EQUIPMENT--Sample Splitting Devices

In Reply Refer To:                                 April 16, 1993
Mail Stop 412


Subject:  EQUIPMENT--Sample Splitting Devices

Within the Water Resources Division (WRD), composited water 
samples traditionally have been subsampled for field and 
laboratory analyses by means of a churn splitter or, less 
frequently, a cone splitter.  Historically, the splitting devices 
have been constructed of plastic, which has proved adequate for 
many water-quality parameters including field measurements, major 
ions, and nutrients.

There are two concerns with using plastic devices for water 
samples that are to be analyzed for trace elements and semi- 
volatile trace organic chemicals (pesticides and base/neutral 
compounds).  The first concern is contamination of the water 
sample by material inherent in the plastic.  The second is analyte 
loss from the water sample due to sorption onto the plastic 
surfaces.  To avoid these two potential problems, an all-Teflon 
cone splitter has been created, and plans are in progress for 
fabricating an all-Teflon churn splitter.  The probability is that 
chemicals will have less of a tendency to sorb to a Teflon surface 
and, if cleaned properly before use, such containers should not 
contaminate water samples.  However, experiments need to be run to 
test:  (a) assumptions concerning contamination and analyte loss 
for all constituents, and (b) the splitting characteristics of the 
churn and cone splitters.

Accordingly, the Office of Water Quality (OWQ) is beginning a 
series of studies aimed at evaluating the usefulness and 
limitations of splitting devices for water samples.  Areas of 
investigation will include:

     1.  Contamination potential and proper cleaning procedures--
         for both polyethylene and Teflon splitters--for the
         various splitting devices for a wide variety of analytes;

     2.  Potential for analyte loss for polyethylene and Teflon 

     3.  Precision and accuracy of solids splitting;

     4.  Precision and accuracy of dissolved chemical splitting;

     5.  Reproducibility between different splitting devices;

     6.  Reproducibility between splitters of the exact same type;

     7.  Effects of different operators on the reproducibility of

Paul Capel will coordinate the studies.  Suggestions/concerns 
should be communicated to Paul by telephone (612/471/0438) or 
FAX (612/471/9070).

The all-Teflon cone splitter has been used successfully within 
the WRD since 1991 for processing water samples for pesticides.  
A recent study (Attachment 1) evaluated the precision of the all-
Teflon cone splitter for splitting water and solids over a range
of particle sizes, sample volumes, and sample introduction 
techniques.  The overall conclusion was that the all-Teflon cone 
splitter is comparable to the traditional plastic cone splitter.

Results of the additional studies will be forthcoming from OWQ 
over the next several years.

                                   David A. Rickert
                                   Chief, Office of Water Quality


This memorandum does not supersede any Office of Water Quality 
Technical Memorandum.

Key Words:  Equipment

Distribution:  A, B. S, FO, PO