The effect of sodium fluoride preservative and storage temperature on the stability of cocaine in horse blood, sheep vitreous and deer muscle

The in vitro stability of cocaine in horse blood, sheep vitreous humour (VH) and homogenised deer muscle is described. The stability of cocaine in horse blood was of interest because many toxicology laboratories utilise horse blood for the preparation of calibration and check standards and the latter are typically stored during routine use. The storage stability of cocaine in human VH and muscle has not been previously reported. In the absence of blank human VH and muscle, cocaine stability under varying conditions was demonstrated in animal tissues. Blood and VH were stored with and without addition of NaF at room temperature (RT), 4°C and -18°C for 84 days. Muscle homogenates were prepared in water, water/2% NaF, and phosphate buffer (pH 6.0)/2% NaF, and stored for 31 days at RT, 4°C and -18°C. Cocaine stability in human muscle obtained from cocaine positive forensic cases was assessed following storage at -18°C for 13 months. Cocaine and benzoylecgonine (BZE) were extracted using SPE and quantified by GC-MS/MS. Cocaine was stable for 7 days in refrigerated (4°C) horse blood fortified with 1 and 2% NaF. In the absence of NaF, cocaine was not detectable by day 7 in blood stored at RT and 4°C and had declined by 81% following storage at -18°C. At 4°C the rate of cocaine degradation in blood preserved with 2% NaF was significantly slower than with 1% NaF. The stability of cocaine in horse blood appeared to be less than that reported for human blood, probably attributable to the presence of carboxylesterase in horse plasma. Cocaine stored in VH at -18°C was essentially stable for the study period whereas at 4°C concentrations decreased by >50% in preserved and unpreserved VH stored for longer than 14 days. Fluoride did not significantly affect cocaine stability in VH. The stability of cocaine in muscle tissue homogenates significantly exceeded that in blood and VH at every temperature. In preserved and unpreserved samples stored at 4°C and below, cocaine loss did not exceed 2%. The increased stability of cocaine in muscle was attributed to the low initial pH of post-mortem muscle. In tissue from one human case stored for 13 months at -18°C the muscle cocaine concentration declined by only 15% (range: 5-22%). These findings promote the use of human muscle as a toxicological specimen in which cocaine may be detected for longer compared with blood or VH.     

Gamma-hydroxybutyric acid stability and formation in blood and urine

Gamma-hydroxybutyric acid (GHB) can cause problems in interpretation of toxicological findings due to its endogenous nature, significant production in tissues after death and potential formation in stored samples. Our study was designed to determine the influence of storage conditions on GHB levels and its possible in vitro formation in blood and urine in cases where no exogenous use of GHB or its precursors was suspected. The samples were prepared by validated method based on liquid-liquid reextraction with adipic acid internal standard and MSTFA derivatization and assayed on a GC-MS operating in EI SIM mode. The first part of the study was performed with pooled blood and urine samples obtained from living and deceased subjects stored with and without NaF (1% w/v) at 4 and -20 degrees C over 8 months. In ante-mortem samples (both blood and urine) no significant GHB production was found. After 4 months of storage, the substantial GHB rise up to 100 mg/Lwas observed in post-mortem blood stored at 4 degrees C without NaF with subsequent gradual decrease in following months. The inhibition of GHB production was apparent during storage in NaF treated frozen blood samples. In post-mortem urine only slight temporary GHB levels were ascertained (up to 8 mg/L). The second part of our study was aimed to analyse 20 individual post-mortem blood samples stored at 4 degrees C for 16-27 days between autopsy and analysis without preservation followed by storage at 4 degrees C with NaF for 4 months. The temporary GHB production with maximum of 28 mg/Lwas detected in some samples.     

Stability of Morphine,Codeine, and 6‐Acetylmorphine in Blood at Different Sampling and Storage Conditions

The stability of drugs in biological specimens is a major concern during the evaluation of the toxicological results. The stability of morphine, codeine, and 6‐acetyl‐morphine in blood was studied after different sampling conditions: (i) in glass, polypropylene or polystyrene tubes, (ii) with addition of dipotassium ethylene diamine tetraacetic acid (K₂EDTA) or sodium oxalate (Na₂C₂O₄), and (iii) with or without the addition of sodium fluoride (NaF). Spiked blood samples were stored at two different temperatures (4 and ?20^°C), analyzed after different storage times and after three freeze–thaw cycles. Opiate concentrations were decreased in all conditions, but the most unstable was 6‐acetyl‐morphine. The addition of NaF as preservative improved the stability of opiates at all conditions studied, whereas the type of anticoagulant did not affect the stability of opiates. It was concluded that blood samples should be stored at ?20^°C in glass tubes containing oxalate and NaF for maximum stability.     

