Solid-phase Extraction Chromatography Method Research Articles

Determination of 90Sr in environmental samples using solid phase extraction chromatography

A simple and rapid method based on solid phase extraction chromatography (SPEC) has been developed for the determination of 90Sr in environmental samples. The SPEC method consists of three steps, namely, (1) carbonate precipitation of alkaline earths, (2) column separation of strontium using 4,4′(5′)-bis(tert-butylcyclohexano)-18-crown-6 based Sr spec resin and (3) beta counting of SrCO3 using low background gas flow counter. Minimum detection limit (MDL) of low beta gas flow counter is 1.42 Bq/kg for 10,000 s counting time. The capacity of the column for strontium was about 12.2 ± 0.5 mg of Sr per g of Sr spec resin. The SPEC method using Sr spec resin was standardized with 90Sr spiked samples and tested on sediment samples of Mumbai harbour bay. The average activity concentration of 90Sr in sediment samples was found to be 2.2–13.7 Bq/kg. The results obtained by SPEC method have been found to be in good agreement with conventional gravimetric method.

Determination of 89Sr and 90Sr in fresh cow milk and raw urine using crystalline synthetic tunnel manganese oxides and layered metal sulfides

89Sr and 90Sr are both fission products of high radiotoxicity, which can be released in significant amounts in the event of a nuclear accident. Radiostrontium isotopes will follow calcium all along the food chain and, after ingestion, accumulate in the bones. Therefore, it is imperative to be able to determine 89Sr and 90Sr in raw milk samples in case of an accidental situation to evaluate the dose given by both radionuclides to the population. Several methods exist for conducting 89Sr and 90Sr determination. However, most of them use at least one chromatographic step to purify strontium. This, unfortunately, increases the analytical time before the results can be released to the authorities. In addition, they often use liquid scintillation counting to determine the 89Sr and 90Sr activities, a method which can handle only one sample at a time. Here we propose using synthetic tunnel manganese oxides such as cryptomelane and todorokite and layered metal sulfides to selectively extract strontium from fresh milk and raw urine in a batch sorption method. We found that the method is very quick and yields very pure sources of (radio)-strontium, which can be counted in a proportional counter. Data (counts per minute) from the counter were fitted to a mathematical expression enabling the simultaneous determination of 89Sr and 90Sr. Because a proportional counter often has several drawers, it is typically possible to measure up to 16 samples at a time. Since cryptomelane is a binding phase easily synthesized in a large quantity, we anticipate that this technique could be an interesting alternative to conventional solid phase extraction chromatography methods.

Utilizing isotope dilution-matrix-assisted laser desorption ionization-time of flight mass spectrometry as a reference procedure for the radioimmunoassay of serum thyroxine

BackgroundThe thyroid hormone, thyroxine (T4), is a tyrosine-based hormone produced by the thyroid gland, which is essential in regulating a number of biological processes, including growth, neurodevelopment, carbohydrate metabolism, oxygen consumption and protein synthesis. Data on human thyroid hormone metabolism were gathered since the middle of the 1970s mainly by the use of radioactive iodinated (125I or 131I) hormones. MethodsWe describe an isotope dilution-matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) method for the simultaneous determination of endogenous thyroid hormone and its 13C6-labeled analogue in serum. The 13C6-thyroxine (13C6-T4) was used as an internal standard; T4 and its isotopically labeled analogue were measured in the selected reaction monitoring mode for the transitions from m/z 777.8 to 732.1 and from m/z 784.2 to 738.1, respectively. ResultsSerum samples were prepared and concentrated by a solid-phase extraction chromatography method. The recovery rate was measured by 125I-T4 and can be up to 82.8±2.8%. The detection limit and linear range for T4 were 5ng/ml and 5–400ng/ml, respectively. The correlation coefficient (R2) between radioimmunoassay (RIA) and isotope dilution-MALDI-TOF MS for detection of serum T4 was 0.982. ConclusionThis assay has a good relationship against a commercial RIA and the isotope dilution-mass spectrometry method and may serve as a reference method for quantitative analysis of T4.