劉玉等
摘要建立了超高效液相色譜串聯質譜(UPLCMS/MS)同時測定3種三硝基酚類殘留量的方法。樣品經改進的QuEChERS(快速、簡單、廉價、高效、靈活和安全)前處理方法一步完成提取凈化,經添加1%甲酸的乙腈提取,C18和石墨化炭黑(GCB)吸附劑填料凈化,提取液經離心后直接過膜上機檢測,提取和凈化的效果能夠滿足檢測要求。UPLCMS/MS方法采用Accucore PFP 色譜柱(150 mm× 2.1 mm,2.6 μm),柱溫30 ℃,流動相為乙腈和乙酸銨緩沖鹽,梯度洗脫,流速0.3 mL/min,電噴霧電離源負離子模式(ESI
Symbolm@@ )、多反應監測(MRM)模式檢測,外標法定量。2,4,6三硝基苯酚、2,4,6三硝基間苯二酚和2,4,6三硝基均苯三酚3種三硝基酚類物質在0.005~5.0 mg/L范圍內線性關系良好,相關系數為0.9942~0.9962。在0.01,0.1和1.0 mg/kg水平下的平均加標回收率為79.3%~94.8%; 相對標準偏差為3.1%~6.6%; 方法的檢出限(S/N=3)為0.002~0.005 mg/kg。本方法簡單、快速、靈敏、準確,滿足環境污染檢測的要求。
關鍵詞超高效液相色譜串聯質譜法; 2,4,6三硝基苯酚; 2,4,6三硝基間苯二酚; 2,4,6三硝基均苯三酚; QuEChERS方法; 土壤
1引言
隨著工業發展,三硝基酚類物質由于其特殊的結構,被廣泛用于含能材料、醫藥、農藥、染料以及橡膠工業生產中\[1,2\]。三硝基酚類主要有2,4,6三硝基苯酚(俗稱苦味酸,TNP)、2,4,6三硝基間苯二酚(俗稱斯蒂芬酸,TNR)、2,4,6三硝基均苯三酚(TNPG)。由于三硝基酚類物質生產和使用過程會流失到土壤和周圍環境中,能持久存在于土壤環境中,破壞土壤結構,阻礙或抑制土壤微生物和植物的生命活動;同時由于其具有較強的水溶性,可以通過滲透和降水的淋洗作用污染地表水體系,導致病變,危害人類健康。因此,三硝基酚類對環境和人類健康造成的危害將備受關注。
目前對于三硝基酚類物質的環境控制研究多集中在降解菌種的培養、降解反應器的研制等污染降解處理方面\[3~7\],在水質、土壤的污染監控檢測方面卻相對滯后,且多采用分光光度法對三硝基酚類總量進行檢測\[8\]。目前,檢測硝基酚類的方法主要有分光光度法\[9\]、氣相色譜法\[10\]、液相色譜法\[11,12\]、氣相色譜質譜聯用法\[13\],這些相關的方法都只涉及部分硝基酚類,對于三硝基酚類特殊的強極性、熱不穩定的化學性質所適合的檢測方法研究較少。
目前,較常用的前處理方法有固相提取(SPE)\[14~17\]、加速溶劑提取(ASE)\[18~20\]、微波輔助提取(MAE)\[21~23\]和超聲波輔助提取(USE)\[24~26\]等,這些方法取代了傳統的耗費大量時間和溶劑的普通液液提取,但是通常需要后續的較繁瑣的操作步驟,甚至要求特殊的設備或者特殊的高溫等環境下進行,而最初應用于農藥殘留檢測的QuEChERS(Quick, Eesy, Cheap, Effective, Rugged and Safe)方法\[27,28\]是一種快速、簡單、高效的樣品前處理方法,在食品和生物安全領域得到了廣泛應用,但在凈化土壤、檢測硝基酚類應用少見報道。本研究將超高效液相色譜質譜聯用法(UPLCMS/MS)應用于三硝基酚類多殘留痕量快速分析,克服了目標化合物強極性、易分解、難以檢測分離所帶來的弊端,具有靈敏度高、確證性強、抗干擾能力強等優勢,將改進的QuEChERS方法應用于土壤樣品前處理,考察了不同吸附劑的凈化效果,同時簡化了前處理步驟,提取液直接進行UPLCMS/MS分析,可實現土壤中3種三硝基酚類物質的同時定性與定量檢測。
2實驗部分
2.1儀器與試劑
AcquityTM超高效液相色譜儀(UPLC), Quattro PremierTMXE三重四級桿質譜儀(Waters 公司); AllegraTM X22R型離心機(Beckman公司); Sk8200LH超聲波清洗器(上海科導公司); MilliQA10超純水機; IKAMS3漩渦混合器; 0.22 μm有機過濾膜(Waters公司)
3種三硝基酚類標準品分別為2,4,6三硝基苯酚(TNP)、2,4,6三硝基間苯二酚(TNR)和2,4,6三硝基均苯三酚(TNPG), 均購自德國Dr. Ehrenstorfer GH公司(純度>98%); 吸附劑填料N丙基乙二胺(PSA)、石墨化碳黑(GCB)、C18(Agela公司); 乙腈(色譜純,德國Merck公司); MgSO4、乙酸銨(分析純); 實驗用水為超純水。
2.2標準品制備
用乙腈將標準品配制成濃度為100 mg/L的單標標準儲備液,再將單標標準儲備液稀釋配制成混合標準儲備液,實驗時以初始流動相將混合標準儲備液配制成不同濃度的標準工作液。
2.3QuEChERS一步提取凈化前處理方法
準確稱取1.00g土壤樣品,置于15 mL塑料離心管中,加入0.5 mL水浸潤20 min,加入5 mL 1%甲酸的乙腈,渦旋提取2 min,離心后,取上清液, 加入1.0 g無水MgSO4、1.0 g NaCl,渦旋20 s后,離心取上清液,加入吸附劑,渦旋2 min,以10000 r/min高速離心3 min,取上清液, 過0.22 μm濾膜, 上機檢測。
3結果與討論
3.1色譜條件的選擇
