EDITORS' COLUMN
A \ SULFUR DIOXIDE pollution mon
itoring device, in which several manufacturers have already shown an interest, has been developed b y National Bureau of Standards Phys ical Chemistry Division researchers Hideo Okabe a n d J o s e p h Ball and N B S guest worker Paul Splitstone. T h e detector, based on t h e measure ment of t h e fluorescence of S 0 2 in air, is rapid, continuous, nearly specific to SO2, a n d linear in re sponse up to 1600 p p m . T h e new device should prove valuable in t h e monitoring of smoke stack gases. About 80 million tons of SO2 a r e released into t h e atmo sphere each year, mainly through the burning of sulfur-bearing coal and oil, a n d . through such indus trial processes as oil a n d metal refining. Concentrations of S 0 2 as low as a few p a r t s per million in t h e air can cause breathing difficulty, kill plants, leach limestone, and de grade paper and leather. A recent California law limits t h e S 0 2 con centration in stack gases to 500 ppm, a n d similar laws are being considered by other states. T h e lower limit of detection of t h e X B S SO2 monitor in its present form is 20 ppb, and a special light source is being developed t h a t should make it possible to reach even lower levels. T h e fluorescence of S 0 2 is pro duced in a cell a t t a c h e d to t h e de tector by radiation from either a zinc or cadmium vapor lamp op erating on alternating current. Be fore entering t h e fluorescence cell, the light passes through a 10-cm chlorine filter t h a t transmits more t h a n 9 0 % of t h e exciting zinc (213.8 nm) or cadmium (228.8 nm) line b u t absorbs almost completely source emission lines from 270 to 390 nm. (This is necessary because t h e fluorescence from S 0 2 covers the region from 240 to 420 nm.) T h e light is t h e n focused a t t h e center of t h e fluorescence cell, and the SO2 fluorescence is detected by a photomultiplier and displayed on a
strip chart. A glass filter between the fluorescence cell a n d photomultiplier rejects those source emis sion lines passed b y t h e chlorine cell. Ozone, H 2 S, N 0 2 , CO, C 0 2 , a n d H 2 do not interfere with S 0 2 detec tion in t h e monitor, whereas large concentrations of CS 2 (500 times t h e S 0 2 concentration), N O (500 times), and C2H4 (4000 times) do interfere. W a t e r vapor decreases t h e S 0 2 signal—at room temperature, a relative humidity of 1 0 0 % reduces the S 0 2 signal by 25%'—and a correction must be applied according to t h e concentration of water vapor in t h e air. T h e response of t h e detector u p to 10 p p m was calibrated with S 0 2 permeation tubes available from N B S under t h e Standard Reference Material program, b y use of air flow rates from 0.3 to 3 l./min. Above 10 p p m t h e device was calibrated with static a i r - S 0 2 mixtures. Our J a n u a r y 1973 I n s t r u m e n t a tion feature, " C u r r e n t I n s t r u m e n t a tion for Continuous Monitoring for S 0 2 , " b y Craig D . Hollowell, Glenn Y. Gee, a n d Ralph D . McLaughlin of t h e Lawrence Berkeley Labora tory, reflects further interest in t h e problem of S 0 2 monitoring. I n strumentation discussed will include conductimetric, colorimetric, amperometric (coulometric), and elec trochemical transducer analyzers; analyzers using flame p h o t o m e t r y or gas chromatography-flame photom etry; nondispersive absorption, dispersive absorption, correlation, and second-derivative spectrom eters, condensation nuclear forma tion analyzers, and a s u m m a r y of new developments in air monitoring instrumentation. T h e I U P A C has announced t h e availability of Nomenclature Ap pendices N o . 23, "Symbols for Amino-Acid Derivatives a n d P e p tides," a n d N o . 25, "Recommenda tions on Nomenclature for Nuclear Chemistry." Interested readers may refer to Anal. Chem., 44 (11), page 69 A for information concern ing procurement of these documents and t h e solicitation of pertinent comments.
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Alan J. Senzel CIRCLE 1 8 0 O N READER SERVICE CARD
ANALYTICAL CHEMISTRY, VOL. 4 4 , NO. 13, NOVEMBER 1 9 7 2 ·
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