四氮杂杯[2]芳烃[2]三嗪键合硅胶固相萃取-高效液相色谱法测定河水中硝基苯酚和己烯雌酚

基于四氮杂杯[2]芳烃[2]三嗪键合硅胶吸附剂（NC-Si）,构建了固相萃取-高效液相色谱法同时测定河水中3种硝基苯酚和己烯雌酚的新方法。考察并获得了固相萃取和液相色谱分离的优化条件：将样品溶液pH调至5,以5 mL/min上样,经自制固相萃取柱净化,2 mL氨水-甲醇（2：98,v/v）洗脱;在C8柱上以甲醇-0.1%磷酸溶液为流动相进行梯度洗脱。4种目标分析物的检出限（LOD,S/N=3）为0.03~0.3 μg/L,定量限（LOQ,S/N=10）为0.1~1.0 μg/L;加标回收率为75.5%~104.2%,相对标准偏差（RSD,n=5）小于6.3%。该方法准确、可靠,可用于河水中硝基苯酚及己烯雌酚的灵敏检测。     

QuEChERS-超高效液相色谱-四极杆/静电场轨道离子阱质谱法检测鱼肉中15种降血脂药

建立了QuEChERS结合超高效液相色谱-四极杆静电场轨道离子阱质谱测定鱼肉中15种降血脂药残留量的方法。样品前处理采用优化的QuEChERS法,通过响应面法优化了吸附剂材料乙二胺-N-丙基硅烷（PSA）（20、60、100、140和180 mg）、C18（40、100、160、220和280 mg）及乙酸钠（0.2、0.6、1.0、1.4和1.8 g）的用量。液相色谱采用XBridge-C18色谱柱（100 mm×2.1 mm,3.5 μm）,以乙腈-0.1%（v/v）甲酸水溶液（含1.5 mmol/L乙酸铵）为流动相进行梯度洗脱,采用加热电喷雾电离（HESI）源,在正、负离子同时检测模式下以全扫描（full-MS）和二级质谱扫描（dd-MS²）方式对目标物进行定性和定量分析。15种降血脂药在各自范围内线性关系良好,相关系数（R²）大于0.99;检出限（LOD,S/N=3）和定量限（LOQ,S/N=10）分别为0.2~1.0 μg/kg和0.3~3.1 μg/kg;鱼肉样品中15种降血脂药在LOQ、2倍LOQ和10倍LOQ水平下的加标回收率为76.4%~116.0%,日内日精密度为1.0%~7.9%,日间精密度为1.7%~18.4%。该法前处理简单,灵敏度高,回收率高,适用于鱼肉中降血脂药的检测。     

固相萃取-衍生化-气相色谱-质谱联用法同时测定尿液中4种阿片类物质

公安机关用胶体金尿检法对海洛因滥用者的检测常常受到阿片类镇咳药的干扰,使用传统液-液提取法进行实验室检验,操作效率低,灵敏度不高,无法满足公安机关打击涉毒案件的需要。为此,该研究建立了尿液中吗啡、O ⁶ -单乙酰吗啡、可待因和乙酰可待因4种阿片类物质的固相萃取和衍生化技术结合气相色谱-质谱联用（GC-MS）同时检测方法。尿样用磷酸盐缓冲液调节至pH=6后,经MCX固相萃取柱净化,用N -甲基-N -（三甲基硅烷基）三氟乙酰胺（MSTFA）对吗啡、O ⁶ -单乙酰吗啡、可待因进行衍生化,供GC-MS检测。考察了上样和洗脱流速、淋洗液中甲酸体积分数、洗脱液中氨水体积分数、3%（v/v）甲酸甲醇淋洗液体积和固相萃取柱吹干时间对萃取效果的影响。确定上样和洗脱流速1.0 mL/min,淋洗液中甲酸体积分数3%,洗脱液中氨水体积分数5%,3%（v/v）甲酸甲醇淋洗液体积1 mL,吹干时间1 min为最佳条件。在此条件下,4种阿片类物质在0.02~0.8 μg/mL范围内线性关系良好（r ² ≥0.998）,检出限（LOD）为0.0016~0.0039 μg/mL,定量限（LOQ）为0.0054~0.0128 μg/mL,当标准添加水平为0.02、0.1、0.2 μg/mL时,回收率为93.0%~110.3%。该方法结合自动化技术,对固相萃取条件精确控制,操作简便、快速、灵敏、准确,适合尿液中吗啡等4种阿片类物质快速测定,可用于海洛因吸食者的大规模监控,并能准确排除因服用含阿片类镇咳药导致的吗啡胶体金尿检假阳性。     