The influence of storage temperature and chemical preservation on the stability of succinylcholine in canine tissue

Succinylcholine (SCh) has been detected six months postmortem in liver, kidney, and injection site muscle of rats given 10 to 200 mg/kg by intramuscular injection. SCh stability was studied in canine tissue to evaluate three storage temperatures and two chemical preservatives at three time periods after injection. Nine mongrel dogs weighing 17.2 to 28 kg were divided equally into three groups and administered either 0.5, 1.0, or 5.0 mg SCh/kg intravenously into the cephalic vein. Liver, kidney, and gastrocnemius muscle were removed 90 min post-injection and divided into twelve portions. Each portion was treated with embalming fluid, physostigmine, the combination (50/50), or nothing. Chemically treated tissues and nontreated tissues were then stored at either 27, 5, or -20 degrees C for a period of up to forty days. Tissue portions were analyzed using ion-pair extraction, chemical demethylation, and gas chromatography with nitrogen phosphorous detection. Stability of SCh was greatest for samples stored at -20 degrees C and preserved with the combination of embalming fluid plus physostigmine. Kidney concentrations of SCh were significantly higher than those in liver or muscle at all doses. SCh was detected 24 h post-injection in all cases. By 40 days, only trace amounts of SCh, if any, could be detected in samples stored at room temperature with no chemical preservatives.     

Instability of pancuronium in postmortem blood and liver taken after a fatal intramuscular Pavulon injection

The present study was designed to determine the stability of pancuronium in postmortem blood and liver during storage. Results were obtained using the method by Kerskes et al. [C.H.M. Kerskes, K.J. Lusthof, P.G.M. Zweipfenning, J.P. Franke, The detection and identification of quaternary nitrogen muscle relaxants in biological fluids and tissues by ion-trap LC-ESI-MS, J. Anal. Toxicol. 26 (2002) 29-34.], modified and validated in our laboratory. Target analytes were isolated after enzymatic hydrolysis followed by solid phase extraction (BondElut C18 column). Internal standardisation was carried out using laudanosine and the target ions were monitored by LC-ESI-MS (monitoring ions m/z 358 for IS and 286 for pancuronium). Materials were taken from a 46-year-old woman, who had been found dead. A syringe (2 ml) and an empty ampoule of Pavulon (4 mg/2 mL) were found in her hand. The residual volume of fluid in the syringe was 0.7 ml. An autopsy was performed six days after death. It revealed a needle mark on the left thigh. Postmortem materials (muscle from the injection site, blood and liver) and the syringe with fluid were stored for four months in a freezer at -20 degrees C. The initial pancuronium concentrations were 81 ng/mL in blood and 532 ng/g in liver. The analyte was stable when stored at -20 degrees C in blood even up to seven months. In liver samples its concentrations were variable. Pancuronium in blood stored at 20 degrees C underwent degradation very rapidly. After three months of storage these blood samples had concentrations not greater about 10% of the initial value. The degradation patterns of pancuronium depended on temperature and the biological matrix.     

Stability of diazepam in blood samples at different storage conditions and in the presence of alcohol

Diazepam is one of the mostly used benzodiazepines and it is frequently analyzed in different biological samples, especially blood samples. The diazepam stability in the sample matrices is an important factor regarding reliable data obtaining. The storage is the main factor determining the stability of diazepam in blood samples and it is the object of the study presented. Remaining diazepam amount in spiked whole blood and plasma samples were tested at different storage temperatures, in the absence or presence of sodium fluoride as stabilizer as well as the influence of ethanol on diazepam stability was evaluated. The results of the study indicated that the temperature is the main storage factor affecting diazepam stability. In the fluoride stabilized blood samples the amount of diazepam decreases up to 85% of initial level when stored at -20° C for the period of testing (12 weeks). The presence of low (0.5 g/L) or high (3g/L) ethanol concentrations influences the stability of diazepam at -20 °C. In whole blood samples, the combination of sodium fluoride and ethanol decreases additionally (15-25%) the concentration of the analyte. Freeze-thaw experiments of whole blood samples show about 5-9% decrease in diazepam concentration after the first cycle. The freeze-thaw experiments on plasma samples, containing ethanol and/or fluoride show insignificant decreases of analyte concentration. Further experiments on benzodiazepines stability at different storage conditions or in combination of different factors should be undertaken in forensic toxicology to ensure the data quality, their reliability and reproducibility.     

