products that can be tailored for d

products that can be tailored for diverse applications beyond just
pesticide residue analysis [8].
With respect to high-throughput analysis, Nanita et al. first
demonstrated in 2009 that modern triple quadrupole MS/MS
instruments could be used to monitor selected pesticide analytes in food and soil samples using flow injection (FI) analysis
rather than undergoing a chromatographic separation [9]. In the
FI-MS/MS approach, analysis times are a matter of 15–90 s rather
than 10–30 min, which takes sample throughput to a new level,
especially if the approach can be adopted to routine multiclass,
multiresidue monitoring. Nanita et al. have improved the concept and evaluated it for up to 14 pesticides in diverse matrices
as described in subsequent publications [10–13]. Mol and van
Dam also evaluated the FI-MS/MS approach for selected pesticides
known to be particularly difficult [14].
Currently, QuEChERS is the sample preparation approach of
choice for FI-MS/MS, but it commonly uses magnesium sulfate in
combination with sodium chloride, acetate, or citrate salts to induce
acetonitrile (MeCN)/water phase separation during the pesticide
extraction step [5–7,15]. Unfortunately, these salts/ions have such
low vapor pressures that they tend to deposit as solids on surfaces in
the MS source and potentially within the analyzer to cause instrument performance loss and need for increased maintenance. In GC,
the salts pose problems by depositing in the inlet liner, which leads
to greater frequency of liner replacement. However, ammonium
salts are more volatile and pose less of a problem at typical GC
inlet and MS ion source temperatures (>280
◦
C). In addition, the
presence of ammonium ions can enhance the formation of ammonium adducts in atmospheric pressure ionization rather than less
desirable sodium adducts [16,17].
Nanita and Padivitage compared the use of different salts in
sample preparation prior to FI-MS/MS. When they achieved equivalent results among certain ammonium salts, they chose ammonium
chloride based on minor practical considerations [11]. However,
they only studied a limited range of pesticides, and if this concept
is to be used more widely in monitoring applications, a wider scope
of analytes needs to be evaluated. Soon after the introduction of the
original QuEChERS method [5], buffering was found to be an important consideration to achieve high recoveries for a wider range of
pesticides independent of sample pH [15]. Similarly, the evaluation of ammonium salts should include buffering to achieve more
consistent results.
The aim of this study was to evaluate three different new versions of the QuEChERS method based on the use of ammonium
chloride and ammonium formate and acetate buffers and to compare them with the QuEChERS AOAC Official Method 2007.01.
For this purpose, both LC-MS/MS and low-pressure (LP)GC-MS/MS
would be used to analyze essentially the same representative pesticides and food matrices as chosen in previous studies of this
nature [6,14,17]. Independently of FI-MS/MS, the use of ammonium
salts could be used to improve performance and reduce instrument
maintenance needs of LC-MS-based methods.
2. Materials and methods
2.1. Reagents
Pesticide reference standards, all 97% purity or higher, were
obtained from the Environmental Protection Agency’s National
Pesticide Repository (Fort Meade, MD, USA), Dr. Ehrenstorfer
GmbH (Augsburg; Germany), and Chemservice (West Chester, PA,
USA). Atrazine-d5 (ethyl-d5) and fenthion-d6 (o,o-dimethyl-d6),
which were used as internal standards (IS), were purchased from
C/D/N Isotopes (Pointe-Claire, QC; Canada). Triphenylphosphate
(TPP) was added to all final extracts for quality control (QC) just
prior to the LPGC-MS/MS and LC-MS/MS analyses. A complete
list of the monitored chemicals, their retention times (tR), and
MS/MS transitions is provided in Table 1. Analyte protectants
consisting of 3-ethoxy-1,2-propanediol (ethylglycerol), l-gulonic
acid--lactone (gulonolactone), d-sorbitol, and shikimic acid (all
with purity ≥95%) were obtained from Sigma-Aldrich (Milwaukee,
WI, USA).
Stock solutions of each pesticide were prepared in toluene or
MeCN at concentrations between 1000 and 4000 ng/L and stored
in amber glass vials at −18
◦
C. For spiking of samples, pesticide
standard mixtures of 0.5, 3.75, and 20 ng/L were prepared in
MeCN containing 0.05% (v/v) formic acid. A mixture of the two
IS at 10 ng/L and a 2 ng/L solution of TPP were also prepared.
