Simple methodology coupling microwave-assisted extraction to SPE/GC/MS for the analysis of natural steroids in biological tissues: Application to the monitoring of endogenous steroids in marine mussels Mytilus sp

Cyanoacetohydrazide as a Novel Derivatization Agent for the Determination of UHPLC-HRMS Steroids in Urine

The possibility of cyanoacetohydrazide usage as a novel derivatizing agent is demonstrated in the presented article, and a comparison with hydroxylamine as the most commonly used reagent is provided. Optimal conditions for steroid derivatization with cyanoacetohydrazide are provided. According to the collected data, the maximum yield of derivatives was observed at pH 2.8 within 70 min at 40 °C with 5 ng/mL limit of detection for all investigated analytes. It was shown that cyanoacetohydrazide derivatives produces both syn- and anti-forms as well as hydroxylamine, and their ratios were evaluated and shown in presented work. An efficiency enchantment from two to up to five times was achieved with a novel derivatization reagent. Its applicability for qualitative analysis of steroids in urine was presented at real samples. Additionally, the reproducible fragmentation of the derivatizing agent in collision-induced dissociation offers opportunities for simplified non-targeted steroidomic screening. Furthermore, cyanoacetohydrazide increases ionization efficiency in positive mode, which can eliminate the need for redundant high-resolution instrument runs required for both positive and negative mode analyses.

A Simple, Efficient, Eco-Friendly Sample Preparation Procedure for the Simultaneous Determination of Hormones in Meat and Fish Products by Gas Chromatography—Mass Spectrometry

Food safety can be severely compromised by the presence of chemical contaminants. This has raised a pressing need to develop efficient analytical methods for their determination at very low levels in complex food matrices. In this manuscript, we developed a simple, sensitive, fast, green analytical method for the determination of thirteen natural and synthetic hormones from different families including progestogens, estrogens and androgens in meat and fish products. The method involves direct extraction with a (9:1) acetonitrile–water mixture and subsequent purification of the extract by semi-automated solid-phase extraction on a sorbent column (hydrophilic–lipophilic copolymer of N-vinylpyrrolidone and divinylbenzene). This treatment enriches samples with the target compounds while removing proteins, lipids and other potential interferences from their matrix for the accurate determination of the analytes by gas chromatography–mass spectrometry, all within 15 min. The proposed method exhibits good linearity (r ≥ 0.996), low limits of detection (0.4–15 ng/kg), acceptable recoveries (90–105%) and relative standard deviations (≤7%); in addition, it is scarcely subject to matrix effects (1–20%). The method was successfully used to determine natural and synthetic hormones in meat and fish products from Spain, Portugal, Italy, Germany, Greece, Norway, Morocco and the USA. The analytes were found at especially high levels (30–1900 ng/kg) in mussels, beef and pork.

GC-MS/MS Determination of Steroid Hormones in Urine Using Solid-Phase Derivatization as an Alternative to Conventional Methods

Solid-phase analytical derivatization (SPAD) is a promising hybrid sample preparation technique combining the clean-up and preconcentration of the sample in a single step. In this work, a novel SPAD method based on the preparation of trimethylsilyl (TMS) derivatives of steroid hormones (testosterone, estrone, DHT, estriol, estradiol, and progesterone) in Phenomenex Strata C18-E (100 mg, 1 mL) cartridges has been developed and applied for their GC-MS/MS determination in human urine samples. The proposed procedure allows the detection and quantification of steroids with limits of 1.0–2.5 and 2.5–5 ng/mL, respectively. These characteristics are comparable with those obtained with a conventional liquid–liquid extraction, while the recovery of analytes in the proposed SPAD procedure is higher. The major advantages of SPAD are a short derivatization time, high efficiency, and the possibility to automatize the procedure. However, its cost-effectiveness in routine practice is still questionable.

