric acid is not critical
so precisely how the stock is made up doesn't matter, but I have not seen
any reports of studies on the optimum concentration of picric acid to use
nor on the sensitivity of the method to variations in the strength of picric
acid.
Peter Howgate
----- Original Message -----
From: "Ted Labuza" <tplabuza@umn.edu>
To: "P Howgate" <phowgate@clara.co.uk>; "Seafood" <seafood@ucdavis.edu>
Sent: Saturday, October 06, 2007 10:18 PM
Subject: Re: how to measure TMA in fish tissue by Dyer method
> Sorry Peter
>
> In a response to a question you stated:
> Dear Shuming
>
> You are right; do not try to dry the picric acid. I still have a copy of
> the
> procedure as used at Torry Research Station and the section on preparation
> of reagents states:
>
> "Approximately 2% picric acid stock solution. Picric acid is normally
> stored
> under water and is unstable when dry. Remove some crystals from the bottle
> and dry as much as possible and dry as much as possible by pressing
> between
> filter paper. Weigh out 3g of the damp crystals and add to 100ml of
> toluene.
> Shake to dissolve."
>
> The weight of damp crystals to take agrees more or less with that
> recommended by Wekell, and the concentration of picric acid is not
> critical
> anyway. Be careful how you dispose of any unused crystals and the filter
> paper; down the sink with plenty of water
>
> This is not acceptable.
>
> In the US , at least in Universities, such as U Mass where Shuming is at,
> the sink is not a disposal route for
> any hazardous material. All procedures with such materials need prior
> approvals, they might accept this but it needs to be approved.
> Perhaps the industry is more lax but we don't train our students
> to accept that. Worse cases with hazardous microbes, see below;
>
> The Chronicle of Higher Education Wednesday, September 5, 2007
>
> Texas A&M Violated Numerous Biosafety Rules, Federal Agency Says
>
>
> By JEFFREY BRAINARD <mailto:jeffrey.brainard@chronicle.com>
>
> Texas A&M University at College Station violated a dozen safety and
> security
> rules for research on dangerous microbes, federal officials say. The
> government says it will continue its two-month-old suspension of such
> studies at the university until the problems are fixed.
>
> The findings came in a letter
> <http://chronicle.com/weekly/documents/v54/i02/2007_09_04_09_56_50.pdf>
> to
> the university on Friday from the federal Centers for Disease Control and
> Prevention, which regulates research on microbes and toxins that could be
> used in biological attacks. The agency's continuing suspension of Texas
> A&M
> has struck a blow at the university's goal of becoming a national leader
> in
> research to counteract such attacks.
>
> The violations alleged by the CDC include the university's inability to
> account for at least three vials of microbes, which the CDC described as
> "missing." In addition, one researcher was working to develop
> antibiotic-resistant strains of a regulated bacterium even though he had
> not
> received the CDC's permission.
>
> What's more, laboratory workers did not don proper laboratory clothing or
> face masks to prevent their becoming infected and sometimes wore the
> clothing outside of the lab before it was decontaminated. At least seven
> times, workers were given access to regulated microbes before they gained
> permission under CDC rules, which require each worker to undergo a
> background security check.
>
> The letter describes the findings of an 18-member CDC inspection team that
> visited Texas A&M for five days in July. In late June, the agency had
> suspended all of the university's research with microbes defined as
> "select
> agents" under federal rules that took effect in 2002 as a result of the
> anthrax attacks a year earlier. The June suspension, the first of its
> kind,
> came after the university failed to promptly report two cases of
> accidental
> exposure of laboratory workers to infectious agents (The Chronicle,
> <http://chronicle.com/weekly/v53/i45/45a00101.htm> July 13).
>
> The inspector general's office of the U.S. Department of Health and Human
> Services, the CDC's parent agency, will now review the center's findings.
> The office has the power to fine the university up to $500,000 per
> violation. Under the rules, individual researchers involved face fines of
> up
> to $250,000 and prison terms of five years for each violation.
>
> In its letter Friday, the Centers for Disease Control did not characterize
> the severity of the alleged violations, and an agency spokesman, Von
> Roebuck, said the CDC would not elaborate.
>
> A Texas A&M spokeswoman, Sherylon Carroll, said university officials had
> scheduled a news conference for Thursday morning and would not comment
> before then. University officials have said that none of the university's
> regulated research threatened the public.
>
> But a critic said the university repeatedly disregarded public safety.
> "It's
> obvious that the program" at Texas A&M "was a disaster," said Edward
> Hammond, director of the American office of the Sunshine Project, an
> arms-control group that first publicized apparent problems at Texas A&M
> after obtaining public documents. "What's really striking" about the
> university, he said, "is the breadth of the violations. It's in all
> different aspects of their program."
>
> Among the problems cited by the CDC are the following: * The three
> "missing"
> vials contained Brucella abortus, a bacterium that causes fevers, but
> rarely
> death, in humans. They were used by a former university researcher. *
> Texas
> A&M's plans for safety, security, and emergency response involving
> research
> on the microbes were listed as drafts, and the university had not
> conducted
> drills at least annually to test the plans' effectiveness. * The
> university
> failed to produce several types of relevant records. They included
> training
> records for regulated lab workers, and documentation that deficiencies
> identified by the university's internal oversight board, the Institutional
> Biosafety Committee, had been corrected. * There was no coordinated
> response
> or assessment after routine blood tests of laboratory workers indicated
> possible exposure to microbes being studied. * Three of four principal
> investigators inspected by the CDC had "poorly organized inventory
> records"
> of the microbes they were studying, making "inventory reconciliation
> difficult and cumbersome." A laboratory device used in the research lacked
> a
> required filter to catch dangerous microbes in its exhaust.
