International Journal of Pharmaceutics288(2005)
157–168
Pharmaceutical Nanotechnology
pDNA loaded calcium phosphate nanoparticles:highly ef?cient
non-viral vector for gene delivery
Savita Bisht,Gajadhar Bhakta,Susmita Mitra,Amarnath Maitra?
Department of Chemistry,University of Delhi,Delhi110007,India
Received13May2004;accepted30July2004
Available online21November2004
Abstract
Nanoparticles of calcium phosphate encapsulating plasmid DNA(pDNA)of size100–120nm in diameter were prepared.XRD studies of these nanoparticles showed them to be crystalline in nature having hydroxyapatite structure.The maximum loading of pDNA and its release from nanoparticles were studied using gel electrophoresis.The time dependent size measurement of these particles demonstrated that these particles show strong aggregational behaviour in aqueous dispersion.Calcium phosphate nanoparticles were found to be dissolved even in low acidic buffer(pH5.0)releasing the pDNA,which suggested that DNA release from these particles in the endosomal compartment was possible.In vitro transfection ef?ciency of these calcium phosphate nanoparticles was found to be higher than that of the commercial transfecting reagent Polyfect.
?2004Elsevier B.V.All rights reserved.
Keywords:Calcium phosphate nanoparticles;Non-viral vectors;Gene delivery;Transfection ef?ciency
1.Introduction
The emerging area of inorganic nanoparticles en-trapping biomolecules has exhibited its diversity and potential applications in many frontiers of modern ma-terial science(Avnir et al.,1994;Dong and Chen, 2002).These inorganic particles have a number of ad-vantages over organic ones,in the sense that they are not usually subjected to microbial attack and exhibit ?Corresponding author.Tel.:+91117257995;
fax:+91117256593.
E-mail address:maitraan@yahoo.co.in(A.Maitra).excellent storage stability.They can be prepared at low temperature and are relatively inexpensive.These inorganic compounds have been explored in various biomedical applications such as adjuvant for vacci-nation process,component in dental hygiene agents, carriers for various proteins and other growth factors, drug delivery and gene therapy vectors(Frey et al., 1997;Tischer et al.,2002;Kneuer et al.,2000;Luo and Saltzman,2000b;Cui and Mumper,2003).Of these inorganic compounds,the most commonly used salt is calcium phosphate whose microparticles and nanopar-ticles have been developed as delivery system as well as adjuvant for DNA vaccines(He et al.,2000,2002).Cal-
0378-5173/$–see front matter?2004Elsevier B.V.All rights reserved. doi:10.1016/j.ijpharm.2004.07.035
158S.Bisht et al./International Journal of Pharmaceutics288(2005)157–168
cium ions are known to form ionic complexes with the helical phosphates of DNA and these complexes have easy transportability across the cell membrane via ion-channel mediated endocytosis(Truong-Le et al.,1999). Although the use of precipitated calcium phosphate for in vitro transfection(James and Grosveld,1987)is a routine laboratory procedure,the method is hampered by the dif?culty of applying it to in vivo studies,espe-cially delivery of DNA to any particular cell type.Due to bulk precipitation of calcium phosphate,the method also suffers from variation in calcium phosphate-DNA particle size that causes variation among experiments (Luo and Saltzmann,2000).
In the use of different types of cationic liposome (Hirko et al.,2003;Kawakami et al.,2002;Audouy et al.,2002),cationic polymers and dendrimers(Chonn and Cullis,1998;Maurer et al.,1999;Han et al.,2000; Hashida et al.,2001)as non-viral vectors for delivery of genes,it has been observed that,in addition to cytotox-icity,these carriers do not lead to satisfactory amount of gene expression in the cells.The reasons are many, particularly,low endosomal escape,no protection of DNA from nuclease degradation and inef?cient nuclear uptake(Orrantia and Chang,1990).It was envisaged that the use of inorganic nanoparticles,a largely unex-plored synthetic system that could be used as vectors for gene delivery,might eliminate many of these limita-tions.The phosphate salts of Ca2+,Mg2+,Mn2+,Ba2+, etc.have never been explored as non-viral vectors for gene delivery although some works have been reported on the in vitro use of silica nanoparticles(Luo et al., 2004;Chen et al.,2003)inorganic nanorods(Salem et al.,2003),nanotubes(Sameti et al.,2003)and other inorganic compounds(Xiang et al.,2003).
Based on this idea we have recently reported the use of plasmid DNA(pDNA)encapsulated in calcium phosphate nanoparticles as DNA delivery carriers and have speci?cally targeted these particles to liver cells after appropriate surface modi?cation(Roy et al.,2003, Maitra et al.,2003;Bhakta et al.,2003).Although the pDNA entrapped in these nanoparticles was highly pro-tected from enzymatic degradation,the transfection ef-?ciency of these synthetic systems was found to be about80%of that exhibited by superfect.As prolonged ultra-sonication was a prerequisite for re-dispersion of these particles in aqueous buffer,it was envisaged that perhaps partial disintegration of DNA molecules might be a plausible reason for lower transfection ef?ciency.The probable loss of pDNA,therefore,led us to mod-ify the preparative method in which the ultrasonication was completely avoided to enhance the ef?ciency of the transfection process.
In this paper we report an optimized method of preparation and a more detailed physicochemical characterization including the in vitro transfection studies of calcium phosphate nanoparticles.These pDNA-loaded nanoparticles have been characterized by their size,surface morphology,crystal structure, surface charge,aggregational behaviour and pH dependent pDNA release.We have also reported that by following the soft preparative method(by avoiding ultrasonication),much-improved in vitro transfection ef?ciency of these particles in HeLa cell lines using pSV?gal as a marker plasmid,has been observed. 2.Experimental
2.1.Materials
Surfactant,Aerosol OT(or AOT),i.e.bis(2-ethylhexyl)sulphosuccinate,of analytical grade,was obtained as a99%pure product from Sigma,USA.n-Hexane(AR grade),was purchased from SRL(India). Analytical grade agarose,calcium chloride,disodium hydrogen phosphate,gel-loading dye(bromophenol blue),ethidium bromide were procured from ACROS (USA).Fetal calf serum(FCS)was purchased from Sigma-Aldrich(USA).Cell culture media(DMEM), antibiotics penicillin,streptomycin and amphotericin B were obtained from Genetix,India.X-Gal was pur-chased from Genei,Bangalore,(India).All other chem-icals used were of the high purity grade commercially available from the local market.pUC19,pSV?gal and pEGFP-N1(expressing GFP protein)were extracted and puri?ed in the laboratory of Dr Daman Saluja of ACBR,Delhi University.Transfection studies were un-dertaken in the tissue culture unit of Prof D.Sarkar of Department of Biochemistry,University of Delhi South Campus using HeLa cell lines,which were gifted by Prof Sarkar.
2.2.Plasmid isolation by alkaline lysis method
Plasmid isolation was done using alkaline lysis method(Sambrook and Russell,2001).The detailed
S.Bisht et al./International Journal of Pharmaceutics288(2005)157–168159
method is as follows:1–5ml culture was centrifuged at10,000rpm for5min at4?C.Alkaline lysis of pel-leted cells was carried out,followed by treatment of the cell lysate with potassium acetate solution.After incubation in ice for5min,the lysed cells were cen-trifuged at10,000rpm for5min at4?C.Five hundred microlitres of1:1(v/v)of phenol and chloroform mix-ture was added to the supernatant,mixed thoroughly and centrifuged at10,000rpm for5min at4?C.To 500?l of this mixture,500?l of isopropanol was added and centrifuged at10,000rpm for5min at4?C.Pellet containing DNA was washed twice with70%ethanol and dried in air.The pellet was dissolved in Tris–EDTA buffer followed by RNase treatment.
2.3.Preparation of pUC19,pSV?gal and
pEGFP-N1DNA loaded calcium phosphate nanoparticles
The basic method of preparation of pDNA loaded nanoparticles of calcium phosphate is similar to that re-ported in our earlier communication(Roy et al.,2003), but with some modi?cations.More speci?cally the de-tails of the method is as follows:0.1M AOT solution in hexane was prepared.In25ml of AOT in hexane, 70?l aqueous solution of1.36M calcium chloride and aqueous solution of2.94?g of pDNA,were added by continuous stirring for12h to form microemulsion A.In another25ml of AOT solution,50?l of0.2M Tris–HCl buffer(pH7.4),70?l aqueous solution of 0.35M Na2HPO4and aqueous solution of2.94?g of pDNA,were dissolved by continuous stirring for12h to form microemulsion B.Before stirring both the mi-croemulsions,excess water was added to make total volume of water to450?l,to adjust w o,i.e.the molar ratio of water to AOT at10.Both the microemulsions were optically clear solutions.Microemulsion B was, then,added to microemulsion A at an extremely slow rate(20drops per min)with continuous stirring at4?C. The resulting solution was,then,further stirred for an-other12h in the above cold condition.Development of translucency indicated the nanoparticle formation in the aqueous core of the microemulsion droplets.Hex-ane was completely removed from the resulting solu-tion,and the nanoparticles containing the solid mass of AOT was dissolved in10ml of absolute ethanol (99.9%)by vortexing.The solutions were centrifuged for half an hour at8000rpm at4?C in a cold centrifuge (Sigma3K18).The pelleted nanoparticles were washed with absolute ethanol three times.Finally,the pelleted nanoparticles were dispersed in double distilled water at4?C by vortexing to give clear dispersion.The dis-persed nanoparticles were dialysed overnight in a cold room using12kD dialysis membrane bag,and were lyophilized to dry powder(yield～1mg)for further characterization.
2.4.Size and morphology of the nanoparticles
2.4.1.Dynamic light scattering(DLS)
In aqueous dispersion,these particles aggregate very rapidly to form the bigger particles.Therefore,the size of the primary particles formed within the aqueous core of microemulsion droplets were determined by DLS experiment.
