Determination of sodium tripolyphosphate in meat samples by capillary zone electrophoresis with on-line isotachophoretic sample pre-treatment

The usefulness of zone capillary electrophoresis (CZE) in combination with isotachophoresis (cITP) as on-line preconcentration technique was examined for analysis of tripolyphosphate (STPP) in meat and meat products. The mean concentrations of STPP in different types of meat products varied from 39 mg P₂O₅/100 g to 219 mg P₂O₅/100 g, these values are below the legal requirements. The detection (LOD) and quantification (LOQ) limits for STPP in extracted solutions were 0.80 mg P₂O₅/dm³ and 2.69 mg P₂O₅/dm³, respectively. Obtained results were compared with the Kjeldahl method. Accuracy (97.4-98.3%) was determined using recovery assay based on standard additions method. Precision was evaluated by within-day R.S.D. (1.40-2.19%), between-days R.S.D. (3.00-3.82%) and demonstrates the benefit of using this procedure for the routine analysis of STPP in meat and their products. The F-Snedecor test was employed to compare the precision of the used methods and calculated F-test values (4.00, 6.13) were less than the theoretical (6.39).     

Validation of a micellar electrokinetic capillary chromatography method for the determination of imidurea, methyl and propylparabens in a pharmaceutical ointment

The quantitative aspects of a micellar electrokinetic chromatographic (MEKC) method for the determination of three preservatives (imidazolidinyl urea, methyl and propylparabens) in a pharmaceutical ointment are presented. Separation was carried out in a 31.2 cm long (21 cm to the detection window) × 50 μm i.d. fused silica capillary at an electric field of 960 V/cm and 25 °C. The electrolyte was 10 mM sodium dihydrogenophosphate containing 40 mM sodium dodecylsulfate (SDS) and adjusted to pH 6.1. Sample preparation consisted of a simple dispersion of the ointment in an internal standard solution (ethylparaben in the electrolyte). A 3.5 nl volume of the sample solution was introduced hydrodynamically into the capillary. The compounds detected at 200 nm were separated within 1.6 min. The method was validated with respect to specificity, linearity, accuracy, repeatability according to the International Conference on Harmonisation guidelines. Calibration curves were found to be linear for each compound (r²>0.999). Recovery studies performed by spiking an ointment placebo with the preservatives between 50 and 150% of their target concentration on 3 different days gave satisfactory results (mean recovery at each of the five concentrations ranging from 99.23 to 101.40%). The repeatability of sample preparation (n=6) was better than 2% for each of the preservatives.     

A simple and sensitive CE method for the simultaneous determination of catecholamines in urine with in-column optical fiber light-emitting diode-induced fluorescence detection

A simple and sensitive method has been developed for simultaneous analysis of three catecholamines: dopamine (DA), epinephrine (EP) and norepinephrine (NE) in urine by capillary electrophoresis (CE) coupled with in-column fiber-optic light-emitting diode-induced fluorescence detection (ICFO-LED-IFD). Fluorescein isothiocyanate was used as the fluorescence tagged reagent for derivatization of DA, EP and NE. The CE conditions for separation of these catecholamines were systematically investigated. It was found that catecholamines could be more effectively separated by adding β-cyclodextin (β-CD) and acetonitrile (ACN) to a background electrolyte (BGE) of sodium borate. The migration times are 10.61, 10.83 and 11.14 min for DA, EP and NE, respectively and the catecholamines are completely separated within 11.5 min under the optimal condition of a BGE containing 10% v/v ACN, 20 mM β-CD and 20 mM sodium borate (pH 9.5), and an applied voltage of 13 kV. The relative standard deviations of migration time and peak area for these catecholamines are less than 0.16 and 2.0%, respectively. The limit of quantifications (LOQs) for DA, EP and NE are 3.5, 1.0 and 3.1 nM whereas the limit of detections (LODs) for DA, EP and NE are 1.0, 0.3 and 0.9 nM, respectively. Our proposed CE method provides low LOQ and LOD values. This CE-ICFO-LED-IFD methodology has been successfully applied to analyze catecholamines in human urine samples with good accuracy and satisfactory recovery.     

