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A simple and effective analytical method for the determination of anabolic steroids and related compounds in nutritional supplements is reported. Target compounds are extracted with ethyl acetate, crude extract is purified using dispersive solid-phase extraction (SPE) with primary secondary amine (PSA) as sorbent, and finally they are identified and quantified as underivatized compounds using two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GCxGC-TOF MS). This method was validated for 25 steroids in two types of commercially available solid nutritional supplements: protein concentrate and creatine monohydrate. Repeatability expressed as the relative standard deviation of analyte concentration ranged from 4.1 to 20.5%. Recoveries between 70.0 and 122.6% were obtained for the target compounds except for oxymetholone in protein concentrate where the recovery was low as a result of strong interactions with PSA. Excellent linearity was obtained for six-point calibration with regression coefficients of 0.997-1.000 for all compounds. The limits of quantification ranged from 0.007 to 0.114 mg kg(-1). For a monitoring programme of 48 samples of nutritional supplements, three were positive. Nandrolone, testosterone, dehydroepiandrosterone (DHEA), 5alpha-androstan-3,17-dione, 19-norandrostendione and progesterone were found in positive samples at concentrations between 0.022 and 0.398 mg kg(-1).

The cross-reactivity of antibodies employed within immunochemistry-based analytical methods may lead to overestimation of the results. Under certain conditions, specifically when controlling mycotoxin maximum limits serious problems can be encountered. Not only the structurally related mycotoxins, such as their masked (conjugated) forms, but also the unidentified matrix components are responsible for concentration overestimation of respective target analytes. The cross-reactivity phenomenon may also pose a risk of miss-interpretation of the proficiency tests results, when the assigned value becomes influenced by over-estimated results reported by users of immunochemical tests. In this paper, the current state of the knowledge on trueness problems associated with the rapid screening immunochemical methods have been reviewed. Special attention is focused on discussion of cross-reactivity in the ELISA tests, because this rapid test dominates the routine screening practice. However, the cross-reactions reported in lateral flow test strips, fluorescence polarisation immunoassay, or immunosensors have also been addressed.

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Natural honey contains several enzymes, which are produced by bees (salivary secretion) and some are found in the nectar or pollen. The most important enzymes are amylases, invertases, glusidases, catalases, fosfatases and other. The activity of diastase (α-, β-, γ-amylase) is the important quality parameter of honey, according to the Directive 2001/110/CE the diastase activity (diastase number) must not be less than or equal to 8, for some kinds of honey also higher or equal to 3 (in these cases the HMF must not be higher than 15 mg/kg). Diastase is used as a marker to evaluate the freshness or the heat damage of honey. When honey is adulterated by addition of inverted sucrose or hydrolysed starch namely high fructose corn syrup (HFCS), then such dilution of honey leads to the reduction of diastase number. Such adulteration can be masked by addition of foreign amylases, e.g. bakery mould amylases. Recently several suspect samples of honey with inconsistent diastase number were found in the market. The possibilities of detection of foreign amylase addition based on the comparison of diastase determination using the Schade and Phadebas procedures are evaluated. The both tests are based on the determination of hydrolytic activity (the Schade number is expressed as g of starch hydrolysed 1 h at 40°C per 100 g honey), but the results depend on the substrate used for the trial (according to the standard procedure an insoluble blue dyed cross-linked type of starch should be used). The results of Schade test are therefore often affected by the choice of substrate. The model samples of honeys with addition of foreign amylase (Aspergillus oryzae) were analysed, the methods of adulteration detection based on the substrate specificity of enzymes is proposed.