本實驗選擇乙腈乙酸銨為流動相,采用梯度洗脫,通過實驗證實,一方面乙腈比甲醇洗脫能力強,各組分的分析時間明顯縮短,各色譜峰相對對稱;另一方面,選擇乙酸銨緩沖體系對于三硝基酚類不但分離效果最好,而且沖洗色譜柱比較便利,同時乙酸銨體系在液相色譜質譜中也很有優勢。選擇優化的最佳色譜條件,在5 min內完成了3種三硝基酚的分離檢測,分離度好,峰形對稱尖銳,無明顯拖尾,具體土壤基質的總離子流圖見圖1。
Symbolm@@ 模式下,對3種三硝基酚物質的質譜條件進行了優化, 分別采用全掃描和子離子掃描方式優化得到了母離子、子離子及各自的最佳錐孔電壓和碰撞能量,以響應值最大的碎片離子為定量離子,次級響應離子為定性離子。圖2為MRM模式下3種三硝基酚類的定量離子對的單通道掃描質譜圖。
3種硝基酚的檢測采用負離子模式,分別選擇其[M-H]
Symbolm@@ 作為母離子,進行二級質譜裂解分析,在15~40 eV區間內, 不斷增加二級碰撞能量,子離子碎片逐漸增多。
通過質譜裂解研究發現,2,4,6三硝基苯酚準分子離子峰m/z 228.1 在二級碰撞裂解下,分別失去一個NO2、兩個NO2,生成子離子m/z 182.1和136.1,且m/z 136.1響應值較大,選擇為定量離子。2,4,6三硝基間苯二酚準分子離子峰m/z 244.1,在二級碰撞裂解下,生成子離子m/z 198.1和181.1,分別代表失去NO2,失去NO2和OH,但m/z 181離子峰極不穩定,繼續裂解為小分子離子峰,所以選擇m/z 198.1為定量離子。2,4,6三硝基均苯三酚準分子離子峰m/z 266.1 在二級碰撞裂解下,失去一個NO2,生成子離子m/z 227.1;苯環上失去硝基和羥基后,再失去CNO2,發生重排, 形成,生成m/z 95.1離子,但兩離子峰相比較,m/z 227.1響應值、質量數均較大,選擇為定量離子。通過對離子對的選擇和相應電壓的確定,得到了最優質譜條件(表2)。
3.3QuEChERS前處理步驟的簡化
土壤樣品因地區差異,性質差別較大,因此本研究選擇添加1%甲酸的乙腈為提取劑,以增加3種酸性目標物在乙腈中的提取率和穩定性,并采用無緩沖溶液的QuEChERS方法,進行液相色譜質譜聯用分析。土壤樣品經提取、凈化,取上清液過膜待測。方法簡便、操作誤差小,適合日常檢驗。
3.4吸附劑的選擇
吸附劑作用于提取液中,既須盡可能地吸附雜質;又要最大限度地保留目標物,保證較高的回收率。吸附劑對雜質的吸附、凈化很大程度上有利于降低基質效應,從而減少對ESI電離源質譜中響應值的干擾。吸附劑的選擇取決于樣品提取物中的脂肪、蛋白、色素等大分子有機物或者雜質等的含量。
土壤樣品中存在脂肪、動植物殘留、色素等雜質,為選擇合適的吸附劑,采用2.3節的操作方法,選擇加入濃度均為25 mg/mL的3種吸附劑C18, GCBC18和PSAC18,分別考察了回收率和凈化效果。 結果表明, GCBC18吸附劑對幾種目標物的回收率最高;且由圖2可知,處理后的土壤基質背景值低,分離度和峰形均較好,說明該組合吸附劑同時對脂肪、蛋白和植物片狀結構色素等雜質的凈化效果較好,因此選擇GCBC18作為吸附劑。
采用經過改進的QuEChERS前處理方法處理土壤樣品并檢測,結果表明,0.1 mg/L的3種硝基酚的基質效應分別為3.9%,4.1%和3.8%, 1 mg/L的3種硝基酚的基質效應分別為4.7%,2.0%和3.2%,均小于10%,基質效應對定量分析的影響較小,可以忽略,這進一步說明改進的前處理方法凈化效果好,可以避免使用基質標準曲線,定量方法更簡便。
3.8實際樣品測定
為了驗證方法的實用性,選擇采集幾個土壤樣品,包括農田、化學工業區、某合成區域附近3個不同地區,同時將不同土壤基質添加50 μg/kg濃度的標準物質作對照,采用本方法進行檢測分析,結果見表4。被測的農田、化學工業區土壤樣品未檢出目標化合物,而某合成區域附近土壤含有一定濃度的2,4,6三硝基間苯二酚。同時,也充分證實本方法符合能夠滿足三硝基酚類快速檢測和確證分析。
4結論
建立了土壤中2,4,6三硝基苯酚、2,4,6三硝基間苯二酚和2,4,6三硝基均苯三酚3種三硝基酚的QuEChERSUPLCMS/MS分析檢測方法。采用改進的QuEChERS一步提取凈化的前處理方法處理土壤樣品,未使用緩沖溶液,考察了不同吸附劑的凈化效果,同時簡化了前處理的步驟,本方法可以作為土壤樣品中三硝基酚類多殘留痕量檢測及常規檢測方法,也可以為土壤及其它沉積物治理、修復工作研究提供方法依據。
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吳 剛, 董鎖拽, 潘璐璐. 色譜, 2013, 31(7): 697-702
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27Luzardo O P, RuizSurez N, AlmeidaGonzlez M. Anal. Bioanal. Chem., 2013, 405(29): 9523-9536
28Lega F, Contiero L, Biancotto G. Food Addit. Contam. Part A, 2013, 30(6): 949-957
29YAO MengKan, MA BingLiang, MA YueMing. Journal of Pharmaceutical Analysis, 2010, 12(5): 2436-2440
姚夢侃, 馬秉亮, 馬越鳴. 藥物分析雜志, 2010, 12(5): 2436-2440
