Amber Glass Vials Research Articles

Pre-analytical challenges from adsorptive losses associated with thiamine analysis

Thiamine (vitamin B1) is an essential vitamin serving in its diphosphate form as a cofactor for enzymes in the citric acid cycle and pentose-phosphate pathways. Its concentration reported in the pM and nM range in environmental and clinical analyses prompted our consideration of the components used in pre-analytical processing, including the selection of filters, filter apparatuses, and sample vials. The seemingly innocuous use of glass fiber filters, glass filter flasks, and glass vials, ubiquitous in laboratory analysis of clinical and environmental samples, led to marked thiamine losses. 19.3 nM thiamine was recovered from a 100 nM standard following storage in glass autosampler vials and only 1 nM of thiamine was obtained in the filtrate of a 100 nM thiamine stock passed through a borosilicate glass fiber filter. We further observed a significant shift towards phosphorylated derivatives of thiamine when an equimolar mixture of thiamine, thiamine monophosphate, and thiamine diphosphate was stored in glass (most notably non-silanized glass, where a reduction of 54% of the thiamine peak area was observed) versus polypropylene autosampler vials. The selective losses of thiamine could lead to errors in interpreting the distribution of phosphorylated species in samples. Further, some loss of phosphorylated thiamine derivatives selectively to amber glass vials was observed relative to other glass vials. Our results suggest the use of polymeric filters (including nylon and cellulose acetate) and storage container materials (including polycarbonate and polypropylene) for thiamine handling. Losses to cellulose nitrate and polyethersulfone filters were far less substantial than to glass fiber filters, but were still notable given the low concentrations expected in samples. Thiamine losses were negated when thiamine was stored diluted in trichloroacetic acid or as thiochrome formed in situ, both of which are common practices, but not ubiquitous, in thiamine sample preparation.

Kinetics of rancidity: 1H-NMR fingerprinting-based photodegradation monitoring of citronella oil

ABSTRACT Although known as a natural mosquito repellent, especially in the tropical region, citronella oil has many other therapeutic properties including antimicrobial and antifungal. Citronella oil can be applied in pure form or as a component in different cosmetic products. As with other essential oils, citronella has specific storage conditions to prevent its rancidity. 1H-NMR fingerprinting was used to monitor the changes in the concentration of citronellal, the main component of citronella oil. Quantitative analysis of the 1H-NMR spectral data digitized the degradation pattern of citronellal to determine the effect of sunlight exposure. Significant spectral changes were observed in clear glass vials starting from the 7th day of sun exposure. The degradation of citronellal followed first-order kinetics with a half-life of 15.7 ± 2.9 days. Moreover, the effect of sunlight exposure to citronellal is highly apparent in clear glass vials than in amber glass vials. The results of this study supported the general storage condition for essential oils to maximize shelf life.

Physicochemical and Microbiological Stability of Two Oral Solutions of Methadone Hydrochloride 10 mg/mL.

In this article, we studied physicochemical and microbiological stability and determined the beyond-use date of two oral solutions of methadone in three storage conditions. For this, two oral solutions of methadone (10 mg/mL) were prepared, with and without parabens, as preservatives. They were packed in amber glass vials kept unopened until the day of the test, and in a multi-dose umber glass bottle opened daily. They were stored at 5 ± 3 °C, 25 ± 2 °C and 40 ± 2 °C. pH, clarity, and organoleptic characteristics were obtained. A stability-indicating high-performance liquid chromatography method was used to determine methadone. Microbiological quality was studied and antimicrobial effectiveness testing was also determined following European Pharmacopoeia guidelines. Samples were analyzed at days 0, 7, 14, 21, 28, 42, 56, 70, and 91 in triplicate. After 91 days of storage, pH remained stable at about 6.5–7 in the two solutions, ensuring no risk of methadone precipitation. The organoleptic characteristics remained stable (colorless, odorless, and bitter taste). The absence of particles was confirmed. No differences were found with the use of preservatives. Methadone concentration remained within 95–105% in all samples. No microbial growth was observed. Hence, the two oral methadone solutions were physically and microbiologically stable at 5 ± 3 °C, 25 ± 2 °C, and 40 ± 2 °C for 91 days in closed and opened amber glass bottles.