Development of a quantitative method for determination of steroids in human plasma by gas chromatography-negative chemical ionization-tandem mass spectrometry

Sex steroids are involved in biological functions that encompass from the complete sexual development of individuals up to the deregulation of metabolic pathways leading to some pathologies. Steroids are present in blood at low concentration levels from pg mL^-1 to ng mL^-1. For this reason, a high sensitive and selective method based on gas chromatography-negative chemical ionization-tandem mass spectrometry (GC-NCI-MS/MS) is here proposed to quantify either androgens (androstenedione, dehydroepiandrosterone, dihydrotestosterone and testosterone), estrogens (estrone and estradiol) and a progestogen (progesterone) in human plasma. The sample preparation steps, protein precipitation and solid phase extraction, were optimized to ensure the sample matrix removal and to extract steroids with high efficiency. The NCI-MS/MS detection approach was compared with that based on electron impact to evaluate the incidence of the ionization source in the determination of steroids. The quantification limits for determination of these analytes were in a range from 10 pg mL^-1 to 5 ng mL^-1, with a high sensitivity for estrogens, typically found at low concentrations. The proposed method was tested for the determination of steroids in male blood samples, in which 6 out of 7 steroids were detected and quantified to report concentration values in agreement with those described in the literature.

Occurrence and level of emerging organic contaminant in fish and mollusk from Klang River estuary, Malaysia and assessment on human health risk

The occurrence, level, and distribution of multiclass emerging organic contaminants (EOCs) in fish and mollusks from the Klang River estuary were examined. The targeted EOCs for this assessment were phenolic endocrine disrupting compounds (bisphenol A, 4-OP, and 4-NP), organophosphorous pesticides (quinalphos, chlorpyrifos, and diazinon), estrogenic hormones (E2, E1, and EE2), and pharmaceutically active chemicals (primidone, sulfamethoxazole, dexamethasone, diclofenac, amoxicillin, progesterone, and testosterone). Results from this study showed that the prevalent contamination of the Klang River estuary by EOCs with diclofenac, bisphenol A, progesterone, and amoxicillin were predominantly detected in fish and mollusks. Among the EOCs, diclofenac and progesterone had the highest concentrations in fish and mollusk samples, respectively. The concentrations of diclofenac and progesterone in fish and mollusk samples range from 1.42 ng/g to 10.76 ng/g and from 0.73 ng/g to 9.57 ng/g, respectively. Bisphenol A should also be highlighted because of its significant presence in both fish and mollusks. The concentration of bisphenol A in both matrices range from 0.92 ng/g to 5.79 ng/g. The calculated hazard quotient (HQ) for diclofenac, bisphenol A, and progesterone without consideration to their degradation byproduct were less than one, thus suggesting that the consumption of fish and mollusks from the Klang River estuary will unlikely pose any health risk to consumers on the basis of the current assessment. Nonetheless, this preliminary result is an important finding for pollution studies in Malaysian tropical coastal ecosystems, particularly for organic micropollutant EOCs, and can serve as a baseline database for future reference.

Multiresidue analytical method for the determination of 41 multiclass organic pollutants in mussel and fish tissues and biofluids by liquid chromatography coupled to tandem mass spectrometry

In this work, the full optimisation and validation procedure to analyse a wide set of emerging organic contaminants in biotissues (mussel and fish muscle, liver, gills and brain) and biofluids (fish plasma and bile) is described. The target families include artificial sweeteners, industrial products, hormones, pharmaceutical and personal care products, pesticides and phytoestrogens. Different clean-up strategies (hydrophilic-lipophilic-balanced (HLB) solid-phase extraction, Florisil solid-phase extraction and liquid-liquid extraction followed by HLB solid-phase extraction and microextraction based on polyethersulfone polymer) were evaluated for the clean-up of focused ultrasonic solid-liquid extraction (FUSLE) extracts before the analysis by liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS/MS). The methods afforded satisfactory apparent recovery values (71-126%) using isotopically labelled analytes and matrix-matched calibration approach, regardless of the matrix. Method detection limits in the range of 4-48 ng/g and 0.3-111 ng/L were obtained for biotissues and biofluids, respectively. The developed method was applied to determine the uptake and tissue distribution in juvenile gilt-head bream (Sparus aurata) during 7 days in seawater, and unexpectedly, perfluoro-1-butanesulfonate tended to accumulate in liver and, to a lesser extent, in muscle and gills. Furthermore, real mussel samples collected in the Basque coast were also analysed and the presence of the highly consumed valsartan (7 ng/g) and telmisartan (6.8 ng/g) compounds in bivalves is reported for the first time here. Graphical abstract ᅟ.

