Ethanol (ethyl alcohol) analysis/testing is only being performed on one fluid due to the lack of buffers.
or reversed:
Due to a/the lack of buffers, ethanol (ethyl alcohol) analysis/testing is only being performed on one fluid.

See this:
Analytical Toxicology: For Clinical, Forensic, and Pharmaceutical Chemists
edited by Hans Brandenberger, Robert A. A. Maes
In a living person, the biological specimens collected for ethanol analysis will always be body fluids: whole blood, plasma, serum, urine and, very seldom , sputum
It sounds like buffers need to be prepared to carry out the analysis, or like the analysis can only be performed properly if buffers are present in the biological liquids being analyzed. If these buffers are lacking, only one biological fluid can be analyzed.

As I don't know much about chemistry, it's not clear to me whether this refers to a lack of buffers PREPARED for the analysis, or to a lack of buffers present in the biological fluids, but perhaps it wouldn't matter so much to your translation? Is this part of a report on forensic toxicology? (in which case the reference to "a living person" wouldn't exactly apply, but the liquids would be the same, no?)

See these links on buffers:
http://www.compacitypro.nl/Portals/3/D_FUN_T_EN.pdf
Several buffers are in our body to keep the pH of blood
constant at 7.4. Find one of the buffers in the list below.
a. acetic acid sodium acetate solution
b. hydrochloric acid sodium chloride solution
c. potassium bromide sodium chloride solution
d. lithium fluoride sulfuric(VI) acid

See this on buffers (this one makes is sound like buffers are prepared):
http://webdoc.nyumc.org/nyumc/files/sun-lab/attachments/MBPS...

http://jcp.bmj.com/content/54/9/699.full
Aims—To determine the concentrations of ethanol in femoral venous blood (FVB) and vitreous humour (VH) obtained during forensic necropsies.

http://ntl.bts.gov/lib/25000/25400/25452/DOT-HS-802-208.pdf
MANUAL FOR ANALYSIS OF ETHANOL IN BIOLOGICAL LIQUIDS

http://emedicine.medscape.com/article/1966150-overview
Vitreous fluid is ideal for postmortem chemical analysis, as it is relatively isolated from blood and other body fluids that are affected by postmortem changes such as redistribution and hemoconcentration.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1731529/
Uncertainty in estimating blood ethanol concentrations by analysis of vitreous humour



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Note added at 1 day1 hr (2012-05-12 07:45:38 GMT)
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Based on the reference to "vitreous humour concentration," this sounds related to a post-mortem toxicological analysis.


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Note added at 1 day10 hrs (2012-05-12 16:56:42 GMT)
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Am adding this note to say I take back what I said about the liquids used for analysis being the same in a living or deceased person. There would clearly be some differences! My point was actually that there would be various liquids to choose from.

In the case of your report, since the heading "vitreous humour concentration" is asterisked, it sounds like the analysis was performed on vitreous fluid (vitreous humour fluid).

See this:
http://emedicine.medscape.com/article/1966150-overview
Vitreous fluid is within the globe of the eye, between the retina and the lens. This substance is acellular, viscous, colorless, normally clear, and it is composed predominantly (99%) of water with glucose, hyaluronic acid, collagen fibers (type II), inorganic salts, and ascorbic acid. Vitreous fluid is ideal for postmortem chemical analysis, as it is relatively isolated from blood and other body fluids that are affected by postmortem changes such as redistribution and hemoconcentration.