Stability Testing of Sirolimus in Medium-Chain Triglyceride Oil Using High-Performance Liquid Chromatography.

Recently, a premature neonate, born at 26.5 weeks, was treated with sirolimus for kaposiform hemangioendothelioma with Kasabach-Merritt phenomenon at the University of New Mexico Children's Hospital. Because of the lipophilic properties of the drug and an inability to draw the correct dose needed for the neonate with the standard 1 mg/mL concentration, sirolimus was diluted to 0.01 mg/mL (10 mg/L) in medium-chain triglyceride (MCT) oil. The objective of this study was to evaluate the stability of sirolimus diluted in MCT oil. Commercially available sirolimus oral solution was diluted with MCT oil from 1 mg/mL to 10 mg/L. The diluted samples were prepared by measuring 0.1 mL of the commercial product in an oral syringe and mixing with 9.9 mL of MCT oil. The 3 diluted samples were placed in amber glass vials, stored at 10°C, and analyzed over 14 days. The initial concentration of the 3 samples ranged from 8.5 to 10.8 mg/L sirolimus, or 85% to 108% of the target value. No significant differences were seen between average concentrations on the days tested. However, the average drug concentration fell to approximately 90% of the theoretical 10 mg/L target concentration between days 7 and 10. This study shows that sirolimus oral solution diluted with MCT oil to a final concentration of 10 mg/L was stable for at least 7 days when stored at 10°C, suggesting that the beyond-use date should be 7 days.

Physicochemical stability of 20 mg/mL amiodarone hydrochloride oral suspension in SyrSpend® SF PH4 (liquid)

Abstract Objectives Amiodarone hydrochloride is a class III antiarrhythmic drug indicated for the treatment of ventricular and supraventricular tachycardias. Oral amiodarone is only available in a tablet dosage form, which is not suitable for pediatric use. The stability of amiodarone hydrochloride suspension at 5 mg/mL was assessed in SyrSpend® SF PH4 (liquid) but oral amiodarone is typically given as a loading dose of 10–15 mg/kg/day for 4–10 days and then reduced to a maintenance dose of 5 mg/kg/day, making the 20 mg/mL concentration a better option. A hospital preparation of 20 mg/mL amiodarone hydrochloride oral suspension was developed. The purpose of this study was to determine the physicochemical stability of a 20 mg/mL amiodarone hydrochloride oral multidose suspension in a commercial compounding excipient, SyrSpend® SF PH4 (liquid) at ambient temperature and under dark conditions. Methods Three batches of oral suspension were prepared using amiodarone hydrochloride powder and SyrSpend SF PH4 (liquid). The suspensions were stored at room temperature and protected from light (amber glass vials). A sample was withdrawn from each bottle immediately after preparation and at 1, 2, 5, 10, 15, 30, 60, and 90 days. After additional dilution to an expected concentration of 100 μg/mL with methanol, the samples were assayed in triplicate using a stability-indicating high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The physicochemical properties (pH, osmolality, amiodarone concentration, macroscopic changes) were assessed over 90 days at each day of analysis. Stability was determined by evaluating the percentage of the initial concentration remaining at each time point and defined as retention of at least 95% of the initial concentration of amiodarone hydrochloride. Results After 90 days, the study showed that amiodarone hydrochloride concentrations did not go below 95% of the initial drug concentration. Neither degradation products nor changes of physicochemical properties were detected. Conclusions Compounded oral suspensions of 20 mg/mL amiodarone hydrochloride in SyrSpend® SF PH4 (liquid) were stable for at least 90 days when stored in amber glass bottles at room temperature.