Analysis of the recent antipsychotic aripiprazole in human plasma by capillary electrophoresis and high-performance liquid chromatography with diode array detection

Two methods, based on the use of capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC), respectively, were developed for the analysis of the atypical antipsychotic aripiprazole in plasma of schizophrenic patients for therapeutic drug monitoring purposes. Good analytical performances were obtained with the CE method, using uncoated fused silica capillaries and a background electrolyte composed of 50 mM phosphate buffer at pH 2.5. With 20 kV voltage, aripiprazole was detectable at 214 nm within 5 min. The second analytical method, based on HPLC with diode array detection, employed a C8 reversed-phase column and a mixture of a 12.5 mM phosphate buffer, pH 3.5, containing triethylamine and acetonitrile as the mobile phase. Aripiprazole was detected at 254 nm and a complete chromatographic run lasted about 10 min. For both analytical methods loxapine was used as the internal standard and the same plasma sample pre-treatment by means of solid-phase extraction on cyano cartridges was carried out, with extraction yield values always higher than 91.3%. Linear responses for aripiprazole were obtained between 70 and 700 ng mL⁻¹ and precision assays (expressed as relative standard deviation values) were lower than 7.0%. After validation, both methods were successfully applied to human plasma samples drawn from schizophrenic patients undergoing therapy with Abilify^® tablets. Accuracy was satisfactory, with recovery value higher than 91.0%.     

Using sweeping-micellar electrokinetic chromatography to determine voriconazole in patient plasma

Invasive fungal infection is a life-threatening condition; its occurrence has increased significantly over the past 20 years. We have developed a sensitive and efficient sweeping-micellar electrokinetic chromatography (sweeping-MEKC) method to quantify voriconazole, a potent triazole antifungal drug, in patient plasma. Solid phase extraction (SPE) conditions were first optimized to minimize plasma interference while maintaining a high recovery; the sweeping-MEKC conditions were then systematically optimized to obtain a high sweeping efficiency with good selectivity. Under the optimal analytical conditions, voriconazole was baseline-separated from endogenous materials within 10.5 min with a limit of detection of 0.075 μg mL⁻¹. The background electrolyte comprised 40 mM phosphoric acid, 110 mM sodium dodecyl sulfate, and 20% acetonitrile. In terms of method repeatability, the relative standard deviations (RSDs) of the migration time and the peak area (intra-day; n = 6) were both less than 5.5%; in terms of intermediate precision, and the RSDs of the peak area and the migration time (inter-day; n = 3) were both less than 6.3%. We successfully applied this developed method to the quantitative determination of plasma voriconazole levels in 16 patients; the results correlated well with those obtained through analyses using high-performance liquid chromatography. This sweeping-MEKC method is accurate and efficient and appears to be applicable to therapeutic drug monitoring and clinical research.     

Determination of the carboxylic acids in acidic and basic process samples by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) with indirect UV detection was used in developing a method for the simultaneous determination of inorganic anions, aliphatic and heterocyclic organic acids in various processed samples. The analytes were determined simultaneously in 10 min using an electrolyte containing 20 mM 2,3-pyrazine dicarboxylic acid, 65 mM tricine, 2 mM BaCl₂, 0.5 mM cetyltrimethylammonium bromide, and 2 M urea at pH 8.06. Linear plots for the analytes were obtained in the concentration range of 2–150 mg L⁻¹. Relative standard deviations (RSDs) of peak areas during a 3-day analysis period varied from 5.5% for glycolate to 9.5% for oxalate. RSDs of migration times varied between 0.4% and 1.1%. The detection limit (at S/N 3) was 1 mg L⁻¹ for all the analytes studied. The proposed method was successfully demonstrated for the determination of carboxylic acids in eight oxygen treated samples of commercial softwood and hardwood kraft lignin and two red wine samples of Pinot Noir grapes. In the kraft lignin samples the concentrations of carboxylic acids correspond to the oxidation time. The acid concentrations of wine varied considerable.     

A novel method for analysis of explosives residue by simultaneous detection of anions and cations via capillary zone electrophoresis

A novel electrolyte has been developed for the simultaneous separation of cations and anions in low explosive residue by capillary electrophoresis. This electrolyte contains 15 mM α-hydroxyisobutyric acid (HIBA) as the buffer, 6 mM imidazole as the cation chromophore, 3 mM 1,3,6-naphthalenetrisulfonic acid (NTS) as the anion chromophore, 4 mM 18-crown-6 ether as a cation selectivity modifier, and 5% (v/v) acetonitrile as an organic modifier. The pH was adjusted to 6.5 using tetramethylammonium hydroxide (TMAOH), an electroosmotic flow modifier. The method was optimized by varying the concentrations of α-HIBA, imidazole, and 1,3,6-NTS at three different pH values. The results provided a simultaneous indirect photometric analysis of both anions and cations with detection limits ranging from 0.5 to 5 ppm for anions and from 10 to 15 ppm for cations with a total run time of under 7 min. The method was then applied to the analysis of Pyrodex^® RS and black powder, as well as several smokeless powders. The results obtained were consistent with previously reported results for separate anion and cation analysis and provide a faster, more complete analysis of each sample in a single chromatographic run.     