The measurements were done with a Brookhaven BI8000instrument?tted with a BI200SM goniome-ter.An argon-ion air-cooled laser was operated at 488nm as a light source and the measurements were done on a scattering angle of90?.The time de-pendent autocorrelation function was derived using a128-channel digital photon correlator.The particle size was calculated from the autocorrelation function using Stokes–Einstein equation:d=kt/3?ηD,where D=translational diffusion coef?cient,d=particle di-ameter,η=viscosity of the liquid in which parti-cles were suspended,k=Boltzmann’s constant and T=absolute temperature.The particle size of calcium phosphate nanoparticles dispersed in aqueous buffer as well as the size of the aggregated nanoparticles were also measured by DLS.
2.4.2.Transmission electron microscopy(TEM)
One drop of the aqueous dispersion of nanoparti-cles followed by one drop of1%phosphotungstic acid were put on a forvmar coated copper grid(1%solution of forvmar was prepared in spectroscopic grade chlo-roform)and air dried in a vacuum desiccator.The dried grid was then examined under an electron microscope (JEOL JEM2000EX200model).
2.5.X-ray diffractogram(XRD)of nanoparticles
The X-ray source used was Cu K?radiation at 40kV and20mA,and diffraction was analyzed with a PHILIPS PW3710diffractometer.0.2g of lyophilized
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nanoparticles was put inside the diffractometer for analysis.
2.6.Determination of plasmid loading capacity
In order to determine the maximum loading in cal-cium phosphate nanoparticles,different amounts of pUC19DNA,(from3to9.0?g)were added in the microemulsions at the time of preparation of nanopar-ticles,keeping the total amount of metal ion and phos-phate ion concentrations same for all the cases.These nanoparticles dispersed in water were then subjected to gel electrophoresis.After saturated loading,the excess pDNA remained as unentrapped free pDNA in aqueous buffer,which was visible as distinct bands in the gel.
2.7.Entrapment ef?ciency(E%)
The pDNA-loaded nanoparticles in reverse micelles were separated after ultra centrifugation(40×103rpm for4h at4?C)and the pellets after washing with hexane was dissolved in acidic buffer(pH=3.0).The amount of pDNA released,[pDNA]r from the nanopar-ticles was estimated spectrophotometrically by mea-suring the OD atλ=260nm.The entrapment ef?ciency was then calculated from the amount of pDNA origi-nally added in the microemulsion,([pDNA]0),using the equation E%=[pDNA]r/[pDNA]0×100.
2.8.Gel electrophoresis experiments
One percent Agarose gel was used for elec-trophoresis experiments.The entrapment of DNA in the nanoparticles,its protection from external Dnase degradation and the pH dependent release of pDNA from these nanoparticles were investigated by gel elec-trophoresis.In each set of100?l of aqueous buffers (pH=5and8),5mg of lyophilized pSV?gal loaded calcium phosphate nanoparticles was dispersed and the mixtures were incubated at37?C for speci?c time in-tervals(0,1,2,4and24h).Twenty microlitre of the sample was removed from each mixture,loaded in the well and was subjected to electrophoresis.
2.9.Confocal microscopy
HeLa cells preparations were observed with a laser scanning confocal microscope(Biorad206Confocal Microscope).The microscope settings were as follows: excitation at488nm,emission at507nm/30BP into channel1to record GFP?uorescence,63×1.4NA oil-immersion lens at an Airy disc setting of0.9.When necessary,serial images were taken,with1.2?m steps to get an overall image of?uorescent objects within the cell.The experiments were done at the Department of Pathology,All India Institute of Medical Sciences, New Delhi.
2.10.In vitro transfection studies in HeLa cell line
For in vitro studies,HeLa cell line were trans-fected with free form as well as encapsulated plasmid, pSV?gal.For these studies,HeLa cell lines were grown in DMEM medium containing10%fetal calf serum, antifungal drug,Amphotericin B and1.6%(w/v)peni-cillin and streptomycin solutions.Twelve well plates were seeded with1×105cells per well,after check-ing for cell viability using trypan blue exclusion,and appropriate dilution.Cells were grown under standard conditions for24h till80%con?uency.1ml of aque-ous dispersion of pDNA loaded calcium phosphate nanoparticles(total amount of pDNA=588ng)was added in each well.After an appropriate time inter-val of4h,the added material was replaced with fresh medium containing10%(v/v)FCS and antibiotics,and incubated for another36h.After36h,cells were lysed with200?l of lysis buffer(pH7.4)containing250mM Tris–HCl and0.5%Triton X-100.Ten microlitres of X-Gal solution was added to each well and the reaction was continued for another36h.The reaction was,then, stopped by the addition of50?l of1M sodium carbon-ate solution.The blue colour developed was measured spectrophotometrically atλmax=616nm and the quan-tity of?-galactosidase produced were calculated from a calibration curve(amount of?-galactosidase versus OD at616nm).
3.Results and discussion
Nanoparticles encapsulating pDNA were formed in the aqueous core of the AOT microemulsion in hexane. The strategy involved the precipitation of the calcium phosphate in the presence of pDNA in the aqueous core of the microemulsion droplets.A?ow chart of the preparative method adopted is represented by Fig.1.
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Fig.1.Flowchart for the preparation of pDNA loaded calcium phosphate nanoparticles.
The centrifuged pellets could be easily redispersed in aqueous buffer.The maximum amount of pDNA, which could be loaded into the nanoparticles,was checked by preparing samples with different amount of pDNA and?nally subjecting the aqueous dispersions of these particles to electrophoresis on1%agarose gel.It was clearly observed that5.88?g of pDNA per mg of calcium phosphate could be easily loaded in the nanoparticles.To measure the entrapment ef?ciency of calcium phosphate nanoparticles,1mg of pUC19 loaded nanoparticles was dissolved in pH=3.0buffer by overnight incubation and the amount of pDNA released was estimated spectrophotometrically at 260nm and the entrapment ef?ciency(E%)was found to be more than99%.
The physiochemical characteristics and the aggrega-tion behaviour of the calcium phosphate particles were studied using DLS,TEM and X-Ray diffractometry. The size of the nanoparticles formed was found to be dependent on w o values(i.e.the molar ratio of water to AOT).The mean size distribution of calcium phosphate nanoparticles while dispersed in microemulsuion at w o=10was in the range of30–40nm.Fig.2is a repre-sentative size distribution pro?le of calcium phosphate nanoparticles encapsulating pSV?gal in AOT mi-croemulsion.The particle size,while dispersed in mi-
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Fig.2.Representative DLS of pDNA loaded calcium phosphate nanoparticles in microemulsion.
croemulsion,depends,however,on the time of stirring.Instead of 12h of stirring as reported in the present pro-tocol,if the microemulsion was stirred for 24–36h,the particle size was found to be increased from 30–40nm to about 80–90nm diameter.The size of the particles in aqueous dispersion was also measured and it was found to be in the range of about 100–130nm diameter.The time dependent size measurement studies at 20?C (Fig.3)clearly indicated that the particles aggregated rapidly with time (more than 100nm jump after 24h)thus leading to the bigger size of the
particles.
Fig.3.Time dependent aggregation studies of pDNA loaded calcium phosphate nanoparticles in aqueous medium at 20?C.
The transmission electron micrographs of pUC 19loaded calcium phosphate nanoparticles (Fig.4a)and void calcium phosphate nanoparticles (Fig.4b)re-vealed the formation of dense particles with spherical morphology.
The surface charge of calcium phosphate nanoparti-cles was determined by measuring the zeta potential in the pH range between 6.0and 10.0.The pH dependent zeta potential as shown in Fig.5indicated that the par-ticles were positively charged in neutral aqueous buffer and were turned negatively charged in strongly alkaline solution above pH ～9.5.
The crystallinity of the calcium phosphate nanopar-ticles was studied by means of an X-ray powder diffractometry.Fig.6a and b show the diffraction patterns of pUC19encapsulated as well as void calcium phosphate nanoparticles respectively.The diffractograms obtained for void and DNA loaded particles indicated the formation of hydroxyapatite [Ca 10(PO 4)6(OH)2]crystals as evidenced from the characteristic peak at 2θ=31.8degree (Shimabayashi et al.,1995).
One of the primary reasons for the low transfection ef?ciency obtained with non-viral vectors,including the precipitated bulk calcium phosphate is the incom-plete protection of the plasmid DNA by the encapsulat-ing material.Such partial protection makes the DNA highly susceptible to aggressive DNase attack in the body as well as inside the cell.In order to check the level of protection being offered to the encapsulated DNA,we subjected the calcium phosphate nanoparticles to extensive DNase treatment followed by electrophore-sis on 1%agarose gel (Fig.7).We found that while free plasmid DNA (pUC 19)moved at its usual posi-tion in the gel,pUC19encapsulated in the matrix of the nanoparticle was right at the top of the gel and hardly moved.Moreover,while free pDNA was completely digested by DNase treatment,encapsulated plasmid was totally protected.As expected,this was quite con-trary to the plasmid DNA adsorbed on the surface of the nanoparticles.In this case,we found that the level of protection offered to the DNA was extremely low and the DNA was highly prone to nearly total degrada-tion by DNase.These results clearly demonstrated that DNA was completely encapsulated in the rigid matrix of the calcium phosphate nanoparticles,which enabled the particles to protect the nucleic acid from external DNase environment.
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Fig.4.Transmission electron micrographs of(a)pDNA loaded and(b)void calcium phosphate nanoparticles.
The primary purpose of using carriers for gene de-livery is to protect and transport the genetic material into the cell,and ultimately into the nuclear compart-ment avoiding intracellular degradation.But,most non-viral vectors are known to internalize into the cells by endocytosis,and this endocytic uptake of particulate carriers,leads to ultimate transport of the vesicles to the lysosomal compartment,where subsequent degra-dation of the particles as well as the encapsulated DNA takes place.Thus,as has been previously indicated by several workers(Cifti and Levy,2001;Wagner,1998; Zauner et al.,1998),low transfection ef?ciency of non-viral vectors may be due to the intracellular degrada-tion of input DNA in the endosomes and/or lysosomes. Also,according to them,DNA degradation can be in-hibited either by inactivating the lysosomal
enzymes Fig.5.pH Dependent zeta potential of calcium phosphate nanoparticles dispersed in aqueous buffers.