Long-term stability of ready-to-use epinephrine 0.02 mg/mL injection solution in 50 mL glass vials

Abstract Objectives In adult intensive care patients, epinephrine is mostly administered by continuous injection with syringe pumps. The objective of this study was to investigate the physicochemical stability of pharmacy prepared ready-to-use epinephrine (E) 0.02 mg/mL injection solutions (total volume 50 mL) for assigning shelf-life. Methods E 0.02 mg/mL injection solution in 50 mL amber type l glass vials was produced batch-wise in the pharmacy department. Stability of the refrigerated (2–8 °C) product was investigated in real time over a period of 36 months by analyzing E concentrations, osmolality, pH, and sub-visible particles at predefined time-points. For E concentration measurements a stability-indicating, validated reversed-phase HPLC-PDA assay was used. Results The autoclaving process of E 0.02 mg/mL injection solution in 50 mL amber type I glass vials caused 5% loss of the active substance. The finished product remained stable over the study period of 36 months when stored refrigerated. Conclusions Batch-wise production of ready-to-use E injection solution 0.02 mg/mL in 50 mL amber glass vials was successfully implemented in our pharmacy department. According to the stability tests, a shelf-life of 36 months can be assigned to the finished product stored refrigerated. Studies concerning stability at room temperature would be useful.

Stability of extemporaneously prepared preservative-free methylphenidate 5 mg/mL intravenous solution.

To advance the implementation of consciousness-promoting therapies in patients with acute disorders of consciousness, the availability of potential therapeutic agents in formulations suitable for administration in hospitalized patients in the presence of complex comorbid conditions is paramount. The purpose of this study is to evaluate the long-term stability of extemporaneously prepared preservative-free methylphenidate hydrochloride (HCl) 5 mg/mL intravenous solution for experimental use. A methylphenidate 5 mg/mL solution was prepared under proper aseptic techniques with Methylphenidate Hydrochloride, USP, powder mixed in sterile water for solution. Methylphenidate HCl 5 mg/mL solution was sterilized by filtration technique under USP <797>-compliant conditions. Samples were stored refrigerated (2-8°C) and analyzed at approximately days 1, 30, 60, 90, 180, and 365. At each time point, chemical and physical stability were evaluated by visual inspection, pH measurement, membrane filtration procedure, turbidometric or photometric technique, and high-performance liquid chromatography analysis. Over the 1-year study period, the samples retained 96.76% to 102.04% of the initial methylphenidate concentration. There was no significant change in the visual appearance, pH level, or particulate matter during the study period. The sterility of samples was maintained and endotoxin levels were undetectable throughout the 1-year stability period. Extemporaneously prepared preservative-free methylphenidate 5 mg/mL intravenous solution was physically and chemically stable at 32, 61, 95, 186, and 365 days when stored in amber glass vials at refrigerated temperatures (2-8°C).

Essential Oils from Piper lhotzkyanum Kunth Leaves from Brazilian Atlantic Forest: Chemical Composition and Stability in Different Storage Conditions.

This work aimed to evaluate the impact of different storage conditions and light and temperature exposures on the visual aspect and chemical composition of the essential oil (EO) of Piper lhotzkyanum Kunth, obtained from leaves by hydrodistillation from a region of high altitude. For this purpose, aliquots of the EO were stored for up to 90 days (a) under a refrigerator condition of 5 ± 3°C, (b) under a long-term (LT) condition of 30 ± 2°C and 75 ± 5% relative humidity (RH) and an accelerated condition (AS) of 40 ± 2°C and 75 ± 5% RH, and (c) in a photostability test achieved in amber and colorless glass vials. The changes were monitored on days 0 (control), 60, and 90 for the refrigerator, LT, and AS conditions. All EO chemical analyses were assessed by GC-FID and GC-MS for quantification and identification, respectively. It is reported, for the first time, that the EO of P. lhotzkyanum is rich in the sesquiterpenes β-elemene and α-zingiberene. No significant changes in the EO was observed, revealing a minimal impact of temperature on the sample at the different storage conditions. However, there was a change in the content of α-zingiberene to bicyclogermacrene after exposure to light. The visual appearance of the samples was altered for all test conditions except the refrigerator condition. These results can potentially contribute to the product development of a bioactive EO from leaves of P. lhotzkyanum, a sesquiterpene rich natural material.