Uptake and metabolism of water-borne progesterone by the mussel, Mytilus spp. (Mollusca)

Previous studies have shown that mussels can pick up 17β-estradiol [E₂] and testosterone [T] from water, metabolize them and conjugate them to fatty acids (esterification), leading to their accumulation in tissue. A key requirement for the esterification process is that a steroid must have a 'reactive' hydroxyl group to conjugate to a fatty acid (which in T, and probably E₂, is the β-hydroxyl group on carbon 17). Progesterone (P) lacks any hydroxyl groups and theoretically cannot be esterified and hence should not accumulate in mussels in the same way as E₂ or T. However, it is already known that mussels have an enzyme that can achieve 5α-reduction of the A ring of T and P and that there is also another reductase that can transform the 3-oxo group of the 5α-reduced A ring of T into a hydroxyl group. We hypothesized that, although intact P cannot be directly esterified, it might nevertheless be transformed into metabolites that can. To test this hypothesis, we investigated the rate and capacity of uptake, metabolism and potential depuration of tritiated P by the common mussel, Mytilus spp. We found that tritiated P was taken up from water at a similar rate to E₂ and T (mean clearance rate 49mL^-1 animal^-1h^-1) and that, as found with the other steroids, the rate of uptake could not be saturated by the addition of non-radioactive steroid (even at 7.6μgL^-1). We found that up to 66% of the radioactivity that was taken up was present in the ester fraction, suggesting that hydroxylation of the P must indeed have occurred. We then definitively identified two metabolites in the ester fraction: 5α-pregnane-3β,20β-diol and 3β-hydroxy-5α-pregnan-20-one. These same two steroids were also present in the free steroid fraction. Intact P was not detected in either of the fractions. When undergoing depuration (under semi-static conditions), the radioactivity in the ester fractions remained at the same concentration in the animals for at least 10 days. Our findings suggest that the lack of reactive hydroxyl groups on P does not preclude it from being taken up, metabolized and subsequently stored. Many questions remain, not least of which is why, when P seems to be so rapidly metabolized, two previous studies on mussels have reported concentrations of up to 30ngg^-1 wet weight of P in their flesh.

Effects of 2,2',4,4'-tetrabromodipheny ether (BDE-47) on gonadogenesis of the manila clam Ruditapes philippinarum

The reported adverse effects of Polybrominated diphenyl ether (PBDE) congeners on gonadogenesis in fish may also occur in marine bivalves especially the burrowing species such as manila clam Ruditapes philippinarum. In this study, clams were exposed to BDE-47 for 25days at 0, 0.1 and 1μg/L. By using the water temperature control method, gonadal maturation from resting to ripe stage were observed successively in both the control and the treatment groups during 25days. The results showed that exposure to BDE-47 at concentration below 1μg/L did not delay the gonadogenesis process of the clam R. philippinarum, and no evidence of adverse effects of BDE-47 on clam gonadal histology was observed. However, exposure to 1μg/L BDE-47 caused significant decreases of haemolymph testosterone levels in both female and male clams at day 5 and day 15. The mRNA expression of 3β-HSD in females exposed to BDE-47 was significantly decreased at day 5, while mRNA expression of 17β-HSD and CYP17 was not significantly changed in either sex. Exposure to BDE-47 also resulted in up-regulation of the mRNA expression of vitellogenin (Vtg) in both sexes and spermatogenesis associated protein 4-homolog (SAP4) in males. These results suggest a potential contribution of BDE-47 to reproductive disruption in the manila clams, especially in males. This study demonstrates the promising utility of water temperature control method in conjunction with histological endpoints and biomarkers such as mRNA levels of Vtg in determining the reproductive disturbances caused by EDCs on bivalves.

Mussels (Mytilus spp.) display an ability for rapid and high capacity uptake of the vertebrate steroid, estradiol-17β from water

