Determination of Menthol in Plasma and Urine by Gas Chromatography/Mass Spectrometry (GC/MS)

Menthol, a monoterpene, is a principal component of peppermint oil and is used extensively in consumer products as a flavoring aid. It is also commonly used medicinally as a topical skin coolant; to treat inflammation of the mucous membranes, digestive problems, and irritable bowel syndrome (IBS); and in preventing spasms during endoscopy and for its spasmolytic effect on the smooth muscle of the gastrointestinal tract. Menthol has a half life of 3-6 h and is rapidly metabolized to menthol glucuronide which is detectable in urine and serum following menthol use. We describe a method for the determination of total menthol in human plasma and urine using liquid/liquid extraction, gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode and menthol-d4 as the internal standard. Controls are prepared with menthol glucuronide and all samples undergo enzymatic hydrolysis for the quantification of total menthol. The method has a linear range of 5-1000 ng/mL, and coefficient of variation <10%.

Quantification of Dehydroepiandrosterone, 11-Deoxycortisol, 17-Hydroxyprogesterone, and Testosterone by Liquid Chromatography-Tandem Mass Spectrometry (LC/MS/MS)

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders due to enzymatic defects in the biosynthetic pathway of cortisol and/or aldosterone. The analysis of cortisol, 17-hydroxyprogesterone (OHPG), dehydroepiandrosterone (DHEA), 11-deoxycortisol, and testosterone is generally performed in the diagnosis and/or follow-up of CAH. Cortisol is generally analyzed by immunoassays whereas other hormones are preferably assayed by liquid chromatography-tandem mass spectrometry (LC/MS/MS). A multiple reaction monitoring, positive mode atmospheric pressure chemical ionization, LC/MS/MS method is described for the simultaneous quantification of 17-hydroxyprogesterone, DHEA, 11-deoxycortisol, and testosterone. Stable-isotope labeled internal standards are added to serum samples and steroids are extracted by liquid-liquid extraction using methyl tert-butyl ether. The extract is evaporated under stream of nitrogen and the residue is reconstituted in methanol and analyzed by LC/MS/MS.

Quantification of Five Clinically Important Amino Acids by HPLC-Triple TOF™ 5600 Based on Pre-column Double Derivatization Method

Phenylalanine, tyrosine, glycine, cystine, and phosphoethanolamine are commonly measured amino acids in various physiological fluids to diagnose or follow-up various inborn errors of metabolism. The gold standard method for the amino acids quantitation has been ion exchange chromatography with ninhydrin post-column derivatization. However, this method is very laborious and time consuming. In recent years, liquid-chromatography mass spectrometry is being increasingly used for the assay of amino acids. Pre-column butyl derivatization with reverse phase chromatography has been widely used for mass spectrometry analysis of amino acids. Phosphoethanolamine is not butylated and cannot be measured by this method. Nevertheless, phosphoethanolamine can be dansyl-derivatized using dansyl chloride. We developed a double derivatization method by using butanol and dansyl chloride to derivatize carboxylic and amino groups separately, and then combining the derivatives to simultaneously measure these five amino acids using TOF-MS scan. Stable isotope-labeled internal standards were used.

Determination of Phenylalanine and Tyrosine by High Performance Liquid Chromatography-Tandem Mass Spectrometry

Hyperphenylalaninemia/phenylketonuria (PKU) is one of the most common inborn errors of amino acid metabolism affecting about 1:15,000 infants in the United States. PKU is an autosomal recessive disorder that if untreated results in mental retardation. The most common cause of PKU is deficiency of the enzyme phenylalanine hydroxylase that converts phenylalanine to tyrosine. Tyrosine deficiency results in impaired synthesis of catecholamines and thyroxine. Less commonly, it can result from defects in the synthesis or regeneration of tetrahydrobiopterin (BH4), an essential cofactor for the enzyme phenylalanine hydroxylase. Increased phenylalanine and decreased tyrosine in blood are used in the diagnosis and follow-up of patients with PKU. LC/MS/MS method is described for the quantification of phenylalanine and tyrosine.

Quantification of Dihydroxyacetone Phosphate (DHAP) in Human Red Blood Cells by HPLC-TripleTOF 5600™ Mass Spectrometer

Triosephosphate isomerase (TPI) is a glycolytic enzyme which catalyzes the interconversion between glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). TPI deficiency results in accumulation of DHAP in human red blood cells and other tissues. The disease is characterized by congenital hemolytic anemia, and progressive neuromuscular dysfunction. The laboratory diagnosis is generally made by measurement of TPI activity in RBCs. Measurement of DHAP can be useful in further confirmation and follow-up of the disease. We developed HPLC/TOF-MS method for quantitation of DHAP in RBCs. The method involves simple protein precipitation, reverse phase C8 column chromatography, ion pairing with tributylamine, and long run time of 50 min to separate the two isomers (G3P and DHAP).