加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱测定水产品中32种多氯联苯

建立了加速溶剂萃取同步净化-同位素内标-气相色谱-高分辨质谱同时测定水产品中32种多氯联苯含量的方法。通过在加速溶剂萃取仪中加入2 g无水硫酸钠、1 g弗罗里硅土、50 g中性氧化铝作为吸附剂实现同步净化的效果，萃取溶剂为二氯甲烷-正己烷（1:1，v/v），萃取温度为100℃，循环2次。萃取结束后分别用0.5 mL浓硫酸净化两次，净化液浓缩定容后，采用气相色谱-高分辨质谱测定，同位素内标法定量。32种多氯联苯在0.1~20 μg/L范围内平均相对响应因子（RRF）的相对标准偏差（RSD）值（n=7）均小于15%，定量限（S/N=10）为0.3~1.9 ng/kg。在草鱼和海鲈鱼空白基质中做加标回收试验，添加水平为5、20和50 ng/kg，得到的平均回收率为71.9%~119.0%（n=6），RSD为3.5%~19.6%。该方法背景干扰低，灵敏度高，重现性好，回收率稳定，适用于水产品中多氯联苯的检测。     

QuEChERS-同位素稀释-气相色谱-串联质谱法测定动物源性食品中9种N-亚硝胺类化合物

建立了同时测定动物源性食品中9种N-亚硝胺类化合物的气相色谱-串联质谱分析方法。当下动物源性食品中N-亚硝胺类化合物污染种类较多,对人体危害较大,但国标GB 5009.26-2016仅针对N-二甲基亚硝胺的检测,且存在样品前处理复杂、标准方法回收率低、再现性差等问题,因此建立同时快速检测多种N-亚硝胺类化合物的方法有一定现实意义。称取10.0 g样品,置于50 mL离心管中,加入200 μL内标工作液和10 mL乙腈,冷冻30 min后,加入4 g硫酸镁和1 g氯化钠进行脱水,以9000 r/min离心5 min。取5 mL上清液使用150 mg聚苯乙烯二乙烯苯(PLS-A)粉末净化,再使用1.6 g MgSO₄和0.4 g NaCl脱水,过0.22 μm滤膜,上机分析。在初始温度为50 ℃时采用程序升温模式,0.16 min后,以900 ℃/min的速率将温度升至220 ℃。采用毛细管气相色谱柱HP-Innowax(30 m×0.25 mm×0.25 μm)分离,使用电子轰击电离(EI)源检测,在多反应监测模式下,以保留时间和特征离子对信息进行定性和定量分析,使用内标法定量N-亚硝胺类化合物。结果表明,N-亚硝胺类化合物在0.1~50.0 μg/L范围内具有良好的线性关系,方法的检出限(S/N=3)和定量限(S/N=10)分别为0.03~0.30 μg/kg和0.10~1.00 μg/kg。对不同样品基质进行0.5、1.0、3.0 μg/kg3个水平的加标回收试验,9种N-亚硝胺类化合物的回收率为80.4%~98.5%, RSD(n=6)为2.41%~12.50%。应用建立的方法检测市面上常见的动物源性食品,除N-亚硝基乙胺、N-亚硝基吗啡胆碱外,其他7种N-亚硝胺类化合物均有不同程度检出。检测结果表明,腌制水产品中N-亚硝胺类化合物含量普遍高于其他样品。研究建立的方法操作简单,不需要长时间蒸馏提取,可快速对动物源性食品中N-亚硝胺类化合物进行定性和定量分析,且样品和试剂的消耗量更少,节省成本,对环境污染小。该法的建立对我国动物源性食品中N-亚硝胺类化合物残留水平的控制、检测标准的制定和采取相应的管理措施具有一定的理论和现实意义。     