AbstractA simple, rapid sensitive and accurate ultra performance liquid chromatography tandem mass spectrometric (UPLCMS/MS) method was developed for the simultaneous determination of 2,4,6trinitrophenol, trinitroresorcinate, trinitrophloroglucinol residues in soil. The sample was pretreated by using the modified QuEChERS (quick, easy, cheap, effective, rigged, and safe) method that completed the extraction and cleanup steps in one procedure. In this none buffer QuEChERS method, samples were extracted with 1% formic acid + acetonitrile, cleaned up with primary graphitized carbon black (GCB) and C18 sorbent, then centrifuged and filtrated before detection. The pretreatment method was simple, rapid and effective and can meet the detection requirements. The UPLCMS/MS method was performed on Waters Accucore PFP (150 mm× 2.1 mm, 2.6 μm) and the column temperature was 30 ℃, the gradient elution with acetonitrile and ammonium acetate as the mobile phase and the flow rate was 0.3 mL/min. The negative electrospray ionization (ESI
Symbolm@@ ) source under the multiple reaction monitoring (MRM) mode and external standard method were used for quantification. The results showed that the correlation coefficients up to 0.9942 were obtained across a concentration range of 0.005-5.0 mg/L. The limits of detection (LOD) ranged from 0.002 to 0.005 mg/kg (S/N=3). The method was validated with soil samples spiked at three fortification levels (0.01, 0.1 and 1 mg/kg) and recoveries were in the range of 79.3%-94.8% with relative standard deviations (RSD) of 3.1%-6.6%.
KeywordsUltra performance liquid chromatography tandem mass spectrery; 2,4,6Trinitrophenol; 2,4,6Trinitroresorcinate; 2,4,6Trinitrophloroglucinol; QuEChERS method; Soil
武 杰, 曹 磊, 李英明. 色譜, 2004, 22(5): 562
11Hu C,Chen B, He M. J. Chromatogr. A, 2013, 1300: 165-172
12Elbarbry F, Wilby K, Alcorn J. J. Chromatogr. B, 2006, 834(2): 199-203
13PdillaSnchez J A, PlazaBolaos P, RomeroGonzlez R, BaracoBoniua N, MartínezVidal J L, GarridoFrenich A. Talanta, 2011, 85(5): 2397-2404
14Zhu S, Niu W, Li H. Talanta, 2009, 79(5): 1441-1445
15Allen D, Bui A D, Cain N. Anal. Bioanal. Chem., 2013, 405(30): 9869-9877
16Liu X, Yang T, Hu J. J. Chromatogr. Sci., 2013, 51(1): 87-91
17Gineys N, Giroud B, Vulliet E. Anal. Bioanal. Chem., 2010, 397(6): 2295-2302