Six experiments were carried out to define the optimum conditions for investigating the dynamics of uptake and metabolism of tritiated E₂ from water by adult blue mussels, Mytilus spp. Optimum uptake was achieved using 400mL aerated sea water animal^-1 and an incubation period of no more than 24h. The pattern of disappearance conformed closest to an inverse hyperbolic curve with the percentage of radiolabel that could be measured in the water reaching an asymptote that was on average 50% of the original. This apparent inability of the animals to absorb all the radiolabel was investigated further. Solvent partition and chromatography revealed that, after 24h, c. 60% of the radiolabel still present in the water was composed of water soluble conjugates, c. 25% was composed of tritiated water and only 15% ran on and around the chromatographic position of E₂. The major water soluble constituent was identified by chromatography and mass-spectrometry as 1,3,5(10)-estratriene-3,17β-diol 3-sulfate (estradiol 3-S). The clearance rate of radiolabel was 46.9±1.8mLanimal^-1h^-1. This was not significantly affected by the addition of as much as 25μgL^-1 cold E₂ to the water, demonstrating that mussels have a large capacity for E₂ uptake. A new procedure involving solvent partition was developed for separating the free, esterified and sulfated forms of E₂ present in the flesh of mussels. This involved extracting the soft tissue with organic solvents and then treating a portion of dried extract with a combination of heptane (dissolved fatty acid esters of E₂) and 80% ethanol (dissolved free and sulfated E₂). The latter fraction was further partitioned between water (sulfate) and diethyl ether (free steroid). This procedure was much cheaper and less time-consuming than chromatography. Approximately 80% of the radioactivity that was taken up by the animals was present in the form of ester. Moreover, E₂ was the only steroid identified after saponification of these esters. Of the remaining radioactivity, c. 10% was in the form of unidentified free steroids and c. 10% was estradiol 3-S. In order to determine how rapidly mussels were able to depurate tritiated E₂ and its metabolites, two experiments were carried out. Animals from the first experiment purged up to 63% of radioactivity in 20days under flow-through conditions; whereas animals from the second experiment released only 16% of radioactivity in 10days under semi-static conditions. The ratios of the different forms of E₂ did not change substantially during the course of depuration.

Vortex-homogenized matrix solid-phase dispersion coupled with gas chromatography – electron-capture negative-ion mass spectrometry to determine halogenated phenolic compounds in seafood

This work represents the development of vortex-homogenized matrix solid-phase dispersion (VH-MSPD) as an effective and simple method to rapidly extract halogenated phenolic compounds in marketed seafood samples.

Variations of estradiol-17β and testosterone levels correlated with gametogenesis in the gonad of Zhikong scallop (Chlamys farreri) during annual reproductive cycle

To assess the potential roles of sex steroids in modulating reproductive processes in the Zhikong scallop (Chlamys farreri (Jones and Preston, 1904)), variations in estradiol-17β (E2) and testosterone (T) levels in gonads were examined monthly from January to December 2012 by enzyme-linked immunosorbent assay (ELISA). The mean concentrations of E2 and T in gonads ranged from 75.07 to 666.24 pg/g and from 91.09 to 506.28 pg/g, respectively. Concentrations of E2 were significantly higher in ovaries than in testes, while T concentrations were higher in testes than in ovaries during gametogenesis. Concentrations of E2 in females and T in males increased with development and maturation of gonad, attained the highest value before spawning, and decreased rapidly after spawning. A positive correlation between E2 levels and oocyte diameters (r = 0.743, P < 0.05, n = 25) was observed, suggesting that E2 may play a role in oogenesis. These findings indicate that E2 and T, which are highly correlated with the reproductive cycle, may play an important role in sex determination, sex differentiation, gametogenesis, and spawning in C. farreri.

A sensitive liquid chromatography/tandem mass spectrometry method for the determination of natural and synthetic steroid estrogens in seawater and marine biota, with a focus on proposed Water Framework Directive Environmental Quality Standards

RATIONALE

Trace levels of natural and synthetic steroid estrogens estrone (E1), 17β-estradiol (E2) and 17α-ethynyl estradiol (EE2) have been demonstrated to exert adverse effects in exposed organisms. E2 and EE2 have been proposed for inclusion in the Water Framework Directive (WFD) list of priority pollutants; however, the detection and accurate quantification of these compounds provide significant challenges, due to the low detection limits required.

METHODS

A sensitive method combining ultrasonication, solid-phase extraction (SPE) and liquid chromatography/tandem mass spectrometry, with electrospray ionisation in negative mode (LC/ESI-MS/MS), capable of determining E1, E2 and EE2 at concentrations between 0.07 and 60 ng/L for seawater and between 0.4 and 200 ng/g wet weight in Mytilus spp. is reported. Recoveries at the limit of quantification (LOQ) ranged from 95 to 102% and 88 to 100% for water and tissue, respectively. Salinity (12 to 35‰) and typical marine particulate matter loadings (between 10 and 100 mg/L) were not found to affect analyte recoveries.

