Serhat Döker

Rapid extraction and reverse phase-liquid chromatographic separation of mercury(II) and methylmercury in fish samples with inductively coupled plasma mass spectrometric detection applying oxygen addition into plasma.

A simple and sensitive procedure was developed for extraction and speciation of mercury in fish. Species separation was accomplished with reverse phase-high performance liquid chromatography (HPLC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS). Oxygen addition into plasma allowed use of organic-rich mobile phase, achieving species separation in 4 min. Mercury species extraction was achieved by microwave exposure for 2 min at mild conditions (60°C, pH 2.0), avoiding necessity of neutralizing sample prior to injection in HPLC, and reducing number of sample preparation steps, analytical source of errors and inter conversion of species. Limit of detection for entire procedure was found to be 0.2 and 0.1 ng g(-1) for mercuric ion and methylmercury, respectively. The method was applied to certified reference materials (TORT-2 and DORM-2) and commercialized fish samples (Mullus barbatus, Sparus aurata, Trachurus mediterraneus, Mugil soiuy, Dicentrarchus labrax, and Pomatomus saltatrix) from Black Sea.

A sensitive method for selective determination of vanadium species by dispersive liquid–liquid microextraction (DLLME) with spectrophotometric detection

A simple, fast, and low-cost analytical procedure was developed for trace-level determination of inorganic vanadium species by dispersive liquid–liquid microextraction in combination with spectrophotometry. Vanadium in pentavalent form, V(V), was quantitatively extracted into organic phase as 4-(2-pyridylazo)-recorcinol (PAR) complex in the presence of N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB) as counter-ion. Vanadium (IV) was masked with 1,2-diaminocyclohexanetetraacetic acid to allow speciation analysis. Total vanadium was determined after oxidation of V(IV) to V(V). The main factors affecting preconcentration and spectrophotometric detection of vanadium species such as pH, concentration of PAR and CTAB, the type and volume of the extraction, and disperser solvents were optimized. The limit of detection and enhancement factor obtained under optimum conditions were found to be 0.06 μg L−1 and 98, respectively. Relative standard deviations for V(IV) and V(V) at 3.0 μg L−1 were less than 2.4%. The presented procedure was applied to environmental water samples for selective determination of vanadium species. Moreover, the method was applied to determination of vanadium in edible salt samples, due to its applicability in high-NaCl-containing solutions. The validity of proposed method was proven by spike recovery experiments and also independent analysis by inductively coupled plasma mass spectrometry.

Evaluation of Digestion Procedures for Trace Element Analysis of Cankiri, Turkey Honey by Inductively Coupled Plasma Mass Spectrometry

The elemental fingerprint of honey provides important information with regard to environmental monitoring, authentication, and quality assurance, including nutritional and toxicological aspects. While inductively coupled plasma mass spectrometry is widely used for the multi-elemental trace analysis, the method of digestion depends on various factors. Six digestion procedures, including a microwave assisted digestion approach using diluted reagents, were evaluated. The methods were assessed in terms of accuracy, precision, sensitivity, cost, simplicity, speed, and sample capacity. In addition, elemental analysis of honey from Cankiri Province (Turkey) was reported for the first time. Twenty-nine elements were determined; of these, concentrations of 14 elements have not been previously reported in Turkish honey. The concentrations of lead and cadmium in Cankiri honey were low compared to levels previously reported for Anatolian honey. Aluminum was the most abundant element among the toxic metals determined; thus, this element should be carefully monitored.

Expression analysis of metallothioneins and mineral contents in tomato (Lycopersicon esculentum) under heavy metal stress.

BACKGROUND Heavy metals are considered to be the most important pollutants in the contamination of soils; they adversely affect plant growth and development and cause some physiological and molecular changes. The contamination of agricultural soils by heavy metals has changed the mineral element content of vegetables. Plant metallothioneins (MTs) are thought to have the functional role in heavy metal homeostasis, and they are used as the biomarkers for evaluating environmental pollution. We aimed to evaluate the expression of MT isoforms (MT1, 2, 3 and 4) and some mineral element composition of tomato roots, leaves and fruits exposed to copper and lead. RESULTS Heavy metal applications increased MT1 and MT2 gene expressions compared to the control in the tissues of tomato. The highest level of MT1 and MT2 transcripts was found in roots and leaves, respectively. The expression of MT3 is induced in roots, leaves and fruits except for Pb treatment in roots. MT4 expression increased in fruits; however, other tissues did not show a clear change. Our results indicated that Cu content was higher than Pb in all tissues of tomato. The lower doses of Cu (10 ppm) increased the content of Mg, Fe, Ca and Mn in roots. Pb generally increased the level of minerals in leaves and fruits, but it decreased Mg, Mn and Fe contents in roots. CONCLUSION Both heavy metals not only moved to aerial parts but also caused alterations to mineral element levels. These results show that MT transcripts are regulated by Cu and Pb, and expression pattern changes to MT isoforms and tissue types.

Exploiting aerosol dilution for the determination of ultra-trace elements in honey by collision/reaction cell inductively coupled plasma mass spectrometry (CRC-ICP-MS) without thermal digestion

A rapid dilute-and-shoot procedure was described for the ultra-trace determination of Li, Al, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Tl, Pb and U in honey by collision/reaction cell inductively coupled plasma mass spectrometry (CRC-ICP-MS). The aerosol dilution technique was found effective in obtaining a better tolerance to the sample matrix, allowing the use of aqueous standards in the analysis. Some instrumental parameters such as the collision gas flow rate, aerosol dilution rate and sampling depth were optimized for reliable determination of elements in the presence of chloride, especially for Cr and As which are severely affected by carbon and chloride-based polyatomic interferents. The limit of detection (0.01–2.9 ng g−1) and precision (<3.3%) values were excellent. The main advantages of the method are the elimination of thermal digestion and aqueous dilution steps in sample preparation, and considerable reduction in reagent consumption and environmental waste. The results showed the applicability of the method in routine single-run multi-element analysis of various honey types (chestnut, multi-floral and sun flower).

Speciation of Arsenic in Spring, Well, and Tap Water by High-performance Liquid Chromatography–Inductively Coupled Plasma–Mass Spectrometry

ABSTRACT Arsenic in water is a serious problem for organisms and the environment. Natural waters mostly consist of inorganic forms of As(III) and As(V) at concentrations below 1 ng/mL. Since the toxicity of these species is different, selective determination of trace As species in drinking water is important. Rapid speciation based on anion exchange chromatography coupled to inductively coupled plasma–mass spectrometry is reported. The species were separated within 4 min with the limits of detection of 0.012 and 0.019 ng/mL for As(III) and As(V), respectively. The method was applied to spring, well, and tap water from Çankırı, Turkey. Out of 25 samples, six samples exceeded the permissible drinking water limit of 10 ng/mL. The results showed that As(V) was predominant, while As(III) was also present, especially in well water making up to 16% of the total As.