Determination of benzoate,sorbate, citrate and orthophosphate ions in beverage samples using two-dimensional isotachophoretic method

A two-dimensional capillary isotachophoretic method (cITP-cITP) using electrolyte system consisting of leading electrolytes (LE1): [10 mM HCl + β-alanine (pH 3.9) + 0.1% hydroxyethylcellulose (HEC)] and (LE2): [10 mM HCl + aminocaproic acid (pH 5.00) + 0.1% HEC], and 5 mM caproic acid as terminating electrolyte (TE) was studied. Two methods of detection, conductometric and UV-Vis, were applied to the determination of selected food preservatives and additives. Practical applicability was demonstrated by simultaneous determination of benzoates, sorbates, citrates and orthophosphates in 12 samples of beverages. The proposed method revealed linearity with R ² between 0.9992 and 0.9999 for the concentration ranges: 10–100 mg/L (orthophosphate and citrate ions), 20–100 mg/L (sorbates) and 40–120 mg/L for benzoates. The detection limits for all studied ions were from 0.85 to 3.1 mg/L whereas the quantification ones were from 2.8 to 10 mg/L. The variation coefficients for five-fold analysis of all ions ranged between 0.4 and 9.1%. Obtained recoveries (from 97 to 104%) confirmed satisfactory accuracy of the proposed cITP-cITP method for the determination of tested food additives.     

Novel, selective sample stacking microemulsion electrokinetic capillary chromatography induced by reverse migrating pseudostationary phase for the determination of the new ultra-short acting hypnotic “HIE-124” in mice serum

Microemulsion electrokinetic capillary chromatography (MEEKC) with sample stacking induced by reverse migrating pseudostationary phase (SRMP) technique in a suppressed electro-osmotic flow (EOF) strategy was investigated for analysing the new ultra-short hypnotic HIE-124 in mice serum. The proposed method utilized fused-silica capillary with a total length of 50 cm (effective length 40 cm), applied voltages for stacking and separation were 5.0 kV for 4.30 min and subsequently 25 kV, respectively, with a sample injection of 0.5 psi for 90 s. All the runs were carried out at 25 °C and detected at 213 nm. The optimum microemulsion background electrolyte (BGE) solution consisted of 0.8% (v/v) ethyl acetate, 6.6% (v/v) butan-2-ol, 1.0% (v/v) acetonitrile, 2.0% (w/v) sodium dodecyl sulfate (SDS), and 89.6 mL with 25 mM phosphate buffer pH 8. When this preconcentration technique was used, the sample stacking and the separation processes took place successively with changing the voltage with an intermediate polarity switching step. The proposed method was validated carefully with respect to high specificity of the method, good linearity (r = 0.9994), fair wide linear concentration range (66-1500 ng mL⁻¹), limit of detection and quantitation were 21.6 and 65.5 ng mL⁻¹, respectively. The mean relative standard deviation (RSD) of the results of intra- and inter-day precision and accuracy were less than 6.0%, and overall recovery higher than 95% of HIE-124 in mice serum. The developed method could be used for the trace analyses of HIE-124 in serum and was finally used for the pharmacokinetic study investigation of HIE-124 in mice serum.     

Method development for the determination of teicoplanin in patient serum by solid phase extraction and micellar electrokinetic chromatography

In-hospital deaths caused by the infection of methicillin-resistant Staphylococcus aureus (MRSA) are on the increase worldwide. Teicoplanin is a potent glycopeptide antibiotic against MRSA. A rapid and cost-saving micellar electrokinetic chromatography (MEKC) method combined with solid phase extraction (SPE) was developed and then validated to quantify teicoplanin in patient serum in this work. The method includes the following steps: (1) pretreatment of the serum samples with 10 M urea to denature proteins, (2) application of SPE by using an OASIS HLB cartridge to clean up and concentrate the serum samples, and (3) use of MEKC for sample analysis. Under the optimized conditions, the SPE recovery of teicoplanin is higher than 90%. The six major components of teicoplanin could be baseline-separated from one another and endogenous materials in 12 min with a background electrolyte composed of 20 mM sodium tetraborate buffer pH 8.8, 40 mM sodium dodecyl sulfate, and 11% (v/v) ACN. The relative standard deviation (R.S.D.) of the peak area ratios for method repeatability (n = 6) and intermediate precision (inter-day, n = 3) were found to be lower than 4.18% and 5.30%, respectively. The calibration curves were linear between the chromatographic response and total teicoplanin concentration over the range of 5 μg/mL to 55 μg/mL. Limit of detection (LOD) for each of the six components was found to be lower than 0.06 μg/mL. Pearson’s correlation revealed that a good correlation (r = 0.98) was obtained between the SPE-MEKC method and the fluorescence polarization immunoassay (FPIA) method. The developed method can be used to quantitatively determine serum teicoplanin concentration in patients for dose monitoring and clinical research.     