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Fig.6.Powder XRD patterns for(a)pDNA loaded and(b)void calcium phosphate nanoparticles.
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Fig.7.Agarose(1%)gel electrophoresis of free,entrapped and ad-sorbed https://www.doczj.com/doc/9d7780914.html,ne1:?DNA digested with Hin dIII enzyme. Lane2:Free https://www.doczj.com/doc/9d7780914.html,ne3pUC19DNA treated with https://www.doczj.com/doc/9d7780914.html,ne4:calcium phosphate nanoparticles containing entrapped https://www.doczj.com/doc/9d7780914.html,ne5:calcium phosphate nanoparticles containing entrapped pUC19treated with https://www.doczj.com/doc/9d7780914.html,ne6:pUC19DNA ad-sorbed on void calcium phosphate https://www.doczj.com/doc/9d7780914.html,ne7:pUC19 DNA adsorbed on void calcium phosphate nanoparticles and then treated with DnaseI.
or obliterating endosome fusion to lysosomes using lysosomotropic agents.Further,prevention of DNA de-struction is also dependent on its release from the endo-somal compartment prior to fusion of the endosome and the lysosome.Upon internalization,endosomal com-partments undergo continuous acidi?cation from the initial cell-surface pH(～7)ultimately to that found in the lysosomes through the action of ATP-dependent proton pumps acting in conjunction with other ion transporters found in the membranes.Ideally,the entire delivered vector should escape from the endosome be-fore degradation along the traf?cking route,either by vector fusion with the endosomal membrane or through endosome disruption,in either event,ultimately result-ing in the release of the nucleic acid(with or without the protective vehicle)into the cytosol(Varga et al.,2000). It is envisaged that the dissolution of inorganic nanopar-ticles in the acidic endosomal compartment may lead to an osmotic disbalance and consequent disruption of the endosomal compartment so that DNA can come out in the cytosol.Ca2+in the form of nascent calcium phosphate microprecipitates and other lysosomolyti-cal agents facilitate endosomal/lysosomal release by their fusigenic and membranolytic activity(Haberland et al.,1999;Haberland et al.,2000).Therefore,keep-ing in mind the endosomal pH(5.0–5.5)and to assess the possible release pro?le of pDNA from the calcium phosphate nanoparticles,pSV?gal release was visual-ized using agarose gel electrophoresis following incu-bation of the loaded particles in buffers(pH=5and 8)for varied time intervals(Fig.8).From the gel pic-ture it is apparent that at pH=5,there is no release of pSV?gal from calcium phosphate nanoparticles at zero hours but the release was observed at2,4and24h.On the other hand there was no release of the plasmid from the nanoparticles at pH=8even after24h.The super-coiled DNA(sc DNA)and double stranded DNA(ds DNA)were the most active and stable forms of the DNA released from the nanoparticles.Electrophore-sis in an agarose gel permitted the identi?cation of the supercoiled,open circular and the linear forms of the DNA.Interestingly the supercoiled form was clearly observed in the released DNA even after incubation in acidic pH for24h(Fig.8).Although,previously it has been reported(Walter et al.,1999;Tinsley-Brown et al.,2000),that plasmid DNA was greatly damaged at acidic pH,our observations indicated to the contrary. Thus,the stabilization of the plasmid in the nanopar-ticles has also been addressed with the observation of plasmid release in the supercoiled form.
The endosomal escape as well as nuclear uptake of the plasmid and subsequent expression had been observed in vitro through confocal microscopy.In the present study,we observed the pathway of FITC-dextran in cytosol after endosomal escape in the whole cell based on the Z-series images sequentially obtained by confocal laser scanning microscopy.FITC-dextran loaded calcium phosphate nanoparticles were added in vitro to HeLa cells and within four hours of addition, the green?uorescence due to FITC,in the entire cy-tosolic region of the cell was observed(Fig.9a).The plasmid expressing GFP encapsulated in calcium phos-phate nanoparticles was also added in vitro to HeLa