RESULTS

The first detection of E1 by LC/MS/MS in Irish marine waters (Dublin Bay, at 0.76 ng/L) is reported. Steroids were not detected in Galway Bay, or in any mussel samples from Dublin, Galway and Clare. The level of E2 detected in the dissolved water phase was below the proposed WFD Environmental Quality Standard (EQS) in other surface waters.

CONCLUSIONS

The proposed method is suitable for the detection of E1, E2 and EE2 at biologically relevant concentrations and, due to the specificity offered, is not subject to potential interferences from endogenous E1 and E2 which often complicate the interpretation of estrogenic biomarker assays.

Annual variation in the levels of transcripts of sex-specific genes in the mantle of the common mussel, Mytilus edulis

Mytilus species are used as sentinels for the assessment of environmental health but sex or stage in the reproduction cycle is rarely considered even though both parameters are likely to influence responses to pollution. We have validated the use of a qPCR assay for sex identification and related the levels of transcripts to the reproductive cycle. A temporal study of mantle of Mytilus edulis found transcripts of male-specific vitelline coat lysin (VCL) and female-specific vitelline envelope receptor for lysin (VERL) could identify sex over a complete year. The levels of VCL/VERL were proportional to the numbers of sperm/ova and are indicative of the stage of the reproductive cycle. Maximal levels of VCL and VERL were found in February 2009 declining to minima between July - August before increasing and re-attaining a peak in February 2010. Water temperature may influence these transitions since they coincide with minimal water temperature in February and maximal temperature in August. An identical pattern of variation was found for a cryptic female-specific transcript (H5) but a very different pattern was observed for oestrogen receptor 2 (ER2). ER2 varied in a sex-specific way with male > female for most of the cycle, with a female maxima in July and a male maxima in December. Using artificially spawned animals, the transcripts for VCL, VERL and H5 were shown to be present in gametes and thus their disappearance from mantle is indicative of spawning. VCL and VERL are present at equivalent levels in February and July-August but during gametogenesis (August to January) and spawning (March to June) VCL is present at lower relative amounts than VERL. This may indicate sex-specific control mechanisms for these processes and highlight a potential pressure point leading to reduced reproductive output if environmental factors cause asynchrony to gamete maturation or release.

Do mollusks use vertebrate sex steroids as reproductive hormones? Part I: Critical appraisal of the evidence for the presence, biosynthesis and uptake of steroids

The consensus view is that vertebrate-type steroids are present in mollusks and perform hormonal roles which are similar to those that they play in vertebrates. Although vertebrate steroids can be measured in molluscan tissues, a key question is 'Are they formed endogenously or they are picked up from their environment?'. The present review concludes that there is no convincing evidence for biosynthesis of vertebrate steroids by mollusks. Furthermore, the 'mollusk' genome does not contain the genes for key enzymes that are necessary to transform cholesterol in progressive steps into vertebrate-type steroids; nor does the mollusk genome contain genes for functioning classical nuclear steroid receptors. On the other hand, there is very strong evidence that mollusks are able to absorb vertebrate steroids from the environment; and are able to store some of them (by conjugating them to fatty acids) for weeks to months. It is notable that the three steroids that have been proposed as functional hormones in mollusks (i.e. progesterone, testosterone and 17β-estradiol) are the same as those of humans. Since humans (and indeed all vertebrates) continuously excrete steroids not just via urine and feces, but via their body surface (and, in fish, via the gills), it is impossible to rule out contamination as the sole reason for the presence of vertebrate steroids in mollusks (even in animals kept under supposedly 'clean laboratory conditions'). Essentially, the presence of vertebrate steroids in mollusks cannot be taken as reliable evidence of either endogenous biosynthesis or of an endocrine role.

Dynamic microwave-assisted extraction coupled with salting-out liquid-liquid extraction for determination of steroid hormones in fish tissues

In this work, a simple and fast sample pretreatment method was proposed for determination of steroid hormones in fish tissues by coupling dynamic microwave-assisted extraction with salting-out liquid-liquid extraction. The steroid hormones were successively extracted with acetonitrile and water under the action of microwave energy. Subsequently, the extract was separated into an acetonitrile phase and an aqueous phase with ammonium acetate. The acetonitrile phase containing the target analytes was concentrated and determined by LC-MS/MS. The limits of detection for the steroid hormones were in the range of 0.03-0.15 ng g(-1). This method was successfully applied to analyze seven kinds of fish tissues, and the recoveries of the steroid hormones for the spiked samples were in the range of 75.3 ± 4.9% to 95.4 ± 6.2%. Compared with the traditional method, the proposed method could reduce the consumption of the organic solvent, shorten the sample preparation time, and increase the sample throughput.