A Simple Liquid Chromatography Tandem Mass Spectrometry Method for Quantitation of Plasma Busulfan

Busulfan is an alkylating agent widely used in the ablation of bone marrow cells before hematopoietic stem cell transplant. Due to large intraindividual and interindividual variations, and narrow therapeutic window, therapeutic drug monitoring of busulfan is warranted. A quick and reliable HPLC-MS/MS method was developed for the assay of plasma busulfan. HPLC involved C18 column, and MS/MS was used in electrospray ionization (ESI) positive mode. Quantitation and identification of busulfan was made using various multiple reactions monitoring (MRMs). Isotopic labeled busulfan-d8 was used as the internal standard. The method is linear from 50 to 2500 ng/mL and has with-in run and between-run imprecision of <10 %.

Mass Spectrometry in Clinical Laboratory: Applications in Biomolecular Analysis

Mass spectrometry (MS) is a technique that can identify analytes on the basis of mass-to-charge (m/z) ratio. Although this technique has been used in research and specialized clinical laboratories for decades, however, in recent years, MS has been increasingly used in routine clinical laboratories. MS, especially when coupled to gas chromatography or liquid chromatography, provides very specific and often sensitive analysis of many analytes. Other advantages of MS include simultaneous analysis of multiple analytes (>100) and generally without need for specialized reagents. Commonly measured analytes by MS include drugs, hormones, and proteins.

Comprehensive Urine Drug Screen by Gas Chromatography/Mass Spectrometry (GC/MS)

Drug screening is an essential component of clinical toxicology laboratory service. Some laboratories use only automated chemistry analyzers for limited screening of drugs of abuse and few other drugs. Other laboratories use a combination of various techniques such as immunoassays, colorimetric tests, and mass spectrometry to provide more detailed comprehensive drug screening. Mass spectrometry, gas or liquid, can screen for hundreds of drugs and is often considered the gold standard for comprehensive drug screening. We describe an efficient and rapid gas chromatography/mass spectrometry (GC/MS) method for comprehensive drug screening in urine which utilizes a liquid-liquid extraction, sample concentration, and analysis by GC/MS.

Mass Spectrometry in Clinical Laboratory: Applications in Therapeutic Drug Monitoring and Toxicology

Mass spectrometry (MS) has been used in research and specialized clinical laboratories for decades as a very powerful technology to identify and quantify compounds. In recent years, application of MS in routine clinical laboratories has increased significantly. This is mainly due to the ability of MS to provide very specific identification, high sensitivity, and simultaneous analysis of multiple analytes (>100). The coupling of tandem mass spectrometry with gas chromatography (GC) or liquid chromatography (LC) has enabled the rapid expansion of this technology. While applications of MS are used in many clinical areas, therapeutic drug monitoring, drugs of abuse, and clinical toxicology are still the primary focuses of the field. It is not uncommon to see mass spectrometry being used in routine clinical practices for those applications.

Quantification of 11-Carboxy-Delta-9-Tetrahydrocannabinol (THC-COOH) in Meconium Using Gas Chromatography/Mass Spectrometry (GC/MS)

Maternal substance abuse is an ongoing concern and detecting drug use during pregnancy is an important component of neonatal care when drug abuse is suspected. Meconium is the preferred specimen for drug testing because it is easier to collect than neonatal urine and it provides a much broader time frame of drug exposure. We describe a method for quantifying 11-carboxy-delta-9-tetrahydrocannabinol (THC-COOH) in meconium. After adding a labeled internal standard (THC-COOH D9) and acetonitrile, samples are sonicated to release both free and conjugated THC-COOH. The acetonitrile/aqueous layer is removed and mixed with a strong base to hydrolyze the conjugated THC-COOH. The samples are then extracted with an organic solvent mixture as part of a sample "cleanup." The organic solvent layer is discarded and the remaining aqueous sample is acidified. Following extraction with a second organic mixture, the organic layer is removed and concentrated to dryness. The resulting residue is converted to a trimethylsilyl (TMS) derivative and analyzed using gas chromatography/mass spectrometry (GC/MS) in selective ion monitoring (SIM) mode.