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Fig.8.Agarose(1%)gel electrophoresis to show DNA release at(a)pH5.0and(b)https://www.doczj.com/doc/9d7780914.html,ne1(in a and b):?DNA digested with Hin dIII https://www.doczj.com/doc/9d7780914.html,ne2(in a and b):free pSV?gal https://www.doczj.com/doc/9d7780914.html,ne3–7(in a and b):DNA released on incubation at37?C from calcium phosphate nanoparticles after0,1,2,4and24h.
Fig.9.(a)Fluorescence picture of FITC-Dx loaded calcium phosphate nanoparticles incubated with HeLa cells.The picture was taken4h after the addition of nanoparticles.(b–d)Time dependent pEGFP-N1expression in HeLa cells(b)12h,(c)20h and(d)24h.
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Fig.10.In vitro transfection studies in HeLa cell-line. cells and the expression was seen.It was observed (Fig.9b–d)that,in the initial12h,there was practi-cally no GFP expression.But after12h of incubation the green?uorescence appeared which increased with time indicating more and more of expression of the plasmid.
To estimate the transfection ef?ciency on mam-malian cells using these nanoparticles,Hela was se-lected and pSV?gal was chosen as a marker DNA.For comparing the extent of transfection a standard labora-tory transfecting reagent,Polyfect(a polyamidoamine dendrimer),was used.From the results(Fig.10),it could be seen that the calcium phosphate nanoparticles showed higher transfection ef?ciency than exhibited by Polyfect.Considering that Polyfect is a highly compe-tent vector used for in vitro transfection(Tang et al., 1996),our results indicate that under in vitro condi-tions calcium phosphate nanoparticles are more effec-tive as non-viral vectors than Polyfect.In our previous communication(Roy et al.,2003)the transfection ef-?ciency of calcium phosphate nanoparticles was noted to be less as compared to that of the Polyfect reagent. The reason could be attributed,besides others,to the partial degradation of DNA due to ultrasonication. 4.Conclusion
Calcium phosphate nanoparticles encapsulating dif-ferent plasmids were prepared and characterized.The size dependent studies of these particles clearly showed the high tendency to aggregation resulting in their larger size.The plasmid DNA was well protected in-side these nanoparticles and these particles were easily dissolved in mild acidic environment releasing DNA. In vitro transfection studies indicated that the transfec-tion ef?ciency of these carriers was as high as Polyfect, a commercially available transfecting reagent.We pre-sume that these calcium phosphate nanoparticles have well-de?ned role in DNA delivery so far as endosomal escape,protection against nuclease degradation and nu-clear uptake are concerned and,therefore,can be used as an effective non-viral vector in gene therapy. Acknowledgements
The authors thank the Department of Science and Technology,Government of India for?nancial assis-tance in the form of a research project.Thanks are also due to Prof D.Sarkar,Department of Biochem-istry,University of Delhi South Campus for allowing us to use his tissue culture facility.We thank Dr Daman Saluja of Ambedkar Centre of Biomedical Research (ACBR),Delhi University,for providing us facilities for extraction and puri?cation of plasmids and Prof.
A.K.Dinda of AIIMS,New Delhi for assisting in con-focal microscopic studies.
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化学与化学工程学院 设计实验报告 姓名文万强李银旭学号20113942 20113918 专业化学工程与工艺班级11级工艺2班 同组设计人员 实验课程名称有机化学实验 设计实验名称鸡蛋壳制备丙酸钙 实验日期2012-05-15 批阅日期 成绩教师签名 化学与化学工程学院
鸡蛋壳制备丙酸钙 摘要 本实验是一种探究利用鸡蛋壳制备丙酸钙简单的方法，随着人民生活水平的提高和食品工业的发展, 鸡蛋的消耗量大幅度增加，但是大量蛋壳却被废弃,因此如何利用这些废弃资源将其变废为宝就成为当今“绿色化学”的走向，而丙酸钙是近几年发展起来的一种新型食品加剂,其毒性远低于我国广泛应用的苯甲酸钠,被认为是食品的正常成分,也是人体内代谢的中间产物加之又较山梨酸钾便宜得多,故可在食品中较多地添加,可延长食品保鲜期,防止食物中毒。丙酸钙不仅对人体无毒、无副作用, 而且还有抑制产生黄曲霉素的作用, 其防腐作用良好, 可广泛用于面包、糕点等食品的防腐，在人的饮食结构中添加少量的丙酸钙可以减少肝癌的发病率。起抑制作用的是丙酸，且丙酸为人体代谢产物之一，不会对人体造成危害。因此，此研究也成了当今热点的研究方向，我们探究这方面也主要是围绕在前人的基础上就如何利用不同的方式，以便能使产率达到最优。 设计（或研究）的依据与意义 近几年来, 随着人民生活水平的提高和食品工业的发展, 鸡蛋的消耗量大幅度增加。由于人们仅利用了可食的蛋清和蛋黄部分, 而大量蛋壳却被废弃, 特别是蛋粉厂和蛋类制品加工厂, 每天都要产生成吨的蛋壳, 对环境造成很大污染。据联合国粮农组织统计，2003年我国鸡蛋总产量为2233．2万t，占世界鸡蛋总产量的40％，我国每年大约产生300万t的蛋壳垃圾。而现在随着人们的生活水平的进一步提高，鸡蛋消费也会进一步增加，必然会产生更多的鸡蛋壳垃圾，而大量的蛋壳垃圾在自然状态下很难被分解。造成了垃圾处理困难以及废弃资源的浪费。然而蛋壳中含93%的CaCO3, 1.0%的MgCO3, 2.8%的Mg3 (PO4)2 和3.2%的有机物, 如以蛋壳为主要原料, 加入丙酸生产丙酸钙, 既可节省资源, 降低成本, 又可解决蛋壳对环境所造成的污染。 丙酸钙是近几年发展起来的一种新型食品加剂,其毒性远低于我国广泛应用的苯甲酸钠,被认为是食品的正常成分,也是人体内代谢的中间产物加之又较山
