Table 111. Results of Analyses Obtained by TSP Method for Various Binary Gas Mixtures Prepared a t Mound Laboratory PVT
Mixture
H, in Ar
H, in Ar CO in Ar CO, i n N e
fabrication value for inert gas, %
95.1 53.7 97.3 97.2
i
*
*
0.5 1.0 0.5 0.5
Mean value for inert
GmgF,e?
Re1 std dev, %
No. of determinations
95.14 53.06 97.34 97.15
0.02 0.06 0.03 0.03
10 6 6 6
in these determinations has been approximately twenty times better than that obtained by mass spectrometry. Also, indications to date are that proof of the accuracy of the TSP method is limited only by the accuracy of the prepared standards. In conclusion, the TSP method has been
demonstrated to be an accurate, highly precise, and versatile one for the determination of noble gases in active gas mixtures. LITERATURE C I T E D (1) R. K. Stump and E. G. Walter, "Analytical Chemistry Quarterly Report: January-March 1971", University of California, Lawrence Livermore Laboratory, Livermore, CA, UCID-15644-71-1, p 12. (2) J. C. Newton, F. 6. Stephens, and R. K. Stump, "Determination of Trace Noble Gases in Air and Natural Gas", Lawrence Livermore Laboratory, Livermore, CA, UCRL 74695, September 1973. (3) B. E. Kietzmann and D. D. Robertson, "General Characteristics of Titanlum Sublimation Pumps", 2nd ed., No. VAC 2224A, Varian Associates, Paio Alto, CA.
RECEIVEDfor review December 11, 1974. Accepted February 7, 1975. Mound Laboratory is operated by Monsanto Research Corporation for the U S . Energy Research Development Administration under contract No. AT-33-1-GEN53.
Quantitative Determination of Tartrate and Formate in Plating Baths M. K. Carter and Madeline Moore Dohrmann Division, Envirotech Corporation, 3240 Scott Boulevard, Santa Clara. CA 95050
Industrial process and wastewater facilities monitor and control total organic carbon (TOC) stream content (1, 2 ) . Analytical determinations of virtually any specific carboncontaining compounds, including all those found in wastewater and chemical process streams, can also be conducted using TOC analyzers (3). In this aid, the authors demonstrate a specific application for determination of the tartrate and formate content of copper process plating baths. The Dohrmann Model DC-50 TOC Analyzer, which uses a reductive conversion of carbon to methane, is sufficiently sensitive (range of 1 to 2000 ppm carbon) and accurate (to f 2 % or 1 ppm carbon, whichever is greater) to yield quantitative determinations of specific chemical components in a mixture of organic compounds. The boat inlet system of this analyzer makes the separation of volatile components from the total sample possible. Plating baths containing copper(I1) salts, formaldehyde, methanol, sodium formate, and potassium sodium tartrate are a mixture of volatile and nonvolatile components. Tartrates are used as a complexing agent to solubilize copper in alkaline solutions. During the plating operation, when copper is removed from solution, some tartrate is lost through dragout or decomposition. Make-up solutions, containing a predetermined quantity of tartrate and copper plus other constituents, must be added to reestablish the original bath condition. A simulated bath was prepared containing 40.4 mg formaldehyde, 13.2 mg methanol, 75.4 mg KNa tartrate, 18.9 mg Na formate, and 2.86 g CuCl2-2HzO dissolved in 100 ml deionized water. All chemicals used were of known purity (Baker Analyzed Reagent). The weight ratios, carbon content, and thermal data of the pure components of the bath are presented in Table I. Quantitative separations were obtained in the DC-50 TOC Analyzer based on widely spaced boiling points and decomposition temperatures. One portion of the bath was analyzed as prepared while another portion was adjusted to a pH 2 by addition of a small quantity of concentrated hydrochloric acid. A 30-111 portion of non-acidified sample was
placed in the platinum boat and held in the 90 "C vaporization zone for three and one-half minutes. The volatile component contained 203 f 2 ppm carbon (C) corresponding to methanol and formaldehyde. The boat was advanced to the 850 OC pyrolysis zone for an additional four minutes. A total (volatile plus residual) carbon content of 371 f 3 ppm C was measured. Analysis of the acidified sample yielded 237 f 1 ppm C as volatiles corresponding to methanol, formaldehyde, and formate (as formic acid) and 366 f 3 ppm C as the total carbon content. The difference of 371 366 or 5 ppm in total carbon values, although within specified error limits of the analyzer, may be due to loss of impurity carbonate upon sample acidification. Total analysis time for one acidified and one non-acidified sample is 15 minutes or 7.5 minutes per sample. Each value reported is an average of ten determinations. A measure of precision is reported by the standard deviations as a fl sigma error. Tartrate concentration of the bath was determined by taking a difference of the total and volatile measurements of the acidified sample. A result of 129 ppm C compares favorably with the theoretical value of 128 ppm C. Similarly, subtraction of the volatile portion of the nonacidified from
Table I. Plating B a t h Composition \ \ e i g h t ratio
Component
Formaldehyde Methanol Formic acid D L - Tartaric acid N a formate NaK tartrate CUC1, 2H2O
of compo-
Carbon contribution
nents in bath
to bath,ppm C
0.54 0.18
... ...
0.25 1.00 37.9
162 49
...
...