高效液相色谱法测定生物转化反应液中N,N'-乙二胺二琥珀酸

建立了高效液相色谱测定生物转化反应液中N,N'-乙二胺二琥珀酸（EDDS）含量的分析方法。采用InertSustain AQ-C₁₈色谱柱（250 mm×4.6 mm,5 μm）,以体积分数25%的甲醇水溶液（含有1.0 g/L一水乙酸铜、2.0 g/L四丁基氢氧化铵,以磷酸调节pH至2.80）为流动相,流速为1.0 mL/min,柱温为30℃,进样量为20 μL,检测波长为254 nm。该方法可在8 min内分离EDDS及其生物合成相关物质（苹果酸、柠檬酸、乙二胺四乙酸（EDTA）和富马酸）,且峰形良好。EDDS在0.06~0.6 g/L范围内线性线性关系良好（相关系数（r）为0.9995）,平均回收率为100.39%（n=9,RSD=1.15%）。EDDS生物合成反应液中EDDS含量为0.25 g/L,大部分底物被转化为苹果酸（36.56 g/L）;而EDDS的水解反应中富马酸产生较少,形成了3.05 g/L的苹果酸。该方法简便快速,灵敏可靠,适用于EDDS生物合成的研究。     

离子交换固相萃取-气相色谱-质谱联用法测定方便面皮复合包装袋中2,4-二氨基甲苯的迁移量

建立了方便面皮复合包装袋中2,4-二氨基甲苯迁移量的离子交换固相萃取-气相色谱-质谱联用检测方法。样品用4%（v/v）乙酸溶液浸泡,然后采用MCX混合型阳离子交换柱富集净化,以5.0 mL水淋洗小柱,用3.0 mL 5%（v/v）氨化甲醇洗脱样品,洗脱液经过溶剂交换,七氟丁酸酐衍生后,用气相色谱-质谱联用仪对目标物进行检测,外标法定量。2,4-二氨基甲苯在1~50 μg/L范围内,线性相关系数（r）为0.9991,检出限（S/N=3）为0.2 μg/L,定量限（S/N=10）为0.6 μg/L,回收率在89.0%~94.2%之间,相对标准偏差为1.9%~3.6%。该方法的前处理过程无需调节提取液的pH值,也不需要液液萃取,大幅简化了前处理过程,降低了有机溶剂的消耗,具有操作便捷、结果准确的优点,适用于方便面皮复合包装袋中2,4-二氨基甲苯迁移量的检测。     

高效液相色谱-串联质谱法测定奶粉中氯酸盐和高氯酸盐

建立了一种测定奶粉中氯酸盐和高氯酸盐含量的高效液相色谱-串联质谱方法。样品经0.1%（v/v）甲酸水-乙腈提取,10000 r/min下离心10 min后,上清液经PRiME HLB固相萃取柱净化;采用离子交换色谱分离,色谱柱为Thermo Scientific Acclaim TRINITY P1复合离子交换柱（50 mm×2.1 mm,3 μm）,以乙腈和20 mmol/L乙酸铵溶液为流动相进行梯度洗脱,MS/MS检测,内标法定量。结果显示,氯酸盐和高氯酸盐分别在2.0~40.0 μg/L和1.0~20.0 μg/L范围内线性关系良好,相关系数（r²）大于0.999,方法的定量限分别为15.0和7.5 μg/kg。氯酸盐和高氯酸盐分别在30.0、60.0、120.0 μg/kg和15.0、30.0、60.0 μg/kg 3个水平下的加标回收率为89.24%~107.85%,相对标准偏差为3.15%~10.42%（n=6）。该方法简便快捷、准确可靠,能适用于奶粉样品的测定。     

直链淀粉-三[(S)-1-苯乙基氨基甲酸酯]手性固定相拆分布地奈德对映体及其制剂含量的测定

22R-布地奈德的药物活性比22S-布地奈德的强2~3倍,开发布地奈德对映体拆分和定量分析方法,可为其药物研发及质量控制提供重要依据。目前,主要以反相C₁₈固定相对布地奈德对映体进行拆分,而采用手性固定相对其进行拆分少有报道。通过考察固定相、流动相和柱温对布地奈德对映体拆分的影响,建立了基于直链淀粉-三[(S)-1-苯乙基氨基甲酸酯]手性固定相快速拆分和检测布地奈德对映体的高效液相色谱方法,其色谱条件如下:色谱柱为Chiralpak AS-RH色谱柱(150 mm×4.6 mm, 5.0 μm),流动相为乙腈-水(45∶55, v/v),柱温40 ℃,流速1.0 mL/min,二极管阵列检测器(DAD),检测波长246 nm,进样量10 μL。在该色谱条件下,布地奈德的两个对映体得到较好拆分,22R-布地奈德和22S-布地奈德的保留时间分别6.40 min和7.77 min,分离度为4.64; 22R-布地奈德和22S-布地奈德分别在各自范围内线性关系良好,相关系数(R²)均为0.9999,检出限分别为0.05 μg/mL和0.07 μg/mL,定量限分别为0.16 μg/mL和0.20 μg/mL; 4个添加水平的样品加标回收率为102.63%~104.17%,相对标准偏差(RSD)为0.08%~0.57%(n=6)。将该方法应用于1批次4个吸入用布地奈德混悬液实际样品进行检测,22R-布地奈德和22S-布地奈德的含量分别为283.15~284.63 μg/mL和259.86~261.51 μg/mL。该方法操作简便,分析时间短,重复性好,准确度高,可用于布地奈德对映体的拆分及其制剂的质量控制。     