Simultaneous determination of uranium carbide dissolution products by capillary zone electrophoresis

Separation and simultaneous determination of a number of organic acid anions (oxalate, mellitate, trimellitate and benzoate) and U(VI) with direct UV detection is developed for analysis of uranium carbide (UC) dissolution products by capillary zone electrophoresis (CZE). Reverse polarity mode is used. It is found that complex formation of U(VI) with carbonate, used as a carrier electrolyte, allows U(VI) to be determined, as negatively charged species, in a single run with organic acid anions. Some parameters such as pH value, composition of electrolyte and detection wavelength are optimized. Under the chosen conditions (carbonate buffer (ionic strength of 100 mM), pH 9.8, 0.15 mM tetradecyltrimethylammonium bromide (TTAB)) a complete separation is achieved. Calibration plots are linear in two ranges of concentration for U(VI) (∼1 × 10⁻⁵ to 1 × 10⁻³), mellitate and trimellitate (∼5 × 10⁻⁶ to 5 × 10⁻⁴), and about one range (∼1 × 10⁻⁴ to 5 × 10⁻³) for oxalate and benzoate. Accuracy of the procedure is checked by the “added-found” method in standard mixture solutions. Relative standard deviation is within the range of 2–10% and the recovery is in the range of 90–110%. This method is applied for the analysis of real UC dissolution samples.     

Separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata by flow injection-micellar electrokinetic chromatography

A simple, rapid, and accurate method for the separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata was developed by combination of flow injection (FI)-micellar electrokinetic chromatography (MEKC) for the first time. The analysis was carried out using an unmodified fused-silica capillary (50 μm i.d.; total length 13.6 cm; effective length 10.3 cm) and direct ultraviolet (UV) detection at 214 nm. The sample throughput was 11-24 samples per hour using the background electrolyte (BGE) containing 4 mM sodium borate-8 mM NaH₂PO₄ (pH 8.1)-8 mM sodium dodecyl sulfate (SDS)-19% (v/v) ethanol. The repeatabilities (n = 4) reached relative standard deviation values (R.S.D.) of 3.0% and 2.5% for the peak areas and 2.5% and 3.1% for peak heights of alpinetin and cardamonin, respectively. Regression equations revealed linear relationships (r²: 0.9993-0.9994) between the peak area of each analyte and the concentration. Recoveries were in the range 90-92% and 99-105% for alpinetin and cardamonin, respectively.     

Field-amplified sample injection coupled with pseudo-isotachophoresis technique for sensitive determination of selected psychiatric drugs in human urine samples after dispersive liquid–liquid microextraction

A field-amplified sample injection (FASI) technique was elaborated for fast and sensitive determination of selected central nervous system drugs in human urine samples. Factors affecting the sensitivity enhancement, such as background electrolyte (BGE) and the analytical matrix composition were optimized and discussed. Pseudo-isotachophoresis (p-ITP) mechanism contribution in preconcentration mechanism was discussed. All separations were performed in uncoated fused silica capillaries 50 μm × 57 cm at 22 kV. The optimized analytical matrix was composed of 0.25 mM HCOOH in 90% (v/v) methanol, while BGE contained 45 mM TRIS/HCl (pH 2.20). The head-column injection was performed in 0.25 mM HCOOH water solution (3 s, 3.45 kPa). Sample was introduced into the capillary by electrokinetic injection (70 s, 5 kV) followed by short BGE plug (3 s, 3.45 kPa). Seven psychiatric drugs (olanzapine, prochlorperazine dimaleate, trifluoperazine dihydrochloride, perphenazine, promazine hydrochloride, clomipramine hydrochloride, and chlorprothixene hydrochloride) were separated in about 6 min. The elaborated method was additionally supported with dispersive liquid–liquid microextraction (DLLME) technique which in summary with FASI provided about 8000–13,000-fold sensitivity enhancement in comparison to the capillary zone electrophoresis (CZE) method with standard hydrodynamic injection (5 s, 3.45 kPa).     