Long-term storage of blood samples as whole blood at extremely low temperatures for methemoglobin determination

Changes in methemoglobin (Met-Hb) concentrations during storage of whole blood and a hemolysate at refrigerated or various freezing temperatures were examined using experimentally prepared blood samples. When whole blood was stored at 3 degrees C, rapid reduction of Met-Hb was observed in the nitrite-treated blood whereas neither reduction nor formation of Met-Hb was observed in the untreated and heated blood within 7 days. When hemolysate was stored at 3 degrees C, Met-Hb concentrations were stable within a few days regardless of the initial values. However, slight autoxidation was observed 7 days after storage in the untreated and heated blood. When whole blood was stored at various freezing temperatures, Met-Hb concentrations were practically stable until at least 30 days at -80 degrees C or -196 degrees C regardless of the initial values, although considerable autoxidation was observed at -30 degrees C especially in the blood containing small amounts of Met-Hb. Based on the results obtained, a new method was devised for long-term storage of whole blood at extremely low temperatures for Met-Hb determinations.     

血液中乙醇保存稳定性研究

目的确定血液中乙醇最佳保存条件,探讨影响血液中乙醇含量稳定性的主要因素。方法对血液保存的温度(-20、4、20℃)、防腐剂(NaF、无防腐剂、Na2O2)、储存容器中空气所占比例(0%、25%、50%)和血醇质量浓度(0.2、0.8、2.0mg/mL)四个因素采用正交试验L9(34)方法分组,样本采用顶空气相色谱法进行测定,测定结果采用方差分析进行讨论。结果在20℃保存且不加入防腐剂的两组样本中血醇浓度变化明显,其余变化不明显。结论血液样本在4℃、储存容器中空气比例为50%和加防腐剂(NaF)的条件下保存,稳定性最佳;四个影响因素中温度为影响血液中乙醇含量稳定性的主要因素。     

In vitro production of GHB in blood and serum samples under various storage conditions

The in vitro production of GHB was observed in freshly collected, untreated whole blood samples using glass BD-Vacutainers and polypropylene S-monovettes. GHB concentrations were determined daily over a period of one week and after 3, 6 and 9 weeks again. Furthermore, the GHB concentration in 40 untreated random whole blood samples stored at 4°C for a longer period of time (10 samples 12 month, 10 samples 24 month and 20 samples 36 month) was also determined. For comparison, the in vitro production of GHB in freshly collected and prepared serum samples was observed. GHB serum concentrations were determined three times over a period of one week and once again after six weeks. Sample preparation was performed by means of methanolic extraction following the precipitation of whole blood and serum samples. A methanolic standard calibration was done in a low range of 0.005-0.1 μg/mL (LOD: 0.004, LLOQ: 0.013). For quantification a spiked blood bank serum with a determined GHB concentration of 0.09 μg/mL was used. Corrected calibrations in the range of 0.09-5.09 μg/mL were used (LOD: 0.08 μg/mL, LLOQ: 0.30 μg/mL), recovery: 91.3% (high level: 4.09 μg/mL) 50.5% (low level: 0.19 μg/mL). RESULTS: Relevant elevation of GHB was observed in all whole blood samples stored in liquid form (4°C or room temperature). In two of the 40 whole blood samples stored over a longer period of time at 4°C, GHB concentrations in the range of 13 μg/mL were even determined. These findings constitute grounds for caution. Even a GHB cut-off level of 5 μg/mL cannot be considered as "absolutely positive" proof of a case of exogenous administration, at least in untreated liquid blood samples in long time storage. However, no significant elevations of GHB were otherwise observed in any of the serum samples independently of storage temperature nor in the whole blood samples that were frozen for storage. CONCLUSIONS: The results suggest that the cut-off for exogenous GHB of 5 μg/mL could be lowered significantly, with the consequence of winning valuable time for the potential victim, but only if serum is collected for GHB determination or if the whole blood sample is frozen immediately after collection and the procedure well documented.     