超高效液相色谱-大气压化学电离-三重四极杆质谱法同时测定血浆、尿液和瓜果类蔬菜中葫芦素B、E和I

建立了超高效液相色谱-三重四极杆质谱测定血浆、尿液和瓜果类蔬菜中葫芦素B、E和I的检测方法。血浆和尿液样品经固相支持液液萃取法（SLE）提取净化,瓜果类蔬菜样品经乙腈提取后用水稀释。以XBridge BEH C₁₈色谱柱（100 mm×3.0 mm,2.5 μm）为分析柱进行分离,以甲醇-0.025%（v/v）氨水溶液为流动相进行梯度洗脱。采用大气压化学电离源,在负离子、多反应监测（MRM）模式下检测,以夹竹桃甙作为内标物,基质工作曲线内标法定量血浆和尿液中3种葫芦素;以溶剂标准曲线外标法定量瓜果类蔬菜中的待测物。血浆和尿液中3种葫芦素的检出限均为0.03 μg/L,平均加标回收率为89.0%~113%,相对标准偏差为1.7%~12.2%（n=6）;瓜果类蔬菜中3种葫芦素的检出限为5~10 μg/kg,平均加标回收率为87.6%~114%,相对标准偏差为4.1%~11.1%（n=6）。该法简单、灵敏、准确,已应用于食用苦葫芦瓜引起中毒的病人血浆和尿液,以及葫芦瓜的检测,并检出了葫芦素B。     

Fast and sensitive high performance liquid chromatography analysis of cosmetic creams for hydroquinone, phenol and six preservatives

A fast and sensitive HPLC method for analysis of cosmetic creams for hydroquinone, phenol and six preservatives has been developed. The influence of sample preparation conditions and the composition of the mobile phase and elution mode were investigated to optimize the separation of the eight studied components. Final conditions were 60% methanol and 40% water (v/v) extraction of the cosmetic creams. A C18 column (100 mm × 2.1 mm) was used as the separation column and the mobile phase consisted of methanol and 0.05 mol/L ammonium formate in water (pH=3.0) with gradient elution. The results showed that complete separation of the eight studied components was achieved within 10 min, the linear ranges were 1.0-200 μg/mL for phenol, 0.1-150 μg/mL for sorbic acid, 2.0-200 μg/mL for benzoic acid, 0.5-200 μg/mL for hydroquinone, methyl paraben, ethyl paraben and propyl paraben, butyl paraben, and good linear correlation coefficient (≥0.9997) were obtained, the detection limit was in the range of 0.05-1.0 μg/mL, the average recovery was between 86.5% and 116.3%, and the relative standard deviation (RSD) was less than 5.0% (n=6). The method is easy, fast and sensitive, it can be employed to analyze component residues in cosmetic creams especially in a quality control setting.     

Rapid liquid chromatographic determination of residual penicillin G in milk

A simple and rapid high-performance liquid chromatographic (HPLC) method for determination of residual penicillin G (benzylpenicillin, PCG) in milk was developed. The sample preparation was performed by stirring with ethanol and reacting with 5 M 1,2,4-triazole-mercury (II) chloride solution at 65?°C for 10 min followed by an ultra centrifugation step. The HPLC separation was carried out using a Mightysil^® RP-4GP column, a mobile phase of acetonitrile and 0.1 M phosphate buffer (pH 6.5) (35:65, v/v) and a photo-diode array detector. The average recoveries from spiked PCG (0.004, 0.01, 0.05 and 0.1 μg/mL) were above 86% with coefficients of variation between 1.2 and 4.5%. The limit of detection was 0.004 μg/mL. This value corresponds to the maximum residue limit (MRL) in milk (0.004 μg/mL, EU and Japan). The total time required for the analysis of one sample was below 40 min.     

