RP-HPLC determination of water-soluble vitamins in honey.

The assessment and validation of reliable analytical methods for the determination of vitamins in sugar-based matrices (e.g. honey) are still scarcely explored fields of research. This study proposes and fully validates a simple and fast RP-HPLC method for the simultaneous determination of five water-soluble vitamins (vitamin B(2), riboflavin; vitamin B(3), nicotinic acid; vitamin B(5), pantothenic acid; vitamin B(9), folic acid; and vitamin C, ascorbic acid) in honey. The method provides low detection and quantification limits, very good linearity in a large concentration interval, very good precision, and the absence of any bias. It has been successfully applied to 28 honey samples (mainly from Sardinia, Italy) of 12 different botanical origins. While the overall amount of the analytes in the samples is quite low (always below 40 mg kg(-1)), we have observed a marked dependence of some of their concentrations (i.e. vitamin B(3) and vitamin B(5)) and the botanical origin of the honey. This insight might lead to important characterization features for this food item.

Reversed-phase liquid chromatographic profile of free amino acids in strawberry-tree (Arbutus unedo L.) honey.

The typical profile of the free amino acids contained in strawberry-tree (Arbutus unedo L.) honey is reported for the first time. An optimized reversed-phase liquid chromatographic (RP-LC) method with phenyl isothiocyanate precolumn derivatization was used. Fourteen free amino acids were identified and quantified in 16 analytical samples. Proline (65.63%) was found to be the most abundant free amino acid, followed by glutamic acid (6.49%), arginine (5.21%), alanine (5.17%), and phenylalanine (4.97%). The total free amino acid content of strawberry-tree honey (average value, 436 mg/kg) was found to be low in comparison to amounts cited in the literature concerning unifloral honeys. The analytical method was optimized and fully validated in terms of detection and quantitation limits, precision (by testing repeatability and reproducibility), linearity, and bias (by means of recovery tests). The acceptability of the validation protocol results was verified using Horwitz's mathematical model and AOAC guidelines.

A direct RP-HPLC method for the determination of furanic aldehydes and acids in honey.

In this study 5-hydroxymethyl-2-furaldehyde (HMF), 2-furaldehyde, 3-furaldehyde, 2-furoic acid and 3-furoic acid are contemporarily determined in honey using a swift and direct RP-HPLC approach. The validation protocol was performed in terms of detection and quantification limits, precision (by repeatability and reproducibility), linearity and accuracy (by recovery tests); the acceptability of the precision and accuracy results was positively verified using Horwitz's model and AOAC guidelines, respectively. The method was tested on 18 honey samples of different ages, and botanical and geographical origin. HMF and 2-furaldehyde correlated highly with the age of the samples, whereas no correlation was observed with regards to 2-furaldehyde and 2-furoic acid. Hypotheses relating to the formation of minority furanic compounds are also proposed.

Dependence of kinetic variables in the short-term release of Hg2+, Cu2+ and Zn2+ ions into synthetic saliva from an high-copper dental amalgam.

The short term (up to 14 days after restoration) release of selected ions (i.e., Hg(2+), Cu(2+) and Zn(2+)) from Dispersalloy into artificial saliva has been evaluated in regards to the nature of the saliva (Fusayama and McCarty and Shklar's solutions), the amount of amalgam, the time of contact and the periodical renewal (every 48 h interval) of artificial saliva. The evaluation of the ionic fraction of such metals has been accomplished by using anodic stripping methods (i.e., Differential Pulse Anodic Stripping Voltammetry, DPASV) with a 7 microm graphite disk microelectrode as a working electrode. Data obtained in this work are almost unprecedented in the literature due the fact that such analytical method exclude metals in non-ionic forms (e.g., metals or organometallic compounds). The high concentrations measured in every experimental condition confirm the concern for the short-term release of metals from amalgam into saliva.

An RP-HPLC determination of 5-hydroxymethylfurfural in honey The case of strawberry tree honey.

The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0mgkg(-1), respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140mgkg(-1).

Direct chromatographic methods for the rapid determination of homogentisic acid in strawberry tree (Arbutus unedo L.) honey.

Two rapid and direct chromatographic methods based on reverse phase-high performance liquid chromatography (RP-HPLC) and ion chromatography (IC) were developed for the determination of homogentisic acid (HA) in honey. This is the marker of the botanic origin of strawberry tree honey. The methods were validated and tested using 22 samples from Sardinia, Italy. The IC method is faster than the RP-HPLC one (6 min versus 13 min of total run), but it is slightly less sensitive (the limit of detection (LOD), is 26 mg kg(-1) versus 15 mg kg(-1)) and reproducible (relative standard deviation, RSD, of 10.4 and 4.4%, respectively). The whole dataset of validation parameters allows both the proposed methods to be considered as bias-free (by recovery tests, comparison of analytical results of the two independent methods and analysis of a synthetic sample) and precise (both the techniques show a repeatability better than 2% repeatability in the range between 70 and 600 mg kg(-1)).

Study of the short-term release of the ionic fraction of heavy metals from dental amalgam into synthetic saliva, using anodic stripping voltammetry with microelectrodes.

The present paper describes a fast and reproducible procedure, employing differential pulse stripping analysis technique with graphite microelectrodes, for the quantitative evaluation of the ionic fraction of heavy metals (namely Hg, Cu, and Zn) released from dental amalgams into synthetic saliva during 6-90 h contact between amalgam and saliva, after completion of the dental restoration (short-term release). The Zn(2+) concentration was evaluated by linear calibration, whereas Cu(2+) and Hg(2+) contents were estimated by the standard additions method. While the concentration of Zn(2+) ion does not increase significantly anymore after a 6-h contact (values from 288+/-12 to 346+/-12 mugdm(-3) at time of contact from 6 to 90 h, respectively), in the same time interval the concentration of both Cu(2+) and Hg(2+) ions progressively increases (from 38+/-6 to 197+/-4 mugdm(-3) and from 15+/-3 to 101+/-2 mugdm(-3), respectively). The results of the release tests reveal that Hg concentration is at the highest level of risk (HBM III), as identified by the three human biomonitoring categories suggested by the Institut für Wasser-, Boden- und Lufthygiene des Umweltbundesamtes (Germany) for the estimation of potential harmful effects on health due to exposure to heavy metals.