Antonín Bednařík

The relationship between the mercury concentration in fish muscles and scales/fins and its significance

AbstractThe determination of mercury in fish typically involves analysis of muscles. For predicting the concentration of mercury in fish muscle on the basis of the analysis of fish scales or fins, the relationship between total mercury concentrations in fish muscles and in fish scales and fins was studied. Mercury content in fish muscles, scales and fins was determined by atomic absorption spectrometry with thermal decomposition of the sample in a flow of oxygen. A number of scale treatments were applied in order to remove impurities and to enhance the prediction quality. For scale treatment, 40 min of washing with DI water in an ultrasonic bath is recommended. A coefficient of determination r2= 0.93 for the relationship between Hg concentrations in muscles and scales was achieved for 40 fish among the different fish species tested (European bream, perch, roach) from the Hamry Reservoir, Czech Republic. With respect to fin sampling, the coefficient of determination r2 for these fish was 0.86. The analysis of fish scales and caudal fins is a useful screening tool for assessing the relative mercury contamination of monitored fish. The method of sampling scales is not suitable for fish species with small scales such as brown trout.

Diode laser thermal vaporization ICP MS with a simple tubular cell for determination of lead and cadmium in whole blood

A new low-cost device suitable for the recently presented sample introduction technique to inductively coupled plasma mass spectrometry (ICP MS), diode laser thermal vaporization (DLTV), is described. DLTV ICP MS is suitable for quantitative elemental analysis of low volume liquid samples and offers an alternative to commonly used liquid sample introduction into inductively coupled plasma. In contrast to the existing sample introduction systems based on laser ablation, the technique relies on low-cost components: a diode laser, a simple laboratory-built cell and a strip of filter paper. The aerosol generation by DLTV is carried out in a simple cell made up of a glass tube, a near infrared continuous-wave diode laser and a common syringe pump. The cell is characterized by minimal dead volume, which reduces turbulent flow and provides very fast wash-out. The paper substrate can hold up to 24 samples; an analysis time per sample of ∼4.7 s has been achieved. The device performance was optimized, compared to a commercial ablation system and applied to the determination of lead and cadmium in whole human blood without any sample treatment. A prearranged calibration set was printed on the paper strip using a piezoelectric dispenser.

Thin-layer chromatography combined with diode laser thermal vaporization inductively coupled plasma mass spectrometry

Here we present a novel coupling of thin-layer chromatography (TLC) to diode laser thermal vaporization inductively coupled plasma mass spectrometry (DLTV ICP MS). DLTV is a new technique of aerosol generation which uses a diode laser to induce pyrolysis of a substrate. In this case the cellulose stationary phase on aluminum-backed TLC sheets overprinted with black ink to absorb laser light. The experimental arrangement relies on economic instrumentation: an 808-nm 1.2-W continuous-wave infrared diode laser attached to a syringe pump serving as the movable stage. Using a glass tubular cell, the entire length of a TLC separation channel is scanned. The 8-cm long lanes were scanned in ∼35 s. The TLC - DLTV ICP MS coupling is demonstrated on the separation of four cobalamins (hydroxo-; adenosyl-; cyano-; and methylcobalamin) with limits of detection ∼2 pg and repeatability ∼15% for each individual species.

Rapid matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging with scanning desorption laser beam.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS) imaging of surfaces and tissues is a rapidly evolving technique having great potential in the field of biosciences. In earlier times, acquisition of a single high-resolution MS image could take days. Despite the recent introduction of high-repetition rate lasers to increase sample throughput of axial TOF MS instruments, obtaining a high-resolution image still requires a few hours. This paper shows that a substantial increase in the throughput of the TOF MS-based tissue imaging can be achieved by incorporating a mirror providing high-speed precision scanning of the laser beam along the sample surface. Equipped with the scanning mirror, a laboratory-built axial MALDI TOF MS instrument utilizing a 4-kHz UV laser recorded a 100 × 100 pixel MS image in ~11 min using 100 laser shots per pixel. This is almost an order of magnitude faster when compared to a modern commercial instrument equipped with 1-kHz laser.

Thin-layer chromatography combined with diode laser thermal vaporization inductively coupled plasma mass spectrometry for the determination of selenomethionine and selenocysteine in algae and yeast

In this work we present a simple and cost-effective approach for the determination of selenium species in algae and yeast biomass, based on a combination of thin-layer chromatography (TLC) with diode laser thermal vaporization inductively coupled plasma mass spectrometry (DLTV ICP MS). Extraction of freeze-dried biomass was performed in 4M methanesulphonic acid and the selenium species were vaporized from cellulose TLC plates employing a continuous-wave infrared diode laser with power up to 4 W using a simple laboratory-built apparatus. Selenomethionine and selenocysteine were quantified with limits of detection 3 μg L-1 in a Se-enriched microalgae Chlorella vulgaris and yeast certified reference material SELM-1. Results delivered by TLC-DLTV ICP MS were consistent with those obtained by a routine coupling of high-performance liquid chromatography (HPLC) to ICP MS. In addition, the TLC approach is capable of analyzing extract containing even undiluted crude hydrolysates that could damage HPLC columns.