Method development and validation for the separation and determination of omeprazole enantiomers in pharmaceutical preparations by capillary electrophoresis

A new capillary zone electrophoresis (CZE) method for the separation of omeprazole enantiomers has been developed. Methyl-β-cyclodextrin (methyl-β-CD) was chosen as the chiral selector, and several parameters, such as cyclodextrin structure and concentration, buffer concentration, pH, and capillary temperature were investigated in order to optimize separation and run times. Analysis times, shorter than 8 min were found using a background electrolyte solution consisting of 40 mM phosphate buffer adjusted to pH 2.2, 30 mM β-cyclodextrin and 5 mM sodium disulphide, hydrodynamic injection, and 15 kV separation voltage. Detection limits were evaluated on the basis of baseline noise and were established 0.31 mg/l for the omeprazole enantiomers. The proposed method was applied to five pharmaceutical preparations with recoveries between 84 and 104% of the labeled contents.     

Quantitative analysis of flavonoids and phenolic acids in Arnica montana L. by micellar electrokinetic capillary chromatography

Arnica montana preparations have been used in Europe for centuries to treat skin disorders. Among the biologically active ingredients in the flower heads of the plant are sequiterpenes, flavonoids and phenolic acids. For the simultaneous determination of compounds belonging to the latter two groups a micellar electrokinetic capillary chromatography (MEKC) method was developed and validated. By using an electrolyte solution containing 50 mM borax, 25 mM sodium dodecyl sulfate and 30% of acetonitrile the separation of seven flavonoids and four caffeic acid derivatives was feasible in less than 20 min. The optimized system was validated for repeatability (σ_rel ≤ 4.4%), precision (inter-day σ_rel ≤ 8.13%, intra-day σ_rel ≤ 4.32%), accuracy (recovery rates from 96.8 to 102.4%), sensitivity (limit of detection (LOD) ≤ 4.5 μg mL⁻¹) and linearity (R² ≥ 0.9996), and then successfully applied to assay several plant samples. In all of them the most dominant flavonoid was found to be quercetin 3-O-glucuronic acid, whereas 3,5-dicaffeoylquinic acid was the major phenolic acid; the total content of flavonoids and phenolic acids varied in the samples from 0.60 to 1.70%, and 1.03 to 2.24%, respectively.     

Direct determination of lead in produced waters from petroleum exploration by electrothermal atomic absorption spectrometry X-ray fluorescence using Ir-W permanent modifier combined with hydrofluoric acid

The present work reports the development of a methodology for the direct determination of lead in high saline waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry with permanent Ir-W and HF as modifiers. These waters, so-called produced waters, have complex composition containing several types of organic and inorganic substances. In order to attain best conditions (highest analytical signal besides lowest background) for the methodology studies about the effect of several variables and the convenient calibration strategy were performed. Also, the efficiency of other modification approaches was evaluated. At best conditions, pyrolysis and atomization temperature were 800 and 2200 °C, respectively, when the modifiers cited above were utilized. Obtained results indicate that, in this kind of sample, lead can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8 mol l⁻¹ NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with six spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8 mol l⁻¹ NaCl were also calculated and the values are 1.5 μg l⁻¹, 5.0 μg l⁻¹ and 5.0% (at 10 μg l⁻¹ level), respectively.     

Development of a microbioreactor with ecto-nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) immobilized on a polyacrylamide-coated capillary at the outlet

A simple and fast method of immobilization of cell membrane suspension containing human ecto-nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) on a polyacrylamide-coated capillary was developed. The enzyme microbioreactor was prepared by hydrodynamic injection of a small plug of the polycationic electrolyte hexadimethrine bromide (HDB) followed by a suspension of an enzyme-containing membrane preparation. In order to shorten the enzyme assay time and to increase the throughput of the assay, the capillary was coated from the outlet end and all injections were performed from the outlet end of the capillary. For the monitoring of the enzymatic reaction, the substrate ATP dissolved in reaction buffer (140 mM NaCl, 5 mM KCl, 1 mM MgCl₂, 2 mM CaCl₂, and 10 mM Hepes, pH 7.4, internal standard: 10 μM UMP) in the absence or presence of inhibitor was injected electrokinetically and incubated in the microbioreactor for 1 min with 1 kV of applied voltage. Then, the electrophoretic separation of the reaction products was initiated by applying a constant current of 60 μA. A 50 mM phosphate buffer (pH 6.5) was used for the separations and the products were detected by UV absorbance at 260 nm. The new method was compared with an at-capillary-inlet method without immobilization of the enzyme. The results (K_m values, K_i values for inhibitor) obtained with both methods were similar and comparable with literature data. The developed outlet immobilized enzyme microreactor using a coated capillary is very fast, simple and most economic allowing multiple use of the enzyme.     