18WU Gang, DONG SuoZhuai, PAN LuLu. Chinese Journal of Chromatography, 2013, 31(7): 697-702
吳 剛, 董鎖拽, 潘璐璐. 色譜, 2013, 31(7): 697-702
19Ge X, Wu X, Liang S. J. Chromatogr. Sci., 2013, 51(11): 233-236
20XU DunMing, LU ShengYu, CHEN DaJie. Chinese Journal of Chromatography, 2013, 31(3): 218-222
徐敦明, 盧聲宇, 陳達捷. 色譜, 2013, 31(3): 218-222
21Prakash Maran J, Sivakumar V, Sridhar R. Carbohydr. Polym., 2013, 97(2): 703-709
22Al Bittar S, PérinoIssartier S, Dangles O. Food Chem., 2013, 141(3): 3268-3272
23Samavati V. Int. J. Biol. Macromol., 2013, 61: 142-149
24Burdel M, andrejov J, Balogh I S. Chem. Commun (Camb)., 2012, 48(41): 5007-5009
25Li S, Li T, Gao P. J. Chromatogr. Sci., 2013, 51(9): 233-236
26MorenoGonzlez D, HuertasPérez J F, GarcíaCamtnpa A M. J. Chromatogr. A, 2013, 58(8)1315-1317
27Luzardo O P, RuizSurez N, AlmeidaGonzlez M. Anal. Bioanal. Chem., 2013, 405(29): 9523-9536
28Lega F, Contiero L, Biancotto G. Food Addit. Contam. Part A, 2013, 30(6): 949-957
29YAO MengKan, MA BingLiang, MA YueMing. Journal of Pharmaceutical Analysis, 2010, 12(5): 2436-2440
姚夢侃, 馬秉亮, 馬越鳴. 藥物分析雜志, 2010, 12(5): 2436-2440
AbstractA simple, rapid sensitive and accurate ultra performance liquid chromatography tandem mass spectrometric (UPLCMS/MS) method was developed for the simultaneous determination of 2,4,6trinitrophenol, trinitroresorcinate, trinitrophloroglucinol residues in soil. The sample was pretreated by using the modified QuEChERS (quick, easy, cheap, effective, rigged, and safe) method that completed the extraction and cleanup steps in one procedure. In this none buffer QuEChERS method, samples were extracted with 1% formic acid + acetonitrile, cleaned up with primary graphitized carbon black (GCB) and C18 sorbent, then centrifuged and filtrated before detection. The pretreatment method was simple, rapid and effective and can meet the detection requirements. The UPLCMS/MS method was performed on Waters Accucore PFP (150 mm× 2.1 mm, 2.6 μm) and the column temperature was 30 ℃, the gradient elution with acetonitrile and ammonium acetate as the mobile phase and the flow rate was 0.3 mL/min. The negative electrospray ionization (ESI