For calibration, mixed standards were prepared at 0.05, 0.1, 0.25,
0.75, 2, 4 and 6 ng/L plus 2 ng/L of both IS in each solution
(to yield 5, 10, 25, 75, 200, 400 and 600 ng/g sample equivalents
for the pesticides and 200 ng/g for the IS). For QC purposes, TPP
solution was also added yield a final concentration of 200 ng/g.
An analyte protectants solution containing 10,000 ng/L of ethylglycerol, 1000 ng/L of gulonolactone, 1000 ng/L of d-sorbitol and
500 ng/L of shikimic acid was prepared in 4/1 (v/v) MeCN/water
containing 0.5% (v/v) formic acid.
All solvents were HPLC-grade. MeCN was from Fisher Scientific (Fair Lawn, NJ, USA) and glacial acetic acid (HOAc) was
from J.T. Baker (Phillipsburg, NJ, USA); formic acid, ammonium
formate (NH4O2CH), and NH4Cl were from Sigma-Aldrich; ammonium acetate (NH4OAc) was from Mallinckrodt (Paris, KY, USA).
Commercial QuEChERS extraction packets containing 6 g of anh.
MgSO4 plus 1.5 g of anh. NaOAc were from Agilent (Little Falls,
DE, USA). For dispersive solid-phase extraction (d-SPE) cleanup,
pre-weighed mixtures containing 150 mg of anh. MgSO4, 50 mg
of primary secondary amine (PSA) and 50 mg of octadecylsilane
(C18) in 2 mL mini-centrifuge tubes were from Phenomenex (Torrance, CA, USA). Graphitized carbon black (GCB) of 120/400 mesh
was from Supelco (Bellefonte, PA, USA), and 7.5 mg was separately added to the d-SPE tubes. For wheat, an additional 100 mg
of PSA from UCT (Bristol, PA, USA) was added to the d-SPE tubes to
provide more cleanup for removal of fatty acids. For use with larger
extract volumes to prepare matrix-matched calibration standards,
commercial tubes of 15 mL containing 1200 mg of anh. MgSO4,
400 mg of PSA and 400 mg of C18 were from Biotage (Hengoed,
UK), adding 60 mg of GCB in all cases and 800 mg of PSA for wheat
grain.
2.2. Samples
Apple, lemon, lettuce, and wheat grain samples were purchased
from a local organic food store and all samples were checked to be
free of pesticides residues. Approximately 1 kg of apple, lemon, and
lettuce samples were cut into small portions with a knife and comminuted in a 2 L chopper (Robotcoupe, Jackson, MS, USA). Dry ice
was used to help process the lettuce. Approximately 1 kg of wheat
grain was ground using a coffee mill. All samples were stored in a
freezer at −18
◦
C until thawed for extraction.
2.3. LPGC-MS/MS conditions
The LPGC-MS/MS analyses were conducted similarly as in previous studies [19–21] using an Agilent 7000A triple-quadrupole
mass spectrometer with electron ionization interfaced to an Agilent
7890 GC, which had a 220 V fast oven heating upgrade. MassHunter
software was used for instrument control and data processing.