The Stability of 4-Chloromethcathinone in Blood and Vitreous Humor

We present results of our study on the stability of 4-chloromethcathinone (4-CMC) in authentic postmortem peripheral blood and vitreous humor samples. The stability of 4-CMC was determined in postmortem blood samples (for a period of 90 days) and vitreous humor (30 days) at three different temperatures: −15°C, +4°C, and + 23°C. The analyses were carried out using ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). In both materials, the lowest 4-CMC stability was demonstrated at room temperature. The blood samples stored in a freezer (−15°C) showed stability for the entire study period (90 days), while in the case of the vitreous humor sample stored at the same temperature the concentration of the substance decreased by 53% after 30 days. The study carried out in authentic postmortem blood and vitreous humor samples confirms the previous reports of 4-CMC instability in biological material. Authors suggest that the biological material should be stored frozen until analyses are carried out as soon as possible after collection of the material.     

Influence of storage on larval length and age determination of the forensically important blow fly Lucilia sericata (Diptera: Calliphoridae)

One of the main tasks in forensic entomology is the determination of the minimum post-mortem interval (PMI_min) based on the age of the juvenile insects feeding and developing on the dead body. An important task is to store the evidence appropriately so that the evaluation and expert report can be used in court. However, existing recommendations can be contradictory or lacking scientific validation, e.g. by proposing various preservation liquids without knowing whether and to what extent the period of storage in such a liquid has an effect on the length of the preserved larvae. Storage time can be an issue since, due to technical and procedural circumstances, killed larvae may be stored for hours, days, weeks or even longer prior length measurement. A changed body length would have consequences for the entomological report, as the age of the larvae is usually derived from their length.This study investigates the effect of four differently concentrated ethanol solutions (70%, 80%, 90% and 96%) during a storage period of up to 196 days on the body length of stored larvae of the forensically important blow fly species L. sericata (Diptera: Calliphoridae). Larvae of different ages (24 h, 48 h and 72 h after hatching) were killed by immersion in hot, non-boiling water (≥80 °C) for at least 30 s. Their lengths were measured immediately. Subsequently samples were stored in ethanol of appropriate concentration at room temperature (approx. 22 °C). Further length measurements were made at 16 different storage intervals between 1 and 196 days.Many specimens showed a length decrease for most storage conditions and all larval ages. However, there was a tendency for 48 h- and 72 h-old larvae to increase in length after the first days of storage of up to 1.1 mm which may lead to an erroneous overestimation of the PMI_min using this kind of specimens. All changes in length within each cohort over total time were in the range of +7% to −9.1%. Significant differences in length changes within the first days of storage were found mainly in larvae stored in 70%- and 80%-ethanol, but larvae stored in 90%- and 96%-ethanol showed first significant differences on day 56 at the earliest.Our results lead to the recommendation that the measurements of fly larvae samples should be taken immediately after killing and before storage to avoid any effects. Ethanol ≥90% should be used for storage.     

Storage of blood for methemoglobin determination: comparison of storage with a cryoprotectant at -30 degrees C and without any additions at -80 degrees C or -196 degrees C

Changes in methemoglobin (Met-Hb) concentrations during storage of whole blood or mixtures of blood and a cryoprotectant at refrigerated or various freezing temperatures were examined using blood samples from nitrite-administered rats and from autopsy cadavers. When whole blood was stored at 3 degrees C, Met-Hb reduction was observed in blood samples from nitrite-administered rats and in the blood from a victim poisoned by a weed killer containing some oxidant. When samples were stored at -30 degrees C, Met-Hb formation by autoxidation was inevitably observed in blood samples stored as whole blood, whereas addition of a cryoprotectant to whole blood could prevent Met-Hb formation in all the blood samples. When whole blood was stored at -80 degrees C or -196 degrees C, Met-Hb concentrations were practically stable until at least 30 days regardless of the initial values except in the control rat blood samples stored at -80 degrees C which showed slight formation of Met-Hb. From the results obtained, both the storage with a cryoprotectant at -30 degrees C and that without any additions at -80 degrees C or -196 degrees C proved to be suitable for long-term storage of blood samples from autopsy cadavers for Met-Hb determination.     

