Ion chromatographic determination of thiosulfate in oil shale leachates

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...

“…Electrochemical methods for cyanide determination include amperometry (3)(4)(5) and polarography (6). Sulfide can be determined by cathodic stripping voltammetry (7).…”

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Separation of sulfite, sulfate, and thiosulfate by ion chromatography with gradient elution

Sundén¹,

Lindgren²,

Cedergren³

et al. 1983

“…in oil shale leachates (23), are well separated in a short time of less than 16 min. It is quite clear from Figure 4 that low ppm detection limits could be easily achieved for the analytes since the absorbance scale is set on 0.1.…”

Section: Resultsmentioning

confidence: 95%

Indirect photometric chromatography of anions using sodium naphthalenetrisulfonate

Maki¹,

Danielson²

1991

A triply charged eluent has been characterized for anion-exchange chromatography with Indirect photometric detection. Sodium naphthalenetrisulfonate has shown particular promise for the separation and detection of N02", Br, N03", S042~, I", and SCN". The analysis of a mixture containing these anions can be performed In less than 16 min with detection limits of 0.4-1 ng for all anions. The determination of the strongly retained sulfur oxides such as dithlonlte, tetrathlonate, and other polythlonates can be easily accomplished with this highly charged eluent In a short time with high sensitivity. The chromatographic performance of this eluent requires no pH adjustment of the mobile phase. In addition, chromatograms obtained with this eluent were free from any system peaks.

“…Conversely, the conditions necessary for the efficient analysis of I™ results in little or no separation between the F™ and Cl™ peaks (3). Three common approaches, when confronted with samples containing species with widely varying retention times, are to use multiple injections under different analytical conditions (4,5), stronger eluents (6), or traditional eluents with a shorter separator column (7). These methods result in either extended analysis time or significant changes in the early portion of the chromatogram including loss of peaks.…”

mentioning

confidence: 99%

Gradient elution ion chromatographic determination of inorganic anions using a continuous gradient

Tarter¹

1984

A method is described for the production of a gradient elution solvent delivery system for ion chromatography. The system uses elther a two pump or a three pump configuration wlth a pressure of less than 400 psi. A 100-mm separator column and a fiber suppressor column are used along with both etectrochemical and conductometrlc detectlon. The Initial eluent is a 0.003 M NaHCO, to which a strong eluent (elther 0.004 M Na,CO, or 0.002 M Na,CO, + 0.002 M NaOH) is added. With the component arrangement described, F-, Ci-, and NO2-elute under essentlaily isocratic conditions. I-, SCN-, Cr2072-, and S20: -ail elute within 22 min. Retention times of less than 22 min are given for 18 different anions. The preparatlon and chemical composltlon of the gradients are discussed and gradlent proflles are presented. Ion chromatography as developed by Small et al.(1) has significantly altered the determination of inorganic and organic ions (2). One of the limitations to ion chromatography that restricts its use is that the relative retention times for species of interest can vary widely reducing the number of species amenable to analysis in any one given sample injection. A prominent example of this variation is in the analysis of the halide ions. The conditions necessary for the analysis of Fand Cl-ions result in an unacceptably long retention time and peak shape for the I-ion. Conversely, the conditions necessary for the efficient analysis of I-results in little or no separation between the F-and C1-peaks (3).Three common approaches, when confronted with samples containing species with widely varying retention times, are to use multiple injections under different analytical conditions (4,5), stronger eluents (6), or traditional eluents with a shorter separator column (7). These methods result in either extended analysis time or significant changes in the early portion of the chromatogram including loss of peaks. Silica-coated polyamide crown resins have been employed (8) but the resolution of common ions suffers to some extent. A method developed by Wang et al. (3) used a sequential electrochemical and conductometric detection scheme to analyze for F-, C1-, Br-, and I-in one sample injection. The analysis time reported by Wang et al. was approximately 30 min, but the method did require that the operator switch a valve a t a critical time in the analysis to redirect the fluid flow and thus minimize the analysis time.The concept of gradient elution chromatography has been widely and successfully employed in high-performance liquid chromatography for the analysis of species with widely varying retention times (9). Gradient elution has been applied to the analysis of SOS2-, Sod2-, and Sz02-containing solutions by Sunden et al. (10) but no attention was given to the early eluting species such as F-or C1-.