Simultaneous Determination of Hydrochlorothiazide and Reserpine in Human Urine by LC with a Simple Pre-Treatment

A simple, selective and sensitive reversed-phase high performance liquid chromatography method for simultaneous analysis of hydrochlorothiazide and reserpine in human urine was developed and subjected to primary pharmacokinetic study. After a simple protein precipitation using methanol and extraction with ethyl acetate, the analytes were separated on an Elite C(18) column at a flow rate of 0.8 mL min(-1). The mobile phase was composed of acetonitrile (A) and 0.2% ammonium chloride solution (B) for a gradient elution starting at A:B at 30:70, v/v for 0~6 min, linearly raising the percent of A from 30% to 50% (6~9 min) and ending at 50:50, v/v (9~25 min). The standard curves were linear over the range of 0.05-20 μg mL(-1) for hydrochlorothiazide and 0.02-5.0 μg mL(-1) for reserpine, respectively (r > 0.999). The limit of detection (LOD) and the limit of quantification (LOQ) were 5.5 ng mL(-1) and 18.2 ng mL(-1) for hydrochlorothiazide, and 7.1 ng mL(-1) and 23.6 ng mL(-1) for reserpine, respectively. The recoveries for both analytes were above 89.0±1.35%. The intra-day and inter-day precision for hydrochlorothiazide were less than 1.91% and 1.38%, and those for reserpine were below 1.61% and 2.64%, respectively. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy, and it was employed successfully for the simultaneous determination of hydrochlorothiazide and reserpine in human urine samples.     

超高效液相色谱-串联质谱法同时测定血浆与尿液中12种脂溶性贝类毒素

生物样品中脂溶性贝类毒素的检测,可为食物中毒等突发公共卫生事件的流行病学调查以及中毒者的临床救治提供技术支持。目前的研究存在目标化合物少,以及方法前处理复杂、灵敏度低等问题。该研究通过优化前处理和色谱分离技术,建立了超高效液相色谱-串联质谱法测定血浆、尿液中12种脂溶性贝类毒素的方法。实验对提取试剂以及流动相的选择进行了优化,采用乙腈对尿液和血浆样品进行提取。采用Phenomenex Kinetex C18色谱柱(50 mm×3 mm, 2.6 μm)进行分离,以0.05%(v/v)氨水水溶液、90%(v/v)乙腈水溶液为流动相,以流速0.40 mL/min梯度洗脱时,12种目标化合物分离效果最好。串联质谱的离子源为电喷雾离子(ESI)源,采用多反应监测(MRM)模式检测。12种目标物的基质效应均在0.8~1.1之间,表明该前处理方法的基质干扰低,采用外标法可对化合物进行准确定量。12种贝类毒素的线性范围为0.03~36.25 μg/L,相关系数均大于0.995。尿液检测的方法定量限为0.23~0.63 μg/L,血浆检测的方法定量限为0.31~0.84 μg/L。3个加标水平的回收率为72.7%~124.1%,日内精密度为2.1%~20.0%,日间精密度为2.1%~15.3%。利用该方法检测健康人尿液和血浆样本,以及经腹腔注射12种贝类毒素的小鼠尿液和血液样本。20份健康人样本中未检出目标物,20份小鼠样本中12种贝类毒素均有检出。该方法操作简便,样品取样量少,方法灵敏高,适用于血浆和尿液中脂溶性贝类毒素的快速检测。     

Determination of metoprolol in human plasma and urine by high‐performance liquid chromatography with fluorescence detection

A simple, specific and sensitive HPLC method has been developed for the determination of metoprolol in human plasma and urine. Separation of metoprolol and atenolol (internal standard) was achieved on an Ace C₁₈ column (5 μm, 250 mm×4.6 mm id) using fluorescence detection with λ_ex=276 nm and λ_em=296 nm. The mobile phase consists of methanol–water (50:50, v/v) containing 0.1% TFA. The analysis was performed in less than 10 min with a flow rate of 1 mL/min. The assay was linear over the concentration range of 3 – 200 and 5 – 300 ng/mL for plasma and urine, respectively. The LOD were 1.0 and 1.5 ng/mL for plasma and urine, respectively. The LOQ were 3.0 and 5.0 ng/mL for plasma and urine, respectively. The extraction recoveries were found to be 95.6 ± 1.53 and 96.4 ± 1.75% for plasma and urine, respectively. Also, the method was successfully applied to three patients with hypertension who had been given an oral tablet of 100 mg metoprolol.     