Pharmacokinetics and bioequivalence of a liquid formulation of hydroxyurea in children with sickle cell anemia

Hydroxyurea (HU) is a crucial therapy for children with sickle cell anemia, but its off-label use is a barrier to widespread acceptance. We found HU exposure is not significantly altered by liquid vs capsule formulation, and weight-based dosing schemes provide consistent exposure. HU is recommended for all children starting as young as 9 months of age with sickle cell anemia (SCA; HbSS and HbSβspan(0) thalassemia); however; a paucity of pediatric data exists regarding the pharmacokinetics (PK) or the exposure-response relationship of HU. This trial aimed to characterize the PK of HU in children and to evaluate and compare the bioavailability of a liquid vs capsule formulation. This multicenter; prospective; open-label trial enrolled 39 children with SCA who provided 682 plasma samples for PK analysis following administration of HU. Noncompartmental and population PK models are described. We report that liquid and capsule formulations of HU are bioequivalent; weight-based dosing schemes provide consistent drug exposure; and age-based dosing schemes are unnecessary. These data support the use of liquid HU in children unable to swallow capsules and in those whose weight precludes the use of fixed capsule formulations. Taken with existing safety and efficacy literature; these findings should encourage the use of HU across the spectrum of age and weight in children with SCA; and they should facilitate the expanded use of HU as recommended in the National Heart; Lung; and Blood Institute guidelines for individuals with SCA.

Heptadecanoylcarnitine (C17) a novel candidate biomarker for newborn screening of propionic and methylmalonic acidemias

BACKGROUND

3-Hydroxypalmitoleoyl-carnitine (C16:1-OH) has recently been reported to be elevated in acylcarnitine profiles of patients with propionic acidemia (PA) or methylmalonic acidemia (MMA) during expanded newborn screening (NBS). High levels of C16:1-OH, combined with other hydroxylated long chain acylcarnitines are related to long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and trifunctional protein (TFP) deficiency.

METHODS

The acylcarnitine profile of two LCHADD patients was evaluated using liquid chromatography-tandem mass spectrometric method. A specific retention time was determined for each hydroxylated long chain acylcarnitine. The same method was applied to some neonatal dried blood spots (DBSs) from PA and MMA patients presenting abnormal C16:1-OH concentrations.

RESULTS

The retention time of the peak corresponding to C16:1-OH in LCHADD patients differed from those in MMA and PA patients. Heptadecanoylcarnitine (C17) has been identified as the novel biomarker specific for PA and MMA patients through high resolution mass spectrometry (Orbitrap) experiments. We found that 21 out of 23 neonates (22 MMA, and 1PA) diagnosed through the Tuscany region NBS program exhibited significantly higher levels of C17 compared to controls. Twenty-three maternal deficiency (21 vitamin B12 deficiency, 1 homocystinuria and 1 gastrin deficiency) samples and 82 false positive for elevated propionylcarnitine (C3) were also analyzed.

CONCLUSIONS

We have characterized a novel biomarker able to detect propionate disorders during expanded newborn screening (NBS). The use of this new biomarker may improve the analytical performances of NBS programs especially in laboratories where second tier tests are not performed.

Systemic exposure to menthol following administration of peppermint oil to paediatric patients

OBJECTIVE

Peppermint oil (PMO) has been used to treat abdominal ailments dating to ancient Egypt, Greece and Rome. Despite its increasing paediatric use, as in irritable bowel syndrome (IBS) treatment, the pharmacokinetics (PK) of menthol in children given PMO has not been explored.

DESIGN AND SETTING

Single-site, exploratory pilot study of menthol PK following a single 187 mg dose of PMO. Subjects with paediatric Rome II defined (IBS; n=6, male and female, 7-15 years of age) were enrolled. Blood samples were obtained before PMO administration and at 10 discrete time points over a 12 h postdose period. Menthol was quantitated from plasma using a validated gas chromatography mass spectrometry technique. Menthol PK parameters were determined using a standard non-compartmental approach.

RESULTS

Following a dose of PMO, a substantial lag time (range 1-4 h) was seen in all subjects for the appearance of menthol which in turn, produced a delayed time of peak (Tmax=5.3 ± 2.4 h) plasma concentration (Cmax=698.2 ± 245.4 ng/mL). Tmax and Tlag were significantly more variable than the two exposure parameters; Cmax, mean residence time and total area under the curve (AUC=4039.7 ± 583.8 ng/mL × h) which had a coefficient of variation of <20%.