>
> Days after the inspectors' visit, the university's vice president for
> research, Richard E. Ewing, resigned from that position. Texas A&M has
> since
> hired Claudia A. Mickelson, a biosafety expert from the Massachusetts
> Institute of Technology, to advise the university about how to improve its
> compliance with all select-agent rules.
>
>
>
> All locations should use approved procedures The solution by dilution is
> no
> longer adequate
>
> --
> Dr. Ted Labuza
> Morse Alumni Distinguished Teaching Professor of Food Science and
> Engineering
> Department of Food Science and Nutrition Univ. of Minnesota Rm. 136 A
> 1354
> Eckles Ave. St Paul 55108
> email - tplabuza@umn.edu Text Msg 6513072985@mobile.mycingular.com Cell
> 651-307-2985
> Office ( 612-624-9701 UM 7 fax 612-625-5272 NFNC 7
> Fax 661-483-3302
> web http://www.ardilla.umn.edu/Ted_Labuza
>
>
> "
>>
>> The weight of damp crystals to take agrees more or less with that
>> recommended by Wekell, and the concentration of picric acid is not
>> critical
>> anyway. Be careful how you dispose of any unused crystals and the filter
>> paper; down the sink with plenty of water.
>>
>> There are a couple of other points with regard to the picrate procedure
>> which are in my opinion not adequately dealt with in descriptions of
>> procedure.
>>
>> The TMA in extract after making alkaline is extracted into toluene and
>> the
>> calibration curve is prepared by similarly extracting standard solutions
>> of
>> TMA into toluene. You should note that the extraction of TMA into the
>> toluene phase is not complete. The proportion is high, around 90%
>> depending
>> on the concentration of alkali used, and is affected by the total solids
>> in
>> solution - a salting out effect. The fish extract is prepared in a TCA or
>> perchloric acid solution whereas the procedures describe the TMA
>> standards
>> being prepared in dilute hydrochloric. I recommend that the working TMA
>> standards be diluted from the stock using TCA or perchloric acid of
>> approximately the same concentration as in the extract. Similarly
>> extracts
>> should be diluted with this solution if they are of high concentration
>> and
>> need to be diluted into the working range. This brings me to the other
>> consideration.
>>
>> Typical demersal fish muscle contains about 80% water. A common
>> extraction
>> ratio for TMA determination is 1:3 fish muscle:extractant. Starting with,
>> say, 100g of fish the final volume of the aqueous phase is 380ml. In my
>> opinion the TMA in the 100g is dissolved in 380 ml and the amount in the
>> aliquot taken for analysis should be scaled up to this volume to give the
>> concentration in the muscle. This is the procedure always used in the
>> laboratory I worked in, but some published procedures, including the AOAC
>> procedure, scale up to the total mass of the extraction blend, 400g in
>> the
>> case of my example. This latter procedure will overestimate the
>> concentration by around 5% compared with the former. The procedure as
>> described by Dyer scales up to total mass, (using 200ml of TCA solution
>> in
>> this case, i.e scaling up to 300 rather than 280). Most papers on TMA
>> contents do not declare the how final concentration are calculated or
>> adequately cite the reference for the procedure used. These comments
>> apply
>> also to determination of TVB by distillation of extracts.
>>
>> Another consideration for reproducible results is to standardise how the
>> sample is taken from the fish. The TMA concentration within a fillet as
>> the
>> fish spoils and the TMA increases varies throughout the fillet. The
>> highest
>> concentration as one might expect are around the belly cavity and lowest
>> near the tail. In the case of a small fish perhaps the whole fillet can
>> be
>> taken, in a large fish perhaps standardise by taking a section above the
>> belly cavity, but not including the belly flaps.
>>
>> Peter Howgate
>>
>> ----- Original Message -----
>> From: "Shuming Ke" <shumingk@foodsci.umass.edu>
>> To: "Seafood research and extension information exchange"
>> <seafood@ucdavis.edu>
>> Sent: Friday, October 05, 2007 4:53 PM
>> Subject: how to measure TMA in fish tissue by Dyer method
>>
>>
>>> hi,
>>> I plan to use picrate method described by Dyer (j fish res bd can,
>>> 1945:351-
>>> 358) to determine TMA content in marine fish tissue. The basic concept
>>> is
>>> to
>>> react TMA extracted in toluene with 0.02% picric acid and measure
>>> absorbance
>>> at 410nm. In Dyer' method, dry picric acid is disolved in toluene to
>>> prepare
>>> 2% picric acid stock solution in toluene. Since dry picric acid is
>>> highly
>>> explosive and shock sensitive, this raises the question-- how to prepare
>>> picric acid solution in toluene? Do I just order dry (moisture free)
>>> picric
>>> acid solid and disolve in toluene? Any one has practical ideas on how to
>>> carry
>>> on the analysis? Many thanks.
>>> --
>>> Shuming Ke, Ph.D.
>>> Research Associate
>>> University of Massachusetts Marine Station
>>> P.O.Box 7128
>>> 932 Washington Street
>>> Gloucester, MA 01930
>>> shumingk@foodsci.umass.edu
>>>
>>> Office: 978-281-1930 x. 2
>>> Fax: 978-281-2618
>>>
>>>
>>>
>>>
>>
>
>
This archive was generated by hypermail 2b29 : Sun Oct 07 2007 - 11:56:05 PDT