Symbolm@@ ) source under the multiple reaction monitoring (MRM) mode and external standard method were used for quantification. The results showed that the correlation coefficients up to 0.9942 were obtained across a concentration range of 0.005-5.0 mg/L. The limits of detection (LOD) ranged from 0.002 to 0.005 mg/kg (S/N=3). The method was validated with soil samples spiked at three fortification levels (0.01, 0.1 and 1 mg/kg) and recoveries were in the range of 79.3%-94.8% with relative standard deviations (RSD) of 3.1%-6.6%.
KeywordsUltra performance liquid chromatography tandem mass spectrery; 2,4,6Trinitrophenol; 2,4,6Trinitroresorcinate; 2,4,6Trinitrophloroglucinol; QuEChERS method; Soil
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AbstractA simple, rapid sensitive and accurate ultra performance liquid chromatography tandem mass spectrometric (UPLCMS/MS) method was developed for the simultaneous determination of 2,4,6trinitrophenol, trinitroresorcinate, trinitrophloroglucinol residues in soil. The sample was pretreated by using the modified QuEChERS (quick, easy, cheap, effective, rigged, and safe) method that completed the extraction and cleanup steps in one procedure. In this none buffer QuEChERS method, samples were extracted with 1% formic acid + acetonitrile, cleaned up with primary graphitized carbon black (GCB) and C18 sorbent, then centrifuged and filtrated before detection. The pretreatment method was simple, rapid and effective and can meet the detection requirements. The UPLCMS/MS method was performed on Waters Accucore PFP (150 mm× 2.1 mm, 2.6 μm) and the column temperature was 30 ℃, the gradient elution with acetonitrile and ammonium acetate as the mobile phase and the flow rate was 0.3 mL/min. The negative electrospray ionization (ESI
Symbolm@@ ) source under the multiple reaction monitoring (MRM) mode and external standard method were used for quantification. The results showed that the correlation coefficients up to 0.9942 were obtained across a concentration range of 0.005-5.0 mg/L. The limits of detection (LOD) ranged from 0.002 to 0.005 mg/kg (S/N=3). The method was validated with soil samples spiked at three fortification levels (0.01, 0.1 and 1 mg/kg) and recoveries were in the range of 79.3%-94.8% with relative standard deviations (RSD) of 3.1%-6.6%.
KeywordsUltra performance liquid chromatography tandem mass spectrery; 2,4,6Trinitrophenol; 2,4,6Trinitroresorcinate; 2,4,6Trinitrophloroglucinol; QuEChERS method; Soil