Model studies on benzene formation from benzaldehyde

The carcinogenic aromatic hydrocarbon benzene has recently been detected in drinks with added cherry flavour, and it was suggested that benzene could be formed from benzaldehyde used as flavouring. To get a deeper insight into parameters favouring benzene formation, the influence of light, pH, oxygen, temperature as well as presence of transition metal ions was studied in model solutions of benzaldehyde. It was found that in particular irradiation with light increased benzene formation. However, this was not observed in a cherry juice most probably due to absorption of light by the red colour. Therefore, the benzene detected in commercial cherry juices may have been added as contaminant of the benzaldehyde used in the flavouring. The assumption was confirmed by the analysis of commercial flavourings. Thus, to avoid benzene formation in flavourings, amber glass vials must be used during production, storage and sale.

Paediatric formulation: budesonide 0.1 mg/mL viscous oral solution for eosinophilic esophagitis using cyclodextrins

Abstract Background Viscous oral solutions of budesonide (dose range: 1 mg to 2 mg) have long been used to treat eosinophilic oesophagitis in children. The objective of the present study was to provide a convenient paediatric pharmaceutical formulation of a viscous budesonide solution at a dose level of 0.1 mg/mL, using cyclodextrin as a solubilizer. Methods Solubility studies were performed with γ-cyclodextrin and hydroxypropyl-β-cyclodextrin, and viscosity was tested with a Brookfield viscometer. The stability of the final formulation was tested in a climatic chamber. Levels of budesonide, budesonide impurities and degradation products were assayed using the HPLC–UV method described for the budesonide-related substance assay in the European Pharmacopoeia monograph. Results The solubility of budesonide increased linearly with both cyclodextrins. Gamma cyclodextrin (complexation efficiency: 0.147) was preferred to hydroxypropyl-β-cyclodextrin (complexation efficiency: 0.064) as a solubilizing agent. Hydroxypropylcellulose (1 % m/v) was added to increase viscosity, and sucralose was added to improve palatability. The sterilized, filtered, final formulation was stable for at least 3 months when packed aseptically in sterile 15 mL type 1 amber glass vials. Conclusions We have developed a convenient, stable, preservative-free, viscous formulation of a budesonide solution for the hospital- and home-based treatment of paediatric patients.

Physicochemical Stability of 5 mg/mL Pediatric Prednisone Oral Suspension in Syrspend® SF PH4

Abstract Background Prednisone is a corticosteroid used in several inflammatory diseases and cancers. In France, no available prednisone drinkable formulation exists. Instead, an oral syrup of prednisone with ethanol, sodium benzoate and simple syrup is produced. However, sodium benzoate can induce neonatal icterus and alcohol is not authorized for children below 3 years of age. The aim of this study was to determine the stability of 5 mg/mL prednisone oral suspension in a commercial compounding excipient: Syrspend® SF PH4. Methods Three batches of oral suspensions were prepared, using micronized prednisone and Syrspend® SF PH4. They were packaged in amber glass vials and stored at room temperature. On day 0, 1, 4, 10, 30, 60 and 90, we observed physical and chemical stability (pH measurement, osmolality measurement, residual concentrations of prednisone and degradation product identification). A stability indicating method was developed using high performance liquid chromatography with Ultraviolet detection at 254 nm. Results Prednisone concentrations remained stable within ± 5 % of nominal values for 60 days. No degradation product and change of physicochemical properties were detected. Conclusion This study showed that 5 mg/mL prednisone oral suspension in Syrspend® SF PH4 is stable for 60 days, at room temperature and protected from light.