An SLBTM
-5ms analytical column (15 m, 0.53 mm i.d., 1 m film
thickness) from Supelco was coupled to a Hydroguard®
(5 m,
0.18 mm i.d.) restriction/guard column from Restek (Bellefonte, PA,
USA). Ultrahigh purity He was used as the carrier gas at 2 mL/min

Hasil (Bahasa Indonesia) 1:

produk yang dapat disesuaikan untuk aplikasi yang beragam luar hanyaAnalisis residu pestisida [8].Sehubungan dengan tinggi-throughput analisis, Nanita et al. pertamaditunjukkan dalam 2009 quadrupole triple yang modern, MS MSinstrumen dapat digunakan untuk memantau analytes dipilih pestisida dalam sampel makanan dan tanah yang menggunakan analisis arus injeksi (FI)daripada menjalani pemisahan kromatografi [9]. DalamFI-MS/MS pendekatan, analisis kali adalah masalah s 15-90 agakdaripada 10-30 menit, yang membawa throughput sampel ke tingkat yang baru,terutama jika pendekatan yang dapat diadopsi untuk rutin multiclass,multiresidue pemantauan. Nanita et al. telah ditingkatkan konsep dan dievaluasi untuk sampai dengan 14 pestisida dalam beragam matriksseperti yang dijelaskan dalam publikasi berikutnya [10 – 13]. Mol dan vanDam juga dievaluasi pendekatan FI-MS/MS untuk dipilih pestisidaDia dikenal sangat sulit [14].Saat ini, QuEChERS adalah pendekatan persiapan sampelpilihan untuk FI-MS/MS, tapi umumnya menggunakan magnesium sulfat dikombinasi dengan natrium klorida, asetat, atau garam sitrat untuk menginduksiasetonitril (MeCN) / air pemisahan fase selama pestisidaekstraksi langkah [5-7,15]. Sayangnya, garam/ion ini memilikirendah tekanan uap yang mereka cenderung untuk deposit sebagai padatan pada permukaan disumber MS dan berpotensi dalam analyzer untuk menyebabkan kerugian kinerja instrumen dan perlu untuk pemeliharaan meningkat. Di GC,garam menimbulkan masalah dengan mendepositokan di liner inlet, yang mengarahfrekuensi lebih besar kapal penggantian. Namun, amoniumgaram lebih mudah menguap dan menimbulkan kurang masalah di khas GCinlet dan MS ion sumber suhu (> 280◦C). Selain itu,kehadiran ammonium ion dapat meningkatkan pembentukan amonium adducts dalam tekanan atmosfer ionisasi daripada kurangdiinginkan natrium adducts [16,17].Nanita dan Padivitage dibandingkan penggunaan garam yang berbeda dalampreparasi sample sebelum FI-MS/MS. Ketika mereka mencapai hasil yang sama antara garam amonium tertentu, mereka memilih amoniumklorida didasarkan pada pertimbangan-pertimbangan praktis kecil [11]. Namun,mereka hanya mempelajari berbagai terbatas pestisida, dan jika konsep iniakan digunakan lebih luas dalam pemantauan aplikasi, luasanalytes kebutuhan untuk dievaluasi. Segera setelah pengenalanmetode QuEChERS asli [5], buffering ditemukan untuk menjadi pertimbangan penting untuk mencapai tinggi pemulihan untuk jangkauan yang lebih luaspestisida independen sampel pH [15]. Demikian pula, evaluasi garam amonium harus mencakup buffering untuk mencapai lebih banyakhasil yang konsisten.Tujuan dari penelitian ini adalah untuk mengevaluasi tiga versi baru yang berbeda metode QuEChERS berdasarkan penggunaan amoniumklorida dan amonium formate dan asetat buffer dan membandingkan mereka dengan QuEChERS AOAC resmi metode 2007.01.Untuk tujuan ini, LC-MS/MS dan tekanan rendah (LP) GC-MS/MSakan digunakan untuk menganalisis pada dasarnya sama perwakilan pestisida dan makanan matriks yang dipilih dalam studi sebelumnya inialam [6,14,17]. Terlepas dari FI-MS/MS, penggunaan amoniumgaram dapat digunakan untuk meningkatkan kinerja dan mengurangi instrumenkebutuhan pemeliharaan LC-MS berbasis metode.2. bahan dan metode2.1. reagenPestisida referensi standar, Semua 97% kemurnian atau lebih tinggi, yangDiperoleh dari badan perlindungan lingkungan NasionalPestisida repositori (Fort Meade, MD, USA), Dr. EhrenstorferGmbH (Augsburg; Jerman), dan Chemservice (West Chester, PA,USA). Atrazine-d5 (etil-d5) dan fenthion-d6 (o, o-dimetil-d6),yang