CONCLUSIONS

Delayed appearance of menthol in plasma after oral PMO administration in children is likely a formulation-specific event which, in IBS, could increase intestinal residence time of the active ingredient. Our data also demonstrate the feasibility of using menthol PK in children with IBS to support definitive studies of PMO dose-effect relationships.

Transverse wobbling in ^{135}pr

A pair of transverse wobbling bands is observed in the nucleus ^{135}Pr. The wobbling is characterized by ΔI=1, E2 transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the tilted axis cranking model and the quasiparticle rotor model.

Measurement of the isoscalar monopole response in the neutron-rich nucleus 68Ni

The isoscalar monopole response has been measured in the unstable nucleus (68)Ni using inelastic alpha scattering at 50A  MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 ± 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 ± 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L = 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

Nuclear structure towards N = 40 60Ca: in-beam γ-ray spectroscopy of 58,60Ti

Excited states in the neutron-rich N = 38, 36 nuclei (60)Ti and (58)Ti were populated in nucleon-removal reactions from (61)V projectiles at 90 MeV/nucleon. The γ-ray transitions from such states in these Ti isotopes were detected with the advanced γ-ray tracking array GRETINA and were corrected event by event for large Doppler shifts (v/c ∼ 0.4) using the γ-ray interaction points deduced from online signal decomposition. The new data indicate that a steep decrease in quadrupole collectivity occurs when moving from neutron-rich N = 36, 38 Fe and Cr toward the Ti and Ca isotones. In fact, (58,60)Ti provide some of the most neutron-rich benchmarks accessible today for calculations attempting to determine the structure of the potentially doubly magic nucleus (60)Ca.

Misleading hepatitis B testing in the setting of intravenous immunoglobulin

Intravenous immunoglobulin (IVIG) is commonly used for a wide range of diagnoses, by multiple pediatric subspecialists. We report two cases of hepatitis B screening results post IVIG infusion, where positive anti-Hepatitis B core antigen serology tests indicated possible occult hepatitis infection, leading to a delay in care. However, serial antibody testing showed results consistent with the passive transfer of antibodies.

Evidence for multiple chiral doublet bands in 133Ce

Two distinct sets of chiral-partner bands have been identified in the nucleus 133Ce. They constitute a multiple chiral doublet, a phenomenon predicted by relativistic mean field (RMF) calculations and observed experimentally here for the first time. The properties of these chiral bands are in good agreement with results of calculations based on a combination of the constrained triaxial RMF theory and the particle-rotor model.

A simple, rapid atmospheric pressure chemical ionization liquid chromatography tandem mass spectrometry method for the determination of 25-hydroxyvitamin D2 and D3

Vitamin D plays a vital role not only in bone health but also in pathophysiology of many other body functions. In recent years, there has been significant increase in testing of 25-hydroxyvitamin D (25-OH vitamin D), a marker of vitamin D deficiency. The most commonly used methods for the measurement of 25-OH vitamin D are immunoassays and liquid chromatography tandem mass spectrometry (LC-MS-MS). Since immunoassays suffer from inaccuracies and interferences, LC-MS-MS is a preferred method. In LC-MS-MS methods, 25-OH vitamin D is extracted from serum or plasma by solid-phase or liquid-phase extraction. Because these extraction methods are time consuming, we developed an easy method that uses simple protein precipitation followed by injection of the supernatant to LC-MS-MS. Several mass-to-charge (m/z) ratio transitions, including commonly used transitions based on water loss, were evaluated and several tube types were tested. The optimal transitions for 25-OH vitamin D2 and D3 were 395.5 > 269.5 and 383.4 > 257.3, respectively. The reportable range of the method was 1-100 ng/mL, and repeatability (within-run) and within-laboratory imprecision were <4% and <6%, respectively. The method agreed well with the solid-phase extraction methods.

Tidal waves in 102Pd: a rotating condensate of multiple d bosons

Low-lying collective excitations in even-even vibrational and transitional nuclei may be described semiclassically as quadrupole running waves on the surface of the nucleus ("tidal waves"), and the observed vibrational-rotational behavior can be thought of as resulting from a rotating condensate of interacting d bosons. These concepts have been investigated by measuring lifetimes of the levels in the yrast band of the (102)Pd nucleus with the Doppler shift attenuation method. The extracted B(E2) reduced transition probabilities for the yrast band display a monotonic increase with spin, in agreement with the interpretation based on rotation-induced condensation of aligned d bosons.