硅钙板吊顶安装施工方案 一、材料准备 轻钢龙骨、配件、吊杆、膨胀螺栓、硅钙板等，进场检验合格，有出厂合格证及材料质量证明。 二、机具准备 型材切割机、电动曲线锯、手电钻、电锤、自攻螺钉钻、手提电动砂纸机等。 三、作业条件 1 在所要吊顶的范围内，机电安装均已施工完毕，各种管线均已试压合格，已经过隐蔽验收。 2 已确定灯位、通风口及各种照明孔口的位置。 3 顶棚罩面板安装前，应作完墙、地湿作业工程项目。 4 搭好顶棚施工操作平台架子。 5 轻钢骨架顶棚在大面积施工前，应做样板，对顶棚的起拱度、灯糟、窗帘盒、通风口等处进行构造处理，经鉴定后再大面积施工。 四、施工工艺 1 工艺流程 弹标高水平、划分龙骨分档线→固定吊杆挂件→安装边龙骨→安装主龙骨→安装大龙骨→安装次龙骨→罩面板安装 2 弹标高水平、划分龙骨分档线：用水准仪在房间内每个墙角上抄出水平点（若墙体较长，中间也应适当抄出几点）弹出水准线，从水准备线量至吊顶高度：3800mm，用粉线沿墙弹出吊顶次龙骨的下皮线。同时，按吊顶平面图，在混凝土顶板弱出主龙骨的位置线。主龙骨宜平行房间长向布置，一般从吊顶中心向两边分。主龙骨及吊杆间距为1000mm。如遇到梁和管道固定点大于1000ｍｍ，增加吊杆固定点，且用5#角钢加强，间距2米。 3 固定吊挂杆件：采用膨胀螺栓固定吊挂件。吊杆采用10号镀锌低碳钢丝吊杆，并设置反向支撑，反向支撑采用5#角钢，间距3米-4米。吊杆用膨胀螺栓固定在楼板上，用冲击电锤打孔，孔径应稍大于膨胀螺栓的直径。吊杆距主龙骨端部距离不得超过300mm，否则应增加吊杆。灯具、风口、及检修口等应设附加吊杆。大于3kg的重型灯具、电扇及其他重型设备严禁安装在吊顶工程的龙骨上，应另设吊挂件与结构连接。 4 安装边龙骨：边龙骨安装应按设计标高要求弹线，采用L形镀锌次龙骨立放，砖砌墙用自攻螺丝固定在预埋的木楔子上，木楔子应做防腐处理，如为混凝土墙面可用射钉固定，射钉间距不应大于吊顶次龙骨间距。 5 安装主龙骨：主龙骨用CB38主龙骨，间距为1000mm。主龙骨应起拱，起拱高度为房间短向跨度的1/500。主龙骨的接头应采用对接，相邻龙骨的对接接头要相互错开。主龙骨挂好后应调平。；走廊内主龙骨沿走廊短方向排布。 6 安装次龙骨：次龙骨采用TB24*38轻钢龙骨，间距为60mm，次龙骨应紧贴主龙骨。用
石膏检测石膏成分检测 一：石膏（003） 石膏是单斜晶系矿物，主要化学成分是硫酸钙（CaSO4）。石膏是一种用途广泛的工业材料和建筑材料。可用于水泥缓凝剂、石膏建筑制品、模型制作、医用食品添加剂、硫酸生产、纸张填料、油漆填料等。 二：石膏的主要化学成分 CaO 32.5，SO3 46.6，H2O+ 20.9。成分变化不大。常有粘土、有机质等机械混入物。有时含SiO2、Al2O3、Fe2O3、MgO、Na2O、CO2、Cl等杂质。 三：主要检测产品 石膏粉：磷石膏粉、脱硫石膏粉、柠檬酸石膏粉和氟石膏粉 石膏板：纸面石膏板、装饰石膏板、石膏空心条板、纤维石膏板、石膏吸音板、定位点石膏板 其他：生石膏，石膏纤维，石膏线，石膏砌块等。 四：主要检测项目 含量分析：含固体含量、硫酸钙含量、不挥发物含量、其他杂质含量 成分配比 物理性质：硬度、灰分、粘度、细度、粒度、挥发分、比重、比表面积、熔点、回粘性、光泽、吸水率、凝结时间、尺寸偏差和表面质量等； 力学性能:抗拉强度、脆性、弯曲试验、拉伸试验、耐冲击性等 化学性能：耐水性、耐久性、耐酸碱性、耐腐蚀性、耐候性、耐热性等。 防火性能：耐燃烧时间、火焰传播比值、质量损失、炭化体积 其他参数：隔音性能等。 五：部分检测标准 JC/T 517-2004 粉刷石膏 GB/T 9776-2008建筑石膏 GB/T 5483-2008 天然石膏 GB/T 5484-2012 石膏化学分析方法 GB/T 9775-2008 纸面石膏板 GB/T 9776-2008 建筑石膏 GB/T 5463.3-2013 非金属矿产品词汇第3部分：石膏
科标无机检测中心可提供专业石膏检测，可依据依照ASTM、ISO、EN、JIS等国际标准和GB国家标准对石膏产品进行相关的分析测试服务。
轻钢龙骨石膏板吊顶施工工艺 1）、工艺流程 弹顶棚标高水平线→划龙骨分档线→专业管线安装→安装主龙骨→安装次龙骨→安装罩面板 2）、弹顶棚标高水平线，根据设计标高在各楼层的四周墙上弹水平控制线，弹线应清晰、准确。 3）、划龙骨分档线，按设计要求的主、次龙骨间距在已弹好的顶棚标高水平线上划龙骨分档线。 4）、安装主龙骨吊杆：为保证骨架的稳定，采用膨胀螺栓固定小角钢，角钢上焊Φ6吊杆。在弹好顶棚标高水平线及龙骨分档线后，确定吊杆下端头的标高，按主龙骨位置及吊杆间距固定吊杆，吊杆另一端焊Φ6螺栓丝杆，吊杆位置长度要准确适宜。吊杆不与专业管道接触。吊杆与专业管道发生冲突时，用型钢支架过渡。5）、龙骨安装：采用 50型龙骨或烤漆龙骨，龙骨中部起拱高度按房间短方向距离在1/200-1/300之间。主龙骨安装好后拉线校正，再安装次龙骨，次龙骨分档
必须按图纸要求进行，四边龙骨贴墙边，所有卡扣，配件位置要准确牢固。主龙骨悬挑端不大于300mm，主龙骨与专业管道和大型灯饰发生冲突时，先将主龙骨断开，再用型钢加固，必要时附加主龙骨。 6）、面层安装：龙骨安装完毕后让专业施工的管线安装完毕后再进 行面层的施工。面层为纸面石膏板或矿棉板，面层必须与龙骨连接牢固，平整，缝隙均匀、正确，各种留洞留设正确。 7）、刷防锈漆：轻钢骨架未做防腐处理的表面，如吊挂件、连接件、钉固附件等，在各工序安装前须刷防锈漆。 8）、与水、电、风等专业的配合： 吊顶工程是与水、电、风等专业交叉较多的施工项目之一，如果配合不好将不仅影响工程进度，而且还会造成材料浪费，所以必须协调好二者的关系。 首先吊顶施工必须在水管试压、保温，电管铺设、穿线完毕及风道安装，风机、调试完毕后进行。 电专业安装灯具及其它专业维修吊顶内的设施时必须有吊顶专业人员陪同，以免损坏或污染罩面板。
硅钙板吊顶施工工艺及措施 一、施工准备 （一）作业条件 1、在所要吊顶的范围内，机电安装均已施工完毕，各种管线均已试压合格，已经隐蔽验收。 2、已确定灯位、通风口及各种照明孔口的位置。 3、顶棚罩面板安装前，应作完墙、地湿作业工程项目。 4、搭好顶棚施工操作平台架子。 5、轻钢骨架顶棚在大面积施工前，应做样板，对顶棚的起拱度、灯槽、窗帘盒、通风口等处进行构造处理，经鉴定后再大面积施工。 （二）材料准备 1、轻钢龙骨采用T 形龙骨，不上人。 2、轻钢骨架主件为中、小龙骨；配件有吊挂件、连接件、插接件。 3、零配件：通丝吊杆、膨胀螺栓、自攻螺钉、电焊机、双螺帽。 4、罩面板采用硅钙板。 5、所有材料进场检验合格且有出厂质量证明文件。 （三）施工机具 1、型材切割机、电动曲线锯、手电钻、电锤、自攻螺钉钻等。 二、操作工艺 （一）工艺流程 1、弹标高线一打孔下胀栓一安装主龙骨吊杆T安装烤漆主龙骨一安装烤漆副龙骨T 调平一安装硅钙板一装饰面清理 （二）主要操作工艺 1、弹线：根据设计标高，沿墙四周弹顶棚标高水平线，并沿水平标高线在墙四周画出龙骨分档位置线。其水平允许偏差± 5mm。 2、打孔下胀栓安装主龙骨吊杆，首先确定吊杆下端标高，安装吊杆，间距900—1200mm吊点分布均匀。 3、安装主龙骨、主龙骨间距900—1200mm主龙骨用配套的吊件安装，吊杆距主龙
骨边缘不大于300mm。 4、安装烤漆主龙骨、主龙骨间距为600mm烤漆主龙骨和吊杆之间用专用的吊件连接，安装后，整体调平。 5、安装烤漆副龙骨，副龙骨安装在烤漆主龙骨上，安装完后，拉通线整体调平。中间起拱高度按短向距离的1/200 起拱。 6、龙骨验收合格后安装硅钙板。硅钙板安装完成后需要进行板面清理。 三、质量要求： （一）主控项目 1、吊顶标高、尺寸、起拱和造型应符合设计要求。检验方法：观察；尺量检查。 2、饰面材料的材质、品种、规格、图案和颜色应符合设计要求。当饰面材料为玻璃板时，应使用安全玻璃或采取可靠的安全措施。检验方法：观察；检查产品合格证书、性能检测报告和进场验收记录。 3、饰面材料的安装应稳固严密。饰面材料与龙骨的搭接宽度应大于龙骨受力面宽度 的2/3 。 检验方法：观察；手扳检查；尺量检查。 4、吊杆、龙骨的材质、规格、安装间距及连接方式应符合设计要求。金属吊杆、龙骨应进行表面防腐处理；木龙骨应进行防腐、防火处理。检验方法：观察；尺量检查；检查产品合格证书进场验收记录和隐蔽工程验收记录。 5、明龙骨吊顶工程的吊杆和龙骨安装必须牢固。检验方法：手扳检查；检查隐蔽工程验收记录和施工记录。 （二）一般项目 1、饰面材料表面应洁净、色泽一致，不得有翘曲、裂缝及缺损。饰面板与明龙骨的搭接应平整、吻合，压条应平直、宽窄一致。检验方法：观察；尺量检查。 2、饰面板上的灯具、烟感器、喷淋头、风口篦子等设备的位置应合理、美观，与饰面板的交接应吻合、严密。检验方法：观察。 3、金属龙骨的接缝应平整、吻合、颜色一致、不得有划伤、擦伤等表面缺陷。木质
FYYYWYD00127 煅石膏 硫酸钙的测定 络合滴定法 F-YY -YW-YD-00127 煅石膏－－硫酸钙的测定—络合滴定法 １ 范围 本方法采用滴定法测定煅石膏中硫酸钙的含量。 本方法适用于石膏的炮制品。 ２ 原理 供试品加稀盐酸，加热使溶解，加水稀释，加甲基红指示液，滴加氢氧化钾试液至溶液显浅黄色，继续多加使过量，加钙黄绿素指示剂少量，用乙二胺四醋酸二钠滴定液滴定，至溶液的黄绿色荧光消失，并显橙色。计算含水硫酸钙的量。 ３ 试剂 （除特殊注明外均为分析纯试剂） ３．１水（新沸放置至室温） ３．２稀盐酸 取盐酸２３４ｍＬ，加水稀释至１０００ｍＬ。 ３．３氢氧化钾试液 取氢氧化钾６．５ｇ，加水使溶解成１００ｍＬ。 ３．４甲基红指示液 取甲基红０．１ｇ，加０．０５ｍｏｌ／Ｌ氢氧化钠溶液７．４ｍＬ使溶解，再加水稀释至２００ｍＬ，变色范围ｐＨ（７．２－８．８）（红→黄）。 ３．５钙黄绿素指示剂 钙黄绿素指示剂 取钙黄绿素０．１ｇ，加氯化钾１０ｇ，研磨均匀。 ３．６铬黑 Ｔ指示剂 取铬黑 Ｔ ０．１ｇ，加氯化钠１０ｇ，研磨均匀。 ３．７乙二胺四醋酸二钠滴定液 配制：取乙二胺四醋酸二钠１９ｇ，加适量的水使溶解成１０００ｍＬ，摇匀。 标定：取于约８００℃灼烧至恒重的基准氧化锌０．１２ｇ，精密称定，加稀盐酸３ｍＬ使溶解，加水２５ｍＬ，加０．０２５％甲基红的乙醇溶液１滴，滴加氨试液至溶液显微黄色，加水２５ｍＬ与氨－氯化铵缓冲液（ｐＨ１０．０）１０ｍＬ，再加铬黑Ｔ指示剂少量，用本液滴定至溶液由紫色变为纯蓝色，并将测定的结果用空白试验校正。每１ｍＬ乙二胺四醋酸二钠滴定液（０．０５ｍｏｌ／Ｌ）相当于４．０６９ｍｇ的氧化锌。根据本液的消耗量与氧化锌的取用量，算出本液的浓度。 贮藏：置玻璃塞瓶中，避免与橡皮塞、橡皮管等接触。 ３．８基准氧化锌 ３．９ 氨－氯化铵缓冲液（ｐＨ １０．０） 取氯化铵５．４ｇ，加水２０ｍＬ溶解后，加浓氨溶液３５ｍＬ，再加水稀释至１００ｍＬ。 ４ 操作步骤 精密称取供试品细粉（全部通过五号筛－８０目，并含能通过六号筛－１００目不少于９５％的粉末）约０．１５ｇ， 置锥形瓶中，加稀盐酸１０ｍＬ，加热使溶解，加水１００ｍＬ与甲基红指示液１滴，滴加氢氧化钾试液显浅黄色，再继续多加５ｍＬ，加钙黄绿素指示剂少量，用乙二胺四醋酸二钠滴定液（０．０５ｍｏｌ／Ｌ）滴定，至溶液的黄绿色荧光消失，并显橙色。每１ｍＬ乙二胺四醋酸二钠滴定液（０．０５ｍｏｌ／Ｌ）相当于８．６０８ｍｇ的含水硫酸钙（ＣａＳＯ４?２Ｈ２Ｏ）。 中国分析网
