An improved version of our magnetic suspension densimeter has been developed for use with samples of aqueous systems as small as 100 μl. The instrument’s sensitivity to a change in density of the solution under test (measured as a voltage shift) is 0.1 mV≊4.5×10−6 g ml−1, with a base‐line drift less than 9 μV/h. The nonlinearity of the densimeter’s response is less than 5 ppm over its calibration range. In this paper, we describe the new magnetic suspension circuit, discuss the precision limits of the instrument, and present the results of measurements made on a tetracarboxylate sequestering agent known as BAPTA which we use as a calcium‐ion indicator.
REFERENCES
1.
2.
D. W.
Kupke
and T. H.
Crouch
, Methods Enzymol.
48
, 29
(1978
).3.
4.
5.
R.
Masui
, W. M.
Haynes
, R. F.
Chang
, H. A.
Davis
, and J. H. M.
Levelt Sengers
, Rev. Sci. Instrum.
55
, 1132
(1984
).6.
7.
D. W.
Kupke
and T. E.
Dorrier
, Biochem. Biophys. Res. Commun.
138
, 199
(1986
).8.
9.
W. M.
Haynes
, M. J.
Hiza
, and N. V.
Frederick
, Rev. Sci. Instrum.
47
, 1237
(1976
).10.
11.
N. V.
Frederick
and W. M.
Haynes
, Rev. Sci. Instrum.
50
, 1154
(1979
).12.
B. H. Pasewark, Masters thesis, University of Virginia, 1979.
13.
14.
15.
A. T.
Carmichael
, S.
Hinchliffe
, P. N.
Murgatroyd
, and I. B.
Williams
, Rev. Sci. Instrum.
57
, 1611
(1986
).16.
M. B.
Scudiere
, R. A.
Willems
, and G. T.
Gillies
, Rev. Sci. Instrum.
57
, 1616
(1986
).17.
Linear Databook (National Semiconductor Corporation, Sunnyvale, CA, 1980), pp. 2‐38–2‐43.
18.
W. A. Koldewyn, Doctoral dissertation, Wesleyan University, 1976.
19.
R. C. Ritter (private communication).
20.
D. V. Stout and M. Kaufman, Handbook of Operational Amplifier Circuit Design (McGraw‐Hill, New York, 1976), pp. 20‐1–20‐4.
21.
G. T. Gillies, Doctoral dissertation, University of Virginia, 1980.
22.
23.
24.
C. K.
Schauer
and O. P.
Anderson
, J. Am. Chem. Soc.
109
, 3646
(1987
).
This content is only available via PDF.
© 1988 American Institute of Physics.
1988
American Institute of Physics
You do not currently have access to this content.
