System peaks Sulfate

Figure 13.7 Electropherograms showing the simultaneous measurement of low- and high-energy explosives as recorded with the (a) conductivity and (b) amperometric detectors. Analytes, ammonium (1), methylammonium (2), sodium (3), TNB (4), TNT (5), 2,4-DNB (6), and 2-Am-4,6-DNB (7), system peak (SP). Explosive concentration, 2 mM (1,2,3) and 15 ppm (4,5,6,7). Conditions MES/His buffer (20 mM, pH 6.1) containing 15 mM lithium dodecyl sulfate as the run buffer separation field strength, +250 V/cm injection field strength, +250 V/cm for 2 s detection at 200 kHz, (a) 5 Vp p and at (b) —0.5 V. (Reprinted in part with permission from [34]. Copyright 2002 American Chemical Society.)...

Figure 13.6 Indirect detection of anions and cations. Stationary phase //-Bondapak-Phenyl. Mobile phase naphthalene-2-sulfonate 4 x 10 M in 0.05 M phosphoric acid. Sample (1) butyl sulfate, (2) pentyl amine, (3) hexane sulfonate, (4) hep-tylamine (5) octane sulfonate (6) octyl sulfate (S) system peak. Reproduced with permission from J. Crommen, G. Schill, D. West-erlund and L. Hackzell, Chromatographia, 24 (1987) 252 (Fig. 1).

Hgure 4 Electropherogram of 100-fold dilution of urine from a subject supplementing with creatine. The separation was carried out at 17kV with hydrostatic injection for 20 s, using a 30 mmol r phosphate-150 mmol r sodium dodecyl sulfate buffer, pH 6, and detection by absorbance at 214nm. The unlabeled peak is a system peak. 

Wescan 269-001 [64], the once popular silica-based ion exchanger, which was based on a macroporous substrate with a pore width of 300 A, is not manufactured anymore. A specific feature of this column was the large retention difference between mono- and divalent anions with a negative signal appearing in the chromatogram after the elution of sulfate at about 20 min. This peak is called system peak (see Section 3.7.4.2), which is inevitable when employing phthal-ates as eluents. 

Also in this case, the appearance of a system peak after about 28 min significantly increases total analysis time and is therefore disadvantageous. However, this is not the only factor limiting the applicability of this method to routine analysis. In real-world samples, environmentally relevant anions such as sulfide and cyanide occur only at very low concentrations in the presence of high amounts of chloride and sulfate. Because divalent anions are strongly retained... 

According to the Kuwabara-Wassink paper, the purified luciferin in aqueous neutral buffer solution showed an absorption maximum at 320 nm, and a fluorescence emission peak at 490 nm. The luminescence emission maximum measured with Airth s fungal luciferase system was 524 nm at pH 6.5, whereas the chemiluminescence emission maximum of the luciferin with H2O2 plus a droplet of strong NaOH plus ferrous sulfate was 542 nm. No information was reported on the chemical nature of the luciferin. 

The distribution of endosulfan and endosulfan sulfate was evaluated in the brains of cats given a single intravenous injection of 3 mg/kg endosulfan (Khanna et al. 1979). Peak concentrations of endosulfan in the brain were found at the earliest time point examined (15 minutes after administration) and then decreased. When tissue levels were expressed per gram of tissue, little differential was observed in distribution among the brain areas studied. However, if endosulfan levels were expressed per gram of tissue lipid, higher initial levels were observed in the cerebral cortex and cerebellum than in the spinal cord and brainstem. Loss of endosulfan was most rapid from those areas low in Upid. Endosulfan sulfate levels peaked in the brain at 1 hour postadministration. In contrast, endosulfan sulfate levels in liver peaked within 15 minutes postadministration. The time course of neurotoxic effects observed in the animals in this study corresponded most closely with endosulfan levels in the central nervous system tissues examined. 

The separation of the two stages is easier to discern when the rates of the two processes are so different, but it can also be seen in the ultrasonic spectra of metal-sulfate systems (Sec. 3.4.4). Ultrasonic absorption peaks can be attributed to formation of outer-sphere complexes (at higher frequency, shorter t) and collapse of outer-sphere to inner-sphere complexes (at lower frequency). In addition to uv spectral and ultrasonic detection, polarimetry and nmr methods have also been used to monitor and measure the strength of the interaction. There are difficulties in assessing the value of ATq, the outer-sphere formation constant. The assemblage that registers as an ion pair by conductivity measurements may show a blank spectroscopically. The value of Aq at T" K may be estimated using theoretically deduced expres-... 

Cysteamine (/3-mercapto-ethylamine) is used for the treatment of nephropathic cystinosis. Cysteamine converts within lysosomes cystine into cysteine and cysteine-cysteamine mixed disulfide, both of which can exit the lysosome thus removing the extra cystine. After oral administration peak plasma levels are reached at about 1.4 hours post dose. It is eliminated as a sulfate in the urine with a half-life of 4-5 hours. The most frequent adverse reactions seen involve the gastrointestinal and central nervous systems. Side effects include abdominal pain, diarrhea, drowsiness, fever, loss of appetite, nausea or vomiting and skin rash. Confusion, dizziness and headache may occur. 

UPD of Cu on Au(lll) electrodes in the presence of sulfate anions has been particularly intensively studied, both experimentally and theoretically [397] (for the review covering the literature up to 1995, see Ref. 398). Sulfate ions are specifically coadsorbed with underpotentially deposited Cu at negative potentials. For this system, a very striking phenomenon is the appearance of two voltammetric peaks, separated by 50-150 mV, upon addition of Cu " " ions to the H2SO4 solution [382, 397, 399-401]. For the potential range separating the peaks, the existence of adsorbate layer of the (. 3 x. 3) structure. 

Subsequently, Carson et al. (1995) and Neubauer et al. (1996, 1997) reported the ability to provide specia-tion of some aerosol components such as ammonium sulfate, ammonium sulfite, and methanesulfonic acid through control of the ionizing laser pulse energy, and Reents et al. (1995) showed that parent peaks could be obtained even for components such as Si02 that are difficult to ionize. Hinz et al. (1996) reported the simultaneous detection of both positive and negative ions produced by laser ionization of a single particle using a dual TOF system. 

System Suitability Make three replicate injections of the Standard Preparation. They should show a relative standard deviation of not more than 4.0% for the response factor of the sodium methyl sulfate peak obtained using the formula... 

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