石膏板吊顶施工工艺 三、石膏板吊顶施工工艺 1、施工准备 1）原材料、半成品要求木料：木龙骨料应为烘干，无扭曲的红、白松树种，并按设计要求进行防火处理。木龙骨规格按设计要求，如设计无明确规定时，大龙骨规格为50mm×70mm或50mm×100mm；小龙骨规格为50mm×50mm 或40mm×50mm；木吊杆规格为50mm×50mm或40mm×40mm。罩面板材及压条。 纸面石膏板选用时严格掌握材质及规格标准。 其它材料φ6或φ8吊筋、膨胀螺栓、射钉、圆钉、角钢、扁钢、胶粘剂、木材防腐剂、防火剂、8号镀锌铁丝、防锈漆。 2）作业条件现浇楼板中按设计间距埋设φ6或φ8吊筋。当设计未做说明时，间距一般不大于1000mm。 墙为砌体时，应根据顶棚标高，在四周墙上预埋固定龙骨的木砖。 直接接触墙体的木龙骨，应预先刷防腐剂。 按工程不同防火等级和所处环境要求，对木龙骨进行喷涂防火涂料或置于防火涂料槽内浸渍处理。
顶棚内各种管线及通风管道均已安装完毕并经验收合格。各种灯具、报警器预留位置已经明确。 墙面及楼、地面湿作业和屋面防水已做完。 室内环境力求干燥，满足木龙骨吊顶作业的环境要求。 2、施工工艺 1）抄平弹线弹线包括：标高线、顶棚造型位置线、吊挂点布局线、大中型灯位线。 确定标高线：根据室内墙上+50cm水平线，用尺量至顶棚设计标高，在该点画出高度线，用一条塑料透明软管灌满水后，将软管的一端水平面对准墙面上的高度线。再将软管的另一端头水平面，在同侧墙面找出另一点，当软管内水平面静止时，画下该点的水平面位置，再将这两点连线，即得吊顶高度水平线。用同样方法在其它墙面做出高度水平线。操作时应注意，一个房间的基准高度点只用一个，各个墙的高度线测点共用。沿墙四周弹一道墨线，这条线便是吊顶四周的水平线，其偏差不能大于5mm。 确定造型位置线：对于较规则的建筑空间，其吊顶造型位置可先在一个墙面量出竖向距离，以此画出其它墙面的水平线，即得吊顶位
酱油中山梨酸、苯甲酸含量的测定 概述：防腐剂是指能防止食品腐败、变质，抑制食品中微生物繁殖，延长食品保存期的物质，它是人类使用最悠久、最广泛的食品添加剂。 目前，我国允许使用的品种主要有苯甲酸及其钠盐、山梨酸及其钾盐、对羟基苯甲酸乙酯和丙酯、丙酸钠、丙酸钙、脱氢乙酸等。 第一部分、苯甲酸 一、实验原理：苯甲酸及苯甲酸钠在近紫外光区具有较强的吸收。通过查找资料，苯甲酸在 230nm处具有最大吸收。另一方面，它在水中具有适当的溶解度，所以，可将标样和样品处理成水溶液，采用紫外分光光度计，通过标准曲线法而实现酸性食品中苯甲酸（钠）含量的测定。 二、实验试剂及器材 试剂：无水乙醚(回收后可重复使用)、苯甲酸标准液(1mg/ml)、5%NaHCO3溶液、5%NaCL 溶液、(1+2v)盐酸溶液 器材：紫外分光光度计、125ml分液漏斗×2，铁架台一套，量筒100ml、容量瓶（100ml、50ml、）移液管（5ml×2、1ml×2）、胶头滴管、试剂瓶100ml×2、水浴锅、蒸馏回流装置一套。 三、实验步骤： 1、试剂准备：标准液：125.0mg苯甲酸+250ml无水乙醚 5%NaHCO3：5.0g NaHCO3+100mlH2O (1+2)HCl：20ml浓盐酸+40mlH2O 2、样品的处理：取酱油5.00ml于125nl分液漏斗中加入（1+2）盐酸2ml酸化，再用无水乙醚萃取三次，每次用量30ml，每次振摇1min。合并乙醚层于另一分液漏斗，用5%NaCl 溶液洗涤二次，每次5—10ml，然后蒸馏回收乙醚，用20ml、5%NaHCO3溶解、定容到100ml 容量瓶中。备用。 3、标准曲线绘制：取苯甲酸标准使用液0、0.1、0.2、0. 4、0.6、0.8ml分别置于100ml 容量瓶中，各加入5%NaHCO3溶液2ml，(1+2v)盐酸溶液2ml，加水至刻度，摇匀。放置15min,尽量让CO2逸尽。 用1cm吸收池于波长230nm处测定其吸光度。以吸光度为纵坐标，以浓度为横坐标绘制标准曲线。 4、取样品处理液5ml于100ml容量瓶中加入(1+2v)盐酸溶液2ml,摇荡以排除CO2，加水至刻度、摇匀、放置15min，与标准系列一起进行比色测定，根据测得吸光度，在标准曲线上查出其对应量，就可以计算出样品中苯甲酸（钠）的含量。 四、数据处理：
硅酸钙板施工 1、作业条件 1）吊顶工程在施工前应热悉施工图纸及设计说明。 2）吊顶工程在施工前应熟悉现场。 3）施工前应按设计要求对房间的净高、洞口标高和吊顶内的管道、设备及其支架的标高进行交接检验。 4）对吊顶内的管道、设备的安装及水管试压进行验收。 5）吊顶工程在施工中应做好各项施工记录，收集好各种有关文件。 6）材料进场验收记录和复验报告，技术交底记录。 7）板安装时室内湿度不宜大于70％以上。 2、施工工艺流程 吊顶标高弹水平线一划龙骨分档线一安装水电管线一安装主龙骨一安装次龙骨一安装罩面板一安装压条 3、操作工艺 1）弹线 用水准仪在房间内每个墙(柱)角上抄出水平点(若墙体较长，中间也应适当抄几个点)，弹出水准线(水准线距地面一般为500mm)，从水准线量至吊顶设计高度加上12mm(一层硅酸盖板的厚度)，用粉线沿墙(柱)弹出水准线，即为吊顶次龙骨的下皮线。同时，按吊顶平面图，在混凝土顶板弹出主龙骨的位置。主龙骨应从吊顶中心向两边分，最大间距为1000mm，并标出吊杆的固定点，吊杆的固定点间900～1000mm。如遇到梁和管道固定点大于设计和规程要求，应增加吊杆的固定点。 2）固定吊挂杆件 现浇钢筋混凝土板底预留直径8mm钢筋吊环双向中距小于1200；直径6mm钢筋吊环，双向中距小于1200吊杆上部与板底预留吊环固定；U型轻钢主龙骨CB38*12，中距小于1200找平后与钢筋吊杆固定；H型轻钢次龙骨LB20*20，中距600。制作好的吊杆应做防锈处理，吊杆用膨胀螺栓固定在楼板上，用冲击电锤打孔，孔径应稍大于膨胀螺栓的直径。 3）在梁上设置吊挂杆件 吊挂杆件应通直并有足够的承载能力。长时，必须搭接焊牢，焊缝要均匀饱满；吊杆距主龙骨端部距离不得超过300mm，否则应增加吊杆；吊顶灯具、风口及检修口等应设附加吊杆。 4）安装边龙骨 边龙骨的安装应按设计要求弹线，沿墙(柱)上的水平龙骨线把L形镀锌轻钢条用自攻螺丝固定在预埋木砖上；如为混凝土墙(柱)，可用射钉固定，射钉间距应不大于吊顶次龙骨的间距。 5）安装主龙骨 主龙骨应吊挂在吊杆上。主龙骨间距900一1000mm。主龙骨分为轻钢龙骨和T形龙骨。轻钢龙骨选用UC50中龙骨和UC38小龙骨。主龙骨应平行房间长向安装，同时应起拱，起拱高度为房间跨度的1／200～1／300。主龙骨的悬臂段不应大于300ram，否则应增加吊杆。主龙骨的接长应采取对接，相邻龙骨的对接接头要相互错开。主龙骨挂好后应基本调平。
食品防腐剂丙酸钙的制备 实 验 报 告 班级：应101-3 指导老师：贺萍 组员：柳林清（201055501305） 王翠翠（201055501307） 柳建嵩（201055501308）
食品防腐剂丙酸钙的制备 【前言】 丙酸钙是我国近几年发展起来的一种新型食品防腐剂，它对霉菌、好气性芽孢杆菌、革兰式阴性菌有很好的杀灭作用，还可抑制黄曲霉素的产生，因而广泛用于面包、糕点和奶酪的保存剂和饲料的防腐剂。随着人民生活水平的提高和食品工业的发展，鸡蛋的消耗量大幅度增加。由于目前国内对鸡蛋壳资源的利用率还很低，人们利用了可食用部分即蛋清、蛋黄，大量鸡蛋壳被扔弃，对环境造成了很大污染。初步估计一个中等城市每月所扔弃的蛋壳总量约为50-80吨。如能充分利用，不仅可变废为宝为社会增加财富，还可减少对环境的污染。 对鸡蛋壳组成成分的分析证明：蛋壳中主要成分为CaCO 3 ，另外含有少量有机物、P、Mg、Fe及微量Si、Al、Ba等元素。 以蛋壳为基本原料制备丙酸钙的方法有两种，一种方法是将蛋壳在1050℃下煅烧2h15min，使蛋丙酸反应成丙酸钙；另一种方法是直接用蛋壳与丙酸反应制备丙酸钙。前一种方法由于需要在高温下煅烧，能耗大、成本高，而且在煅烧 过程中会产生大量C0 2 污染环境，并破坏了蛋壳的天然活性；后一种方法产率却比较低。因此以研究蛋壳为基本原料如何用直接法制备丙酸钙，提高丙酸钙产率，使其成为一种既节省能源，又降低成本，同时有利环保的工业生产方法，成为当务之急。 【实验目的】 1.了解防腐剂的相关知识清楚丙酸钙作为防腐剂的优点； 2.了解丙酸钙性质和制备原理及方法； 3. 掌握固体试样的粉碎方法，过筛要求，减压过滤及蒸发浓缩的实验方法； 4. 掌握EDTA的标定，产品纯度的测定及相关的分析方法； 5. 掌握重结晶技术。 【实验原理】 1.丙酸钙，Ca(CH 3CH 2 COO) 2 ，性状白色结晶性粉末，熔点400℃以上（分解）， 无臭或具轻微特臭。可制成一水物或三水物，为单斜板状结晶，可溶于水（1g 约溶于3mL水），微溶于甲醇、乙醇，不溶于苯及丙酮。10%水溶液pH等于7.4。
