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Title:Določanje neonikotinoidov v medu in cvetnem prahu s HPLC-DAD in TLS detekcijo
Authors:Mejač, Irena (Author)
Franko, Mladen (Mentor) More about this mentor... New window
Files:URL http://www.ung.si/~library/diplome/OKOLJE/8Mejac.pdf
 
.pdf 8Mejac.pdf (713,06 KB)
 
Language:Slovenian
Work type:Undergraduate thesis (m5)
Tipology:2.11 - Undergraduate Thesis
Organization:FZO - Faculty of Environmental Sciences
Abstract:Razvili smo kromatografsko metodo HPLC za določevanje nekaterih neonikotinoidov (imidakloprid, tiametoksam, acetamiprid in tiakloprid) v vzorcih medu in cvetnega prahu. Neonikotinoide smo iz vzorcev medu ekstrahirali z ekstrakcijo tekoče-tekoče v diklorometan, iz cvetnega prahu pa z ekstrakcijo trdno-tekoče v diklorometan:aceton. Z dodatkom standardnih raztopin neonikotinoidov vzorcem medu in cvetnega prahu pred ekstrakcijo smo pripravili umeritvene premice z visokimi regresijskimi koeficienti (> 0,994) v koncentracijskem območju 0,1-5 mg/kg. Vzorce smo analizirali na reverzno-fazni kromatografski koloni C[sub]18 ob uporabi izokratične metode elucije z acetonitrilom:10mM amonijevim acetatom (3:7, v/v) in pretoka 1 mL/min. Za detekcijo neonikotinoidov po kromatografski ločbi smo uporabili spektrofotometrično metodo z diodno matriko DAD in spektrometrijo s toplotnimi lečami TLS. Zaradi različnih absorbcijskih spektrov posameznih neonikotinoidov smo v primeru DAD določevali insekticide pri štirih valovnih dolžinah (254, 270, 245 in 242 nm), v primeru TLS pa smo lahko uporabili le valovno dolžino vzbujevalnega laserja 244 nm. Doseženi izkoristki ekstrakcij iz medu so bili med 76 in 83 % za acetamiprid, tiakloprid in tiametoksam ter 99 % za imidakloprid. Relativni standardni odmiki pri koncentraciji 1 mg/kg in petih ponovitvah so bili v območju 15-38 %. Meje zaznavnosti so bile 50 [mi]g/kg za imidakloprid, 100 [mi]g/kg za tiametoksam in acetamiprid ter 250 [mi]g/kg za tiakloprid. Izkoristki ekstrakcij iz cvetnega prahu so bili občutno nižji, v območju 45-54 %, in so omogočali doseganje meje zaznavnosti 500 [mi]g/kg za vse štiri insekticide. Z metodo HPLC-TLS smo za primer standardnih raztopin neonikotinoidov dosegli meje zaznavnosti v območju 10 [mi]g/kg za acetamiprid do 25 [mi]g/kg za tiametoksam in imidakloprid in s tem znižanje vrednosti LOD v primerjavi s HPLC-DAD metodo.
Keywords:diplomske naloge, ekstrakcija, med, cvetni prah, kromatografija
Year of publishing:2006
Publisher:I. Mejač
Number of pages:IV, 54 str.
Source:Nova Gorica
COBISS_ID:536315 Link is opened in a new window
UDC:504
URN:URN:SI:UNG:REP:DMUP8GXK
Views:3058
Downloads:222
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Secondary language

Language:English
Abstract:A HPLC chromatographic method combined with liquid-liquid extraction into dichloromethane and solid-liquid extraction into acetone:dichloromethane was developed for simultaneous determination of some neonicotinoids (imidacloprid,thiamethoxam, acetamiprid and thiacloprid) in pollen and commercial honey samples. Calibration curves with high regression coefficients(> 0.994) were prepared in the 0.1-5 mg/kg concentration range by adding appropriate amounts of neonicotinoids to honey or pollen samples before the extraction. Samples were analyzed on a reverse-phase C[sub]18 chromatographic column using isocratic elution with acetonitrile:10 mM ammonium acetate (3:7, v/v) as eluent, and 1 mL/min flow rate. Detection of neonicotinoids was performed by DAD diode-array spectrophotometric method or by thermal lens spectrometry (TLS). Due to differences in absorption spectra of studied insecticides all chromatograms were recorded at four wavelengths (254, 270, 245 and 242 nm) in case of DAD. For TLS measurements only the wavelength of the excitation laser (244 nm) was used. Recoveries from honey were between 76 and 83 % for acetamiprid, thiacloprid, and thiametoxam, and 99% for imidacloprid. Relative standard deviations of five determinations in honey fortified at 1 mg/kg level were in the range of 15-38 % depending on the insecticide. The achieved limits of detection (LOD) were from 50 [mu]g/kg for imidacloprid to 100 [mu]g/kg for thiametoxam and acetamiprid, and 250 [mu]g/kg for thiacloprid. In case of pollen recoveries were significantly lower and ranged from 45-54 %, while the achieved LODs were at 500 [mu]g/kg for all four insecticides. In case of HPLC-TLS only standard neonicotinoid solutions were analyzed, and the LOD values ranging from 10 [mu]g/kg for acetamiprid up to 25 [mu]g/kg for thaimethoxam and imidacloprid were achieved. This represents an improvement compared to the HPLC-DAD method.


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