Stability of Ready-to-Administer and Ready-to-Use Epinephrine and Norepinephrine Injection Solutions

AbstractBackgroundIn the University Medical Centre Mainz, standard concentrations are defined for medicinal products to be administered by continuous injection with syringe pumps in adult intensive care patients. The objective of this study was to evaluate the physicochemical stability of ready-to-use and ready-to-administer preparations containing Epinephrine (E) and Norepinephrine (NE) in standardized concentrations and prepared batch wise in the pharmacy department as basis for assigning shelf-lives.MethodsE 20 µg/mL and NE 10 µg/mL in disposable syringes and NE 40, 100, 200, 400 µg/ml in 50 ml amber type I glass vials were prepared batch wise and the concentrations were analyzed by stability-indicating, validated reversed-phase HPLC-PDA assays. Test solutions for long-term stability studies were stored under refrigeration (2–8 °C) for 6–12 months or at elevated temperatures (21–27 °C) light protected for up to 6 months or without light protection for up to one month. Osmolality and pH were measured on predefined intervals.ResultsThe concentrations of E in 50 mL syringes and NE in 10 mL syringes remained unchanged over a period of 6 months when stored at 2–8 °C. NE preparations of different concentrations prepared in amber glass vials remained stable over a study period of 12 months. At RT the shelf-life decreased to about 6 months and the exposure to mixed daylight at RT caused loss of stability in only few days.ConclusionsBatch wise preparation of ready-to-administer (RTA) preparations containing 20 µg/mL E or 10 µg/mL NE in disposable syringes as well as ready-to-use (RTU) preparations containing 40, 100, 200 and 400 µg/mL NE was successfully implemented in a pharmacy department. Storage of the preparations at refrigerated temperatures is required to obtain acceptable shelf-lives of 6–12 months. Elevated temperatures and especially exposure to mixed daylight significantly decreased the shelf life.

Stability of Hydrocortisone Preservative-Free Oral Solutions.

The physical and chemical stability of a preservative-free oral solution of hydrocortisone succinate was studied at different pH values and storage temperatures. Oral solutions of hydrocortisone 1 mg/mL were prepared by dissolving hydrocortisone succinate powder in citrate buffers at pH 4.0, 5.5, and 6.5, or with sterile water (pH 7.4) stored in amber glass vials. Three identical samples of the formulations were prepared and stored under refrigeration (3-7°C), ambient temperature (20-22°C) and high temperature (29-31°C). A 200-μL sample was withdrawn from each of the 3 samples immediately after preparation and at 1, 7, 14, 21, and 35 days. Samples were assayed in duplicate using stability-indicating liquid chromatography. Stability was determined by evaluating the percentage of the initial concentration remaining at each time point; stability was defined as the retention of at least 90% of the initial concentration of hydrocortisone succinate. At least 92% of the initial hydrocortisone succinate concentration in solutions pH 5.5, 6.5, and 7.4 remained throughout the 14-day study period under refrigeration. There were no detectable changes in color, odor, or pH and no visible microbial growth in these samples. In other storage conditions, hydrocortisone succinate was rapidly degraded. The hydrocortisone succinate preservative-free oral solutions at pH 5.5, 6.5, or 7.4 are chemically stable when stored under refrigeration for at least 14 days. They provide flexible and convenient dosage forms without any preservatives for pediatric patients.