Detection of ABH blood group antigens in the saliva of Koreans and their stability according to storage of saliva samples

The purpose of the present study was to identify salivary molecules carrying the ABH blood group antigens in Koreans and to investigate the changes in these antigens according to processing and storage of saliva samples. Secretor or non-secretor phenotypes and salivary components carrying the ABH antigens were identified in 90 subjects, 30 subjects in each ABO blood group, by SDS-PAGE and immunoblotting. Saliva samples were then obtained from 12 secretors-two males and two females in each ABO blood group and aliquots of both fresh saliva samples and their supernatants after centrifugation were stored at room temperature, 4, -20 and -70 degrees C. The same experiments were performed after 1, 3 and 6 months to investigate changes in the blood group antigens. In all 68 secretors, high-molecular-weight salivary mucin (MG1) was found to be the primary carrier of the ABH antigens. A salivary component of approximately 80 kDa also carried H antigen in seven saliva samples of 22 blood type O secretors. The blood group antigens were better detected in centrifuged samples. In saliva samples preserved at room temperature and 4 degrees C, the blood group antigens were either not detected or detected as degraded molecules. No change was found in the blood group antigens in saliva samples preserved at -20 and -70 degrees C for 6 months.     

Detection of cocaine in blood stains]

Cocaine is rapidly degraded in blood samples, and its degradation was found to be highly dynamic in nature. The analysis of blood spots dried on filter paper may provide a method to minimize the break-down of cocaine and to largely preserve the analytical profile of the parent drug and its hydrolysis products at the time of sampling. The short term stability of cocaine in 100 microL blood spots prepared from unpreserved and preserved (sodium fluoride, 0.25%) blood samples was compared to the stability of the particular whole blood specimens stored in tubes at ambient temperature and at -20 degrees C. Due to dehydration, both the chemical and the enzymatic hydrolysis of cocaine and its products could be stopped in dried blood spots. More than 75% of the initial cocaine concentration could be detected in the blood spots, and the analytical profile was ensured for 17 days. Provided its practical suitability, the spot technology should offer a simple approach to detect actual impairment of motorists taken in police custody in the view of section 24a of the German traffic act as well as in cocaine associated criminal cases.     

The effect of storage at various temperatures on blood alcohol concentration

There is a paucity of data available on the effect of storage on blood alcohol concentration (BAC) at elevated temperatures. Changes in serum alcohol concentration (SAC) and BAC were studied. Serum samples spiked with alcohol in the presence or absence of preservative were stored at 26.7 °, 32.2 ° or 37.8 °C respectively. Serum alcohol concentrations were determined daily on days 1 through 14, and on days 21 and 35. Under these controlled conditions, no significant change in SAC was observed at the aforementioned temperatures. Whole blood samples submitted from outside agencies were initially analyzed (day 1), then stored for 35 days at different elevated temperatures before a second analysis. The average loss in BAC was 19.20 ± 15.6, 9.95 ± 5.7, and 15.60 ± 6.9% when the samples were stored at 26.7, 32.2 and 37.8 °C, respectively. The alcohol loss from whole blood samples may be attributed to chemical oxidation rather than to elevated temperatures. It is, therefore, concluded that a whole blood sample obtained from a living individual and stored in a locker, glove compartment or other environment where the temperature is elevated, may lose 10–19% of its alcohol content over 35 days of storage. On the other hand, when a serum or plasma sample is exposed to the same environment, no significant change in SAC was observed. The utility of this information is significant to the forensic toxicologist. The results of this study suggest that a whole blood sample analyzed after exposure to elevated temperature may have had, originally, a higher BAC.     

The effect of temperature on Y-chromosome detection in blood stains

The present investigation is an extension of an earlier work on the effect of various temperatures on Y-chromosome detection. The deteriorating effect of storage at 53 °C was again demonstrated. Liquid blood samples stored at 5 °C were better preserved with regard to Y-chromosomes than those stored at room temperature. This was in conflict with the earlier results on blood stains. New experiments were therefore performed. The results varied. It is suggested that this variation was due to low temperatures having two contrary effects on the results: the well-known preserving effect on biological material and a previously described constricting effect on the heterochromatic areas of the chromosomes making Y-body detection more difficult.     