digunakan sebagai standar internal (IS), itu dibeli dariIsotop C/D N (Pointe-Claire, QC; Kanada). Triphenylphosphate(TPP) telah ditambahkan ke semua akhir ekstrak untuk quality control (QC) hanyasebelum analisis LPGC-MS/MS dan LC-MS/MS. LengkapDaftar bahan kimia dipantau, retensi mereka kali (tR), danMS MS transisi disediakan dalam tabel 1. Analyte protectantsterdiri dari 3-ethoxy-1,2-propanediol (ethylglycerol), l-gulonicasam - asam laktone (gulonolakton), d-sorbitol, dan shikimic (semuadengan kemurnian ≥95%) Diperoleh dari Sigma Aldrich (Milwaukee,WI, AMERIKA SERIKAT).Saham solusi setiap pestisida yang disiapkan di toluena atauMeCN pada konsentrasi antara 1000 dan 4000 ng / L dan disimpandalam botol kaca kuning di −18◦C. untuk spiking sampel, pestisidastandar campuran 0,5, 3,75 dan 20 ng / L yang disiapkan diMeCN yang mengandung asam formiat 0,05% (v/v). Campuran dari duaDI 10 ng / L dan 2 ng / L larutan TPP juga disusun.Kalibrasi, standar campuran disiapkan di 0,05, 0.1, 0,25,0.75, 2, 4 dan 6 ng / L ditambah 2 ng / L dari kedua dalam setiap solusi(untuk menghasilkan 5, 10, 25, 75, 200, 400 dan 600 ng/g sampel setarauntuk pestisida dan 200 ng g untuk IS). Untuk tujuan QC, TPPsolusi ini juga ditambahkan hasil kadar akhir 200 ng/g.Analyte protectants larutan yang mengandung 10.000 ng / L ethylglycerol, 1000 ng / L gulonolakton, 1000 ng / L d-sorbitol dan500 ng / L shikimic asam disiapkan di 4/1 (v/v) MeCN airmengandung asam formiat 0,5% (v/v).Semua pelarut yang HPLC-grade. MeCN adalah dari Fisher Scientific (Fair Lawn, NJ, Amerika Serikat) dan asam asetat glacial (selesai)dari J.T. Baker (Phillipsburg, NJ, Amerika Serikat); formic asam, amoniumformate (NH4O2CH), dan NH4Cl adalah dari Sigma-Aldrich; amonium asetat (NH4OAc) adalah dari Mallinckrodt (Paris, KY, Amerika Serikat).Komersial QuEChERS ekstraksi paket yang mengandung 6 g anh.MgSO4 ditambah 1,5 g anh. NaOAc berasal dari Agilent (sedikit jatuh,DE, USA). Untuk pembersihan solid-fase sinar-x dispersif ekstraksi (d-SPE),pra-ditimbang campuran yang mengandung 150 mg anh. MgSO4, 50 mgAmina sekunder utama (PSA) dan 50 mg octadecylsilane(C18) pada 2 mL Mini centrifuge tabung berasal dari Phenomenex (Torrance, CA, USA). Graphitized karbon hitam (GCB) 120/400 meshwas from Supelco (Bellefonte, PA, USA), and 7.5 mg was separately added to the d-SPE tubes. For wheat, an additional 100 mgof PSA from UCT (Bristol, PA, USA) was added to the d-SPE tubes toprovide more cleanup for removal of fatty acids. For use with largerextract volumes to prepare matrix-matched calibration standards,commercial tubes of 15 mL containing 1200 mg of anh. MgSO4,400 mg of PSA and 400 mg of C18 were from Biotage (Hengoed,UK), adding 60 mg of GCB in all cases and 800 mg of PSA for wheatgrain.2.2. SamplesApple, lemon, lettuce, and wheat grain samples were purchasedfrom a local organic food store and all samples were checked to befree of pesticides residues. Approximately 1 kg of apple, lemon, andlettuce samples were cut into small portions with a knife and comminuted in a 2 L chopper (Robotcoupe, Jackson, MS, USA). Dry icewas used to help process the lettuce. Approximately 1 kg of wheatgrain was ground using a coffee mill. All samples were stored in afreezer at −18◦C until thawed for extraction.2.3. LPGC-MS/MS conditionsThe LPGC-MS/MS analyses were conducted similarly as in previous studies [19–21] using an Agilent 7000A triple-quadrupolemass spectrometer with electron ionization interfaced to an Agilent7890 GC, which had a 220 V fast oven heating upgrade. MassHuntersoftware was used for instrument control and data processing.An SLBTM-5ms analytical column (15 m, 0.53 mm i.d., 1 m filmthickness) from Supelco was coupled to a Hydroguard®(5 m,0.18 mm i.d.) restriction/guard column from Restek (Bellefonte, PA,USA). Ultrahigh purity He was used as the carrier gas at 2 mL/min