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A simple gradient apparatus, consisting of a perlstaltic pump in addltlon to a standard hlgh-pressure pump, Is descrlbed. The device is used to make a slngle-run ion chromatographic separation of sulfite, sulfate, and thiosulfate In less than 15 min. This separatlon requlred a step gradlent with 4.8 mM NaHC0,/4.7 mM Na,CO, as start eluent and 6.9 mM NaH-COJ8.6 mM Na,CO, as final eluent when two (4 X 50) mm Dionex anion precolumns In serles were used as separator. The eluent compositions were slmplex optlmlzed.Ion chromatography (IC) (1) has been shown to be a suitable analytical technique for determination of sulfur anions such as sulfite, sulfate, and thiosulfate. One of the major problems concerned with these analyses is that the retention time for thiosulfate is unacceptably long when determined under the same ion chromatography (IC) conditions as for sulfite/sulfate. Holcombe et al.(2) have reported IC determinations of these sulfoxy ions, but two separate IC runs with different eluents for sulfite/sulfate and thiosulfate, respectively, were required. Trujillo et al. (3) reported on the use of a very short column with high eluent flow rate to elute thiosulfate in about 4 min. However, this short retention time for Sz032-caused the other anions present, such as F-, C1-, NO;, NO3-, PO?-, and Sod2-to elute as a single peak. As a consequence, two separate IC runs are required for the sulfite, sulfate, and thiosulfate analyses. Gjerde et al. (4, 5 ) have shown chromatograms with thiosulfate and sulfate well separated, with a retention time for thiosulfate of about 12 min. However, their tabulated retention times for sulfite and sulfate indicate poor separation of these ions.The purpose of this paper was to investigate the possibility of separating sulfite, sulfate, and thiosulfate in an acceptable time in a single IC run. EXPERIMENTAL SECTION Instrumentation.A diagram of the complete ion chromatograph is presented in Figure 1. The system consisted of the following parts: (1) a Constametric I11 Pump (Laboratory Data Control) which delivers the eluent at a constant flow rate through the sample loop, the analytical column, the suppressor column and the conductivity cell; (2) a stepper motor driven peristaltic pump P-1 (Pharmacia Fine Chemicals) used to generate gradients in eluent strength, the pump speed was controlled by a homemade variable frequency sweep generator (F.S.G.); (3) a sample injection valve (Rheodyne 70-10) with 50-, loo-, or 200-pL sample loops;(4) two plastic (4 X 50) mm anion precolumns (Dionex Corp., catalog no. 030825) were coupled in series to serve both as precolumn and analytical column; (5) a laboratory made (5.7 X 300) mm glass column packed with Amberlite AG, 100-200 mesh (Serva AG), in the hydrogen form serves as suppressor column, the suppressor was regenerated with 0.5 M H2S04; (6) a Conducto Cell with Conducto Monitor (LDC) to serve as the detector; (7) a Vitatron two-channel recorder to trace the chromatograms.Chemicals. All solutions were prepared in doubly deionized water using reage...

Gas permeable poly(tetrafluoroethylene) (PTFE) tubings were used to lower the background conductivity from hydrogen carbonate/carbonate eluents in suppressed Ion chromatography (IC). The carbonic acid concentration In the effluent c c tubing Specifications according to manufacturer. 6 Not known by the authors. c Not specified.EXPERIMENTAL SECTION Instrumentation. The ion chromatograph described in a previous paper (1) was used with an additional postsuppressor device. The separator columns used were either one (4 X 250 mm) anion separator column (No. 030827 Dionex Corp., Sunnyvale, CA) or two (4 X 50 mm) anion precolumns (No. 030825 Dionex Corp., Sunnyvale, CA). The two precolumns were joined together by a special connector with no dead volume in order to get one

Abstract:The built environment accounts for a significant share of energy consumption and energy efficiency in this sector is important for the Swedish environmental objectives. Only a limited share of the total new construction of multifamily houses are constructed as low-energy buildings. Current building regulations lay down requirements for energy efficiency for new construction, and these will be tightened further in the future. Public housing companies often aim to be at the forefront, and the public housing sector has now built half of Sweden's low-energy blocks of flats. Many public housing companies have tried, but it is uncertain if they will, or have, the possibilities to construct low-energy buildings on a large scale. Twenty public housing companies around Sweden have been interviewed with the aim of identifying obstacles and possibilities to be forerunners and build better than required by the building regulations. The study shows that the public housing companies build better than the law demands and intend to continue doing so. Low-energy buildings are particularly suitable in central locations where land is attractive and the required returns lower. The driving motivation is to be at the forefront and to build green. The new pressure to increase house building can lead to a risk of energy and quality issues being passed over. For the increase in the construction of low-energy buildings to continue, extended, shared and comparable decision making support for the public housing companies is needed.

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