石膏板吊顶工艺 一、施工准备 （一）作业条件 1.在所要吊顶的范围内，机电安装均已施工完毕，各种管线均已试压合格，已经隐蔽验收。 2.已确定灯位、通风口及各种照明孔口的位置。 3.顶棚罩面板安装前，应作完墙、地湿作业工程项目。 4.搭好顶棚施工操作平台架子。 5.轻钢骨架顶棚在大面积施工前，应做样板，对顶棚的起拱度、灯槽、窗帘盒、通风口等处进行构造处理，经鉴定后再大面积施工。 （二）材料准备 轻钢龙骨、配件、吊杆、膨胀螺栓、自攻螺钉、拉铆钉、石膏板、纸带、石膏粉等，进场检验合格且有出厂质量证明文件。 （三）施工机具 型材切割机、电动曲线锯、手电钻、电锤、自攻螺钉钻、手提电动砂纸机等。 二、质量要求 （一）暗龙骨吊顶工程 质量要求符合《建筑装饰装修工程施工质量验收规范》（GB50209－2002）的规定。 （二）明龙骨吊顶工程 质量要求符合《建筑装饰装修工程施工质量验收规范》（GB50209－2002）的规定。 三、工艺流程 弹顶棚标高水平线--画龙骨分档线--安装主龙骨吊杆--安装主龙骨--安装边龙骨--安装次龙骨--安装石膏板--涂料--饰面清理--分项--检验批验收
四、施工工艺 1.弹顶棚水平线：根据设计标高，沿墙四周弹顶棚标高水平线，并沿顶棚的标高水平线，在墙上画好龙骨分档位置线。 2.安装主龙骨吊杆：在弹好顶棚标高水平线及龙位置线后，确定吊杆下端头的标高，安装∮8吊杆。直安装选用膨胀螺栓固定到结构顶棚上。吊杆选用规格符合设计要求，间距小于1200mm。 3.安装主龙骨：主龙间距为900~1200mm。主龙骨用与之配套的龙吊件与吊杆相连。 4.安装次龙骨：次龙骨间距为500mm～600mm，采用次挂件与主龙骨连接。 5.刷防锈漆：轻钢骨架罩面板顶棚吊杆、固定吊杆铁件，在封罩面板前应刷防锈漆。 6.安装石膏板：石膏板与轻钢骨架固定的方式采用自攻螺钉固定法，在已装好并经验收轻钢骨架下面（即做隐蔽验收工作），安装9.5mm厚反。安装石膏板用自攻螺丝固定，固定间距板边为200mm，板中为300mm。自攻螺丝固定后点刷防锈漆。 7.接缝处理：在板缝间采用粘贴纸带嵌缝膏进行嵌缝处理。 8.吊顶验收时应检查下列文件和记录： ①吊顶工程的施工图、设计说明及其他设计文件； ②材料的产品合格证书、性能检测报告、进场验收记录和复验报告； ③隐蔽工程验收记录； ④施工记录。 五、成品保护 1.轻钢骨架、罩面板及其他吊顶材料在入场存放、使用过程中应严格管理，保证不变形、不受潮，不生锈。 2.装修吊顶用吊杆严禁挪做机电管道、线路程吊挂用；机电管道、线路如与吊顶吊杆位置矛盾，须经过项目技术人员同意后更改、不得随意改变、挪动吊杆。 3.吊顶龙上禁止铺设机电管道、线路。
四硅钙板吊顶施工方案 1、材料及配件要求 1.1硅钙板的规格、品种、表面形式必须达到设计要求和使用功能的要求。 1.2吊顶使用的轻钢龙骨分为U形骨架和T形骨架两种，并按照荷载不同分为上人和不上人两种。 1.3轻钢龙骨分为主龙骨、次龙骨、边龙骨；配件有吊件、连接件、挂插件等材质必须符合设计要求。 1.4零配件：吊杆、花篮螺丝、射钉、自攻螺丝等。 1.5按照设计或样品要求可选用各种罩面板 2、主要施工机具 电锯、射钉枪、手锯、钳子、螺丝刀、方尺、钢尺、钢水平尺等。 3、施工作业的相关条件 3.1材料准备：在施工前必须提前准备好吊顶所用的吊杆，一般吊杆选用Φ6～Φ10的钢筋，并且一端需要进行套丝（长度不小于50mm），如果顶棚有预埋件可以将吊杆直接与之焊接，没有预埋件则需要用30*3的角钢切成40mm左右一段，一边打孔，一边与吊杆焊接（焊接长度不小于20mm，双面焊）。设计无要求时预埋件间距为900-1200mm。 在房间的四周墙、柱上，按照吊顶标高位置打孔预埋好防腐木楔，间距600mm左右（按照矿棉板的规格设置）。 3.2顶棚内的各种设备安装工程必须施工完毕，通风管道的标高与吊顶标高无矛盾，检查口、风洞口以及各种明露孔位置确定。 3.3吊顶所需的龙骨、配件、面板提前准备齐全。 3.4安装矿棉板或安装边龙骨前墙面的必须刮两遍腻子找平，否则造成墙面与顶棚阴角处不易处理好。
4、施工工艺 4.1工艺流程： 4.2.施工技术措施： （1）弹线：根据事先从标高点引出的标高弹出50cm 控制线，并依据弹出的控制线确定各房间吊顶设计标高的标准线。在墙上划出龙骨的分档控制点，一般距离900-1200mm 左右。 （2）安装吊筋：根据施工大样图纸要求确定吊筋的位置，安装吊筋前，刷防锈漆。吊杆采用直径为Φ6的钢筋制作并刷防锈漆，吊点间距900-1200mm 。安装时上端与铁胀栓连接，下端套丝后与吊件连接。安装完毕的吊杆端头外露长度不小于3MM 。 （3）安装主龙骨：采用UC50或U38龙骨，吊顶主龙骨间距为小于1200MM 。安装主龙骨时，应将主龙骨吊挂件连接在主龙骨上，拧紧螺丝，并根据设计要求吊顶起拱 ，起拱高度约为短跨的1/200，并且安装的主龙骨接长应错开，在接头处增加吊点，随时检查龙骨的平整度。当遇到通风管道较大超过龙骨最大间距要求时，必须采用30*3以上的角钢做龙骨骨架，并且不能将骨架与通风管道等设备工程接触。 （4）安装次龙骨：按照面板的不同安装方式和规格，次龙骨分为T 形和C 形两种，次龙骨间距为600mm ，将次龙骨通过挂件吊挂在大龙骨上，在与主龙骨平行方向安装600MM 的横撑龙骨，间距为600MM 或1200MM 。当采用搁置法和企口法安装时次龙骨为T 形，粘贴法或者其他固定法时选用C 形。 （5）安装边龙骨：采用L 型边龙骨，与墙体用塑料胀管或自攻螺钉固定，固定
食品防腐剂碳酸钙的制备综述 食品防腐剂概述 食品防腐剂是抑制物质腐败的药剂。即对以腐败物质为代谢底物的微生物的生长具有持续的抑制作用。重要的是它能在不同情况下抑制最易发生的腐败作用，特别是在一般灭菌作用不充分时仍具有持续性的效果。对纤维和木材的防腐用矿油、煤焦油、丹宁，对用甲醛、升汞、甲苯、对羟基苯甲酸丁酯、硝基糠腙衍生物或香脂类树脂。在食品中使用防腐剂受到限制，因此多靠干燥、腌制等一些物理的方法。特殊的防腐剂有乙酸等有机酸、以油酸脂为成分的植物油、芥子等特殊的精油成分。对于生物体的局部（如人体表面或消化道），可以根据具体条件采用各种防腐剂（如碘仿、水杨酸苯酯、苯胺染料或吖啶类色素等）。 我国规定使用的防腐剂有苯甲酸、山梨酸、丙酸钙等25种。 应具备的条件 1）性质较稳定：加入到食品中后在一定的时期内有效，在食品中有很好的稳定性 2）低浓度下具有较强的抑菌作用 3）本身不应具有刺激气味和异味 4）不应阻碍消化酶的作用，不应影响肠道内有益菌的作用 5）价格合理，使用较方便。 作用机理 ①能使微生物的蛋白质凝固或变性，从而干扰其生长和繁殖。 ②防腐剂对微生物细胞壁、细胞膜产生作用。由于能破坏或损伤细胞壁，或能干扰细胞壁合成的机理，致使胞内物质外泄，或影响与膜有关的呼吸链，从而具有抗微生物的作用。 ③作用于遗传物质或遗传微粒结构，进而影响到遗传物质的复制、转录、蛋白质的翻译等。 ④作用于微生物体内的酶系，抑制酶的活性，干扰其正常代谢。 种类 食品防腐剂按作用分为和。二者常因浓度、作用时间和微生物性质等的不同而不易区分。按性质也可分为有机化学防腐剂和无机化学防腐剂两类。此外还有乳酸链球菌素，是一种由乳链球菌产生、含34个的肽类抗菌素。目前世界各国所用的食品防腐剂约有30多种。食品防腐剂在被划定为第17类，有28个品种。防腐剂按来源分，有化学防腐剂和天然防腐剂两
硫酸钙含量测定 概述 钻井液中的硫酸钙含量可以用钙离子测定程序中所描述的EDTA方法测定。首先用此测定钻井液滤液和钻井液中的钙离子含量，而后可计算得到硫酸钙总量和未溶解的硫酸钙含量。 仪器和药品 1、EDTA溶液：0.01mol/L的二水合乙二胺四乙酸钠盐的标准溶液（1cm3=1000mg/LCaCO3, 1cm3=400mg/LCa2+）。 2、测钙离子用缓冲溶液：1mol/L氢氧化钠溶液。 3、钙指示剂：Calver?Ⅱ或羟基苯酚蓝。 4、冰乙酸。 5、滴定瓶：150ml烧杯。 6、刻度移液管：10ml 2支，1ml一支。 7、移液管：1ml,2ml,5ml，10ml各一支。 8、加热板（滤液有颜色时需要）。 9、掩蔽剂：体积比为1：1：2的三乙醇胺、四乙烯基戊胺和去离子水的混 合液。 10、pH试纸。 11、量筒：50ml 12、次氯酸钠溶液：5.25％次氯酸钠的去离子水溶液。注：出售的许多次氯 酸钠中含有次氯酸钙或草酸，不应使用此类药品。要确保所使用的药品 是新鲜的，因为时间久了将会变质。 13、去离子水或蒸馏水。 注：试验前应测定去离子水和次氯酸钠溶液中的钙离子含量，以便在测定样品后减去这一含量。 测定程序 1、将5ml钻井液加入到245ml去离子水中，搅拌15分钟后用标准API滤失仪过滤，只收集澄清的滤液。用10ml移液管移取10ml澄清滤液到50ml烧杯中，然后按钙离子测定程序，用EDTA滴定至终点，记录EDTA体积V1。 2、用EDTA滴定1ml 原始钻井液滤液至终点。此时消耗EDTAD的体积为V2。 3、用蒸馏器蒸馏钻井液。用液相和固相含量测定中所获得的水的体积百分数确定钻井液中水的体积分数F W。 4、计算 以Kg/m3为单位的钻井液中硫酸钙含量： = 6.80V1 C CaSO 4 以Kg/m3为单位的钻井液中未溶解的硫酸钙含量： ＝6.80V1-1.37V2F W C'CaSO 4
三、石膏板吊顶施工工艺 令狐采学 1、施工准备 1）原材料、半成品要求 木料：木龙骨料应为烘干，无扭曲的红、白松树种，并按设计要求进行防火处理。木龙骨规格按设计要求，如设计无明确规定时，大龙骨规格为50mm×70m m或50mm×100m m；小龙骨规格为50mm×50m m或40mm×50m m；木吊杆规格为50mm×50m m或40mm×40m m。罩面板材及压条。 纸面石膏板选用时严格掌握材质及规格标准。 其它材料 φ6或φ8吊筋、膨胀螺栓、射钉、圆钉、角钢、扁钢、胶粘剂、木材防腐剂、防火剂、8号镀锌铁丝、防锈漆。 2）作业条件 现浇楼板中按设计间距埋设φ6或φ8吊筋。当设计未做说明时，间距一般不大于1000mm。 墙为砌体时，应根据顶棚标高，在四周墙上预埋固定龙骨的木砖。 直接接触墙体的木龙骨，应预先刷防腐剂。 按工程不同防火等级和所处环境要求，对木龙骨进行喷涂防火涂料或置于防火涂料槽内浸渍处理。
