Eluents perchloric acid

Magnesium, calcium, barium, and strontium can also be deterrnined by ion chromatography with y -phenylenediamine in perchloric acid as the eluent. Ion chromatography by conductimetric detection has been described, and appHcations to environmental waters have been discussed (1,22—23). 

HPLC on a Cosmosil 5 Cis column, using a perchloric acid-acetonitrile eluent (pH 7.6), followed by CLD in the presence of hydrogen peroxide and bis(2,4,6-trichlorophenyl) oxalate (42), was applied to the determination of 1-aminopyrene (43a) and various diaminopyrenes (43b-d). Ascorbic acid was added to avoid oxidative degradation of the aminopyrenes in the presence of metals LOD in the sub-fmol range (SNR 3)147. A fast (less than 10 min) HPLC-ELCD method was proposed for determination of dopamine (19b) and its metabolites in microdialysates, using packed fused silica capillary columns LOD 0.05 Xg/L of dopamine in a 2 XL sample, RSD 3% (n = 10)148. 

Figure 4.7 Anion exchange separation of carboxylic acids in red wine. Column, Shodex C811, 100 cm x 7.6 mm i.d. eluent, 3 mM perchloric acid flow rate, 0.9 ml min-1 temperature, 60 °C detection, reaction detection using chloro-phenol red at 430 nm. Peaks 1, citric acid 2, tartaric acid 3, malic acid 4, succinic acid 5, lactic acid 6, formic acid and 1, acetic acid.

When sample components having ionizable groups are chromatographed the use of a background electrolyte and control of the eluent pH with an m>propridte buffer are mandatory. It is advisable to maintain a fairly high concentration of buffer in the medium in order to rapidly reestablish protonic equilibria and to thereby avoid peak sjditting or asymmetrical peaks due to slow kinetic processes. Acetic acid, phosphoric acid, and perchloric acid and their salts have been used for the control of pH. 

Davenport and Johnson [30] used ion exchange chromatography on Amberlite IRA-900 strongly basic resin to determine nitrate and nitrite in water. 0.10M perchloric acid was used as eluent and an electrochemical cadmium electrode detector was used. 

The cell free samples were mixed with perchloric acid/perchlorate and stored at low temperature for 48 h, at 6000 rpm centrifuged, decanted, stored at -22°C for a week and centrifuged again for deproteination. The separation was performed on an ion exclusion polystyrene/divinylbenzene column at 40 °C with 15 mM sulfuric acid as eluent and detection at 205 nm. For the quantification a standard was applied. A typical chromatogram is shown in Figure 6. Pyruvate, succinate, lactate, formate and acetate were detected in the cultivation medium. 

Acid eluents serve a dual function. First, the acid will protonate the amine so that the amine will interact with the resin and the hydrogen ion will serve as the exchange ion in the chromatographic process. The eluent suitable for the separation of aromatic amines is an aqueous perchloric acid solution. Other mineral acids can also be used but may form complexes with metals in the sample or the chromatograph or oxidize components of the sample., ... 

A series of perchloric acid solutions were prepared as the eluent. Each eluent was flushed through the chromatograph until a stable baseline was obtained. Each individual amine was injected onto the column using the 0.5 ml sample loop. The amine was allowed to elute if possible. If after sixty minutes the amine had not eluted, the system was flushed with 1 M HCIO4 to remove the compound. The order of elution of the amine and the effect of eluent concentration on the retention time were determined. 

Because of the cobalt(II) contamination, the perchlorate salt is synthesized and then converted to other salts. Cobalt(II) chloride 6-hydrate (1.0 g, 4 mmole) and free [15]aneN4 (05 g, 4.2 mmole) are warmed in 100 mL of methanol for 15 minutes. Concentrated hydrochloric add is added dropwise (1 mL) and air is bubbled through the solution for at least 2 hours. Several drops of perchloric acid are added to precipitate the products as the perchlorates. The yield is 72%. The product is brown and is about 90% pure isomer I. The brown perchlorate salt is dissolved in acetonitrile and passed through a Dowex 1X8,200-400 mesh anion exchange column (Cl form) at a rate of 10 sec/drop. The eluent is concentrated by rotary evaporation. Some green solid (isomer II) precipitates. This is filtered and the volume of the filtrate is further reduced to precipitate the tan isomer (I) as the chloride salt. Yield 60% Anal. Calcd. for CoC2r H26N4a3 C, 34.80 H, 650 N, 14.76. Found C, 34.35 H, 7.09 N, 14.50. 

Benzodiazepines can be chromatographed with methanolic eluents containing perchloric acid (typically 0.001 M). Retention can be modified by the addition of other organic solvents (e.g. ether) or by changes to the acid concentration. 

Eluent. Methanol to which has been added 100 pi of perchloric acid per litre. 

Human serum analysis Eluent A (0.05 M perchloric acid ACN = 60 40)/eluent B (0.05 M perchloric acid ... 