33 128 5 (a blank)
Thermal data of pure components,'
c
bp = -21 bp = 68 bp = 100 mp = 209-211 dec. mp = 253 mp > 250
.. .
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the acidified sample yields 237 - 203 = 34 ppm C as formate (33 ppm C theoretical). A second bath prepared as above, but with no copper salt, produced identical results. Thus, the large excess of copper salt present in the original bath caused no deleterious effect. These excellent results demonstrate the useful function a TOC analyzer serves in industrial process control. Specifically, both the tartrate and formate contents of the bath can be quantitatively determined using a TOC analyzer,
which can affect the separate analysis of volatile and total components.
LITERATURE CITED (1) Fed. Regist., pp 34541-34558, Dec. 14, 1973. (2) Fed. Regist., pp 28758-28760, Oct. 16, 1973; Note 1 (3) M.K. Carter and C.Goodell, Am. Lab., 6, 43 (1974).
RECEIVEDfor review November 7 , 1974. Accepted March 21, 1975.
Low Power, Programmable, Non-Reactive Air Sampler for Field Use S. 0. Farwell,’ H. H. Westberg, and R. A. Rasmussen Air Pollution Research, Engineering Research Division, Washington State University, Pullman, Wash. 99 163
The need for an inexpensive, yet versatile, air-sample collection system originated as a result of our current research in the analysis of ambient air for ozone and light hydrocarbons ( I , 2). For example, in addition to extensive aircraft monitoring along different flight paths and routine sampling at the location of the mobile field laboratory, integrated bag samples of air would be collected for variable sampling times at several remote sampling sites. These bag samples would be collected for subsequent analysis at the mobile field laboratory. In order to satisfy our sampling requirements, the collection system would incorporate the following design features: (a) low power consumption to permit battery operation, (b) adequate temperature stability for field use, (c) automatic collection of an integrated air sample, (d) programmable sampling times, (e) a cycle timer with sufficient noise immunity to operate in a relatively high noise environment (e.g., close proximity to the dc pump motor), (f) both the controller and the pump should be capable of operating a t the same dc supply voltage, (g) optimum operational simplicity and reliability, and (h) small in size and light-weight. In addition, the sampling pumps and sample bags should not contaminate or destroy the gases being collected. A digital timer constructed with integrated circuits, a non-reactive sampling pump with gas-contacting parts of Teflon, and a Teflon sample bag have been combined to produce an air collection system with the above-mentioned characteristics. Timer Circuit Design and Operation. Figure 1 shows the detailed circuit diagram of the programmable, control timer. This sampling controller actually consists of two individual timers: (a) the two uppermost XR-2340 integrated circuits in Figure 1 have been cascaded to generate the longer time delays associated with the specific time intervals between initial field triggering and the period of time before the sampling pump is turned on; (b) the lower XR2340 unit in Figure 1 controls the shorter duration of the actual sampling period, or the length of time that the pump motor operates. The two cascaded XR-2340 units are connected for low-power operation by leaving the Vf+ terminal (pin 16) of the second XR-2340 open-circuited; thus the second XR-2340 is powered from the regulated output of the first XR-2340 by connecting pins 15 of both units ( 3 ) .
Author to whom correspondence should be addressed. 1490
ANALYTICAL CHEMISTRY, VOL. 47, NO. 8, JULY 1975
Unlike integrated circuit timers such as the popular 555 ( 4 ) that have a time delay which is determined by a single charging cycle of the external timing capacitor, the XR2340 uses a time-base oscillator to provide multiple cycles. These multiple cycles of the XR-2340 permit reasonable values of timing capacitance for time delays in excess of several days without a deterioration in timing accuracy because of excessive leakage contributed by the circuit components. The XR-2340 timer/counter circuit consists of three basic sections: (a) a time-base oscillator, constructed from two voltage comparators and a R-S flip-flop, that acts as a relaxation oscillator; (b) a control flip-flop that includes a trigger input and a reset input; and (c) a programmable %bit binary counter. Prior to the application of a trigger input, the circuit is in its reset state where both the time-base and the counter sections are disabled and all the counter outputs are at a high logic state. The timing cycle is initiated by a positive-going pulse at the trigger input which in turn actuates the time-base, enables the counter section, and sets all the counter outputs to their low logic state. The time-base oscillator generates precise timing pulses of period T , where T is equal to the time constant determined by an external timing resistor and timing capacitor. The clock pulses coming out of the time-base oscillator are counted by the binary counter section. Two XR2340 circuits can be cascaded in which case the delay provided is increased in a geometric rather than an arithmetic progression. When the pre-programmed count is reached, the circuit completes the timing cycle and resets itself. The XR-2340 integrated circuit has been recently described in a laboratory timer designed by Karlsson (5). His timer was constructed by combining a XR-2340 with standard T T L logic devices, and consequently is designed for applications in the laboratory. The CMOS circuit components shown in Figure 1 were selected so that the resulting timer would be suited for field application rather than use in a ordinary laboratory. The advantages of the CMOS logic family over their equivalent T T L designs for low power, portable equipment have been recently demonstrated and reported (6, 7). The delay function of the timer is programmed by selectively shorting any one of the switches, S5-Sl2, or any multiple of these switches from the second XR-2340 circuit to its output bus. In this manner, one can program the delay timing cycle from T2 I T,ff I 255 TP,where Teff is the total time delay and T2 is the time-base period of five min-