顶棚内各种管线及通风管道均已安装完毕并经验收合格。各种灯具、报警器预留位置已经明确。 墙面及楼、地面湿作业和屋面防水已做完。 室内环境力求干燥，满足木龙骨吊顶作业的环境要求。 2、施工工艺 1）抄平弹线 弹线包括：标高线、顶棚造型位置线、吊挂点布局线、大中型灯位线。 确定标高线：根据室内墙上+50cm水平线，用尺量至顶棚设计标高，在该点画出高度线，用一条塑料透明软管灌满水后，将软管的一端水平面对准墙面上的高度线。再将软管的另一端头水平面，在同侧墙面找出另一点，当软管内水平面静止时，画下该点的水平面位置，再将这两点连线，即得吊顶高度水平线。用同样方法在其它墙面做出高度水平线。操作时应注意，一个房间的基准高度点只用一个，各个墙的高度线测点共用。沿墙四周弹一道墨线，这条线便是吊顶四周的水平线，其偏差不能大于5mm。 确定造型位置线：对于较规则的建筑空间，其吊顶造型位置可先在一个墙面量出竖向距离，以此画出其它墙面的水平线，即得吊顶位置外框线，而后逐步找出各局部的造型框架线。对于不规则的空间画吊顶造型线，宜采用找点法，即根据施工图纸测出造型边缘距墙面的距离，从墙面和顶棚基层进行实测，找出吊顶
MMFSCNG0088 食品 丙酸钠 丙酸钙 气相色谱法 MM_FS_CNG_0088 食品中丙酸钠、丙酸钙的测定方法 1．适用范围 本方法适用于酱油、醋、面包和糕点中丙酸盐的测定。本方法最低检出量为面包、糕点0.05g/kg，酱油、醋0.02g/kg。 2．原理概要 样品酸化后，丙酸盐转化为丙酸，经水蒸气蒸馏，收集后直接进气相色谱，用氢火焰离子化检测器检测，与标准系列比较定量。 3．主要仪器和试剂 3.1 试剂 3.1.1 磷酸溶液：取10mL磷酸(85％)加水至100mL。 3.1.2 甲酸溶液：取1mL甲酸(99％)加水至50mL。 3.1.3 硅油。 3.1.4 丙酸标准溶液：标准储备液(10mg/mL)，准确称取250mg丙酸于25mL容量瓶中，加水至刻度。标准使用液，将储备液用水稀释成10～250μg/mL的标准系列。 3.2 仪器 3.2.1 气相色谱仪：具有氢火焰离子化检测器。 3.2.2 水蒸气蒸馏装置。 4．过程简述 4.1 提取 准确称取30g事先均匀化的样品，置于500mL蒸馏瓶中，加入100mL水，再用50mL 水冲洗容器，转移到蒸馏瓶中，加10mL磷酸溶液，2～3滴硅油，进行水蒸气蒸馏，将250mL容量瓶置于冰浴中作为吸收液装置，待蒸馏液约250mL时取出，在室温下放置30min，加水至刻度，吸取10mL该溶液于试管中，加入0.5mL甲酸溶液，混匀，供色谱测定用。 4.2 色谱条件 色谱柱：玻璃柱，内径3mm，长1m，内装80～100目 仪器条件:柱温180℃，进样口、检测器温度220℃。 气流条件：氮气 50mL/min； 氢气 50mL/min； 空气 500mL/min。 4.3 测定 取标准系列中各种浓度的标准使用液10mL，加0.5mL甲酸溶液，混匀。取5 μL 进气相色谱，测定不同浓度丙酸的峰高，根据浓度和峰高绘制标准曲线。同时进样品溶液，根据样品的峰高与标准曲线比较定量。 5．结果计算： 0001250×=m A X
硅酸钙板施工工艺及流 程 集团公司文件内部编码：（TTT-UUTT-MMYB-URTTY-ITTLTY-
硅酸钙板施工 1、作业条件 1）吊顶工程在施工前应热悉施工图纸及设计说明。 2）吊顶工程在施工前应熟悉现场。 3）施工前应按设计要求对房间的净高、洞口标高和吊顶内的管道、设备及其支架的标高进行交接检验。 4）对吊顶内的管道、设备的安装及水管试压进行验收。 5）吊顶工程在施工中应做好各项施工记录，收集好各种有关文件。 6）材料进场验收记录和复验报告，技术交底记录。 7）板安装时室内湿度不宜大于70％以上。 2、施工工艺流程 吊顶标高弹水平线一划龙骨分档线一安装水电管线一安装主龙骨一安装次龙骨一安装罩面板一安装压条 3、操作工艺 1）弹线 用水准仪在房间内每个墙(柱)角上抄出水平点(若墙体较长，中间也应适当抄几个点)，弹出水准线(水准线距地面一般为500mm)，从水准线量至吊顶设计高度加上12mm(一层硅酸盖板的厚度)，用粉线沿墙(柱)弹出水准线，即为吊顶次龙骨的下皮线。同时，按吊顶平面图，在混凝土顶板弹出主龙骨的位置。主龙骨应从吊顶中心向两边分，最大间距
为1000mm，并标出吊杆的固定点，吊杆的固定点间900～1000mm。如遇到梁和管道固定点大于设计和规程要求，应增加吊杆的固定点。 2）固定吊挂杆件 现浇钢筋混凝土板底预留直径8mm钢筋吊环双向中距小于1200；直径6mm钢筋吊环，双向中距小于1200吊杆上部与板底预留吊环固定；U型轻钢主龙骨CB38*12，中距小于1200找平后与钢筋吊杆固定；H型轻钢次龙骨LB20*20，中距600。制作好的吊杆应做防锈处理，吊杆用膨胀螺栓固定在楼板上，用冲击电锤打孔，孔径应稍大于膨胀螺栓的直径。 3）在梁上设置吊挂杆件 吊挂杆件应通直并有足够的承载能力。长时，必须搭接焊牢，焊缝要均匀饱满；吊杆距主龙骨端部距离不得超过300mm，否则应增加吊杆；吊顶灯具、风口及检修口等应设附加吊杆。 4）安装边龙骨 边龙骨的安装应按设计要求弹线，沿墙(柱)上的水平龙骨线把L形镀锌轻钢条用自攻螺丝固定在预埋木砖上；如为混凝土墙(柱)，可用射钉固定，射钉间距应不大于吊顶次龙骨的间距。 5）安装主龙骨 主龙骨应吊挂在吊杆上。主龙骨间距900一1000mm。主龙骨分为轻钢龙骨和T形龙骨。轻钢龙骨选用UC50中龙骨和UC38小龙骨。主龙骨应平行房间长向安装，同时应起拱，起拱高度为房间跨度的1／200～1／300。主龙骨的悬臂段不应大于300ram，否则应增加吊杆。主龙骨的接长应采取对接，相邻龙骨的对接接头要相互错开。主龙骨挂好后应
前言：防腐剂，英语为Preservative，是指天然或合成的化学成分，用于加入食品、药品、颜料、生物标本等，以延迟微生物生长或化学变化引起的腐败从今后防腐剂的发展趋势看，天然防腐剂将成为发展主角。 一、防腐剂 防腐剂的基本名防腐剂有苯甲酸钠、山梨酸钾、脱氢乙酸钠、丙酸钙、双乙酸钠、乳酸钠、对羟基苯甲酸丙防腐剂酯、乳酸链球菌素、过氧化氢等防腐剂是用于保持食品原有品质和营养价值为目的食品添加剂，它能抑制微生物的生长繁殖，防止食品腐败变质而延长保质期。 防腐剂的防腐原理，大致有如下3种： 一是干扰微生物的酶系，破坏其正常的新陈代谢，抑制酶的活性。 二是使微生物的蛋白质凝固和变性，干扰其生存和繁殖。 三是改变细胞浆膜的渗透性，抑制其体内的酶类和代谢产物的排除，导致其失活。 谈到防腐剂，人们往往认为有害，其实在安全使用范围内，对人体是无毒副作用的。我国防腐剂使用有严格的规定，防腐剂应符合以下标准： 1.合理使用对人体无害； 2.不影响消化道菌群； 3.在消化道内可降解为食物的正常成分； 4.不影响药物抗菌素的使用； 5.对食品热处理时不产生有害成分。 我国已批准了32种使用的食物防腐剂，其中最常用的有苯甲酸钠、山梨酸钾等。苯甲酸钠的毒性比山梨酸钾强，而且在相同的酸度值下抑菌效力仅为山梨酸的1/3，因此许多国家逐渐用山梨酸钾。但因苯甲酸钠价格低廉，在我国仍普遍使用，主要用于碳酸饮料和果汁饮料。山梨酸钾抗菌力强，毒性小，可参与人体的正常代谢，转化为CO2和水。从防腐剂的发展趋势上看，以生物发酵而成的生物防腐剂，成为未来的发展趋势。复配糕点防腐剂 二．丙酸钙 丙酸钙是酸型食品防腐剂，在酸性条件下，产生游离丙酸，具有抗菌作用。其抑菌作用受环境pH值的影响，在pH值5.0时霉菌的抑制作用最佳；pH值6.0
本帖最后由asc3793 于2016-6-10 21:40 编辑 1；石膏板吊顶施工标准做法 一、工艺流程 1、适用范围 适用于电梯前室、首层大堂顶棚装修施工 2、工艺流程 弹线→水电隐蔽工程安装→安装吊筋→安装主龙骨→安装次龙骨→隐蔽工程检验→安装面层石膏板→腻子及表面涂料施工→安装灯具电器→清洁。 二、控制标准及注意事项 1、公装施工前，必须做公装施工样板，对吊顶内管线等进行优化，明确各部件的位置关系及施工工艺，公装样板经技术部确认后，方可进行大面积施工。 2、公装过程需报质监站验收，施工单位应提前咨询主管部门，否则有可能影响单位工程质监验收。 3、总包单位与公装单位顶棚部位交接面为素混凝土交接。 4、进场材料的品牌与甲方指定品牌相符，且需提供材料合格证、质保书、3C认证等书面资料；并按以下要求对材料进行检查： 1）胶合板：主要检测甲醛释放量和胶合强度，以及标称厚度与实际厚度是否相符； 2）铝扣板：主要检测外观质量、厚度（批量装修时，采购的厚度宜≥0.7mm）、静载加载挠度以及相应的表面处理质量等。龙骨及配件的质量检查，要注意尺寸要求，外观要求，镀锌量以及弹塑性变形量，挠度等。 3）纸面石膏板：应平整，对于波纹、沟槽、污痕和划伤等缺陷，按规定方法检测时，应符合规定。检测外观质量时应在0.5m远处光照明亮的条件下，进行目测检查。
5、石膏板吊顶，宜采用不锈钢螺丝钉，且所有螺丝必须做防锈处理；螺丝头宜略埋入板面，约0.5mm； 4、主龙骨的相互间距≤1.2m，固定板材的次龙骨间距≤600mm；吊杆长度≥1.5m时，应设置反支撑，禁止采用铁丝代替吊杆；当吊杆与设备相遇时，应调整吊点构造或增设吊杆。主龙骨应根据设计要求起拱，如设计中无明确要求时，应按吊顶区域短向跨度的1/200～1/300起拱。主龙骨安装后应及时校正其位置和标高。 5、顶棚采用的材料必须达到耐火等级要求，采用木质构件等可燃物必须经过防火处理。 6、天花封板前，必须检查天花电管线安装，包括电气及消防管线等，电线穿线完成，管道通水打压完成，防止天棚安装完成后，再进行调整。 7、天花板安装时，应调整灯位、烟感探头、消防喷嘴等外露部位，灯位、烟感等应按图纸对称或居中分布，消防喷嘴外露长度应合适且每个喷嘴的外露长度应相同。 8、大堂内较重的灯具等，必须连接到混凝土顶板上，不得直接挂到吊顶龙骨上。顶棚内的管线必须单独设置吊杆，不得借用龙骨吊杆。 9、纸面石膏板吊顶工程，如设计无明确要求时，应在边角隐蔽处或吊顶内重要设备部位，设置检查孔，以便于设备检修。 10、吊顶安装后如需上人维修吊顶内部设备，应踩踏龙骨，不得直接踩踏石膏板、木夹板等吊顶板面部位，以免造成板面断裂。 三、记录控制 1、施工样板验收记录 2、材料进场检查记录 3、天棚管线等隐检记录。 2；块料铺装施工标准做法 一、工艺流程： 1、适用范围 适用于电梯厅、大堂墙面块料铺装施工。 2、工艺流程 基层处理→弹线→贴面砖或石材→勾缝→表面清洁（及打磨）→成品保护。