The classification of eluents into the two categories mentioned above is only meaningful and necessary in the framework of conductivity detection with its different application requirements. Eluent selection is much easier for applications using spectrophoto-metric or amperometric detectors, respectively. In photometric detection, both the photometric properties of the eluent ions and their chemical properties have to be taken into account nevertheless, a large number of eluents are available. The alkali salts of phosphoric acid, sulfuric acid, and perchloric acid have proved successful, because they all feature a good UV transmittance. In the field of amperometric detection, the choice... 

Columns packed with the 12 % cross-linked resin, 6.1 mequiv/g exchange capacity gave good separations of metal cations. Using 8 different concentrations of perchloric acid eluents, from 0.10 to 1.00 M, retention times for 36 metal ions were measured... 

The selectivity of sulfonated ion-cxchange resins for metal cations is often expressed qualitatively in terms of elution orders. Numerical selectivity data for cations are limited [3-5]. Strelow and co-workers [6-8] published comprehensive lists of distribution coefficients for metal ions with perchloric acid and other mineral acid eluents. However, their data are for sulfonated gel resins of high exchange capacity. 

The approach is to measure retention times of metal cations on columns containing low-capacity resins with eluents containing perchloric acid or various perchlorate salt.s. The perchlorate anion is used to eliminate any possible complexing of a metal ion by the eluent anion. Retention factors (k) are calculated from the retention data. 

The elution order of metal ions reported in Table 5.5 is similar to that reported earlier by Strelow and Sondorp [8] with perehloric acid eluent and gel resins of high exchange capacity. Strelow and co-workers noted anion-complexing effects on elution orders in several cases when eluent acids other than perchloric acid were used. 

The data in Table 5.4 (perchloric acid eluent) and Table 5.5 (sodium perchlorate eluent) were plotted according to Eq. 5.19. Linear plots were obtained in all ca.ses. (See Fig. 1 for an example.) The slopes, obtained by linear regression, arc given in Table 5.4 for perchloric acid and in Table 5.5 for sodium perchlorate. In most cases, the negative slope was very close to the charge on the metal ion. The somewhat low values obtained for Be(II) and Bi(III) in Table 5.6 may be due to partial hydrolysis of... 

Table 5.4. Retention factors (k) for various cations when perchloric acid eluents are used.

The capacity factors for metal cations were measured with 0.75 M perchloric acid eluent on resins of 6.1,13.8, and 24.9 pequiv/g exchange capacity. The results, shown in Table 5.9, show a substantial increase in capacity factors with increased resin capacity. According to Eq. 5.19, the logarithm of k should vary linearly with the logarithm of resin capacity, C. Linear plots are indeed obtained but the slopes are lower than the theoretical values and they vary from one metal ion to another. 

A 1-g portion of the modified catalyst was washed with THF (two 10 cm portions), methanol (two 10 cm portions), and distilled water (two 10 cm portions). The catalyst was suspended in 15 cm of a 1 mol dm NaOH solution at 373 K to remove the tartaric acid from the surface to the solution. The supernatant was collected by decantation, and the remaining catalyst was washed three times with lOcm water. After the combination of the supernatant and the washings, the solution was filled to 50 cm with water. The amormt of tartaric acid was determined by an ion chromatograph equipped with a Shodex KC-811 (8 mm ID X 300 mm) at 313 K. The eluent 1 mmol dm perchloric acid. 

The alkylating agent melphalan (Figure 6.3) has been measured in plasma using a phenyl-modified silica column with acetonitrile-aq. sodium phosphate buffer (0.1 mol L pH 4.5) (6 + 44) as eluent and ED (PGEs, Ei -fO.l V, E2 -1-0.6 V, vs Pd)." Sample preparation involved perchloric acid treatment and LLE into chloroform to remove interferences. No internal standard was used. The LoD was 2 pg L (1 mL sample). 

Substituted propionic acid derivatives and related compounds form an important class of non-steroidal anti-inflammatory drugs, but most do not contain readily oxidisable groups. However, pirprofen and diclofenac (Figure 6.53) have been assayed by HPLC-ED. Diclofenac has been measured in plasma using an amino-propyl-modified silica column with acetonitrile-aq. perchloric acid (2.5 mmol L ) (35 + 65) as eluent after LLE into benzene. ED was at a GCE (+0.9 V vs Ag/AgCl). 4-(2,6-Dichloro-4-methoxyphenyl)aminophenylacetic acid was the internal standard. The LoD was 5 pgL (2mL sample). An alternative method for diclofenac in plasma and synovial fluid has been described. LLE into dichloro-methane was followed by analysis using an ODS-modified silica column with acetonitrile-aq. sodium acetate (50mmolL pH 3) (40 + 60) as eluent and ED... 

Table 5.6 Retention factors [k) for cations with resins of different bulk densities (eluent 0.75 M perchloric acid). 

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