Formulation and stability study of a pediatric 2% phenylephrine hydrochloride eye drop solution

We present formulation and stability evaluation of a 2% (w/v) phenylephrine hydrochloride biocompatible eye drop solution, routinely prepared in hospital pharmacy under aseptic conditions, for retinal examination of neonates and premature infants. Eye drop solution was formulated by dissolution of phenylephrine hydrochloride and disodium hydrogen phosphate as buffering agent in sterile water for injection and sodium chloride for injection as isotonic agent. The previous solution was sterile filtered through under aseptic conditions, in an iso class 5 air quality clean room under horizontal laminar airflow hood. Physical stability (visual inspection, osmolality measurements), chemical stability (pH measurement, phenylephrine assay by liquid chromatography coupled with an ultra-high resolution and accurate mass) and sterility evaluation of phenylephrine eye drop solution stored at ambient temperature were studied during 60 days. The formulated eye drop solution had a pH of 6.90±0.05 and an osmolality of 285±2 mOsm/kg. Throughout the 60 days study the solutions remained clear without any precipitation or color modification, sterility was maintained, pH and osmolality were not significantly modified and no significant loss of product was detected using liquid chromatography coupled with an ultra-high resolution and accurate mass instrument suggesting the lack of degradation. These results indicate that 2% phenylephrine hydrochloride eye drop solutions were physically, chemically and microbiologically stable for at least 60 days when stored in type I amber glass vials at room temperature, allowing the compounding of higher batch sizes.

Optimization of parameters for storage of biocolour extracted from citrus peel

Efforts were made to optimize the conditions for storage of carotenoids extracted from citrus peel. The crude carotenoids pigment was treated with different antioxidants viz. butylated hydroxyl toluene (BHT) @ 0.015 per cent, ascorbic acid @ 500 ppm, tertiary butylhudroquinone (TBHQ) @ 0.02 per cent and potassium metabisulphite (KMS) @ 1000 ppm and packed in transparent glass vials (TGV) as well as amber glass vials (AGV) and stored at ambient and refrigerated temperature for a period of 90 days. During storage, it was found that BHT treated sample had remained higher carotenoids content (192.6 mg/g) even after 90 days of storage than those treated with KMS and ascorbic acid (186.4 and 182.5 mg/g), respectively. Further, the crude carotenoids pigment packed in AGV and stored under refrigerated temperature had retained significantly higher carotenoids content and tintometer reading (yellow and red units) compared to those packed in TGV which were stored at ambient temperature. Conclusively, carotenoids extracted from citrus peel treated with BHT@0.015%, packed in AGV and stored under refrigerated temperature were optimized.

Stability of explosive residues in methanol/water extracts, on alcohol wipes and on a glass surface

The stability of four target organic explosives [pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and triacetone triperoxide (TATP)] and two inorganic anions (chlorate and nitrate) on polyester-based alcohol wipes and in 60% (v/v) methanol/water extracts, stored over 30 days in clear and amber glass vials at three different temperatures, was investigated in order to establish storage recommendations. The retention of all six representative compounds on a glass surface at two different storage temperatures was also included as a preliminary study on the stability of explosive residues on stored exhibits (such as post-blast debris).The results from the stability study suggested that, after sampling, the wipes should be stored in a dark and low temperature environment. Also, after extracting the wipes with 60% (v/v) methanol/water (as in our previously reported recommended protocol), the extracts should be stored in a similar fashion.The results from the retention study on the glass substrate suggested that exhibits should be stored at the lowest temperature possible to minimise the loss of TNT or TATP (or similar target compounds) that might be present as residues.

Production of a Solvent Yellow 124 “euromarker” reference material certified for purity

Solvent Yellow 124 (SY124, N-ethyl-N-[2( isobutoxyethoxy) ethyl]-4-( phenylazo) aniline) is used as a common low tax fuel marker in European Union member countries. It is added to these fuels which may also contain traditional dyes, to prevent misuse. SY124 is produced industrially in solution (typically aromatic hydrocarbons) and its purity can vary from batch to batch. This is particularly a problem for the petroleum industry which risks large fines if SY124 levels are found to be below 6 mg/L or above 9 mg/L. A new reference material for SY124, certified for purity was prepared to address this problem. A SY124 CRM was prepared from a commercially procured solution of SY124. The details of the preparation and certification will be discussed. The material is commercially available as ERM-AC316a, packaged as 200 mg units in screw cap 4 mL amber glass vials. Its purity value is 95.0 ± 1.2% m/m at the 95% confidence interval.