High‐performance liquid chromatographic analysis: applications to nutraceutical content and urinary disposition of oxyresveratrol in rats

A high‐performance liquid chromatographic (HPLC) method was developed for the analysis of the stilbene, oxyresveratrol. This method involves the use of a Luna® C₁₈ column with ultraviolet detection at 320 nm. The mobile phase consisted of acetonitrile, water and formic acid (30 : 70 : 0.04 v/v) with a flow rate of 0.6 mL/min. The calibration curves were linear over the range of 0.5–100.0 μg/mL. The mean extraction efficiency was between 98.9 and 109%. The precision of the assay was 0.069–18.4% (RSD%), and within 20% at the limit of quantitation (0.5 μg/mL). The bias of the assay was <15% and within 15% at the limit of quantitation. This assay was successfully applied to pre‐clinical pharmacokinetic samples from rat urine and to nutraceutical product analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

基质固相分散-高效液相色谱法测定鲫鱼肌肉中残留的辛硫磷

建立了鲫鱼肌肉中残留的辛硫磷的基质固相分散-高效液相色谱-二极管阵列检测(MSPD-HPLC-DAD)的分析方法。通过优化样品处理条件,确定选取0.50 g鲫鱼肌肉样品与1.5 g弗罗里硅土、0.5 g无水硫酸钠混合研磨,并采用丙酮-正己烷溶液(体积比为40:60)为洗脱剂,洗脱剂用量为25 mL。优选的最佳色谱条件为：ODS色谱柱(250 mm×4.6 mm,5 μm),流动相为甲醇-水(体积比为50:50),流速0.6 mL/min,检测波长270 nm,进样量为20 μL。在上述条件下,辛硫磷质量浓度在0.01～10 mg/L范围内与响应信号呈良好的线性关系(r20.9994),检出限为3.3 μg/kg;相对标准偏差为1.1%～6.3%(n7);3个添加水平(0.05,0.1,1 mg/kg)下得到的回收率为88%～112%。该方法操作简单,耗时少,精密度高,符合农残分析的要求。     

Determination of Cefpodoxime Levels and Cefpodoxime Stability In Human Urine By Direct Injection HPLC with Column-Switching

Abstract

A semi-automated method providing on-line sample extraction and quantitative analysis for cefpodoxime in human urine, injected directly into the HPLC, is reported.

Samples were filtered by the analyst, injected into the HPLC system with an autosampler and loaded onto a 3 cm RP-18 precolumn with a mobile phase consisting of 10% methanol in 0.2% phosphoric acid and then automatically eluted onto a RP-18 analytical column using a mobile phase containing 7% acetonitrile in pH 5.2 sodium acetate buffer. the mean between-day precision of the standards was ± 4.29%. Spiked urine control recovery averaged 96 ± 6% for controls ranging from 1.0 to 20.0 μg/mL. the limit of quantitation for the method was 0.11 μg/mL.     

An HPLC‐UV method for determining plasma dimethylacetamide concentrations in patients receiving intravenous busulfan

Dimethylacetamide (DMA) is a solvent used in the preparation of intravenous busulfan, an alkylating agent used in blood or marrow transplantation. DMA may contribute to hepatic toxicity, so it is important to monitor its clearance. The aim of this study was to develop an HPLC‐UV assay for measurement of DMA in human plasma. After precipitation of plasma proteins with acetonitrile followed by dilution (1:4) with water, the extract was injected onto the HPLC and detected at 195 nm. Separation was performed using a Cogent‐HPS 5 μm C₁₈ column (250 × 4.6 mm) preceded by a Brownlee 7 μm RP₁₈, pre‐column (1.5 cm × 3.2 mm). The mobile phase was 25 mm sodium phosphate buffer (pH 3), containing 2.5% (v /v) acetonitrile and 0.0005% (v /v) sodium‐octyl‐sulfonate. Using a flow rate of 1 mL/min, the retention times of DMA and the internal standard (IS), 2‐chloroacetamide, were 9.5 and 3.5 min, respectively. Peak area ratio (DMA:IS) was a linear function of concentration from 1 to 1000 μg/mL. There was excellent intraday precision (<5% for 5–700 μg/mL DMA), accuracy (<3% deviation from the true concentration) and recovery (74–98%). The limits of detection and quantification were 1 and 5 μg/mL, respectively. In eight children who received intravenous busulfan, DMA concentrations ranged from 110 to 438 μg/mL.