In vitro biomonitoring of contamination by estrogenic compounds in coastal environments: comments on the use of M. galloprovincialis

The use of mussel extracts in in vitro bioassays which express the estrogen receptor could provide valuable information on the bioavailability of endocrine disruptors in coastal environments. The aim of this study was to assess the temporal variability of the estrogenic responses in bioassays in Mytilus galloprovincialis. A 6-month in situ experiment was conducted in order to follow the estrogenic activity on MELN cell line during the reproduction stages of mussels. Estradiol equivalents (EEQ) determined in mussels using the MELN cell lines ranged from 0.79 to 3.72 ng/g dry weight (d.w.) in males, from 0.42 to 2.33 ng/g d.w. in females and from 3.41 to 4.2 d.w. in undifferentiated bivalves. We observed an increase in EEQ values during the spawning stage for males, not for female. The maximal EEQ values were observed at the indifferent stage. We discuss these results in regards to the actual knowledge on mussels' reproductive cycle and to the possible impact of xeno-estrogens. Variations of E2 levels in mussels must be taken into account for further studies on xeno-estrogens monitoring using hER reporter cell-lines bioassays.

Microwave-assisted extraction in natural products isolation

Microwave-assisted extraction (MAE) or simply microwave extraction is a relatively new extraction technique that combines microwave and traditional solvent extraction. Application of microwaves for heating the solvents and plant tissues in extraction process, which increases the kinetic of extraction, is called microwave-assisted extraction. MAE has a number of advantages, e.g., shorter extraction time, less solvent, higher extraction rate and lower cost, over traditional method of extraction of compounds from various matrices, especially natural products. The use of MAE in natural products extraction started in the late 1980s, and through the technological developments, it has now become one of the popular and cost-effective extraction methods available today, and several advanced MAE instrumentations and methodologies have become available, e.g., pressurized microwave-assisted extraction (PMAE) and solvent-free microwave-assisted extraction (SFMAE). This chapter provides an overview of the MAE and presents a number of specific protocols for natural products extraction.

Distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals in wild fish species from Dianchi Lake, China

The distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals (EDCs) were studied in various tissues of wild fish species from Dianchi Lake, China. In muscle tissue, 4-tert-octylphenol, 4-cumylphenol, 4-nonlyphenol and bisphenol A were detected in fish from each sampling site, with maximal concentrations of 4.6, 4.4, 18.9 and 83.5 ng/g dry weight (dw), respectively. Steroids (estrone, 17β-estradiol 17α-ethynylestradiol and estriol) were found at lower levels (<11.3 ng/g dw) and less frequently in muscle samples. The highest concentrations of steroids and phenols were found in liver, followed by those in gill and the lowest concentration was found in muscle. The field bioconcentration factors (BCFs) of phenols were calculated in fish species ranged from 18 to 97. Moreover, the measured tissue concentrations were utilized in order to estimate water concentration of steroids (4.4-18.0 ng/L). These results showed that steroidal and phenolic EDCs were likely ubiquitous contaminants in wild fish.

Microwave-accelerated derivatization prior to GC-MS determination of sex hormones

A new microwave-accelerated derivatization method was developed for rapid determination of 13 natural sex hormones in feeds. Sex hormones were isolated from the sample matrix by ultrasonic extraction, followed by solid-phase extraction, derivatized under microwave irradiation, and then analyzed directly by gas chromatography-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The key parameters affecting derivatization efficiency, including microwave irradiation time, microwave power, and reaction solvent were studied. Under microwave power of 360 W and microwave irradiation for 3 min, 13 natural sex hormones were simultaneously derivatized using heptafluorobutyric acid anhydride (HFBA) as derivatization reagent. This method was applied to the determination of 13 natural sex hormones in different feed samples, and the obtained results were compared with those obtained by the traditional thermal derivatization. The recoveries from 58.1 to 111% were obtained at sex hormone concentrations of 10-300 μg/kg with RSDs ≤12.0%. The results showed that the proposed method was fast, simple, efficient and can be applied to the determination of 13 natural sex hormones in different feed samples.