Identification of the date‐rape drug GHB and its precursor GBL by Raman spectroscopy

Gamma hydroxybutyric acid (GHB), also known as 'liquid ecstasy', has recently become associated with drug-facilitated sexual assaults, known colloquially as 'date rape', due to the ability of the drug to cause loss of consciousness. The drug is commonly found 'spiked' into alcoholic beverages, as alcohol increases its sedative effects. Gamma hydroxybutyric acid and the corresponding lactone gamma-butyrolactone (GBL) will reach an equilibrium in solution which favours the lactone in basic conditions and GHB in acidic conditions (less than pH 4). Therefore, we have studied both GHB and GBL, as a mildly acidic beverage 'spiked' with GHB will contain both GHB and GBL. We report the analysis of GHB as a sodium salt and GBL, its precursor, using bench-top and portable Raman spectroscopy. It has been demonstrated that we are able to detect GHB and GBL in a variety of containers including colourless and amber glass vials, plastic vials and polythene bags. We have also demonstrated the ability to detect both GBL and GHB in a range of liquid matrices simulating 'spiked' beverages.

Online measurement of water content in candidate reference materials by acousto-optical tuneable filter near-infrared spectrometry (AOTF-NIR) using pork meat calibrants controlled by Karl Fischer titration

Certified reference materials (CRMs) are prepared from a wide variety of matrices. Water removal is an excellent way of achieving increased matrix lifetime and hence CRM stability. High-speed acousto-optical tuneable filter near-infrared spectrometry (AOTF-NIR) has been implemented for measurement of water content in powder matrix reference materials in amber glass vials. Almost 50,000 spectra were collected from 1300 to 2100 nm with a 2 nm increment for powders of meat, rye grass, potato, cotton seed and sugar beet. The AOTF-NIR instrument was placed in a capping machine, with a measurement frequency of 10–15 vials/min and a trigger signal for reproducible collection of spectra. The calibrants comprised 19 pork meat powder samples equilibrated with different hygrostatic solutions or subjected to oven drying to achieve different water concentrations. Mixtures of powders with different water content were also prepared in order to obtain a calibration range from 0.5 to 8.3% water (m/m). All calibration samples were measured by volumetric Karl Fischer titration (V-KFT), accredited under ISO 17025. The calibrants were then measured by AOTF-NIR together with the samples. Multiplicative scatter correction (MSC) was applied to the absorbance spectra in order to correct for the scattering of light in the different powders and scattering effects from the vials. A partial least squares regression model (PLS) based on two principal components was created and applied for prediction of water content in the samples with a standard error of 0.5% water (m/m). The AOTF-NIR has the potential of rapidly monitoring a large number of samples of different materials with good accuracy as demonstrated by the good agreement with V-KFT. Nevertheless, it is necessary to expand the number of calibration models for different vial sizes as it turns out that MSC cannot correct properly for the influence of scattering of light due to the different vial sizes, in this case 100 mL and 10 mL vials. The influence of the matrix seems not to be critical because the prediction of the water content in a wide variety of matrices was successful using the meat powder as a universal calibrant.

Simultaneous determination of total hypericin and hyperforin in St. John's wort extracts by HPLC with electrochemical detection

An analytical procedure was developed for the simultaneous determination of total hypericin (protopseudohypericin, pseudohypericin, protohypericin and hypericin) and hyperforin in Hypericum perforatum (St. John's wort) extracts and its preparations. The determination of total hypericin and hyperforin in one step was achieved by exposing the samples to artificial daylight in amber glass vials. This procedure allows both the photoconversion of the protoforms into the appropriate hypericins and the protection of the photosensitive hyperforin. For quantification, an HPLC method with electrochemical detection was applied. As an example of the application of the principle, two preparations containing St. John's wort were assayed.