Ethanol stability in unpreserved refrigerated antemortem blood

Ethanol stability in preserved antemortem blood has been widely studied since it is a common practice in cases involving suspected impaired driving to collect antemortem blood in evacuated blood tubes containing sodium fluoride. In some situations, antemortem blood is submitted to a forensic laboratory for ethanol analysis in evacuated blood tubes that contain only an anticoagulant. There has been limited research on ethanol stability in antemortem blood stored without a preservative. On two occasions, antemortem blood was collected from five ethanol-free individuals into 6-ml Vacutainer® tubes containing only 10.8 mg potassium EDTA. The blood tubes were spiked with ethanol to approximately either 0.08 or 0.15 g/dl. Dual-FID headspace gas chromatography was used to analyze 58 blood tubes, 29 from each session, for ethanol 1 day after sample collection and again after 1 year of refrigerated storage (~4°C). Statistically significant decreases in ethanol were detected at the 0.05 level of significance. Mean decreases in ethanol after 1 year of storage for the 0.08 and 0.15 g/dl samples were 0.013 and 0.010 g/dl, respectively. The mean ethanol decrease across all tubes was 0.012 g/dl. The range of decreases for the 58 blood tubes was 0.003–0.018 g/dl. The mean ethanol decreases measured in this unpreserved antemortem blood are comparable in magnitude to those previously observed in antemortem blood containing sodium fluoride after 1 year of refrigerated storage. Ethanol did not increase in the antemortem blood samples despite the absence of sodium fluoride.     

Quantitative and qualitative analysis of DNA extracted from postmortem muscle tissues

DNA extracted from 33 postmortem muscle specimens was analyzed using MZ 1.3, a hypervariable minisatellite probe, as well as locus-specific minisatellite probes (g3, MS1 and MS43). After storage at -25 degrees C for 10 months, DNA from all the samples was partially (approximately 21% of total DNA) degraded even when autopsy was performed 1 day postmortem. However, more than 90% of DNA samples up to at least 3 days postmortem were suitable to obtain good restriction fragment length polymorphism (RFLP) patterns. When small strips of specimen were stored for 8 days at room temperature in moist chambers, approximately 42% of total DNA was degraded. Only 30% of these DNA samples still showed good RFLP patterns. However, no obvious relation between qualities of DNA analyzed by detection of RFLP and quantities of total and high-MW DNA became apparent. A case of familial relationship was ascertained by DNA fingerprints. Since DNA of good quality can be recovered from muscle tissues in large quantities, DNA extraction from muscle tissues and detection of RFLP patterns should be very useful for individual identification in autopsy cases.     

Blood, bone marrow and eye fluid ethanol concentrations in putrefied rabbits

The effect of putrefaction on postmortem blood, bone marrow and eye fluid ethanol levels was evaluated in rabbits. Control and dosed animals were sacrificed and stored at either room temperature (approx. 19 degrees C) or cold temperature (approx. 3.5 degrees C) for as long as 28 days. Control animals stored at room temperature showed ethanol levels in the bone marrow that peaked at 7 days after sacrifice, followed by decreases to a nondetectable level at 21 days. Overall decreases were demonstrated in bone marrow of dosed rabbits stored at room temperature for all postmortem intervals. The control animals stored at low temperature showed no ethanol in the bone marrow and blood until 21 days after sacrifice. Dosed rabbits stored at low temperature showed no significant changes in blood and marrow ethanol until 21 days after sacrifice.     

血液和尿液样品中海洛因代谢物稳定性研究

目的对尿液和血液中海洛因代谢物3-β-D-葡萄糖醛酸吗啡（M3G）,吗啡,O6-单乙酰吗啡（O6）在180d内的稳定性进行研究。方法准备空白添加血液、尿液、染毒动物（大白兔）血液、尿液和吸食海洛因者血液、尿液样本,分别置于20℃、4℃、-20℃下,分别于0、1、2、4、7、14、28、56、112、156、180d时间点测定样品中M3G、吗啡,O6相对含量。结果在3种不同温度下,随保存时间的延长,血液、尿液中的O6含量均逐渐下降至零;血液中吗啡含量升高（空白血液添加组）或下降（染毒动物组）,在尿液则均升高;血液样中M3G含量均升高,尿样中则略有下降。下降和升高的幅度均随保存温度的下降而缩小。结论海洛因代谢物在-20℃时保存稳定性最佳。