Method development and validation for trifluoroacetic acid determination by capillary electrophoresis in combination with capacitively coupled contactless conductivity detection (CE-C4D)

A method was developed to determine traces of trifluoroacetic acid as impurity in synthetic or semi-synthetic drugs as antibiotics, macropeptides, etc. Capillary electrophoresis in combination with capacitively coupled contactless conductivity detection (CE-C⁴D) was used due to lack of UV absorbance property of trifluoroacetic acid (TFA). The optimized method took less than 1 min with good linearity (R² = 0.9995) for trifluoroacetic acid concentration from 2 to 100 ppm. It also has a good repeatability expressed by the relative standard deviation (% RSD) which is 1.2 and 2.1% for intraday and interday precision, respectively, at 50 ppm TFA, and good sensitivity with 0.34 ppm, 1.2 ppm LOD and LOQ, respectively. In addition, the content of TFA in synthetic drug, was determined using the validated method which gave good linearity (R² = 0.9996) for trifluoroacetic acid spiked into drug in a concentration range of 2-80 ppm, with good intraday repeatability of 2.0%.The analysis is performed in a background electrolyte composed of 20 mM morpholinoethane-sulfonic acid (Mes) and 20 mM l-histidine (l-His) pH 6.1. Cetyltrimethylammonium bromide (CTAB) was added as flow modifier in a concentration (0.2 mM) lower than the critical micellar concentration. Ammonium formate 6 ppm was used as internal standard. The applied voltage was 30 kV in reverse polarity. A fused silica capillary with 75 μm internal diameter and total length 47 cm (31 cm to C⁴D detector and 37 cm to DAD detector) was used.     

Accurate determination of trace amounts of phosphorus in geological samples by inductively coupled plasma atomic emission spectrometry with ion-exchange separation

In order to determine trace amounts of phosphorus in geological and cosmochemical rock samples, simple as well as reliable analytical schemes using an ICP-AES instrument were investigated. A (conventional) ICP-AES procedure could determine phosphorus contents at the level of several 100 μg g⁻¹ with a reasonable reproducibility (<10% for 200 μg g⁻¹; 1σ). An ICP-AES procedure coupled with matrix-separation using cation and anion exchange resins could lower the quantification level down to 1 μg g⁻¹ or even lower under the present experimental conditions. The matrix-separation ICP-AES procedure developed in this study was applied to twenty-one geological reference samples issued by Geological Survey of Japan. Obtained values vary from 1250 μg g⁻¹ for JB-3 (basalt) to 2.07 μg g⁻¹ for JCt-1 (carbonate). Matrix-separation ICP-AES yielded reasonable reproducibility (less than 8.3%; 1σ) of three replicate analyses for all the samples analyzed. In comparison of our data with certificate values as well as literature or reported values, there appear to be an apparent (and large) discrepancy between our values and certificate/reported values regardless of phosphorus contents. Based on the reproducibility of our data and the analytical capability of the matrix-separation ICP-AES procedure developed in this study (in terms of quantification limit, recovery, selectivity of an analyte through pre-concentration process, etc.), it is concluded that certified values for several reference standard rocks should be reevaluated and revised accordingly. It may be further pointed that some phosphorus data reported in literatures should be critically evaluated when they are to be referred in later publications.     

Separation of open-cage fullerenes using nonaqueous capillary electrophoresis

In this study, nonaqueous capillary electrophoresis (NACE) was used to separate three open-cage fullerenes. Trifluoroacetic acid (TFA) was used as the nonaqueous background electrolyte to change the analytes’ mobilities. The selectivity and separation efficiency were critically affected by the nature of the buffer system, the choice of organic solvent, and the concentrations of TFA and sodium acetate (NaOAc) in the background electrolyte. The optimized separation occurred using 200 mM TFA/20 mM NaOAc in MeOH/acetonitrile (10:90, v/v), providing highly efficient baseline separation of the open-cage fullerenes within 5 min. The migration time repeatability for the three analytes was less than 1% (relative standard deviation). Thus, NACE is a rapid, useful alternative to high-performance liquid chromatography for the separation of open-cage fullerenes.